Turning a Methanation Co Catalyst into an In–Co Methanol Producer

Materials

Methanol synthesis from the hydrogenation of carbon dioxide (CO2) with green H2 has been proven as a promising method for CO2 utilization. Among the various catalysts, indium oxide (In2O3)-based catalysts received tremendous research interest due to the excellent methanol selectivity with appreciable CO2 conversion. Herein, the recent experimental and theoretical studies on In2O3-based catalysts for thermochemical CO2 hydrogenation to methanol were systematically reviewed. It can be found that a variety of steps, such as the synthesis method and pretreatment conditions, were taken to promote the formation of oxygen vacancies on the In2O3 surface, which can inhibit side reactions to ensure the highly selective conversion of CO2 into methanol. The catalytic mechanism involving the formate pathway or carboxyl pathway over In2O3 was comprehensively explored by kinetic studies, in situ and ex situ characterizations, and density functional theory calculations, mostly demonstrating that th...

COMMUNICATION Yun Guo, Guanzhong Lu et al. Ultralow-temperature CO oxidation on an In 2 O 3 –Co 3 O 4 catalyst: a strategy to tune CO adsorption strength and oxygen activation simultaneously

Chemical Communications, 2014

Yun Guo, Guanzhong Lu et al. Ultralow-temperature CO oxidation on an In 2 O 3 -Co 3 O 4 catalyst: a strategy to tune CO adsorption strength and oxygen activation simultaneously Highly efficient In 2 O 3 -Co 3 O 4 catalysts were prepared for ultralowtemperature CO oxidation by simultaneously tuning the CO adsorption strength and oxygen activation over a Co 3 O 4 surface, which could completely convert CO to CO 2 at temperatures as low as À105 8C compared to À40 8C over pure Co 3 O 4 , with enhanced stability.

Nanomaterials

The growing demand for new energy sources governs the intensive research into CO2 hydrogenation to methanol, a valuable liquid fuel. Recently, indium-based catalysts have shown promise in this reaction, but they are plagued by shortcomings such as structural instability during the reaction and low selectivity. Here, we report a new strategy of controlling the selectivity and stability of bimetallic magnetically recoverable indium-based catalysts deposited onto a solid support. This was accomplished by the introduction of a structural promoter: a branched pyridylphenylene polymer (PPP). The selectivity of methanol formation for this catalyst reached 98.5%, while in the absence of PPP, the catalysts produced a large amount of methane, and the selectivity was about 70.2%. The methanol production rate was higher by a factor of twelve compared to that of a commercial Cu-based catalyst. Along with tuning selectivity, PPP allowed the catalyst to maintain a high stability, enhancing the CO2...

Inorganic chemistry frontiers, 2024

Carbon dioxide (CO 2) hydrogenation to obtain valuable chemicals and fuels via thermocatalysis or electrocatalysis is a promising and sustainable method for CO 2 utilization. Here, binary In-Cu oxide co-precipitated materials were investigated to evaluate the catalytic performance in the mentioned conversion processes. The In-rich binary material exhibits remarkable selectivity (>60%) to methanol along with high activity for CO 2 conversion (>2%) at 21 bar and 300°C, achieving a productivity of about 265 mg MeOH h −1 g In 2 O 3 −1 , which is almost 3 times higher than that of the bare In 2 O 3 catalyst. CO 2-temperature programmed desorption revealed that the basicity of the In-rich catalyst remains constant between the calcined and spent samples, so the capacity to adsorb CO 2 does not vary when the catalyst is exposed to the reaction atmosphere. Such a catalyst was demonstrated to be active for formate production in the electrochemical process as the main product. Ex situ characterization after testing proved that the In 2 O 3 phase was the active site of methanol synthesis during CO 2 hydrogenation at high temperatures and pressures. In contrast, depending on the cell configuration, different indium interfaces were stabilized at the electrocatalyst surface under ambient conditions. It is envisioned that the co-presence of In 0 , In 2 O 3 , and In(OH) 3 phases increases the local amount of *CO intermediates, promoting the formation of more reduced products, such as ethanol and 2-propanol, through the *CO dimerization reaction in the electrochemical process. These findings highlight the potential of nonreducible hydroxides as promoters in the electrochemical CO 2 reduction process. CO 2 þ 3H 2 Ð CH 3 OH þ H 2 O Δ R H°¼ À49:5 kJ mol À1 ð1Þ CO 2 þ H 2 Ð CO þ H 2 O Δ R H°¼ þ41:5 kJ mol À1 ð2Þ † Electronic supplementary information (ESI) available. See

Physical Chemistry Chemical Physics, 2015

Designing catalytic nanostructures that can convert gaseous CO2 into carbon based fuels is a significant challenge, which requires a keen understanding of the chemistry of reactants, intermediates and products on surfaces.

