Papers by Shiva Mohajernia
Chemistry: A European Journal, Jul 19, 2017
In the present work we report on the key factors dictating the photoelectrochemical (PEC) perform... more In the present work we report on the key factors dictating the photoelectrochemical (PEC) performance of suboxide titania (TiO x)n anotubes.T iO x nanotubes were produced by asystematic variation of reduction heat treatments of TiO 2 in Ar/H 2 .T he properties of the TiO x tubes were investigated by electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), solid-state conductivity,r eflectivitym easurements, photocurrents pectroscopy,a nd photoelectrochemi-cal hydrogen evolution. In line with earlier literature, these suboxide tubes show ad rastically improved photoelectrochemicalw ater-splitting performance compared to non-reduced anatase TiO 2 tubes. In this work we show that the key improvement in water-splitting performance is due to the strongly improved conductivity of TiO x semimetalic tubes, reaching1 3.5 KW per tube compared to 70 MW (for non-reduced anatase), and is not due to the enhanced visible-light absorbance.
Applied Materials Today, Dec 1, 2019
In the current energy scenario, electrochemical capacitors hold the promise to fulfil requirement... more In the current energy scenario, electrochemical capacitors hold the promise to fulfil requirements of high power densities, short charging-discharging times, and long lifetimes. For such supercapacitors, MoO3 is one of the most potent candidate as a negative electrode material, due to a very high theoretical charge density ascribed to easily-switchable multiple oxidation states. Nevertheless, the extremely poor electrochemical stability of MoO3 in aqueous electrolytes prevents any practical use. In the present work, we outline a strategy to overcome the poor stability of MoO3 electrodes: we produce by thermal phosphidation an amorphous MoP protective shell on Mo oxide nanotube arrays. This not only leads to an outstanding stability of the electrode but the phosphidized hybrid structures even maintains a capacitance as high as the initial capacitance (i.e. measured before deterioration) of unprotected pure oxide structures: the phosphidized hybrid structure, used as binder-free electrodes, can deliver a non-intercalation-based volumetric capacitance of over 2'000 F cm-3 with an outstanding capacitance retention of ~ 93 % over 10'000 charging/discharging cycles.
Chemistry - European Journal, 2017
Electrochimica Acta, Aug 1, 2017
In the present work we investigate the effect of the surface electrokinetic properties and presen... more In the present work we investigate the effect of the surface electrokinetic properties and presence of background ions on the flow of a marker dye through TiO2 nanotube membranes. We believe the results to be of high significance not only for filtration but also for the design of microphotoreactor application based on photoactive TiO2 nanotubes membrane. First, bothside open, high aspect ratio TiO2 nanotube membranes were obtained by fast anodization of Ti to self-aligned TiO2 nanotube layers, followed by a lift-off process. Then we investigated the permeation through the TiO2 nanotube membranes by diffusion of acid orange 7 (AO7) and extracted the dye diffusion rates. The effects of pH, ionic concentration, and size of ions were investigated, and the results were compared with theoretical modeling of the surface charge of TiO2 and the neighbouring electric double layer as a function of different species of ions; the modeling confirms the experimental data. We observed a remarkable influence of the background ion species, as well as of ion concentrations and pH in the feed solution on the diffusion rate of AO7. The results of modeling are well in line with the observed influence of TiO2 nanotube inner surface charge and effective size (hydrodynamic radius) of the ions in the background solution. It is also observed that the absolute permeate flux and the membrane's permeability strongly depend on the electric and wetting conditions of the membrane surface.
Meeting abstracts, Jul 7, 2022
Journal of materials chemistry. A, Materials for energy and sustainability, 2020
In this letter, we report a facile self-foaming strategy to synthesize Ni 3 C nanoparticles embed... more In this letter, we report a facile self-foaming strategy to synthesize Ni 3 C nanoparticles embedded in porous carbon network (Ni 3 C@PCN) by rationally incorporating Ni precursor into carbon source. As a novel hydrogen evolution reaction (HER) catalyst, the Ni 3 C@PCN shows superior catalytic activity with an onset potential of-65 mV, an overpotential of 262 mV to achieve 50 mA cm-2 current density, a Tafel slope of 63.4 mV/dec and durability over 12 h in acidic media. The excellent performance of the novel 3D composite material along with its low-cost merits is suggestive of great potential for scalable electrocatalytic H 2 production.
