One-step co-electrodeposition of SnBi for efficient electrochemical reduction of carbon dioxide to formic acid

With the industrial development and improvement of living standards, carbon dioxide emissions are increasing year on year and have been causing serious environmental issues, such as global warming. Hence, it is urgent to develop effective, low-cost technologies for trapping or converting CO2. The electrochemical reduction of carbon dioxide can not only solve the issue of global warming but also can effectively convert CO2 into useful chemicals. For the efficient electrochemical reduction of carbon dioxide under mild conditions, high-performance catalysts are required. In this work, metallic tin and bismuth compounds were deposited on carbon paper via a facile co-electrodeposition strategy and their catalytic performance was comprehensively evaluated. The results showed that the SnBi catalyst with the Sn2+/Bi3+ molar ratio of 1.0(Sn1.0Bi) in the preparation solution offered the largest formic acid selectivity with an excellent FE of 96.4% at a partial current density of 36.7 mA cm(-2) when the reduction potential was -1.06 V vs. RHE. A good formic acid yield of 684.7 mu mol h(-1) cm(-2) was achieved from this catalyst. The formic acid yield further increased to 733.2 mu mol h(-1) cm(-2) using the Sn-0.Bi-5 catalyst (0.5 Sn2+/Bi3+ molar ratio) at a slightly reduced selectivity with a lower FE of 96.1% at -1.06 V vs. RHE and increased partial current density of 40.3 mA cm(-2). The results are better than most of the reported electrocatalysts. The helical pyramid-like structure of the SnBi catalyst provides a large exposed area with a large number of active sites and a large number of screw dislocation defects. Its fast electron transfer is favorable for the formation of the key radical of CO2- intermediate and the tin metal oxide/bismuth metal oxide interface is favorable for stabilizing CO2- with suppressed hydrogen evolution reaction. In addition, the electronic coupling between Sn and Bi at their interfaces strengthens the pathway involving the OCHO intermediate, which is important to promote the conversion of CO2 to formic acid. In conclusion, the SnBi catalyst with a helical platform structure is a promising and efficient catalyst for the reduction of CO2.