Revealing the Molecular Interplay of Coverage, Wettability, and Capacitive Response at the Pt(111)-Water Solution Interface under Bias

Abstract While electrified interfaces are crucial for electrocatalysis and corrosion, their molecular morphology remains largely unknown. Through highly realistic ab-initio molecular dynamics simulations of the Pt(111)-water solution interface in reducing conditions, we reveal a deep interconnection among electrode coverage, wettability, capacitive response, and catalytic activity. We identify computationally for the first time the experimentally hypothesised states for adsorbed hydrogen on Pt, HUPD and HUPD, revealing their role in governing interfacial water reorientation and hydrogen evolution. The transition between these two H coverage regimes with increasing potential, induces a shift from a hydrophobic to a hydrophilic interface and correlates with a change in the primary electrode screening mechanism. This results in a slope change in differential capacitance, marking the onset of the experimentally observed peak around the potential of zero charge. Our work produces crucial insights for advancing electrocatalytic energy conversion, developing deep understanding of electrified interfaces.