Unlocking the catalytic potential of iMXenes: selective electrochemical CO2 reduction for methane production

Abstract

Electrochemical CO₂ reduction (CO₂RR) has emerged as a pivotal technology for mitigating climate change by converting CO₂ into valuable chemicals. This study investigates the catalytic potential of various iMXenes for the CO₂RR, focusing on their electronic and structural properties, and their efficacy in producing methane (CH₄) and other hydrocarbons. Using first-principles, density functional theory (DFT) and climbing image nudged elastic band (CI-NEB) calculations, we systematically evaluate the performance of both bare and O-terminated in-plane ordered MXenes (iMXenes). Our results reveal that the electronic structure and surface terminations significantly influence the catalytic activity. O-terminated iMXenes exhibit enhanced CO₂ activation and more favorable reaction pathways compared to their bare counterparts. The oxygen passivation enhances the interaction between the surface and reactant molecules, optimizes adsorption energies, and facilitates easier surface reconstruction, particularly in the later stages of the reaction. Notably, specific iMXenes (MoScO₂) show high selectivity and efficiency towards CH₄ production, outperforming many traditional catalysts. The kinetic stability of MoScO₂ is supported using ab initio molecular dynamics simulations based on the machine learning potential generated through on-the-fly sampling combined with the sparse Gaussian regression algorithm. By leveraging scaling relations based on OH* adsorption energy and limiting potential, we simplified the catalyst screening process, and weaker OH* adsorption indicates a higher likelihood of efficient CO₂RR. This comprehensive study not only elucidates the fundamental mechanisms and synergetic effects of bimetals underlying the CO₂RR on iMXenes but also provides actionable insights for the design of advanced catalysts.