Hexagonal Defect‐Rich MnOx/RuO2 with Abundant Heterointerface to Modulate Electronic Structure for Acidic Oxygen Evolution Reaction

Abstract Developing green hydrogen energy to power future societies has driven the progress of proton‐exchange membrane water electrolyzers (PEMWE). However, due to the complex anode oxygen evolution reaction (OER) electron transfer process and the strong acidic environment, the most effective catalysts are still Ir‐based nanomaterials. Therefore, exploiting low cost acidic OER catalysts to meet the needs of PEMWE remains a challenging and rewarding task. Herein, hexagonal‐shaped and defect‐rich MnO x /RuO 2 heterojunction nanosheets (H/d‐MnO x /RuO 2 ) is designed. The oxygen vacancies and heterogeneous structure enable the H/d‐MnO x /RuO 2 catalyst to reach 10 mA cm −2 with only overpotential 178 mV in 0.5 m H 2 SO 4 . Density functional theory shows that the oxygen vacancies and heterogeneous interface facilitates the reduction of the adsorption energy of *OOH and the reduction of the energy level of Ru‐Oads, thus suppressing the involvement of lattice oxygen and enhancing the durability. This study provides an effective way to design efficient catalysts for hydrogen production in PEMWE.