Effects of thicknesses and sizes of BiOX nanoplates precursors on derived Bi nanosheets for efficient CO2 electroreduction

Electroreduction of carbon dioxide (CO2) into formic acid (HCOOH) or formate can alleviate energy crises and simultaneously decrease the content of one of the main greenhouse gases. Herein, two-dimensional (2D) Bi nanosheets electrocatalyst can be obtained via in situ transformations from optimized thickness and sizes of the bismuth oxychloride (BiOCl) precursors while the precursors with improper thicknesses or sizes were electeoreduced into nanoparticles. The 2D Bi nanosheets derived from BiOCl nanoplates precursors which were synthesized with solvent of EG/H2O (1:1) show CO2 reduction reaction (CO2RR) activity with high selectivity (92 % at −0.9 V vs reversible hydrogen electrode (RHE)), and high stability (15 h) with a current density of 10.5 mA cm−2. In addition, FEs over 80 % in a wide potential window (−0.8 to −1.3 V) are obtained in an optimal range of thickness (20∼25 nm) and sizes (40∼497 nm). This work shows that the optimal thicknesses and sizes of BiOX (X = Br, Cl) nanoplates derived Bi can maintain the 2D structures and the excellent electrocatalytic activity in CO2RR might be attributed to more exposed active sites, enhanced electrochemical active areas, and lowered contact resistance. Furthermore, the in situ transformed electrocatalysts from the BiOX precursors is a promising and general way for regulating the activity and selectivity for CO2 reduction to formate.