Electrochemical Transformation of Facet‐Controlled BiOI into Mesoporous Bismuth Nanosheets for Selective Electrocatalytic Reduction of CO2 to Formic Acid

Abstract Mesoporous bismuth nanosheets are prepared through electrochemical transformation of (100)‐facet exposed BiOI. Theoretical modeling and calculations are used to simulate the in situ morphological transformation of BiOI into Bi. Mesoporous Bi nanosheets show superior electrochemical CO 2 reduction performance. A faradaic efficiency of 95.9 % at −0.77 V RHE for the conversion of CO 2 into formic acid, is achieved for the mesoporous Bi nanosheet catalyst compared with 93.8 % at −0.87 V RHE for the smooth Bi nanosheets. Tafel analysis and DFT calculations indicate that the electrochemical CO 2 reduction on mesoporous Bi nanosheets is kinetically faster with a higher resistance to H 2 generation than that on smooth Bi(001) nanosheets. The CO 2 ‐to‐HCOOH pathway is preferred through formation of an *OCHO intermediate on the (012) and (001) planes of Bi. The mesoporous structure induces a more accessible interaction with CO 2 , which makes a predominant contribution to the enhanced performance compared with the subsequent CO 2 activation on different facets of Bi.