Trends and descriptors for tuning CO2 electroreduction to synthesis gas over Ag and Au supported on transition metal carbides and nitrides

Synthesis gas produced from the electrochemical carbon dioxide reduction reaction (CO2RR) using renewable energy represents a promising solution toward carbon neutrality. Both high activity and controlled CO/H2 ratios are crucial for coupling CO2RR with downstream thermochemical reactions. In the current study, transition metal carbides (TMCs) and nitrides (TMNs) of Group VB elements (V, Nb and Ta) were used as supports to tune the CO2RR activity and CO/H2 ratios over Ag- and Au-based electrocatalysts. Combined electrochemical measurements and density functional theory (DFT) calculations identified the Gibbs free energy for adsorption of the *HOCO intermediate (ΔG(*HOCO)) as a potential descriptor for CO2RR, which could be adjusted by using different TMC and TMN supports. As opposed to structural strain effects, the electronic modification was found to be the key controlling factor in the interactions between TMC/TMN and supported Ag/Au. TaC and TaN have been identified as promising supports for Ag- and Au-based electrocatalysts for CO2RR to synthesis gas production.