Trends in CO₂ Reduction on Transition Metal Dichalcogenide Edges

Electrocatalytic CO₂ reduction is a promising solution to close the anthropogenic carbon cycle. However, linear scaling relations among reaction intermediates of the CO₂ reduction reaction (CO2RR) and the competing hydrogen evolution reaction (HER) limits the Faradaic efficiencies and selectivities of traditional transition metal catalysts. The two-dimensional transition metal dichalcogenides (TMDCs) is a promising class of catalysts for the reaction. Selected transition metal dichalcogenides have been shown experimentally to effectively reduce CO₂ and in some cases produce “beyond CO” products. The majority of theoretical investigations have focused on MoS₂ and WS₂, materials that have been widely studied for various applications, e.g desulfurization, HER, Li metal batteries and optical devices. In this computational study, we go beyond Mo and W and study the edge configurations, adsorption properties and aqueous stability of a range of TMDC materials in the 2H phase. We show that the most stable edge configuration is highly dependent on the specific composition of the material, while adsorption properties of H, CO, and COOH vary significantly with edge configuration. We furthermore find that, while a linear scaling among H and CO adsorbates is observed within each group of the sulfides, selenides, and tellurides, respectively, the scaling is shifted toward weaker H bonding and stronger CO bonding going from sulfides to selenides to tellurides. A similar trend is observed for CO/COOH for some edge configurations. The results indicate that the transition metal ditellurides are a promising class of materials with the potential of reducing CO₂ further than CO while limiting HER.