Corrosion, Apr 1, 2023
The effects of near-surface severe plastic deformation (NS-SPD) on the inhibition performance of ... more The effects of near-surface severe plastic deformation (NS-SPD) on the inhibition performance of sodium molybdate (SM) and 1H-benzotriazole (BTA) for mild steel were investigated using weight loss, polarization and electrochemical impedance spectroscopy measurements. The crystal grain size of NS-SPD-processed surface was analyzed by x-ray diffractometry and field emission scanning electron microscopy. A deformed layer with thickness of 20 ± 5 lm was produced on mild steel surface after NS-SPD process due to accumulated strains. The NS-SPD process caused more effective adsorption of corrosion inhibitors due to the fabrication of a surface with a high density of preferential adsorption sites. However, the stability of protective layer was predominantly influenced by the effect of NS-SPD process on inhibition efficiency. The fairly good persistence of protective layer formed on the surface by SM-containing solution and also positive effect of NS-SPD process on adsorption of molybdate ions caused higher inhibition performance for sodium molybdate. However, NS-SPD process encouraged deterioration of protective layer formed on steel surface in the presence of BTA inhibitor. It was ascribed to partial coverage of surface, low stability of adsorbed layer and thus more adsorption of aggressive ions on unprotected area which was uncovered during immersion time.
2022 19th International Bhurban Conference on Applied Sciences and Technology (IBCAST), Aug 16, 2022
arXiv (Cornell University), Apr 14, 2020
Au and Pt do not form homogeneous bulk alloys as they are thermodynamically not miscible. However... more Au and Pt do not form homogeneous bulk alloys as they are thermodynamically not miscible. However, we show that anodic TiO2 nanotubes (NTs) can in-situ be uniformly decorated with homogeneous AuPt alloy nanoparticles (NPs) during their anodic growth. For this, a metallic Ti substrate containing low amounts of dissolved Au (0.1 at%) and Pt (0.1 at%) is used for anodizing. The matrix metal (Ti) is converted to oxide while at the oxide/metal interface direct noble metal particle formation and alloying of Au and Pt takes place; continuously these particles are then picked up by the growing nanotube wall. In our experiments the AuPt alloy NPs have an average size of 4.2 nm and, at the end of the anodic process, are regularly dispersed over the TiO2 nanotubes. These alloyed AuPt particles act as excellent co-catalyst in photocatalytic H2 generation-with a H2 production of 12.04 μL h-1 under solar light. This represents a strongly enhanced activity as compared with TiO2 NTs decorated with monometallic particles of Au (7 μL h-1) or Pt (9.96 μL h-1).
Acta Biomaterialia, Oct 1, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Catalysts
H2 generation from photocatalytic water splitting is one of the most promising approaches to prod... more H2 generation from photocatalytic water splitting is one of the most promising approaches to producing cost-effective and sustainable fuel. Nanostructured TiO2 is a highly stable and efficient semiconductor photocatalyst for this purpose. The main drawback of TiO2 as a photocatalyst is the sluggish charge transfer on the surface of TiO2 that can be tackled to a great extent by the use of platinum group materials (PGM) as co-catalysts. However, the scarcity and high cost of the PGMs is one of the issues that prevent the widespread use of TiO2/PGM systems for photocatalytic H2 generation. Single-atom catalysts which are currently the frontline in the catalysis field can be a favorable path to overcome the scarcity and further advance the use of noble metals. More importantly, single-atom (SA) catalysts simultaneously have the advantage of homogenous and heterogeneous catalysts. This mini-review specifically focuses on the single atom decoration of TiO2 nanostructures for photocatalyti...
