Passivation Engineering toward Integrated Acidic Oxygen Evolution Electrodes with Stable Catalytic Activity for over 3000 h

Acidic oxygen evolution electrodes are essential anodes in acidic water splitting, carbon dioxide, nitrogen electrochemical reduction, etc. The iridium–ruthenium (Ir–Ru)-based catalysts have the potential to withstand the harsh acid corrosion and oxidation environments of the oxygen evolution reaction, but there are still challenges in designing and preparing highly active and stable integrated Ir–Ru electrodes. Herein, we develop a cost-effective and scaled-up passivation engineering strategy to prepare an integrated Ir–Ru anode containing a Ti substrate, a manganese titanate (MnTiO3) passivation layer, and an Ir–Ru oxide catalytic layer. By uniformly loading an appropriate amount of divalent Mn ions (Mn2+) on the surface of zerovalent Ti metal (Ti0) and heating to 350 °C in air, a special passivation reaction occurred between Mn2+ and Ti0, producing a dense MnTiO3 passivation layer. The conductive MnTiO3 passivation layer forms a strongly bonded interface with the Ti substrate, effectively protecting the Ti substrate from electrochemical oxidation to insulating TiO2. Then, on the surface of MnTiO3, a thin layer of complex ions of Ir and Ru is uniformly adsorbed, and after secondary heat treatment, Ir–Ru mixed oxides are generated. Interestingly, the lattice of MnTiO3 perfectly matches that of Ir and Ru oxides, thus achieving the epitaxial growth of Ir–Ru mixed oxides on the surface of MnTiO3 with strong interaction interfaces. These result in the high activity and stability of low-loading Ir–Ru oxides, with an overpotential of only 165 mV at 10 mA cm–2 and over 3000 h of stable operation at 300 mA cm–2 in acidic electrolytes. In situ Raman spectroscopy combined with isotope labeling experiments further confirms that the Ir–O–Ru local structure suppresses the participation of lattice oxygen and enhances the stability of active Ru species.