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.

Keywords

• Transition metal carbides
• CO2 capture and conversion
• M2C catalyst
• DFT