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

Electrocatalytic CO2 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-CO2 batteries applying PNCB as anode catalysts displayed the maximum power density of 1.43 mW cm−2 with CO emission below 11%. For coupled CO2 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 CO2 reduction to formate as well as related clean energy devices.