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Jordi Llorca

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Born in Barcelona in 1966, Jordi Llorca graduated and earned his PhD in Chemistry at the University of Barcelona, where he was later appointed Associate Professor and Ramón y Cajal Fellow. In 2005, he joined the Technical University of Catalonia as Professor and in 2014 he became Full Professor as Serra Húnter Fellow. He has been visiting professor at several universities. He has received the Distinction of Generalitat de Catalunya to the Promotion of the University Research in 2003, the Humbert Torres Prize in 2003 and the ICREA Academia in 2009, 2014 and in 2019. He has been Director of the Institute of Energy Technologies, Director of the Center for Research in NanoEngineering and Director of the Barcelona Research Center in Multiscale Science and Engineering. In 2017 he became Academic member of the Institute for Catalan Studies, Division of Science and Technology. He has published over 450 scholarly articles and authored 10 patents. He is the Vice-rector for Research at UPC.

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Papers by Jordi Llorca

Co–Sn Nanocrystalline Solid Solutions as Anode Materials in Lithium‐Ion Batteries with High Pseudocapacitive Contribution

Chemsuschem, Apr 5, 2019

Co-Sn solid-solution nanoparticles with the Sn crystal structure and tuned metal ratios were synt... more Co-Sn solid-solution nanoparticles with the Sn crystal structure and tuned metal ratios were synthesized by a facile onepot solution-based procedure involving the initial reduction of a Sn precursor and the posterior incorporation of Co within the Sn lattice. Such nanoparticles were used as anode materials for Li-ion batteries. Among the different compositions tested, Co0.7Sn and Co0.9Sn electrodes provided the highest capacities, with values above 1500 mAh g-1 at a current density of 0.2 A g-1 after 220 cycles and up to 800 mAh g-1 at 1.0 A g-1 after 400 cycles. Up to 81 % pseudocapacitance contribution at a sweep rate of 1.0 mV s-1 were measured for these electrodes, providing fast kinetics and long durability. The excellent performance of Co-Sn alloy nanoparticlebased electrodes was associated to both the small size of the crystal domains and their suitable composition, which buffered volume changes of Sn and contributed to a suitable electrode restructuration.  J. Li and X. Xu equally contributed to this work. Supporting information for this article is given via a link at the end of the document.

Surface Chemistry and Nano-/Microstructure Engineering on Photocatalytic In2S3 Nanocrystals

Zenodo (CERN European Organization for Nuclear Research), May 11, 2018

Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysi... more Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysis, offering an easier recyclability and a number of additional functionalities. Using high throughput printing technologies, colloidal NCs can be also supported onto substrates to produce cost-effective electronic, optoelectronic, electrocatalytic and sensing devices. In these 2 two broad areas, NCs surface chemistry and supracrystal organization are key parameters determining final performance. Here, we study the influence of the surface ligands and the NC organization on the catalytic properties of In 2 S 3 , both in colloidal form and as a supported layer. In solution, well dispersed NCs stabilized in solution by inorganic ligands show the highest photocatalytic activities. On the other hand, when NCs are supported on a substrate, their organization becomes an essential parameters determining performance, and NC-based films produced through a gelation process provided five-fold higher photocurrent densities than those obtained from dense films produced by the direct printing of NCs.

Synthesis and characterization of nanoparticles of CZTSe by microwave-assited chemical synthesis

Materials research express, Dec 8, 2016

In this study we present the synthesis of Cu2ZnSnSe4 (CZTSe) nanoparticles by microwaveassisted c... more In this study we present the synthesis of Cu2ZnSnSe4 (CZTSe) nanoparticles by microwaveassisted chemical synthesis employing organic solvents. The effect of reaction time, reactant concentration, solvent and additives (inorganic material) was studied on the structural and optical properties of the nanomaterials. The powder samples were analyzed by X-ray diffraction (XRD), Raman spectroscopy, X-ray energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The results show that the synthesis performed with triethanolamine and deionized water is better than others solvents, producing nanocrystals of quaternary phase (CZTSe) with stoichiometric relations similar to the reported research in the literature, which falls in the range of Cu/(Zn+Sn): 0.8-1.0, Zn/Sn: 1.0-1.20. The nanoparticles of CZTSe synthesized in this study present desirable properties in order to use them in solar cell and photoelectrochemical cell applications.

A High Conductivity 1D π–d Conjugated Metal–Organic Framework with Efficient Polysulfide Trapping‐Diffusion‐Catalysis in Lithium–Sulfur Batteries

Advanced Materials, Jan 28, 2022

Lithium-sulfur batteries (LSBs) offer notable advantages over conventional lithium ion batteries,... more Lithium-sulfur batteries (LSBs) offer notable advantages over conventional lithium ion batteries, but their implementation is limited by the sluggish conversion kinetics of lithium polysulfides (LiPS), the dissolution and diffusion of LiPS, and the poor electrical conductivity of sulfur and lithium sulfide. Herein, we present a one-dimensional (1D) π-d conjugated metalorganic framework, Ni-MOF-1D, as an efficient sulfur host to overcome these limitations. Experimental results and density functional theory (DFT) calculations demonstrate that Ni-MOF-1D is characterized by a remarkable binding strength for trapping soluble LiPS species. Ni-MOF-1D also acts as an effective catalyst for S reduction during the discharge process and Li2S oxidation during the charge process. In addition, the delocalization of electrons in the π-d system of Ni-MOF-1D provides a superior electrical conductivity to improve electron transfer. Thus, cathodes based on Ni-MOF-1D enable LSBs with excellent performance, including a remarkable initial capacity of 1491 mA h g −1 , superior rate performance of 575 mAh g −1 at 8 C, impressive cycling stability with over 82% capacity retention over 1000 cycles at 3 C, and a high areal capacity of 5.36 mAh cm −2 under a high sulfur loading of 4.3 mg cm −2. While this work particularly focuses on the synthesis and performance of a Ni-based MOF, the strategies and advantages here demonstrated can be extended to a broader range of π-d conjugated MOFs materials, which we believe have a high potential as sulfur host in LSBs.

