Elucidating the Electrocatalytic CO 2 Reduction Reaction over a Model Single‐Atom Nickel Catalyst

Designing effective electrocatalysts for the carbon dioxide reduction reaction (CO 2 RR) is an appealing approach to tackling the challenges posed by rising CO 2 levels and realizing a closed carbon cycle. However, fundamental understanding of the complicated CO 2 RR mechanism in CO 2 electrocatalysis is still lacking because model systems are limited. We have designed a model nickel single‐atom catalyst (Ni SAC) with a uniform structure and well‐defined Ni‐N 4 moiety on a conductive carbon support with which to explore the electrochemical CO 2 RR. Operando X‐ray absorption near‐edge structure spectroscopy, Raman spectroscopy, and near‐ambient X‐ray photoelectron spectroscopy, revealed that Ni + in the Ni SAC was highly active for CO 2 activation, and functioned as an authentic catalytically active site for the CO 2 RR. Furthermore, through combination with a kinetics study, the rate‐determining step of the CO 2 RR was determined to be *CO 2 − +H + →*COOH. This study tackles the four challenges faced by the CO 2 RR; namely, activity, selectivity, stability, and dynamics.