A nanosheet CH 3 COO(BiO) topotactically converted into nanocomposite of bismuth clusters and Bi 2 O 2 CO 3 for highly efficient electrocatalytic reduction of CO 2 to formate

Hydrogen is a promising clean energy source, and formic acid serves as a significant hydrogen storage material. The electrocatalytic reduction of carbon dioxide (ECO 2 RR) is a promising approach to produce fromate. However, the challenge lies in developing high-performance electrocatalysts for the conversion of CO 2 to formate, due to the limited intrinsic activity, conductivity, and the low density of active sites. In this work, we have fabricated highly active and selective CH 3 COO(BiO) (BiOAc) nanosheets. These nanosheets undergo a transformation into Bi clusters-BiO 2 CO 3 during electrolysis, endowing the material with superior electrocatalytic capabilities for CO 2 reduction to formate, with a Faradaic selectivity of over 90 % across a wide potential window from -0.8 to -1.3 V. Additionally, this catalyst can sustain high current densities above 80 mA cm -2 at low applied potentials without compromising selectivity in a H type electron reactor. Both density functional theory (DFT) and in situ attenuated total reflection -infrared spectroscopy (in situ ATR-IR) findings indicate that the Bi 3+ with reduced density facilitate the activation of CO 2 to *CO 2 , while the charge density -enriched Bi 0 atoms in Bi cluster promote the capture of HCO 3 - and enhance subsequent proton -coupled electron transfer reactions. Collectively, these factors significantly reduce the energy barrier for *OCHO formation on BiOAc, thereby enhancing its catalytic activity and Faradaic efficiency for the electroreduction of CO 2 .