B‐Doped Manganese Dioxide Achieves Synchronous Multi‐Scale Structural Regulation for Enhanced Oxygen Evolution Reaction Electrocatalytic Performance

Manganese dioxide (MnO 2 ), as a promising electrocatalyst for the oxygen evolution reaction (OER), is limited in practical application by its poor electrical conductivity and insufficient exposure of active sites. In this study, a boron (B) doping strategy is proposed, in which ammonium pentaborate tetrahydrate (NH 4 B 5 O 8 ·4H 2 O) is introduced during a hydrothermal process to synthesize α‐MnO 2 with a nanoneedle‐like structure rich in oxygen vacancies (O V ) and Mn 3+ content. Systematic characterization combined with density functional theory calculations reveals that B doping not only induces a crystal‐phase transition from β‐MnO 2 to α‐MnO 2 possessing a large‐tunnel structure, accompanied by the formation of a high‐surface‐area nanoneedle morphology, but also promotes the generation of O V and significantly increases the Mn 3+ content. Electrochemical tests show that the optimized B‐doped MnO 2 requires an overpotential of only 411 mV to achieve a current density of 10 mA cm −2 in 1 M KOH electrolyte. Its OER performance surpasses that of most reported powder‐based MnO 2 catalysts and demonstrates good stability.