In Situ Electrochemical Oxidation of Cu<sub>2</sub>S into CuO Nanowires as a Durable and Efficient Electrocatalyst for Oxygen Evolution Reaction

Chemistry of Materials, Aug 15, 2019

Effect of Fe–Zn–Mg–Al hydrotalcites on the methane potential of synthetic sulfate-containing wastewater

Journal of water process engineering, Apr 1, 2016

Three hydrotalcites of M 2+-Mg-Al were synthesized using the co-precipitation method, where M 2+ ... more Three hydrotalcites of M 2+-Mg-Al were synthesized using the co-precipitation method, where M 2+ was Fe 2+ , Zn 2+ and Fe 2+ + Zn 2+. The hydrotalcites and their calcined form of mixed oxides obtained by their thermal decomposition were characterized by FTIR, XRD and SEM. Subsequently their effect on the methane potential of synthetic wastewater comprised of sucrose and sulfur was evaluated in a multiple batch system at 37 ± 0.5 °C. The best methane potential was observed from the Fe-Zn-Mg-Al hydrotalcite at 500 mg/L yielding 3712mL CH 4 /gVS which corresponds to an 8.1% increment against the control. The better performance of the Fe-Zn-Mg-Al hydrotalcite can be attributed to the Zn 2+ ions. These react with S 2in the substrate to yield zinc sulfide and therefore prevent it from forming H 2 S by sulfate reducing bacteria, meanwhile reducing competition for methanogens to form methane. Calcined hydrotalcites neither stimulated nor inhibited the methane production which suggests that the enhancement of methane produced by the Fe-Zn-Mg-Al hydrotalcite was related to the presence of Fe 2+ and Zn 2+ cations incorporated and immobilized in the layered sheet structure of the hydrotalcite.

A comparative study of water-immiscible organic solvents in the production of furfural from xylose and birch hydrolysate

Journal of Industrial and Engineering Chemistry, Apr 1, 2019

The production of furfural (FUR) from xylose was carried out using a biphasic batch reaction syst... more The production of furfural (FUR) from xylose was carried out using a biphasic batch reaction system. Isophorone, 2-methyltetrahydrofuran (2-MTHF) and cyclopentyl methyl ether (CPME) were used to extract FUR and enhance the overall furfural yield by limiting its degradation to humins. The effect of time, temperature, organic solvent and organicto-aqueous ratio on xylose conversion and FUR yield were investigated. Experiments conducted at three temperatures (170, 190 and 210 °C) were investigated in a stirred microwave-assisted batch reactor, which established the optimal conditions to obtain the highest FUR yield. The maximum FUR yields obtained from xylose were 78 mol% when using CPME, 48 mol% when using isophorone (due to its phase-behavior nature) and 71 mol% when employing 2-MTHF with an aqueous to organic phase ratio of 1:1. Birch hydrolysate was also used to show the high furfural concentration that can be obtained in the bi-phasic system under optimized conditions. The present study suggests that CPME can be used as a green and efficient extraction solvent for the conversion of xylose into furfural without salt addition.

Effect of the Annealing Atmosphere on Crystal Phase and Thermoelectric Properties of Copper Sulfide

ACS Nano, Mar 1, 2021

Cu 2−x S has become one of the most promising thermoelectric materials for application in the mid... more Cu 2−x S has become one of the most promising thermoelectric materials for application in the middle-high temperature range. Its advantages include the abundance, low cost, and safety of its elements and a high performance at relatively elevated temperatures. However, stability issues limit its operation current and temperature, thus calling for the optimization of the material performance in the middle temperature range. Here, we present a synthetic protocol for large scale production of covellite CuS nanoparticles at ambient temperature and atmosphere, and using water as a solvent. The crystal phase and stoichiometry of the particles are afterward tuned through an annealing process at a moderate temperature under inert or reducing atmosphere. While annealing under argon results in Cu 1.8 S nanopowder with a rhombohedral crystal phase, annealing in an atmosphere containing hydrogen leads to tetragonal Cu 1.96 S. High temperature X-ray diffraction analysis shows the material annealed in argon to transform to the cubic phase at ca. 400 K, while the material annealed in the presence of hydrogen undergoes two phase transitions, first to hexagonal and then to the cubic structure. The annealing atmosphere, temperature, and time allow adjustment of the density of copper vacancies and thus tuning of the charge carrier concentration and material transport properties. In this direction, the material annealed under Ar is characterized by higher electrical conductivities but lower Seebeck coefficients than the material annealed in the presence of hydrogen. By optimizing the charge carrier concentration through the annealing time, Cu 2−x S with record figures of merit in the middle temperature range, up to 1.41 at 710 K, is obtained. We finally demonstrate that this strategy, based on a low-cost and scalable solution synthesis process, is also suitable for the production of high performance Cu 2−x S layers using high throughput and cost-effective printing technologies.

SnP nanocrystals as anode materials for Na-ion batteries

Journal of materials chemistry. A, Materials for energy and sustainability, 2018

Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the ethical guidelines, outlined in our author and reviewer resource centre, still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

PbS–Pb–Cu<i><sub>x</sub></i>S Composites for Thermoelectric Application

ACS Applied Materials & Interfaces, Oct 19, 2021

Composite materials offer numerous advantages in a wide range of applications, including thermoel... more Composite materials offer numerous advantages in a wide range of applications, including thermoelectrics. Here semiconductor-metal composites are produced by just blending nanoparticles of a sulfide semiconductor obtained in aqueous solution and at room temperature, with a metallic Cu powder. The obtained blend is annealed in a reducing atmosphere and afterwards consolidated into dense polycrystalline pellets through spark plasma sintering (SPS). We observe that, during the annealing process, the presence of metallic copper activates a partial reduction of the PbS, resulting in the formation of PbS-Pb-CuxS composites. The presence of metallic lead during the SPS process habilitates the liquid-phase sintering of the composite. Besides, by comparing the transport properties of PbS, the PbS-Pb-CuxS composites, and PbS-CuxS composites obtained by blending PbS and CuxS nanoparticles, we demonstrate that the presence of metallic lead decisively contributes to a strong increase of the charge carrier concentration through spillover of charge carriers enabled by the low work function of lead. The increase in charge carrier concentration translates into much higher electrical conductivities and moderately lower Seebeck coefficientsThese properties translate into power factors up to 2.1 mWm-1 K-2 at ambient temperature, well above those of PbS and PbS+CuxS. Additionally, the presence of multiple phases in the final composite results in a notable decrease in the lattice thermal conductivity. Overall, the introduction of metallic copper in the initial blend results in a significant improvement of the thermoelectric performance of PbS, reaching a dimensionless thermoelectric figure of merit ZT = 1.1 at 750 K, which represents about a 400% increase over bare PbS. Besides, an average ZTave = 0.72 in the temperature range 320-773 K is demonstrated.

Nickel Iron Diselenide for Highly Efficient and Selective Electrocatalytic Conversion of Methanol to Formate

Small, Jan 18, 2021

The electrooxidation of methanol to formate is an example of the potential use of renewable energ... more The electrooxidation of methanol to formate is an example of the potential use of renewable energies to add value to a biosourced chemical commodity. Additionally, methanol electrooxidation can replace the sluggish oxygen evolution reaction for hydrogen evolution or the electroreduction of other biomass-derived intermediates. Here, we demonstrate a noble metal-free catalyst, Ni 1-x Fe x Se 2 , with a high potential for an efficient and selective methanol conversion to formate. At its optimum composition, Ni 0.75 Fe 0.25 Se 2 , this diselenide is able to produce 0.47 mmol cm-2 h-1 of formate at 50 mA cm-2 with a Faradaic conversion efficiency of 99 %. We further demonstrate that Ni 1-x Fe x Se 2-based catalysts are able to continuously work for over 50,000 s with a minimal loss of efficiency, delivering initial current densities above 50 mA cm-2 and 2.2 A mg-1 in a 1.0 M KOH electrolyte with 1.0 M methanol at 1.5 V vs. RHE.

