Electrochemical Formation of a MnO 2 Nanoshield on Ru-Doped Mn 3 O 4 for Ultrastable Acidic Oxygen Evolution Catalysis

Proton exchange membrane (PEM) water electrolysis is a promising strategy for large-scale hydrogen production; however, its industrial feasibility is hampered by the lack of highly active and durable oxygen evolution reaction (OER) catalysts in acidic environments. Ru-based catalysts offer high intrinsic activity but are susceptible to dissolution and structural degradation. To address this, this study proposes an electrically induced “nanoshield” strategy. A Ru single atom-doped Mn 3 O 4 (Ru–Mn 3 O 4 ) catalyst enables the in situ spontaneous reconstruction of the catalyst surface structure. Under an electric field, Mn 3 O 4 crystals undergo interlayer slip and polarization rotation, inducing the growth of a porous MnO 2 nanoshield on the catalyst surface, that effectively inhibits the dissolution of Ru active sites without compromising reaction activity. The catalyst exhibits excellent OER performance, delivering 10 mA cm geo –2 at an overpotential of only 176 mV in 0.5 M H 2 SO 4, and remains stable for over a year (8800 h) at a current density of 50 mA cm geo –2 . The PEM electrolyzer based on Ru–Mn 3 O 4 shows a decay rate of 0.15 mV h –1 at 1000 mA cm geo –2 and only 0.06 mV h –1 at 500 mA cm geo –2, outperforming commercial RuO 2 . This study provides a new path for the construction of high-performance acidic OER catalysts and demonstrates the great potential of the nanoshield strategy in electrocatalytic structural protection.