Decoupling charge and ion transport in oxygen evolution reaction through surface hydration engineering of molecular graphene catalysts

Abstract

Interfacial microenvironments play a critical role in regulating the kinetics and stability of the oxygen evolution reaction (OER), yet their dynamic effects remain poorly understood. Herein, we developed a molecularly defined catalyst platform to systematically investigate the influence of surface hydration layers on OER activity. A hydrazinecarbonylferrocene-functionalized nitrogen-doped graphene (HFc-NG) electrocatalyst was synthesized and subsequently coated with a polyvinyl alcohol (PVA)-derived hydrogel layer to form HFc-NG-OH, enabling a direct comparison between hydrated and non-hydrated interfaces. Electrochemical measurements revealed that HFc-NG-OH exhibits significantly enhanced OER performance, characterized by lower overpotentials, reduced Tafel slopes, and improved long-term stability under both alkaline and neutral conditions. Redox probe analysis and electrochemical impedance spectroscopy indicated that the hydration layer facilitates inner-sphere electron transfer and ion transport through hydrogen-bonded networks. In situ ATR-FTIR spectroscopy further confirmed accelerated formation and stabilization of key OER intermediates at the hydrated interface. This work underscores the dual functionality of hydration layers in modulating interfacial charge dynamics and intermediate evolution, offering valuable insights into surface hydration engineering for advanced electrocatalysis.