Efficient Conversion of CO₂ to CO Using Tin and Other Inexpensive and Easily Prepared Post-Transition Metal Catalysts

The development of affordable electrocatalysts that can drive the reduction of CO₂ 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 Sn²⁺, Pb²⁺, Bi³⁺, and Sb³⁺ can be used as precursors for the electrodeposition of CO₂ 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 CO₂ 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/cm² 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 CO₂ 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 CO₂, the imidazolium promoter, and the cathode surface are all critical to the observed catalysis.