Electrochemical conversion of CO2 to fuel by MXenes (M2C): A first principles study

Abstract

Herein we have made a comprehensive analysis for the conversion of CO₂ to fuel (CH₄) on two dimensional MXenes (M=Mo, Hf) of the type M₂C. Evaluation of parameters like Mulliken charge, adsorption energy, bond angle and bond distance demonstrated that activation is more pronounced with Hf₂C compared to Mo₂C due to transfer of higher electron density to CO₂ in the former than in the latter case. CO₂ adsorbed M₂C realizes large shift of valance and conduction band vis-a-vis free M₂C, leading to substantial charge transfer from MXenes. The enhanced activation of CO₂ over Hf₂C has been confirmed from the increased splitting of π and π* energy level of CO₂ for Hf₂C compared to Mo₂C. The dense electron localization contour maps further explained the ease of electron transfer to CO₂ involving Hf₂C. Analysis of Gibbs free energy for successive steps for the conversion of CO₂ to CH₄ revealed that fuel conversion is more feasible with Hf₂C over Mo₂C.