Electron accumulation enables Bi efficient CO2 reduction for formate production to boost clean Zn-CO2 batteries.

Electrocatalytic CO 2 reduction to value-added chemicals is of great potential in maintaining carbon balance and alleviating energy shortage. Stabilizing and accelerating the formation of *OCHO intermediate is the key to achieve high-selectivity formate production. Herein, Bi nanoparticles embedded in pyrrolic-N-dominated doped carbon nanosheets (~10 nm) (PNCB) delivered a maximum formate selectivity of 94.8% (−1.05 V) and a partial current density of − 22 mA cm⁻² in H-type electrolyzers. According to theoretical calculation results, the critical pyrrolic-N doping in carbon nanosheets promoted electron transfer from N to Bi atoms, which facilitates stabilizing *OCHO intermediate and boosting formate formation. The rechargeable Zn-CO 2 batteries applying PNCB as anode catalysts displayed the maximum power density of 1.43 mW cm⁻² with CO emission below 11%. For coupled CO 2 reduction (catalyzed by PNCB) and oxygen evolution (catalyzed by 10 wt% Ir/C), a large current density up to 180 mA cm⁻² in flow cells was also achieved. This work provides an effective strategy to regulate the support components and electron accumulation towards electrocatalytic CO 2 reduction to formate as well as related clean energy devices. [Display omitted] • TThe PNCB achieved a high HCOO- selectivity (94.8%) and a large current density (-22 mA cm^-2) at -1.05 V. • Pyrrolic-N doping induced electron accumulation towards Bi to reduce *OCHO formation energy barrier. • The Zn-CO 2 batteries with low CO emission (< 11%) displayed a maximum power density of 1.43 mW cm⁻². • Coupling CO 2 RR with OER, a larger current density of 180 mA cm⁻² in flow cells was achieved. [ABSTRACT FROM AUTHOR]