Simulation of two-step redox recycling of non-stoichiometric ceria with thermochemical dissociation of CO2/H2O in moving bed reactors – Part II: Techno-economic analysis and integration with 100 MW oxyfuel power plant with carbon capture

Chemical Engineering Science, Sep 1, 2019

This paper presents a solar thermochemical looping CO2/H2O dissociation reactors unit (CL) with c... more This paper presents a solar thermochemical looping CO2/H2O dissociation reactors unit (CL) with commercial ceria as redox oxygen carrier. The CL unit is integrated to a 100 MW oxyfueled natural gas combined cycle with carbon capture to investigate the efficiency benefit obtained. A moving bed counter-current reactor model is developed in Aspen Plus considring rigorous continuous stirred reactors (RCSTRs) for both reduction and oxidation. A userkinetic subroutine is developed in FORTRAN and linked with each RCSTR in both reduction and oxidation reactor with their respective kinetics. It is found that efficiency of the chemical looping unit varies widely with reduction reactor temperature and vacuum pressure. Chemical looping unit efficiency is obtained for three conditions considering only CO2 and only H2O it was found to be 35.41% and 30.84% respectively, and for mixture (86% CO2, 14% H2O) 35.26%. The efficiency drop for only H2O is due to heat needed for phase change and more vacuum pump required for hydrogen compare to CO2. The maximum solar to electrical efficiency for the whole system layout was found to be 25.4% with a reduction temperature of 1600 o C and 10-7 bar vacuum pressure. With a 0.5 m 3 reduction reactor and 5 m 3 oxidation reactor the maximum net electricity produced by add-on unit is 12.85 MWe. Economic analysis revealed that the major contributor to the total project cost is hydrogen compressor (19%) and solar field and tower represent 39% of the total equipment costs giving a specific overnight capital cost of 12136 $/kW with LCOE of 1100 S/MWh.

The Importance of Surface Adsorbates in Solution‐Processed Thermoelectric Materials: The Case of SnSe

Advanced Materials, Oct 22, 2021

Thermoelectric devices reversibly convert heat into electricity both for power harvesting and for... more Thermoelectric devices reversibly convert heat into electricity both for power harvesting and for active cooling and heating. The efficiency of a thermoelectric device is determined by the temperature-dependent properties of the materials that constitute it. These are summarized in the thermoelectric figure of merit of the material, zT = S 2 σκ-1 T, that combines Seebeck coefficient (S), electrical conductivity (σ), thermal conductivity (κ), and absolute temperature (T). [1,2] Thermoelectric materials are often dense, polycrystalline inorganic semiconductors. Usually, the processing of such materials has two steps: preparation of the semiconductor in powder form and the consolidation of the powder into a dense sample. The most common route to prepare powders among the thermoelectric community is through high-temperature reactions and ball milling. [3] Alternatively, solution methods to produce powders with much less demanding conditions (e.g., lower reagent purity, lower temperatures, and shorter reaction times) have been explored to reduce the production costs. [1,4] These methods also provide opportunities to produce particles with better-controlled features, such as crystallite size, shape, composition, and crystal phase, which allow modifying the properties of the consolidated material. [5-7] Lastly, solution processing facilitates device fabrication versatility, including flexible, conformable, and rigid modules with customized geometries. [8,9] To date, solution synthesis has enabled the production of several materials with state-of-the-art performances, as is the case of PbS, [6] Bi 0.5 Sb 1.5 Te 3 , [10] Bi 2 Te 3−x Se x , [11] and SnTe, [12] demonstrating the potential of this strategy. However, when dealing with powders produced in solution, one should pay special attention to potential undesired elements coming from the reactants. Those elements may not affect the crystal structure and bulk composition of the powder but can be present as surface adsorbates. [13] The composition, chemical stability, and bonding nature of surface species can influence the sintering process, and reaction byproducts can determine the final properties of the consolidated material. Surface species have been carefully considered in surfactantassisted colloidal synthesis because of the insulating nature of the long-chain aliphatic surfactants generally used [14] and Solution synthesis of particles emerges as an alternative to prepare thermoelectric materials with less demanding processing conditions than conventional solid-state synthetic methods. However, solution synthesis generally involves the presence of additional molecules or ions belonging to the precursors or added to enable solubility and/or regulate nucleation and growth. These molecules or ions can end up in the particles as surface adsorbates and interfere in the material properties. This work demonstrates that ionic adsorbates, in particular Na + ions, are electrostatically adsorbed in SnSe particles synthesized in water and play a crucial role not only in directing the material nano/microstructure but also in determining the transport properties of the consolidated material. In dense pellets prepared by sintering SnSe particles, Na remains within the crystal lattice as dopant, in dislocations, precipitates, and forming grain boundary complexions. These results highlight the importance of considering all the possible unintentional impurities to establish proper structure-property relationships and control material properties in solution-processed thermoelectric materials.

Furfural production from xylose and birch hydrolysate liquor in a biphasic system and techno-economic analysis

Biomass Conversion and Biorefinery, Apr 8, 2020

Furfural has been highlighted as one of the top ten most rewarding bio-based building blocks by t... more Furfural has been highlighted as one of the top ten most rewarding bio-based building blocks by the US Department of Energy. In this study, furfural was produced from xylose and birch hydrolysate liquor employing a batch reactor in a biphasic system. The formation of furfural was conducted under auto-catalyzed conditions. 2-sec-Butylphenol was used as extractant to promptly extract furfural from the aqueous phase in order to minimize furfural degradation reactions. The effect of time, temperature, and organic-to-aqueous phase ratio were investigated. The maximum furfural yields from xylose and birch hydrolysate liquor as feedstock under auto-catalyzed conditions when employing 2-sec-butylphenol (SBP) were 59 mol% and 54 mol%, respectively. In the monophasic system when using hydrolysate, 46% furfural was yielded. Based on a techno-economic analysis carried out for furfural, the total investment cost for a plant integrated with an existing pulp mill or bio-refinery is estimated as 14 M€. The minimum selling price of furfural found to be 1.62 € kg −1. With a furfural selling price of 1.93 € kg −1 , the payback period is approximately 5 years and an internal rate of return (IRR) of 20.7% is achieved at the end of the project lifetime.

