Optimization of Interfacial OH− Accessibility by Constructing a Delayed–Release Membrane Electrode for Ampere–Level Hydrogen Production

Abstract Achieving a high current density during electrochemical overall water splitting is a promising strategy for industrial energy conversion. The mass diffusion rate of OH − ions from the electrolyte to the interfacial active sites strongly influences the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) . Herein, the delayed‐release of OH − ions modulated by a proper organic polymer membrane on the electrode surface can optimize the OH − accessibility to the active sites (as indicated by the molecular dynamics simulations) is demonstrated and that van der Waals interaction force modulates the OH − residence time in the reaction system. The remarkable performance of the membrane‐modified electrode is achieved at ultra‐high current densities of 1.9 A cm −2 (with an HER overpotential of 602 mV) and 2 A cm −2 (with an OER overpotential of 459 mV) in 1 M KOH solution. Consequently, a super‐high current density of 1.3 A cm −2 is obtained for overall water splitting (at a voltage of only 2.2 V), which is 1.9‐fold higher than that of a benchmarked Pt/C‐IrO 2 (684 mA cm −2 ). Therefore, the delayed‐release of OH − has optimized the mass conversion efficiency of the active sites, thus improving the electrochemical performance of overall water splitting.