Applied Surface Science, 2018

Methanol synthesis from CO 2 hydrogenation on the ZrO 2 doped In 2 O 3 (110) surface (Zr-In 2 O 3 (110)) with oxygen vacancy has been studied using the density functional theory calculations. The calculated results show that the doped ZrO 2 species prohibits the excessive formation of oxygen vacancies and dissociation of H 2 on In 2 O 3 surface slightly, but enhances the adsorption of CO 2 on both perfect and defective Zr-In 2 O 3 (110) surface. Methanol is formed via the HCOO route. The hydrogenation of CO 2 to HCOO is both energetically and kinetically facile. The HCOO hydrogenates to polydentate H 2 CO (p-H 2 CO) species with an activation barrier of 0.75 eV. H 3 CO is produced from the hydrogenation of monodentate H 2 CO (mono-H 2 CO), transformation from p-H 2 CO with 0.82 eV reaction energy, with no barrier whether there is hydroxyl group between the mono-H 2 CO and the neighboring hydride or not. Methanol is the product of H 3 CO protonation with 0.75 eV barrier. The dissociation and protonation of CO 2 are both energetically and kinetically prohibited on Zr-In 2 O 3 (110) surface. The doped ZrO 2 species can further enhance the adsorption of all the intermediates involved in CO 2 hydrogenation to methanol, activate the adsorbed CO 2 and H 2 CO, and stabilize the HCOO, H 2 CO and H 3 CO, especially prohibit the dissociation of H 2 CO or the reaction of H 2 CO with neighboring hydride to form HCOO and gas phase H 2. All these effects make the ZrO 2 supported In 2 O 3 catalyst exhibit higher activity and selectivity on methanol synthesis from CO 2 hydrogenation.

Lewis bases have shown their capacity for capturing and reacting with a variety of small molecules, including H 2 and CO 2 , and thereby creating a new strategy for CO 2 reduction. Here, the photocatalytic CO 2 reduction behavior of defect-laden indium oxide (In 2 O 3−x (OH) y ) is greatly enhanced through isomorphous substitution of In 3+ with Bi 3+ , providing fundamental insights into the catalytically active surface FLPs (i.e., InOH···In) and the experimentally observed "volcano" relationship between the CO production rate and Bi 3+ substitution level. According to density functional theory calculations at the optimal Bi 3+ substitution level, the 6s 2 electron pair of Bi 3+ hybridizes with the oxygen in the neighboring InOH Lewis base site, leading to mildly increased Lewis basicity without influencing the Lewis acidity of the nearby In Lewis acid site. Meanwhile, Bi 3+ can act as an extra acid site, serving to maximize the heterolytic splitting of reactant H 2 , and results in a more hydridic hydride for more efficient CO 2 reduction. This study demonstrates that isomorphous substitution can effectively optimize the reactivity of surface catalytic active sites in addition to influencing optoelectronic properties, affording a better understanding of the photocatalytic CO 2 reduction mechanism. Solar Fuels

Ordered mesoporous indium oxide nanocrystal (m-In 2 O 3 ) was synthesized by nanocasting technique, in which highly ordered mesoporous silca (SBA-15) was used as structural matrix. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halanda (BJH) studies were carried out on m-In 2 O 3 and the results revealed that this material has a highly ordered mesoporous surface with reduced grain size, increased surface area and surface volume compared to the non porous indium oxide. The diffuse reluctance spectrum exhibited substantially improved light absorption efficiency in m-In 2 O 3 compared to normal indium oxide, however, no considerable change in the band gap energies of these materials was observed. When m-In 2 O 3 was used as a photo-catalyst in the photo-catalytic process of converting carbon dioxide (CO 2 ) into methanol under the pulsed laser radiation of 266-nm wavelengths, an enhanced photo-catalytic activity with the quantum efficiency of 4.5% and conversion efficiency of 46.3% were observed. It was found that the methanol production yield in this chemical process is as high as 485 mlg ¡1 h ¡1 after 150 min of irradiation, which is substantially higher than the yields reported in the literature. It is quite clear from the results that the introduction of mesoporosity in indium oxide, and the consequent enhancement of positive attributes required for a photo-catalyst, transformed photo-catalytically weak indium oxide into an effective photocatalyst for the conversion of CO 2 into methanol.

ACS Catalysis, 2014

ABSTRACT The doping of In2O3 significantly promoted the catalytic performance of Co3O4 for CO oxidation. The activities of In2O3–Co3O4 increased with an increase in In2O3 content, in the form of a volcano curve. Twenty-five wt % In2O3–Co3O4 (25 InCo) showed the highest CO oxidation activity, which could completely convert CO to CO2 at a temperature as low as −105 °C, whereas it was only −40 °C over pure Co3O4. The doping of In2O3 induced the expansion of the unit cell and structural distortion of Co3O4, which was confirmed by the slight elongation of the Co–O bond obtained from EXAFS data. The red shift of the UV–vis absorption illustrated that the electron transfer from O2– to Co3+/Co2+ became easier and implied that the bond strength of Co–O was weakened, which promoted the activation of oxygen. Low-temperature H2-TPR and O2-TPD results also revealed that In2O3–Co3O4 behaved with excellent redox ability. The XANES, XPS, XPS valence band, and FT-IR data exhibited that the CO adsorption strength became weaker due to the downshift of the d-band center, which correspondingly weakened the adsorption of CO2 and obviously inhibited the accumulation of surface carbonate species. In short, the doping of In2O3 induced the structural defects, modified the surface electronic structure, and promoted the redox ability of Co3O4, which tuned the adsorption strength of CO and oxygen activation simultaneously.Keywords: Co3O4; In2O3; CO oxidation; CO adsorption strength; redox ability; surface carbonate species