The Promoting Role of Ni on In2O3 for CO2 Hydrogenation to Methanol

Mitigating the Poisoning Effect of Formate during CO2 Hydrogenation to Methanol over Co-Containing Dual-Atom Oxide Catalysts

During the hydrogenation of CO2 to methanol over mixed-oxide catalysts, the strong adsorption of CO2 and formate poses a barrier for H2 dissociation, limiting methanol selectivity and productivity. Here we show that by using Co-containing dual-atom oxide catalysts, the poisoning effect can be countered by separating the site for H2 dissociation and the adsorption of intermediates. We synthesized a Co- and In-doped ZrO2 catalyst (Co-In-ZrO2) containing atomically dispersed Co and In species. Catalyst characterization showed that Co and In atoms were atomically dispersed and were in proximity to each other owing to a random distribution. During the CO2 hydrogenation reaction, the Co atom was responsible for the adsorption of CO2 and formate species, while the nearby In atoms promoted the hydrogenation of adsorbed intermediates. The cooperative effect increased the methanol selectivity to 86% over the dual-atom catalyst, and methanol productivity increased 2-fold in comparison to single-atom catalysts. This cooperative effect was extended to Co-Zn and Co-Ga doped ZrO2 catalysts. This work presents a different approach to designing mixed-oxide catalysts for CO2 hydrogenation based on the preferential adsorption of substrates and intermediates instead of promoting H2 dissociation to mitigate the poisonous effects of substrates and intermediates.

Cr2 O3 Promoted In2 O3 Catalysts for CO2 Hydrogenation to Methanol

Cr2 O3 was applied to study the modification of In2 O3 based catalysts for CO2 hydrogenation to methanol reaction. Combined with X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), etc., the structure of the catalysts was characterized. The reaction performances for CO2 hydrogenation to methanol were evaluated on a stainless-steel fix-bed reactor. The results showed that solid solutions were formed for the Cr2 O3 promoted In2 O3 catalysts. The important role of electronic interaction between Cr2 O3 and In2 O3 was revealed in the hydrogenation reaction. In1.25 Cr0.75 O3 sample exhibited the highest methanol yield, which was 2.8 times higher than that of pure In2 O3 . No deactivation was observed for In1.25 Cr0.75 O3 sample during the 50 hours of reaction. The improved catalytic performance may be due to the formation of the solid solutions and the highest amount of oxygen vacancies.

Computational screening of single-atom doped In2O3 catalysts for the reverse water gas shift reaction

The reverse water gas shift (RWGS) reaction is an important method for converting carbon dioxide (CO2) into valuable chemicals and fuels by hydrogenation. In this paper, the catalytic activity of single-atom metal-doped (M = Pt, Ir, Pd, Rh, Cu, Ni) indium oxide (c-In2O3) catalysts in the cubic phase for the RWGS reaction was investigated using density functional theory (DFT) calculations. This was achieved by identifying metal sites, screening oxygen vacancies, followed by further calculating the energy barriers for the direct and indirect dissociation pathways of the RWGS reaction. Our results show that the single-atom dopant in the indium oxide lattice promotes the creation of oxygen vacancies on the In2O3 surface, thereby facilitating the adsorption and activation of CO2 by the oxide surface and initiating the subsequent RWGS reaction. Furthermore, we find that the oxygen vacancy (OV) formation energy on the surface of the single-atom metal doped c-In2O3(111) surface can be used as a descriptor for CO2 adsorption, and the higher the OV formation energy, the more stable the CO2 adsorption structure is. The Cu/In2O3 structure has relatively high energy barriers for both direct (1.92 eV) and indirect dissociation (2.09 eV) in the RWGS reaction, indicating its low RWGS reactivity. In contrast, the Ir/In2O3 and Rh/In2O3 structures are more conducive to the direct dissociation of CO2 into CO, which may serve as more efficient RWGS catalysts. Furthermore, microkinetic simulations show that single atom metal doping to In2O3 enhances CO2 conversion, especially under high reaction temperatures, where the formation of oxygen vacancies is the limiting factor for CO2 reactivity on the M/In2O3 (M = Cu, Ir, Rh) models. Among these three single-atom catalysts, the Ir/In2O3 model was predicted to have the best CO2 reactivity at reaction temperatures above 573 K.

Embedding CsPbBr3 Quantum Dots into an In2O3 Nanotube for Selective Photocatalytic CO2 Reduction to Hydrocarbon Fuels

Halide perovskite quantum dots (QDs) are one of the most prospective candidates for photocatalytic CO2 reduction, but their photocatalytic performances are far from satisfactory due to structural instability and severe charge recombination. In this study, we demonstrated a CsPbBr3 QDs/In2O3 hierarchical nanotube (CPB/IO) for efficient CO2 conversion, in which CsPbBr3 QDs were well-dispersed on the In-MOF-derived In2O3 nanotube by a facile self-assembly process. The optimized CPB/IO catalyst displayed an enhanced photocatalytic CO2 performance with a (CO + CH4) generation rate of 16.37 μmol·g-1·h-1 upon simulated solar illumination without a photosensitizer and sacrificial agent, which is 3.59 times stronger than that of pristine CsPbBr3 QDs (4.56 μmol·g-1·h-1). Besides, the modified CsPbBr3 QD catalyst exhibited an obvious increase of CH4 selectivity and excellent stability after four cycles. The unique zero-dimensional (0D)/one-dimensional (1D) heterostructure and matching band potentials between CsPbBr3 and In2O3 supply an intimate interfacial contact, numerous active sites, and effective charge transfer for CO2 photoreduction. This work can inspire the formation of novel halide-perovskite-involving photocatalysts for solar fuel formation.