Electrochemistry Communications, 2022
Au nanoparticles at the TiO_2 surface can enhance the photocatalytic H_2 generation performances ... more Au nanoparticles at the TiO_2 surface can enhance the photocatalytic H_2 generation performances owing to their electron transfer co-catalytic ability. Key to maximize the co-catalytic effect is a fine control over Au nanoparticle size and placement on the photocatalyst, in relation to parameters such as the TiO_2 morphology, illumination wavelength and pathway, and light penetration depth in the photocatalyst. Here we present an approach for site-selective intrinsic-decoration of anodic TiO_2 nanotubes (TNs) with Au nanoparticles: we produce, by Ti and Au co-sputtering, Ti-Au alloy layers that feature compositional gradients across their thickness; these layers, when anodized under self-ordering electrochemical conditions, can form Au-decorated TNs where the Au nanoparticle density and placement vary according to the Au concentration profile in the metal alloy substrates. Our results suggest that, the Au co-catalyst placement strongly affects the photocatalytic H_2 evolution perfor...
In the present work, adsorption properties of a thiazole-prymidine derivative on mild steel surfa... more In the present work, adsorption properties of a thiazole-prymidine derivative on mild steel surface in 0.5 M H2SO4 solutions was investigated employing electrochemical impedance spectroscopy (EIS). The results indicates by increasing the inhibitor concentration from 50 to 200 ppm, charge transfer resistance increase from 10 to 127 ohms.cm; i.e. 92% inhibition efficiency. Additionally double layer capacitance in the presence of 200 ppm inhibitor is 3.67 times lower than uninhibited condition. In other word by steady replacement of water molecules by inhibitor molecules, the double layer thickness increases 3.67 times. Isotherm adsorption model shows that this component obeys the Langmuir adsorption role and it shows ΔG value of 34.36 Kj/mol for adsorption process. This indicates that the adsorption mechanism is more likely chemical on mild steel surface for this component.
In the present work, we investigate the efficiency of TiO2 photoelectrode layers on boron doped d... more In the present work, we investigate the efficiency of TiO2 photoelectrode layers on boron doped diamond foil (BDDF) in comparison with a classic conducting glass (FTO) back contact. Crystalline thin TiO2 layers were prepared on the substrates by two different methods: (i) deposition of metallic Ti thin films followed by thermal oxidation to form TiO2 (TO-TiO2), (ii) reactive sputter deposition of TiO2 thin films and crystallization of these layers (SP-TiO2). Optimized layers show that TO-TiO2 films on BDDF deliver a significantly higher incident photon to current efficiency (IPCE) compared to directly sputtered SP-TiO2 layers and these layers on BDDF also outperform conducting glass (FTO) as a back contact. We ascribe this beneficial effect of the BDDF back contact to the formation of an intermediate conductive phase of Ti-carbides at the TO-TiO2/BDDF interface.
Electrochemistry Communications, 2021
The present work describes a self-assembling photocatalytic system that is observed when illumina... more The present work describes a self-assembling photocatalytic system that is observed when illuminating grey titania nanoparticles in suspension with a plain aqueous Ni2+ solution. Such a suspension (in contrast to white titania), under UV illumination, increasingly produces H2 from neutral water. We show that the origin of this self-activation is not the light-induced deposition of Ni0 or another Ni-catalyst compound on the titania surface. Rather, in-situ electron paramagnetic resonance (EPR) clearly indicates that the activation is due to a light-induced formation of a suitable defect structure (Ti3+-OV) on grey titania, combined with the formation of an intermediate monovalent nickel (Ni(I)) electron transfer relay. Remarkably, the resulting Ni+/TiO2/Ti3+ photocatalyst operates in absence of any noble metal or sacrificial agent.
Journal of Physical Chemistry C, 2021
In the present research, we investigate the synergistic effects of Ru-doping and Ar/H2 reduction ... more In the present research, we investigate the synergistic effects of Ru-doping and Ar/H2 reduction treatment on the photoelectrochemical water splitting performance and hydrogen evolution rate of TiO...
Uploads
Papers by Shiva Mohajernia