Lanthanum-Induced MnO₂/Mn₂O₃ Dual-Phase Heterostructure for Efficient and Stable Acidic Oxygen Evolution

The development of low-cost, highly active, and durable nonprecious metal acid oxygen evolution reaction (OER) electrocatalysts is a key bottleneck for the large-scale commercialization of proton exchange membrane water electrolyzers. Despite the promising prospects of manganese (Mn)-based oxides, they face a severe "activity-stability" trade-off due to the high solubility of highly active Mn³⁺ species in acidic media. This article reports a simple one-step heating strategy that successfully synthesized lanthanum (La)-doped MnO₂/ Mn₂O₃ on carbon cloth. The introduction of large-radius La³⁺ ions induced significant lattice distortion and charge compensation, successfully enriching the active Mn³⁺ species and generating abundant oxygen vacancies. The leaching of unstable La triggered in situ deep hydroxylation, forming a dense passivation layer. This restructured surface not only facilitates rapid proton transport but also provides significant protection for the internal framework against acid corrosion. As a result, the optimized La3-MnO_X catalyst exhibits outstanding acidic OER performance, with an overpotential of only 294 mV at a current density of 10 mA/cm², and maintains stability for over 110 h in 0.5 M H₂SO₄. This study proposes a novel rare-earth-element-inducing strategy for the design of high-performance electrocatalysts for OER.