Engineering Under-Coordinated Active Sites with Tailored Chemical Microenvironments over Mosaic Bismuth Nanosheets for Selective CO 2 Electroreduction to Formate.

Selective electrochemical reduction of CO 2 into fuels or chemical feedstocks is a promising avenue to achieve carbon-neutral goal, but its development is severely limited by the lack of highly efficient electrocatalysts. Herein, cation-exchange strategy is combined with electrochemical self-reconstruction strategy to successfully develop diethylenetriamine-functionalized mosaic Bi nanosheets (mBi-DETA NSs) for selective electrocatalytic CO 2 reduction to formate, delivering a superior formate Faradaic efficiency of 96.87% at a low potential of -0.8 V RHE . Mosaic nanosheet morphology of Bi can sufficiently expose the under-coordinated Bi active sites and promote the activation of CO 2 molecules to form the OCHO - * intermediate. Moreover, in situ attenuated total reflectance infrared spectra further corroborate that surface chemical microenvironment modulation of mosaic Bi nanosheets via DETA functionalization can improve CO 2 adsorption on the catalyst surface and stabilize the key intermediate (OCHO - *) due to the presence of amine groups, thus facilitate the CO 2 -to-HCOO - reaction kinetics and promote formate formation.