Atomically dispersed nickel-bismuth dual-atom sites for high rate electrochemical CO2 reduction

We report a diatomic-site catalyst configuration constituted by Ni-N₃ and Bi-N₄ embedded in ultrathin nitrogenated carbon nanosheets (Ni/Bi-N-C) which showed dramatically improved activity and selectivity for the conversion of CO₂ to CO. Specifically, the catalyst exhibited high CO Faradaic efficiency (FE_CO) of above 90 % over a wide potential window from −0.76 to −2.22 versus reversible hydrogen electrode with the maximum CO partial current density up to 312 mA cm⁻² in a flow cell, and coupled with robust durability. Ni/Bi-N-C-based membrane electrode assembly (MEA) device presented ultrahigh FE_CO of 95.7 % at 750 mA and over 100 h of continuous operation without decay under constant current density of 100 mA cm⁻². Mechanistic studies and density functional theory calculations reveal that regulating the CO₂RR catalytic performance via nearby Ni and Bi active sites can potentially break the activity benchmark of the single metal counterparts because the neighboring Ni and Bi active sites work in synergy to decrease the reaction barrier for the formation of *COOH and desorption of *CO. This work presents an efficient combination of two metal atomic sites which was designed by optimizing the interaction between the atomic sites and key reaction intermediates, resulting in the high-rate electrocatalytic CO₂ reduction.