Understanding of Electrochemical Mechanisms for CO₂ Capture and Conversion into Hydrocarbon Fuels in Transition-Metal Carbides (MXenes)

Two-dimensional (2D) transition-metal (groups IV, V, VI) carbides (MXenes) with formulas M₃C₂ have been investigated as CO₂ conversion catalysts with well-resolved density functional theory calculations. While MXenes from the group IV to VI series have demonstrated an active behavior for the capture of CO₂, the Cr₃C₂ and Mo₃C₂ MXenes exhibit the most promising CO₂ to CH₄ selective conversion capabilities. Our results predicted the formation of OCHO^• and HOCO^• radical species in the early hydrogenation steps through spontaneous reactions. This provides atomic level insights into the computer-aided screening for high-performance catalysts and the understanding of electrochemical mechanisms for CO₂ reduction to energy-rich hydrocarbon fuels, which is of fundamental significance to elucidate the elementary steps for CO₂ fixation.