Mechanistic insights for electrochemical reduction of CO2 into hydrocarbon fuels over O-terminated MXenes

Abstract

Two-dimensional (2D) transition metal carbides/nitrides (MXenes) have attracted intensive attention for the electrochemical reduction of CO₂ into renewable fuels and chemical feedstock. Although encouraging progress has been made so far, many advances are still needed to understand and clarify the CO₂RR mechanism over functionalized MXenes. In this regard, we present the promising selective conversion capabilities of group IV (Ti₂X and Zr₂X; X = C, N or B) MXenes with O-termination for catalyzing the carbon dioxide reduction reaction (CO₂RR) to methane (CH₄). The unique CO₂RR behavior observed on O-terminated MXenes is mainly due to the choice of *HCOOH pathway, where the majority of electrocatalytic CO₂ reductions prefer the ubiquitous *CO intermediates. The proposed reliable scaling relationships demonstrate better coordination between the reaction intermediates and binding energies of *COOH/*HCOOH, thereby indicating its importance as a key descriptor to assess the catalytic performance of O-terminated MXenes. The catalytic selectivity for the CO₂RR is higher than HER, indicating that the selectivity between them is crucial and depends on the efficiency of the catalyst. Our theoretical findings provide useful insight and opportunities to develop advanced MXene based catalysts for electrochemical CO₂ reduction into valuable chemicals and fuels.