M2C-type MXenes: Promising catalysts for CO2 capture and reduction

Novel catalysts for carbon dioxide (CO2) reduction into specific energy -rich products with great activity and selectivity is highly desired, which is closely related to the adsorption ability of substrate with specific inter- mediates and/or products. In this work, via first principles calculations we have extensively studied the prop- erties of two-dimensional transition metal carbides (MXenes) for efficient CO2 capture and reduction. Our results suggest that all the investigated MXenes exhibit excellent CO2 capture abilities, which are demonstrated to be originated from the surface lone pair electrons of MXenes and can be described via the effective charge numbers of their transition metal atoms. Then we highlight that the activated CO2 can be selectively reduced to methane (CH4) with a moderate limiting step, where the Mo2C MXene exhibit higher catalytic efficiency than the other MXenes. Further analysis on transition states confirms that the largest energy demand during CO2 reduction happens on the surface regeneration of Mo2C MXene, which is critical to realize sustainable catalytic activity. The stability of Mo2C MXene has been confirmed via phonon dispersion and ab initio molecular dynamics si- mulations. Our findings pave the way of MXenes for CO2 capture and pioneer the application of Mo2C MXene as novel CO2 reduction catalyst.