Ultrathin Bismuth Nanosheets as a Highly Efficient CO₂ Reduction Electrocatalyst

Electrochemical reduction of CO₂ to value-added products is an important and challenging reaction for sustainable energy study. Herein, bismuth nanosheets with thickness of around 10 nm were prepared through the electrochemical reduction of Bi³⁺ . Ultrathin Bi nanosheets with numerous low-coordination sites can efficiently reduce CO₂ to formate in aqueous solution. Within the potential range of -0.9 to -1.2 V vs. reversible hydrogen electrode (RHE), the faradaic efficiency of formate is over 90 %, outperforming many Bi catalysts. At -0.7 V, the Bi nanosheets exhibit much higher current for formate generation than that of bulk Bi, attributed to a high surface area and also modified intrinsic electronic properties brought about by the ultrathin structure. DFT calculations demonstrate that Bi nanosheets have much higher density of states at the Fermi level compared to bulk Bi, favoring improved CO₂ reduction on Bi nanosheets. At -1.0 V, Bi nanosheets exhibit high selectivity for formate and excellent stability during 5 h of electrolysis.