In-Situ Hydrogen-Bond Tailoring To Construct Ultrathin Bi 2 O 2 O/Bi 2 O 2 (OH)(NO 3 ) Nanosheets: Interactive CO 2 RR Promotion and Bismuth-Oxygen Moiety Preservation.

Bismuth-oxygen moieties are beneficial for high-efficiency electrochemical CO 2 reduction (CO 2 RR) to produce formate; however, preserving bismuth-oxygen moieties while applying a cathodic potential is challenging. This work reports the preparation of ultrathin Bi 2 O 2 O/Bi 2 O 2 (OH)(NO 3 ) nanosheets (BiON-uts) by in-situ tailoring of hydrogen bonds in a Bi 2 O 2 (OH)(NO 3 ) 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 Bi 2 O 2 CO 3 as intermediate, and adsorption of CO 2 with surface Bi 2 O 2 O. DFT calculations reveal that the rate-limiting first electron transfer is effectively improved by the high electron affinity of Bi 2 O 2 CO 3 . More importantly, high-efficiency CO 2 RR in turn protects the bismuth-oxygen moieties from being reduced and thus helps to maintain the excellent CO 2 RR activity. This work offers an interactive mechanism of CO 2 RR promotion and bismuth-oxygen moiety preservation, opening up new opportunities for developing high-performance catalysts.