Oxidative dissolution mechanism of both undoped and Gd<sub>2</sub>O<sub>3</sub>-doped UO<sub>2</sub>(s) at alkaline to hyperalkaline pH

Dalton Transactions, 2023

The dissolution rates of unirradiated UO 2 and unirradiated UO 2 doped with Gd 2 O 3 were determi... more The dissolution rates of unirradiated UO 2 and unirradiated UO 2 doped with Gd 2 O 3 were determined as a function of pH using flow-through experiments in the presence of O 2 (g) and bicarbonate. The dissolution rate of non-doped UO 2 was very low under hyperalkaline conditions (pH 12-13) whereas it increased drastically as the pH decreased to 9. The dissolution of non-doped UO 2 in the pH range of 9-13 was consistent with the oxidative dissolution mechanism already described for UO 2 dissolution in the presence of bicarbonate and oxygen. XPS analysis performed on the solid after dissolution experiments at pH 10 and 13 supported the bicarbonate effect to complex UO 2 2+ and accelerate dissolution. Moreover, UO 2 doped with Gd 2 O 3 (5 wt% and 10 wt%) showed dissolution rates as low as non-doped UO 2 under hyperalkaline conditions, which were maintained throughout the pH range studied (9-13). No substantial differences in the dissolution rates between these two doping levels were found. XPS analysis evidenced a similar surface composition both at pH 10 and 13, with U(V) being the dominant oxidation state. The low dissolution rates were assumed to be a consequence of the gadolinium capacity to retard the oxidation of U(V) to U(VI). The slight increase in dissolution rates observed in the hyperalkaline region was attributed to a shift in the oxidative dissolution mechanism, in which the presence of OH − promotes the formation of soluble uranyl hydroxo complexes.

CuGaS2 and CuGaS2–ZnS Porous Layers from Solution-Processed Nanocrystals

Zenodo (CERN European Organization for Nuclear Research), Apr 5, 2018

The manufacturing of semiconducting films using solution-based approaches is considered a low cos... more The manufacturing of semiconducting films using solution-based approaches is considered a low cost alternative to vacuum-based thin film deposition strategies. An additional advantage of solution processing methods is the possibility to control the layer nano/microstructure. Here, we detail the production of mesoporous CuGaS2 (CGS) and ZnS layers from spin-coating and subsequent cross-linking through chalcogen-chalcogen bonds of properly functionalized nanocrystals (NCs). We further produce NC-based porous CGS/ZnS bilayers and NC-based CGS-ZnS composite layers using the same strategy. Photoelectrochemical measurements are used to demonstrate the efficacy of porous layers, and particularly the CGS/ZnS bilayers, for improved current densities and photoresponses relative to denser films deposited from as-produced NCs.

UO 2 surface oxidation by mixtures of water vapor and hydrogen as a function of temperature

Journal of Nuclear Materials, Dec 1, 2015

In the present work, X-Ray Photoelectron Spectroscopy (XPS) was used to study the effect of water... more In the present work, X-Ray Photoelectron Spectroscopy (XPS) was used to study the effect of water vapor on the UO2 surface as a function of temperature. The experiments were performed in situ inside a high pressure chamber attached to the XPS instrument. UO2 samples were put in contact with either hydrogen or argon streams, saturated with water at room temperature, and the sample surface evolution was analyzed by XPS. In the case of the water vapor/argon experiments, one experiment at 350ºC was performed and, in the case of the water vapor/hydrogen experiments, the temperatures used inside the reactor were 60, 120, 200 and 350ºC. On one hand, in presence of argon, the results obtained showed that the water vapor in the argon stream oxidized 93% of the U(IV) in the sample surface. On the other hand, the degree of UO2 surface oxidation showed a different dependence on the temperature in the experiments performed in the presence of hydrogen: the maximum surface oxidation occurred at 120ºC, where 65.4% of U(IV) in the sample surface was oxidized, while at higher temperatures, the surface oxidation decreased. This observation is attributed to the increase of hydrogen reducing effect when temperature increases which prevents part of the oxidation of the UO2 surface by the water vapor.

Atomically dispersed Fe in a C <sub>2</sub> N Based Catalyst as a Sulfur Host for Efficient Lithium–Sulfur Batteries

Advanced Energy Materials, Dec 18, 2020

$Research paper thumbnail of Investigation of physicochemical and electrical properties of $$\hbox {TiO}_{{2}}$$ nanotubes/graphene oxide nanocomposite$

Investigation of physicochemical and electrical properties of $$\hbox {TiO}_{{2}}$$ nanotubes/graphene oxide nanocomposite

Bulletin of Materials Science

GO/HNT400 nanocomposite was prepared by incipient impregnation of TiO 2 nanotubes (HNT400) with g... more GO/HNT400 nanocomposite was prepared by incipient impregnation of TiO 2 nanotubes (HNT400) with graphene oxide (GO) dispersion. GO was elaborated by an improved Hummer's method while HNT400 was obtained using alkaline hydrothermal treatment of TiO 2 P25 followed by calcination at 400°C. Raman results showed the characteristic bands of GO in addition to anatase. TEM analysis confirmed the formation of GO nanosheets assembled to TiO 2 nanotubes. XRD analysis showed that GO nanosheets do not change neither the structural nor the morphological properties of TiO 2 nanotubes. XPS and EPR measurements confirmed the electron transfer between GO and TiO 2 nanotubes. PL analysis revealed that GO inhibits the recombination of photogenerated electron-hole pairs in the GO/HNT400 nanocomposite. The ac conductivity measurements suggested the presence of bulk and grain boundary effect in the nanocomposite.

Recycled Low-Density Polyethylene for Noninvasive Glucose Monitoring: A Proposal for Plastic Recycling that Adds Technological Value

ACS Sustainable Chemistry & Engineering, 2020

In this work we present a successful strategy to convert recycled LDPE films, which usually end u... more In this work we present a successful strategy to convert recycled LDPE films, which usually end up in landfills or leak into the environment, in an advanced biomedical product. More specifically, LDPE films for food packaging have been treated with atmosphere corona discharge plasma for electrochemical detection of glucose. Enzymefunctionalized sensors manufactured using such recycled material, which acts as a mediator capable of electro-communicating with the glucose oxidase (GOx) enzyme, are able to detect glucose concentrations in sweat that are fully compatible with the levels of such bioanalyte in both healthy and diabetic patients. Covalent immobilization of the GOx enzyme on the plasma treated LDPE films has been successfully performed using the carbodiimide method, as proved by X-ray photoelectron spectroscopy. Then, the electronic communication between the deeply buried active site of the GOx and the reactive excited species formed at the surface of the plasma-treated LDPE has been demonstrated by linear sweep voltammetry. Finally, cyclic voltammetry in artificial sweat has been used to show that the LDPE-functionalized sensor has a linear response in the concentration of range of 50 M to 1 mM with a limit of detection of 375 A•M-1 •cm-2. Comparison of the performance of sensors prepared using recycled (i.e. with additives) and pristine (i.e. without additives) LDPE indicates that the utilization of the former does not require any pre-treatment to eliminate additives. The present strategy demonstrates a facile approach for recycling LDPE waste into a high valueadded product, which will potentially pave the way for the treatment of plastic waste in the future. Non-invasive glucose sensors based on recycled LDPE may play a crucial role for monitoring diabetes in underdeveloped regions.

