Two-Dimensional Titanium and Molybdenum Carbide MXenes as Electrocatalysts for CO Reduction.

Electrocatalytic CO reduction reaction (CORR) is an attractive way to produce renewable fuel and chemical feedstock, especially when coupled with efficient CO capture and clean energy sources. On the fundamental side, research on improving CORR activity still revolves around late transition metal-based catalysts, which are limited by unfavorable scaling relations despite intense investigation. Here, we report a combined experimental and theoretical investigation into electrocatalytic CORR on Ti- and Mo-based MXene catalysts. Formic acid is found as the main product on TiCT and MoCT MXenes, with peak Faradaic efficiency of over 56% on TiCT and partial current density of up to -2.5 mA cm on MoCT. Furthermore, simulations reveal the critical role of the T group: a smaller overpotential is found to occur at lower amounts of -F termination. This work represents an important step toward experimental demonstration of MXenes for more complex electrocatalytic reactions in the future.