Hydrogen-Induced Restructuring of a Cu(100) Electrode in Electroreduction Conditions

The rearrangement of Cu surfaces under electrochemical conditions has been demonstrated to play a key role in the surface activation for major electrocatalytic reactions. Despite the extensive experimental insights from surface-sensitive spectroscopic and microscopic methods, their spatial and temporal resolution are far from ideal. Theoretical investigations have also been challenged by the diversity of restructuring configurations, surface stoichiometry, adsorbate configurations, and the effect of electrode potential. Here, we tackle this complexity of the electrochemical interface by grand canonical DFT and global optimization techniques, which explore the chemical space of Cu(100) restructuring with varying applied potential and adsorbate coverage from first principles. We show that electroreduction conditions cause the formation of a shifted-row reconstruction on Cu(100), induced by hydrogen adsorption. The simulated STM images of the calculated reconstructed structures agree with experimental in situ STM images, which validates our results. The found shifted-row reconstruction is initiated and stabilized 1/6 ML H coverage since this weakens the Cu-Cu bonds between top- and sub-layer and at 1/3 ML fills all the created 3-fold hollow sites with H adsorbates. Different statistical models are used to study the potential- and pH-dependence of the surface stability diagram. The kinetics and dynamics of surface atoms are studied with BOMD simulations, and their dependence on H coverage and initial configuration is discussed. This manuscript provides rich insight into surface restructuring in electroreduction conditions, which is required for the understanding and rational design of Cu-based materials for electrocatalytic processes and beyond.