Co–Sn Nanocrystalline Solid Solutions as Anode Materials in Lithium‐Ion Batteries with High Pseudocapacitive Contribution

Chemsuschem, Apr 5, 2019

Co-Sn solid-solution nanoparticles with the Sn crystal structure and tuned metal ratios were synt... more Co-Sn solid-solution nanoparticles with the Sn crystal structure and tuned metal ratios were synthesized by a facile onepot solution-based procedure involving the initial reduction of a Sn precursor and the posterior incorporation of Co within the Sn lattice. Such nanoparticles were used as anode materials for Li-ion batteries. Among the different compositions tested, Co0.7Sn and Co0.9Sn electrodes provided the highest capacities, with values above 1500 mAh g-1 at a current density of 0.2 A g-1 after 220 cycles and up to 800 mAh g-1 at 1.0 A g-1 after 400 cycles. Up to 81 % pseudocapacitance contribution at a sweep rate of 1.0 mV s-1 were measured for these electrodes, providing fast kinetics and long durability. The excellent performance of Co-Sn alloy nanoparticlebased electrodes was associated to both the small size of the crystal domains and their suitable composition, which buffered volume changes of Sn and contributed to a suitable electrode restructuration.  J. Li and X. Xu equally contributed to this work. Supporting information for this article is given via a link at the end of the document.

Surface Chemistry and Nano-/Microstructure Engineering on Photocatalytic In2S3 Nanocrystals

Zenodo (CERN European Organization for Nuclear Research), May 11, 2018

Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysi... more Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysis, offering an easier recyclability and a number of additional functionalities. Using high throughput printing technologies, colloidal NCs can be also supported onto substrates to produce cost-effective electronic, optoelectronic, electrocatalytic and sensing devices. In these 2 two broad areas, NCs surface chemistry and supracrystal organization are key parameters determining final performance. Here, we study the influence of the surface ligands and the NC organization on the catalytic properties of In 2 S 3 , both in colloidal form and as a supported layer. In solution, well dispersed NCs stabilized in solution by inorganic ligands show the highest photocatalytic activities. On the other hand, when NCs are supported on a substrate, their organization becomes an essential parameters determining performance, and NC-based films produced through a gelation process provided five-fold higher photocurrent densities than those obtained from dense films produced by the direct printing of NCs.

Synthesis and characterization of nanoparticles of CZTSe by microwave-assited chemical synthesis

Materials research express, Dec 8, 2016

In this study we present the synthesis of Cu2ZnSnSe4 (CZTSe) nanoparticles by microwaveassisted c... more In this study we present the synthesis of Cu2ZnSnSe4 (CZTSe) nanoparticles by microwaveassisted chemical synthesis employing organic solvents. The effect of reaction time, reactant concentration, solvent and additives (inorganic material) was studied on the structural and optical properties of the nanomaterials. The powder samples were analyzed by X-ray diffraction (XRD), Raman spectroscopy, X-ray energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The results show that the synthesis performed with triethanolamine and deionized water is better than others solvents, producing nanocrystals of quaternary phase (CZTSe) with stoichiometric relations similar to the reported research in the literature, which falls in the range of Cu/(Zn+Sn): 0.8-1.0, Zn/Sn: 1.0-1.20. The nanoparticles of CZTSe synthesized in this study present desirable properties in order to use them in solar cell and photoelectrochemical cell applications.

A High Conductivity 1D π–d Conjugated Metal–Organic Framework with Efficient Polysulfide Trapping‐Diffusion‐Catalysis in Lithium–Sulfur Batteries

Advanced Materials, Jan 28, 2022

Lithium-sulfur batteries (LSBs) offer notable advantages over conventional lithium ion batteries,... more Lithium-sulfur batteries (LSBs) offer notable advantages over conventional lithium ion batteries, but their implementation is limited by the sluggish conversion kinetics of lithium polysulfides (LiPS), the dissolution and diffusion of LiPS, and the poor electrical conductivity of sulfur and lithium sulfide. Herein, we present a one-dimensional (1D) π-d conjugated metalorganic framework, Ni-MOF-1D, as an efficient sulfur host to overcome these limitations. Experimental results and density functional theory (DFT) calculations demonstrate that Ni-MOF-1D is characterized by a remarkable binding strength for trapping soluble LiPS species. Ni-MOF-1D also acts as an effective catalyst for S reduction during the discharge process and Li2S oxidation during the charge process. In addition, the delocalization of electrons in the π-d system of Ni-MOF-1D provides a superior electrical conductivity to improve electron transfer. Thus, cathodes based on Ni-MOF-1D enable LSBs with excellent performance, including a remarkable initial capacity of 1491 mA h g −1 , superior rate performance of 575 mAh g −1 at 8 C, impressive cycling stability with over 82% capacity retention over 1000 cycles at 3 C, and a high areal capacity of 5.36 mAh cm −2 under a high sulfur loading of 4.3 mg cm −2. While this work particularly focuses on the synthesis and performance of a Ni-based MOF, the strategies and advantages here demonstrated can be extended to a broader range of π-d conjugated MOFs materials, which we believe have a high potential as sulfur host in LSBs.

In Situ Electrochemical Oxidation of Cu<sub>2</sub>S into CuO Nanowires as a Durable and Efficient Electrocatalyst for Oxygen Evolution Reaction

Chemistry of Materials, Aug 15, 2019

Effect of Fe–Zn–Mg–Al hydrotalcites on the methane potential of synthetic sulfate-containing wastewater

Journal of water process engineering, Apr 1, 2016

Three hydrotalcites of M 2+-Mg-Al were synthesized using the co-precipitation method, where M 2+ ... more Three hydrotalcites of M 2+-Mg-Al were synthesized using the co-precipitation method, where M 2+ was Fe 2+ , Zn 2+ and Fe 2+ + Zn 2+. The hydrotalcites and their calcined form of mixed oxides obtained by their thermal decomposition were characterized by FTIR, XRD and SEM. Subsequently their effect on the methane potential of synthetic wastewater comprised of sucrose and sulfur was evaluated in a multiple batch system at 37 ± 0.5 °C. The best methane potential was observed from the Fe-Zn-Mg-Al hydrotalcite at 500 mg/L yielding 3712mL CH 4 /gVS which corresponds to an 8.1% increment against the control. The better performance of the Fe-Zn-Mg-Al hydrotalcite can be attributed to the Zn 2+ ions. These react with S 2in the substrate to yield zinc sulfide and therefore prevent it from forming H 2 S by sulfate reducing bacteria, meanwhile reducing competition for methanogens to form methane. Calcined hydrotalcites neither stimulated nor inhibited the methane production which suggests that the enhancement of methane produced by the Fe-Zn-Mg-Al hydrotalcite was related to the presence of Fe 2+ and Zn 2+ cations incorporated and immobilized in the layered sheet structure of the hydrotalcite.

