Active-Site Computational Screening: Role of Structural and Compositional Diversity for the Electrochemical CO2 Reduction at Mo Carbide Catalysts

The surfaces of compound catalyst materials generally exhibit a wide range of geometric and compositional motives that could act as active sites. We address this inherent complexity by extending computational materials screening over a diverse set of such sites. For the electrochemical CO2 reduction reaction (CO2RR) at molybdenum carbides, extensive density functional theory (DFT) calculations for key reaction intermediates at these sites show that differing adsorption modes break many of the scaling relations known to hold across transition metals. Despite the resulting inherently rich reduction chemistry, clear trends emerge. Notably, this includes a product selectivity governed by the metal/carbon ratio of the active site. The trend toward methanol formation for C-containing active sites mirrors thermal heterogeneous CO2 activation and suggests a shift of focus toward more C-rich carbides for CO2RR to methanol.