Theoretical Investigation of Nanoscale Metal ClustersSupported 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-H_<i>x</i>MoO_3–<i>y</i> is capable of completely converting CO₂ into methane (CH₄). In contrast, Pt-H_<i>x</i>MoO_3–<i>y</i> 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 H_<i>x</i>MoO_3–<i>y</i>-based catalytic systems. This study employs density functional theory to examine the mechanism of CO₂ reduction on Ru-H_<i>x</i>MoO_3–<i>y</i>. The d⁷ configuration of Ru enables the transfer of d electrons from the Ru-H_<i>x</i>MoO_3–<i>y</i> 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-H_<i>x</i>MoO_3–<i>y</i> 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 H_<i>x</i>MoO_3–<i>y</i>-based catalysts is significantly influenced by the d configuration of the metal cluster. The theoretically designed Fe/Ru-H_<i>x</i>MoO_3–<i>y</i> exhibits the most favorable catalytic activity. These insights offer critical mechanistic guidance for the design of advanced photocatalysts to convert CO₂ into solar fuels.