Hydrangea-like Superstructured Micro/Nanoreactor of Topotactically Converted Ultrathin Bismuth Nanosheets for Highly Active CO Electroreduction to Formate.

An electrocatalytic carbon dioxide reduction reaction (CORR) is an appealing route to obtain the value-added feedstocks and alleviate the energy crisis. However, how to achieve high-performance electrocatalysts for CO reduction to formate is challenging owing to the poor intrinsic activity, insufficient conductivity, and low surface density of active sites. Herein, we fabricated an extremely active and selective hydrangea-like superstructured micro/nanoreactor of ultrathin bismuth nanosheets through an electrochemical topotactic transformation of hierarchical bismuth oxide formate (BiOCOOH). The resulted bismuth nanosheet superstructure is in the form of three-dimensional intercrossed networks of ultrathin nanosheets, forming an ordered open porous structure through self-assembly, which can be used as a micro/nanoreactor to enable a large electrochemically active surface area as well as high atomic utilization. Such a distinctive nanostructure endows the material with high electrocatalytic performances for CO reduction to formate with near-unity Faradaic selectivity (>95%) in a wide potential window from -0.78 to -1.18 V. Furthermore, this micro/nanoreactor can give the high current densities over 300 mA cm at low applied potentials without compromising selectivity in a flow cell reactor. Density functional theory (DFT) and attenuated total reflection-infrared spectroscopy ( ATR-IR) were further conducted to interpret the CORR mechanisms.