Unraveling the Potential-Dependent Volcanic Selectivity Changes of an Atomically Dispersed Ni Catalyst During CO₂ Reduction

Abstract

Potential-dependent selectivity changes exist widely in electrocatalysis. However, an atomistic view of such changes remains a vital missing piece of the puzzle. Here, we employ a model atomically dispersed nickel catalyst to obtain the first full view of potential-induced structure changes at an atomic level during the electrochemical CO2 reduction reaction. The model catalyst consists of a single Ni site coordinated with pyrrole nitrogen in the form of Ni-N4, as confirmed by comprehensive X-ray absorption spectroscopy (XAS) analyses. The catalyst exhibits typical potential-dependent volcanolike selectivity changes. Operando XAS revealed that the peak ∼99% CO selectivity is achieved when the distance between the Ni atom and the carbon basal plane reaches an optimal distance of ∼0.1 Å in the potential range of −0.5 to −0.8 V (vs RHE). The selectivity drops as the distance changes, induced by a potential shift. Theoretical calculations suggested that local dynamic behaviors directly regulate the distribution of the d band center of Ni. Our work provides a clear quantitative correlation between the dynamic configuration and the catalytic properties, which should benefit the future design of atomically dispersed catalysts.