Efficient Conversion of CO_2 to CO Using Tin and Other Inexpensive and Easily Prepared Post-Transition Metal Catalysts

摘要

The development of affordable electrocatalysts that can drive the reduction of CO_2 to CO with high selectivity, efficiency, and large current densities is a critical step on the path to production of liquid carbon-based fuels. In this work, we show that inexpensive triflate salts of Sn~(2+), Pb~(2+), Bi~(3+), and Sb~(3+) can be used as precursors for the electrodeposition of CO_2 reduction cathode materials from MeCN solutions, providing a general and facile electrodeposition strategy, which streamlines catalyst synthesis. The ability of these four platforms to drive the formation of CO from CO_2 in the presence of [BMIM]OTf was probed. The electrochemically prepared Sn and Bi catalysts proved to be highly active, selective, and robust platforms for CO evolution, with partial current densities of j_(CO) = 5-8 mA/cm~2 at applied overpotentials of η ＜ 250 mV. By contrast, the electrodeposited Pb and Sb catalysts do not promote rapid CO generation with the same level of selectivity. The Pb material is only ～10% as active as the Sn and Bi systems at an applied potential of E = -1.95 V and is rapidly passivated during catalysis. The Sb-comprised cathode material shows no activity for conversion of CO_2 to CO under analogous conditions. When taken together, this work demonstrates that 1,3-dialkylimidazoliums can promote CO production, but only when used in combination with an appropriately chosen electrocatalyst material. More broadly, these results suggest that the interactions between CO_2, the imidazolium promoter, and the cathode surface are all critical to the observed catalysis.