In-Situ Hydrogen-Bond Tailoring To Construct Ultrathin Bi2O2O/Bi2O2(OH)(NO3) Nanosheets: Interactive CO2RR Promotion and Bismuth-Oxygen Moiety Preservation

Bismuth–oxygen moieties are beneficial for high-efficiency electrochemical CO₂ reduction (CO₂RR) to produce formate; however, preserving bismuth-oxygen moieties while applying a cathodic potential is challenging. This work reports the preparation of ultrathin Bi₂O₂O/Bi₂O₂(OH)(NO₃) nanosheets (BiON-uts) by in-situ tailoring of hydrogen bonds in a Bi₂O₂(OH)(NO₃) precursor. The BiON-uts exhibits a formate faradaic efficiency of 98 % with higher partial current density than that of most reported bismuth-based catalysts. Mechanistic studies demonstrate that the ultrathin nanosheet morphology facilitates ion-exchange between BiON-uts and the electrolyte to produce Bi₂O₂CO₃ as intermediate, and adsorption of CO₂ with surface Bi₂O₂O. DFT calculations reveal that the rate-limiting first electron transfer is effectively improved by the high electron affinity of Bi₂O₂CO₃. More importantly, high-efficiency CO₂RR in turn protects the bismuth–oxygen moieties from being reduced and thus helps to maintain the excellent CO₂RR activity. This work offers an interactive mechanism of CO₂RR promotion and bismuth–oxygen moiety preservation, opening up new opportunities for developing high-performance catalysts.