A comparative study of water-immiscible organic solvents in the production of furfural from xylose and birch hydrolysate

Journal of Industrial and Engineering Chemistry, Apr 1, 2019

The production of furfural (FUR) from xylose was carried out using a biphasic batch reaction syst... more The production of furfural (FUR) from xylose was carried out using a biphasic batch reaction system. Isophorone, 2-methyltetrahydrofuran (2-MTHF) and cyclopentyl methyl ether (CPME) were used to extract FUR and enhance the overall furfural yield by limiting its degradation to humins. The effect of time, temperature, organic solvent and organicto-aqueous ratio on xylose conversion and FUR yield were investigated. Experiments conducted at three temperatures (170, 190 and 210 °C) were investigated in a stirred microwave-assisted batch reactor, which established the optimal conditions to obtain the highest FUR yield. The maximum FUR yields obtained from xylose were 78 mol% when using CPME, 48 mol% when using isophorone (due to its phase-behavior nature) and 71 mol% when employing 2-MTHF with an aqueous to organic phase ratio of 1:1. Birch hydrolysate was also used to show the high furfural concentration that can be obtained in the bi-phasic system under optimized conditions. The present study suggests that CPME can be used as a green and efficient extraction solvent for the conversion of xylose into furfural without salt addition.

Effect of the Annealing Atmosphere on Crystal Phase and Thermoelectric Properties of Copper Sulfide

ACS Nano, Mar 1, 2021

Cu 2−x S has become one of the most promising thermoelectric materials for application in the mid... more Cu 2−x S has become one of the most promising thermoelectric materials for application in the middle-high temperature range. Its advantages include the abundance, low cost, and safety of its elements and a high performance at relatively elevated temperatures. However, stability issues limit its operation current and temperature, thus calling for the optimization of the material performance in the middle temperature range. Here, we present a synthetic protocol for large scale production of covellite CuS nanoparticles at ambient temperature and atmosphere, and using water as a solvent. The crystal phase and stoichiometry of the particles are afterward tuned through an annealing process at a moderate temperature under inert or reducing atmosphere. While annealing under argon results in Cu 1.8 S nanopowder with a rhombohedral crystal phase, annealing in an atmosphere containing hydrogen leads to tetragonal Cu 1.96 S. High temperature X-ray diffraction analysis shows the material annealed in argon to transform to the cubic phase at ca. 400 K, while the material annealed in the presence of hydrogen undergoes two phase transitions, first to hexagonal and then to the cubic structure. The annealing atmosphere, temperature, and time allow adjustment of the density of copper vacancies and thus tuning of the charge carrier concentration and material transport properties. In this direction, the material annealed under Ar is characterized by higher electrical conductivities but lower Seebeck coefficients than the material annealed in the presence of hydrogen. By optimizing the charge carrier concentration through the annealing time, Cu 2−x S with record figures of merit in the middle temperature range, up to 1.41 at 710 K, is obtained. We finally demonstrate that this strategy, based on a low-cost and scalable solution synthesis process, is also suitable for the production of high performance Cu 2−x S layers using high throughput and cost-effective printing technologies.

SnP nanocrystals as anode materials for Na-ion batteries

Journal of materials chemistry. A, Materials for energy and sustainability, 2018

Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the ethical guidelines, outlined in our author and reviewer resource centre, still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

PbS–Pb–Cu<i><sub>x</sub></i>S Composites for Thermoelectric Application

ACS Applied Materials & Interfaces, Oct 19, 2021

Composite materials offer numerous advantages in a wide range of applications, including thermoel... more Composite materials offer numerous advantages in a wide range of applications, including thermoelectrics. Here semiconductor-metal composites are produced by just blending nanoparticles of a sulfide semiconductor obtained in aqueous solution and at room temperature, with a metallic Cu powder. The obtained blend is annealed in a reducing atmosphere and afterwards consolidated into dense polycrystalline pellets through spark plasma sintering (SPS). We observe that, during the annealing process, the presence of metallic copper activates a partial reduction of the PbS, resulting in the formation of PbS-Pb-CuxS composites. The presence of metallic lead during the SPS process habilitates the liquid-phase sintering of the composite. Besides, by comparing the transport properties of PbS, the PbS-Pb-CuxS composites, and PbS-CuxS composites obtained by blending PbS and CuxS nanoparticles, we demonstrate that the presence of metallic lead decisively contributes to a strong increase of the charge carrier concentration through spillover of charge carriers enabled by the low work function of lead. The increase in charge carrier concentration translates into much higher electrical conductivities and moderately lower Seebeck coefficientsThese properties translate into power factors up to 2.1 mWm-1 K-2 at ambient temperature, well above those of PbS and PbS+CuxS. Additionally, the presence of multiple phases in the final composite results in a notable decrease in the lattice thermal conductivity. Overall, the introduction of metallic copper in the initial blend results in a significant improvement of the thermoelectric performance of PbS, reaching a dimensionless thermoelectric figure of merit ZT = 1.1 at 750 K, which represents about a 400% increase over bare PbS. Besides, an average ZTave = 0.72 in the temperature range 320-773 K is demonstrated.

Nickel Iron Diselenide for Highly Efficient and Selective Electrocatalytic Conversion of Methanol to Formate

Small, Jan 18, 2021

The electrooxidation of methanol to formate is an example of the potential use of renewable energ... more The electrooxidation of methanol to formate is an example of the potential use of renewable energies to add value to a biosourced chemical commodity. Additionally, methanol electrooxidation can replace the sluggish oxygen evolution reaction for hydrogen evolution or the electroreduction of other biomass-derived intermediates. Here, we demonstrate a noble metal-free catalyst, Ni 1-x Fe x Se 2 , with a high potential for an efficient and selective methanol conversion to formate. At its optimum composition, Ni 0.75 Fe 0.25 Se 2 , this diselenide is able to produce 0.47 mmol cm-2 h-1 of formate at 50 mA cm-2 with a Faradaic conversion efficiency of 99 %. We further demonstrate that Ni 1-x Fe x Se 2-based catalysts are able to continuously work for over 50,000 s with a minimal loss of efficiency, delivering initial current densities above 50 mA cm-2 and 2.2 A mg-1 in a 1.0 M KOH electrolyte with 1.0 M methanol at 1.5 V vs. RHE.

