A general strategy for obtaining BiOX nanoplates derived Bi nanosheets as efficient CO2 reduction catalysts by enhancing CO2•- adsorption and electron transfer

Abstract

Electroreduction of carbon dioxide (CO2) into formic acid/formate has been considered as one of the most promising strategies for obtaining value-added fuels and chemical productions. Herein, we present a general method for preparing Bi-based electrocatalysts via in situ reduction of bismuth oxyiodide (BiOI) in CO2-saturated electrolyte. The precursors of BiOI nanoplates (P-nanoplates) with thickness of 30–40 nm could be easily obtained and provide a concise model to probe the mechanisms of CO2 reduction to formate. BiOI nanoplates precursors derived Bi nanosheets (P-nanoplates-Bi) exhibited an excellent performance for CO2 reduction to formate, achieving Faradaic efficiencies (FEs) over 80% in a wide potential window and a maximum FE approaching of 95% with a current density of 13.3 ± 0.6 mA cm−2 at −0.9 V versus reverse hydrogen electrode (υs. RHE). Such P-nanoplates-Bi nanosheets showed a stable electrocatalytic actitivity during 15 h operation in 0.5 M KHCO3 aqueous solution. The superior performance is mainly attributed to the two-dimensional (2D) Bi nanosheets, which can increase CO2•- adsorption, enlarge active surface area, show better reaction kinetics and provide lower contact resistance with accelerated electron transfer. For comparison, precursors of BiOI plate-like (P-bulk) with doubled thicknesses and ultrathin BiOI with a few nanometers derived Bi catalysts tend to agglomerate and appear as irregular structured Bi nanoparticles during the reaction. Their peak FEs for formate are much lower than those of P-nanoplates derived Bi nanosheets at −0.9 V.