Reaction mechanism and kinetics for CO2 reduction on nickel single atom catalysts from quantum mechanics

Abstract

Abstract Experiments have shown that graphene-supported Ni-single atom catalysts (Ni-SACs) provide a promising strategy for the electrochemical reduction of CO 2 to CO, but the nature of the Ni sites (Ni-N 2 C 2 , Ni-N 3 C 1 , Ni-N 4 ) in Ni-SACs has not been determined experimentally. Here, we apply the recently developed grand canonical potential kinetics (GCP-K) formulation of quantum mechanics to predict the kinetics as a function of applied potential (U) to determine faradic efficiency, turn over frequency, and Tafel slope for CO and H 2 production for all three sites. We predict an onset potential (at 10 mA cm −2 ) U onset = −0.84 V (vs. RHE) for Ni-N 2 C 2 site and U onset = −0.92 V for Ni-N 3 C 1 site in agreement with experiments, and U onset = −1.03 V for Ni-N 4 . We predict that the highest current is for Ni-N 4 , leading to 700 mA cm −2 at U = −1.12 V. To help determine the actual sites in the experiments, we predict the XPS binding energy shift and CO vibrational frequency for each site.