Simulation of two-step redox recycling of non-stoichiometric ceria with thermochemical dissociation of CO2/H2O in moving bed reactors – Part II: Techno-economic analysis and integration with 100 MW oxyfuel power plant with carbon capture

Chemical Engineering Science, Sep 1, 2019

This paper presents a solar thermochemical looping CO2/H2O dissociation reactors unit (CL) with c... more This paper presents a solar thermochemical looping CO2/H2O dissociation reactors unit (CL) with commercial ceria as redox oxygen carrier. The CL unit is integrated to a 100 MW oxyfueled natural gas combined cycle with carbon capture to investigate the efficiency benefit obtained. A moving bed counter-current reactor model is developed in Aspen Plus considring rigorous continuous stirred reactors (RCSTRs) for both reduction and oxidation. A userkinetic subroutine is developed in FORTRAN and linked with each RCSTR in both reduction and oxidation reactor with their respective kinetics. It is found that efficiency of the chemical looping unit varies widely with reduction reactor temperature and vacuum pressure. Chemical looping unit efficiency is obtained for three conditions considering only CO2 and only H2O it was found to be 35.41% and 30.84% respectively, and for mixture (86% CO2, 14% H2O) 35.26%. The efficiency drop for only H2O is due to heat needed for phase change and more vacuum pump required for hydrogen compare to CO2. The maximum solar to electrical efficiency for the whole system layout was found to be 25.4% with a reduction temperature of 1600 o C and 10-7 bar vacuum pressure. With a 0.5 m 3 reduction reactor and 5 m 3 oxidation reactor the maximum net electricity produced by add-on unit is 12.85 MWe. Economic analysis revealed that the major contributor to the total project cost is hydrogen compressor (19%) and solar field and tower represent 39% of the total equipment costs giving a specific overnight capital cost of 12136 $/kW with LCOE of 1100 S/MWh.

The Importance of Surface Adsorbates in Solution‐Processed Thermoelectric Materials: The Case of SnSe

Advanced Materials, Oct 22, 2021

Thermoelectric devices reversibly convert heat into electricity both for power harvesting and for... more Thermoelectric devices reversibly convert heat into electricity both for power harvesting and for active cooling and heating. The efficiency of a thermoelectric device is determined by the temperature-dependent properties of the materials that constitute it. These are summarized in the thermoelectric figure of merit of the material, zT = S 2 σκ-1 T, that combines Seebeck coefficient (S), electrical conductivity (σ), thermal conductivity (κ), and absolute temperature (T). [1,2] Thermoelectric materials are often dense, polycrystalline inorganic semiconductors. Usually, the processing of such materials has two steps: preparation of the semiconductor in powder form and the consolidation of the powder into a dense sample. The most common route to prepare powders among the thermoelectric community is through high-temperature reactions and ball milling. [3] Alternatively, solution methods to produce powders with much less demanding conditions (e.g., lower reagent purity, lower temperatures, and shorter reaction times) have been explored to reduce the production costs. [1,4] These methods also provide opportunities to produce particles with better-controlled features, such as crystallite size, shape, composition, and crystal phase, which allow modifying the properties of the consolidated material. [5-7] Lastly, solution processing facilitates device fabrication versatility, including flexible, conformable, and rigid modules with customized geometries. [8,9] To date, solution synthesis has enabled the production of several materials with state-of-the-art performances, as is the case of PbS, [6] Bi 0.5 Sb 1.5 Te 3 , [10] Bi 2 Te 3−x Se x , [11] and SnTe, [12] demonstrating the potential of this strategy. However, when dealing with powders produced in solution, one should pay special attention to potential undesired elements coming from the reactants. Those elements may not affect the crystal structure and bulk composition of the powder but can be present as surface adsorbates. [13] The composition, chemical stability, and bonding nature of surface species can influence the sintering process, and reaction byproducts can determine the final properties of the consolidated material. Surface species have been carefully considered in surfactantassisted colloidal synthesis because of the insulating nature of the long-chain aliphatic surfactants generally used [14] and Solution synthesis of particles emerges as an alternative to prepare thermoelectric materials with less demanding processing conditions than conventional solid-state synthetic methods. However, solution synthesis generally involves the presence of additional molecules or ions belonging to the precursors or added to enable solubility and/or regulate nucleation and growth. These molecules or ions can end up in the particles as surface adsorbates and interfere in the material properties. This work demonstrates that ionic adsorbates, in particular Na + ions, are electrostatically adsorbed in SnSe particles synthesized in water and play a crucial role not only in directing the material nano/microstructure but also in determining the transport properties of the consolidated material. In dense pellets prepared by sintering SnSe particles, Na remains within the crystal lattice as dopant, in dislocations, precipitates, and forming grain boundary complexions. These results highlight the importance of considering all the possible unintentional impurities to establish proper structure-property relationships and control material properties in solution-processed thermoelectric materials.

Furfural production from xylose and birch hydrolysate liquor in a biphasic system and techno-economic analysis

Biomass Conversion and Biorefinery, Apr 8, 2020

Furfural has been highlighted as one of the top ten most rewarding bio-based building blocks by t... more Furfural has been highlighted as one of the top ten most rewarding bio-based building blocks by the US Department of Energy. In this study, furfural was produced from xylose and birch hydrolysate liquor employing a batch reactor in a biphasic system. The formation of furfural was conducted under auto-catalyzed conditions. 2-sec-Butylphenol was used as extractant to promptly extract furfural from the aqueous phase in order to minimize furfural degradation reactions. The effect of time, temperature, and organic-to-aqueous phase ratio were investigated. The maximum furfural yields from xylose and birch hydrolysate liquor as feedstock under auto-catalyzed conditions when employing 2-sec-butylphenol (SBP) were 59 mol% and 54 mol%, respectively. In the monophasic system when using hydrolysate, 46% furfural was yielded. Based on a techno-economic analysis carried out for furfural, the total investment cost for a plant integrated with an existing pulp mill or bio-refinery is estimated as 14 M€. The minimum selling price of furfural found to be 1.62 € kg −1. With a furfural selling price of 1.93 € kg −1 , the payback period is approximately 5 years and an internal rate of return (IRR) of 20.7% is achieved at the end of the project lifetime.

