Understanding the C–C coupling mechanism in electrochemical CO reduction at low CO coverage: Dynamic change in site preference matters

Abstract

A thoroughly mechanistic understanding of the electrochemical CO reduction reaction (eCORR) at the interface is significant for guiding the design of high-performance electrocatalysts. However, unintentionally ignored factors or unreasonable settings during mechanism simulations will result in false positive results between theory and experiment. Herein, we computationally identified the dynamic site preference change of CO adsorption with potentials on Cu(100), which was a previously unnoticed factor but significant to potential-dependent mechanistic studies. Combined with the different lateral interactions among adsorbates, we proposed a new C–C coupling mechanism on Cu(100), better explaining the product distribution at different potentials in experimental eCORR. At low potentials (from –0.4 to –0.6 V_RHE), the CO forms dominant adsorption on the bridge site, which couples with another attractively aggregated CO to form a C–C bond. At medium potentials (from –0.6 to –0.8 V_RHE), the hollow-bound CO becomes dominant but tends to isolate with another adsorbate due to the repulsion, thereby blocking the coupling process. At high potentials (above –0.8 V_RHE), the CHO intermediate is produced from the electroreduction of hollow-CO and favors the attraction with another bridge-CO to trigger C–C coupling, making CHO the major common intermediate for C–C bond formation and methane production. We anticipate that our computationally identified dynamic change in site preference of adsorbates with potentials will bring new opportunities for a better understanding of the potential-dependent electrochemical processes.