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

Electroreduction of carbon dioxide (CO) 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 CO-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 CO reduction to formate. BiOI nanoplates precursors derived Bi nanosheets (P-nanoplates-Bi) exhibited an excellent performance for CO 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 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 KHCO aqueous solution. The superior performance is mainly attributed to the two-dimensional (2D) Bi nanosheets, which can increase CO 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.