Unravelling the Effects of Anions on the Vicinal H-Bonding Network near an Electrode and Activity of Single-Atom Electrocatalysts

While extensive research has been devoted to studying the electrochemical performance of single-atom catalysts (SACs), the impact of electrolyte anions on their electrochemical activity remains largely unexplored. We performed multiscale molecular dynamics (MD) simulations to examine how anions affect the vicinal hydrogen-bonding network and associated water dissociation dynamics at the SAC electrode/electrolyte interface. Constant-potential MD simulations demonstrate the presence of two distinct hydrogen bond gap regions at the interface and that hydrogen bond connectivity may be highly sensitive to the anion type and electrode potential. In particular, at the interface, differences in anion adsorption strength can lead to opposite trends in hydrogen bond connectivity. Another key insight obtained from ab initio MD simulations is that anions act as active modulators rather than passive bystanders. Nonspecific anion adsorption tends to modulate water activation due to the asymmetry in the local hydrogen-bonding environment. Overall, molecular-level insights into the effects of anions at the SAC electrode/electrolyte interface will lead to new electrolyte engineering strategies to optimize electrochemical performance.