IrO2/MnO2 metal oxide-support interaction enables robust acidic water oxidation

Abstract

The sluggish kinetics, poor stability, and high iridium loading in acidic oxygen evolution reaction (OER) present significant challenges for proton exchange membrane water electrolyzers (PEMWE). While supported catalysts can enhance the utilization and activity of Ir atoms, they often fail to mitigate the detrimental effects of over-oxidation and dissolution of Ir. Here, we leverage the redox properties of the Mn³⁺/Mn⁴⁺ couple as electronic modulators to develop a low-iridium, durable electrocatalyst for acidic OER. Specifically, IrO₂ nanoparticles are anchored onto MnO₂ nanowires (denoted as IrO₂/MnO₂), through a molten salt-assisted synthesis method. This optimized IrO₂/MnO₂ electrocatalyst features a substantially reduced iridium content and enhanced electronic structure due to strong metal-support interactions. Remarkably, the IrO₂/MnO₂ catalyst demonstrates 7-fold increase in intrinsic activity and superior durability compared to commercial IrO₂. Both theoretical and experimental results indicate that dynamic electron transfer between Ir and Mn facilitates the rapid formation of highly oxidized iridium sites while simultaneously preventing excessive oxidation, thereby enhancing both the kinetics and stability for OER. A PEMWE utilizing IrO₂/MnO₂ as the anode catalyst achieves 2000 mA cm⁻² @ 1.89 V without requiring supporting acidic electrolyte. Importantly, the PEMWE exhibits negligible degradation under harsh industrial operating conditions (1000 mA cm⁻²) with an Ir loading as low as 0.5 mg cm⁻², while maintaining a low energy consumption of 45.58 kWh kg⁻¹ H_2, corresponding to the green hydrogen production cost of $0.9 kg⁻¹ H₂, significantly lower than the 2026 US-DOE target, underscoring its potential for practical application.