A theoretical and experimental study on CO 2 reduction selectivity of Mo 2 CT x MXene catalysts: Influence of surface termination

Understanding the relationship between CO2 reduction reaction (CO2RR) performance and surface terminations of MXenes is crucial for designing effective electrocatalysts. This study explores the impact of common terminations on Mo2CTx using a Computational Hydrogen Electrode (CHE) model integrated with a pseudo-Microkinetic Model (pseudo-MM). Unlike traditional CHE methods, CHE/pseudo-MM considers the energy differences of all steps, providing a comprehensive view of CO2RR mechanisms while reducing computational cost generated from calculating transitional state. The electrolyte is considered as acetonitrile with EMIMBF4 to inhibit the generation of hydrogen. Theoretical predictions reveal surface terminations dictate the selectivity of C1 products, whose proton is provided by EMIMBF4. The selectivity for fully -F, -O- and -OH-terminated Mo2CTx surfaces vary with the applied potential, as confirmed by experiments. Electrochemical CO2RR in acetonitrile with EMIMBF4 electrolyte confirm these predictions, showing that CH4 outperforms CO and gradually becomes the dominant product as the applied potential increases. These findings demonstrate the qualitative accuracy of the proposed CHE/pseudo-MM for predicting CO2RR selectivity, particularly for gaseous products, over Mo2CTx systems.