Activating Basal Planes in Transition Metal Dichalcogenides for CO2 Reduction to CO through Alloying
Transition metal dichalcogenides (TMDCs) have emerged as highly tunable platforms for electrocatalysis, particularly for the CO2 reduction reaction (CO2RR). While TMDC edge sites exhibit catalytic activity, the basal plane is typically inert, severely limiting the overall active site density. In this work, we show that sulfur vacancies activate the basal plane of 1H-TMDCs, while concurrent solid-solution alloying provides a mechanism to broadly tune intermediate adsorption energies. We evaluate a library of quasi-binary TMDC sulfide alloys comprising V, Nb, Ta, Mo, and W, screening them by stability, defect energetics, and competitive selectivity to identify the most effective catalysts for CO2RR. Electronic-structure analysis reveals that a d-band center closer to the Fermi energy weakens intermediate binding by leaving key bonding states unoccupied above the Fermi energy. Our calculations identify (Nb,Ta)S2 as a promising catalyst with low sulfur vacancy formation energies, near-optimal CO2RR intermediate binding, and selectivity against the hydrogen evolution reaction. Overall, this work establishes a rational design framework for TMDC alloy catalysts through the simultaneous use of defect engineering and alloying.