Lewis–Brønsted Dual-Acid Sites Induced H-Down Interfacial Water Configuration and Accelerated Proton Transfer toward Enhanced Acidic Oxygen Evolution

Abstract

Efficient activation of interfacial water molecules and fast proton transfer are critical but challenging for the acidic oxygen evolution reaction (OER). Herein, a Lewis–Brønsted dual-acid catalyst design strategy is proposed to achieve accelerated acidic OER by synergistically optimizing the configuration of interfacial water molecules and proton transfer kinetics on Mn-doped IrO2. In this catalyst, the Mn dopant serves as a Lewis acid site that readily captures hydroxyl groups, which perturbs the local hydrogen-bonding network and induces interfacial water molecules to form an H-down configuration toward surface active sites, thereby promoting the enrichment and dissociation of reactive interfacial water. On this basis, the formation of the Mn–Obri–Ir local structure enhances the Brønsted acidity of the bridge oxygen (Obri) site, accelerates the deprotonation of the Obri–H bond, promotes the formation of key OER intermediates and accelerates the reaction kinetics. Mn dopant also induces electron enrichment around Ir, suppresses excessive oxidation and dissolution of Ir species, and enhances catalyst stability performance. These synergistic effects enable Mn-IrO2 to achieve a 160 mV overpotential at 10 mA cm–2 and to operate stably for 1500 h at 10 mA cm–2 and 1200 h at 1.0 A cm–2 in proton exchange membrane water electrolysis (PEMWE), demonstrating the promising potential of the Lewis–Brønsted dual-acid strategy in acidic OER catalyst design.