Oxidative dissolution mechanism of both undoped and Gd<sub>2</sub>O<sub>3</sub>-doped UO<sub>2</sub>(s) at alkaline to hyperalkaline pH

Dalton Transactions, 2023

The dissolution rates of unirradiated UO 2 and unirradiated UO 2 doped with Gd 2 O 3 were determi... more The dissolution rates of unirradiated UO 2 and unirradiated UO 2 doped with Gd 2 O 3 were determined as a function of pH using flow-through experiments in the presence of O 2 (g) and bicarbonate. The dissolution rate of non-doped UO 2 was very low under hyperalkaline conditions (pH 12-13) whereas it increased drastically as the pH decreased to 9. The dissolution of non-doped UO 2 in the pH range of 9-13 was consistent with the oxidative dissolution mechanism already described for UO 2 dissolution in the presence of bicarbonate and oxygen. XPS analysis performed on the solid after dissolution experiments at pH 10 and 13 supported the bicarbonate effect to complex UO 2 2+ and accelerate dissolution. Moreover, UO 2 doped with Gd 2 O 3 (5 wt% and 10 wt%) showed dissolution rates as low as non-doped UO 2 under hyperalkaline conditions, which were maintained throughout the pH range studied (9-13). No substantial differences in the dissolution rates between these two doping levels were found. XPS analysis evidenced a similar surface composition both at pH 10 and 13, with U(V) being the dominant oxidation state. The low dissolution rates were assumed to be a consequence of the gadolinium capacity to retard the oxidation of U(V) to U(VI). The slight increase in dissolution rates observed in the hyperalkaline region was attributed to a shift in the oxidative dissolution mechanism, in which the presence of OH − promotes the formation of soluble uranyl hydroxo complexes.

CuGaS2 and CuGaS2–ZnS Porous Layers from Solution-Processed Nanocrystals

Zenodo (CERN European Organization for Nuclear Research), Apr 5, 2018

The manufacturing of semiconducting films using solution-based approaches is considered a low cos... more The manufacturing of semiconducting films using solution-based approaches is considered a low cost alternative to vacuum-based thin film deposition strategies. An additional advantage of solution processing methods is the possibility to control the layer nano/microstructure. Here, we detail the production of mesoporous CuGaS2 (CGS) and ZnS layers from spin-coating and subsequent cross-linking through chalcogen-chalcogen bonds of properly functionalized nanocrystals (NCs). We further produce NC-based porous CGS/ZnS bilayers and NC-based CGS-ZnS composite layers using the same strategy. Photoelectrochemical measurements are used to demonstrate the efficacy of porous layers, and particularly the CGS/ZnS bilayers, for improved current densities and photoresponses relative to denser films deposited from as-produced NCs.

UO 2 surface oxidation by mixtures of water vapor and hydrogen as a function of temperature

Journal of Nuclear Materials, Dec 1, 2015

In the present work, X-Ray Photoelectron Spectroscopy (XPS) was used to study the effect of water... more In the present work, X-Ray Photoelectron Spectroscopy (XPS) was used to study the effect of water vapor on the UO2 surface as a function of temperature. The experiments were performed in situ inside a high pressure chamber attached to the XPS instrument. UO2 samples were put in contact with either hydrogen or argon streams, saturated with water at room temperature, and the sample surface evolution was analyzed by XPS. In the case of the water vapor/argon experiments, one experiment at 350ºC was performed and, in the case of the water vapor/hydrogen experiments, the temperatures used inside the reactor were 60, 120, 200 and 350ºC. On one hand, in presence of argon, the results obtained showed that the water vapor in the argon stream oxidized 93% of the U(IV) in the sample surface. On the other hand, the degree of UO2 surface oxidation showed a different dependence on the temperature in the experiments performed in the presence of hydrogen: the maximum surface oxidation occurred at 120ºC, where 65.4% of U(IV) in the sample surface was oxidized, while at higher temperatures, the surface oxidation decreased. This observation is attributed to the increase of hydrogen reducing effect when temperature increases which prevents part of the oxidation of the UO2 surface by the water vapor.

Atomically dispersed Fe in a C <sub>2</sub> N Based Catalyst as a Sulfur Host for Efficient Lithium–Sulfur Batteries

Advanced Energy Materials, Dec 18, 2020

$Research paper thumbnail of Investigation of physicochemical and electrical properties of $$\hbox {TiO}_{{2}}$$ nanotubes/graphene oxide nanocomposite$

Investigation of physicochemical and electrical properties of $$\hbox {TiO}_{{2}}$$ nanotubes/graphene oxide nanocomposite

Bulletin of Materials Science

GO/HNT400 nanocomposite was prepared by incipient impregnation of TiO 2 nanotubes (HNT400) with g... more GO/HNT400 nanocomposite was prepared by incipient impregnation of TiO 2 nanotubes (HNT400) with graphene oxide (GO) dispersion. GO was elaborated by an improved Hummer's method while HNT400 was obtained using alkaline hydrothermal treatment of TiO 2 P25 followed by calcination at 400°C. Raman results showed the characteristic bands of GO in addition to anatase. TEM analysis confirmed the formation of GO nanosheets assembled to TiO 2 nanotubes. XRD analysis showed that GO nanosheets do not change neither the structural nor the morphological properties of TiO 2 nanotubes. XPS and EPR measurements confirmed the electron transfer between GO and TiO 2 nanotubes. PL analysis revealed that GO inhibits the recombination of photogenerated electron-hole pairs in the GO/HNT400 nanocomposite. The ac conductivity measurements suggested the presence of bulk and grain boundary effect in the nanocomposite.

Recycled Low-Density Polyethylene for Noninvasive Glucose Monitoring: A Proposal for Plastic Recycling that Adds Technological Value

ACS Sustainable Chemistry & Engineering, 2020

In this work we present a successful strategy to convert recycled LDPE films, which usually end u... more In this work we present a successful strategy to convert recycled LDPE films, which usually end up in landfills or leak into the environment, in an advanced biomedical product. More specifically, LDPE films for food packaging have been treated with atmosphere corona discharge plasma for electrochemical detection of glucose. Enzymefunctionalized sensors manufactured using such recycled material, which acts as a mediator capable of electro-communicating with the glucose oxidase (GOx) enzyme, are able to detect glucose concentrations in sweat that are fully compatible with the levels of such bioanalyte in both healthy and diabetic patients. Covalent immobilization of the GOx enzyme on the plasma treated LDPE films has been successfully performed using the carbodiimide method, as proved by X-ray photoelectron spectroscopy. Then, the electronic communication between the deeply buried active site of the GOx and the reactive excited species formed at the surface of the plasma-treated LDPE has been demonstrated by linear sweep voltammetry. Finally, cyclic voltammetry in artificial sweat has been used to show that the LDPE-functionalized sensor has a linear response in the concentration of range of 50 M to 1 mM with a limit of detection of 375 A•M-1 •cm-2. Comparison of the performance of sensors prepared using recycled (i.e. with additives) and pristine (i.e. without additives) LDPE indicates that the utilization of the former does not require any pre-treatment to eliminate additives. The present strategy demonstrates a facile approach for recycling LDPE waste into a high valueadded product, which will potentially pave the way for the treatment of plastic waste in the future. Non-invasive glucose sensors based on recycled LDPE may play a crucial role for monitoring diabetes in underdeveloped regions.