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

[Display omitted] • Ag and Au electrocatalysts supported on transition metal carbides (TMCs) and nitrides (TMNs) were synthesized and evaluated for CO 2 RR. • TaC and TaN were identified as promising supports for Ag and Au catalysts for electroreduction of CO 2 to synthesis gas. • ΔG (*HOCO) was identified as a key descriptor for CO 2 RR based on a linear correlation between ΔG (*HOCO) and J ECSA (CO). • Electron transfer from TMC/TMN substrates to Ag/Au played a dominant role in controlling the CO 2 RR activity. Synthesis gas produced from the electrochemical carbon dioxide reduction reaction (CO 2 RR) using renewable energy represents a promising solution toward carbon neutrality. Both high activity and controlled CO/H 2 ratios are crucial for coupling CO 2 RR 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 CO 2 RR activity and CO/H 2 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 CO 2 RR, 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 CO 2 RR to synthesis gas production. [ABSTRACT FROM AUTHOR]