Two-Dimensional Titanium and Molybdenum Carbide MXenes as Electrocatalysts for CO₂ Reduction

Electrocatalytic CO₂ reduction reaction (CO₂RR) is an attractive way to produce renewable fuel and chemical feedstock, especially when coupled with efficient CO₂ capture and clean energy sources. On the fundamental side, research on improving CO₂RR 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 CO₂RR on Ti- and Mo-based MXene catalysts. Formic acid is found as the main product on Ti₂CT_x and Mo₂CT_x MXenes, with peak Faradaic efficiency of over 56% on Ti₂CT_x and partial current density of up to -2.5 mA cm^-2 on Mo₂CT_x. Furthermore, simulations reveal the critical role of the T_x 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.