Theoretical Investigation of Nanoscale Metal Clusters Supported on H_<i>x</i>MoO_3–<i>y</i> for CO₂ Reduction

The photothermal catalysis of carbon dioxide (CO2) reduction into value-added solar fuels represents a promising approach to addressing the energy crisis and mitigating global warming. Recent experimental findings indicate that Ru-HxMoO3–y is capable of completely converting CO2 into methane (CH4). In contrast, Pt-HxMoO3–y has been observed to produce a range of products, with carbon monoxide (CO) being the most prevalent. A comprehensive understanding of the reaction mechanism is essential to elucidate the different sensitivities of catalysts and to facilitate the development of HxMoO3–y-based catalytic systems. This study employs density functional theory to examine the mechanism of CO2 reduction on Ru-HxMoO3–y. The d7 configuration of Ru enables the transfer of d electrons from the Ru-HxMoO3–y catalyst to CO via π-back-bond, which results in the weakening of the C–O bond and the preferential formation of CH4. Moreover, Ru-HxMoO3–y has been identified as a promising candidate for the production of ethylene (C2H4), with its selectivity being adjustable through variations in reaction temperature and pressure. Our findings demonstrate that the performance of C–C coupling in HxMoO3–y-based catalysts is significantly influenced by the d configuration of the metal cluster. The theoretically designed Fe/Ru-HxMoO3–y exhibits the most favorable catalytic activity. These insights offer critical mechanistic guidance for the design of advanced photocatalysts to convert CO2 into solar fuels.