Selective Carbon Dioxide-to-Formic Acid Conversion via Composition and Vacancy Engineering of Mo_xNb_yV_1-(x+y)Se₂ Alloys

The electrochemical reduction of carbon dioxide (CO₂) to formic acid (HCOOH) offers a promising route for sustainable carbon utilization. Here, we employ density functional theory (DFT) calculations to investigate the catalytic behavior of multicomponent Mo_xNb_yV_1-(x+y)Se₂ transition metal chalcogenide alloys. Four representative compositions—Mo-rich, Nb-rich, equimolar, and V-rich—are examined in both pristine and Se-vacancy-engineered forms to elucidate the effects of alloy composition and local defect structures. Our results show that Se-vacancy formation alters the surface electronic environment and substantially lower the Gibbs free energy for OCHO adsorption, a key intermediate in the CO₂-to-HCOOH pathway. In particular, the V-rich and Mo-rich alloys with Se vacancies exhibit nearly thermoneutral Gibbs free energies for OCHO adsorption, suggesting an optimal balance between intermediate binding and catalytic turnover. These findings underscores the synergistic impact of compositional tuning and vacancy engineering in enhancing CO₂ reduction performance and offers rational design principles for high-efficiency transition metal chalcogenide-based electrocatalysts.