A theoretical and experimental study on CO <sub>2</sub> reduction selectivity of Mo <sub>2</sub> CT <sub> <i>x</i> </sub> MXene catalysts: Influence of surface termination
Caihong Liang, Zhonghan Zhang, Teddy Salim, Zhihao Yen, Daniel Yongyi Goh, Lydia Helena Wong, Zheng Liu, Liang Wang, Yeng Ming Lam
Abstract
Understanding the relationship between CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR) performance and surface terminations of MXenes is crucial for designing effective electrocatalysts. This study explores the impact of common terminations on Mo<sub>2</sub>CT<sub>x</sub> 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 CO<sub>2</sub>RR mechanisms while reducing computational cost generated from calculating transitional state. The electrolyte is considered as acetonitrile with EMIMBF<sub>4 </sub>to inhibit the generation of hydrogen. Theoretical predictions reveal surface terminations dictate the selectivity of C<sub>1</sub> products, whose proton is provided by EMIMBF<sub>4</sub>. The selectivity for fully -F, -O- and -OH-terminated Mo<sub>2</sub>CT<sub>x</sub> surfaces vary with the applied potential, as confirmed by experiments. Electrochemical CO<sub>2</sub>RR in acetonitrile with EMIMBF<sub>4</sub> electrolyte confirm these predictions, showing that CH<sub>4</sub> 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 CO<sub>2</sub>RR selectivity, particularly for gaseous products, over Mo<sub>2</sub>CT<sub>x</sub> systems.