Photocatalytic and electrocatalytic reduction of CO2 by MXene-based nanomaterials: A review

Recently, transition metal carbide or nitride (MXene)-based nanomaterials have been broadly investigated as new photocatalysts and electrocatalysts for the reduction of CO2 into valuable energy-rich fuels due to their unique properties such as rich surface chemistries, flexible morphologies, bandgap structures, considerable electrical conductivities, thermal stabilities, and significant specific surface areas. Nevertheless, only a few reviews have been reported on the application of MXenes or MXene-based nanomaterials as advanced photocatalysts and/or electrocatalysts for CO2 reduction, which do not cover new findings and the current development in the application of MXene-based nanomaterials for CO2 reduction. Accordingly, herein, we present a comprehensive review of current findings on the photocatalytic and electrocatalytic reduction of CO2 by various MXene-based nanomaterials. Particularly, this review focuses on the (i) photocatalytic reduction of CO2 by functionalized Ti3C2, TiO2/Ti3C2, g-C3N4/Ti3C2, and other/Ti3C2 catalysts, (ii) electrocatalytic CO2 reduction; (iii) CO2 reduction associated with photothermal catalysis and hydrogenation, and (iv) stability of MXene-based photoelectrocatalysts. Additionally, we have briefly explored the challenges in the large-scale fabrication of MXene-based nanomaterials and proposed the future research prospects of MXene-based nanomaterials.