Coverage-Induced Cation Dehydration and Migration for Enhanced CO-CO Coupling on Cu Electrocatalysts

Copper is a promising catalyst for the electroreduction of CO2/CO (CO2RR/CORR) to valuable multicarbon products, but the origin of its CO-CO coupling activity remains unresolved. This greatly limits the rational design and practical application of copper-based catalysts. Herein, we have performed extensive ab initio molecular dynamics simulations with explicit solvation to investigate the free energy profile of CO-CO coupling at the complex electrochemical interface and discovered the critical role of the interplay between the alkali metal cation and CO intermediates. We have found that due to the hydrophobicity of CO, the solvated alkali metal cation (Li+, Na+, K+, or Cs+) in the electric double layer (EDL) could dynamically dehydrate and migrate toward the copper surface as the CO coverage increases. The closer-to-surface dehydrated alkali metal cation can significantly promote CO-CO coupling by stabilizing the largely polarized transition state. Notably, once CO-CO coupling is completed, the cation can be released from the product state to participate in the next catalytic cycle. The adaptive coordination environment of the alkali metal cation to the reaction coordinate makes a dynamic local environment which promotes CO-CO coupling both kinetically and thermodynamically. Our obtained insight into the dynamic process unravels the significant role of alkali metal cations and provides a perspective to understand how C-2 products are generated at the complex electrochemical interface during the CO2RR/CORR.