Sr-Stabilized IrMnO₂ Solid Solution Nano-Electrocatalysts with Superior Activity and Excellent Durability for Oxygen Evolution Reaction in Acid Media

The development of cost-effective catalysts for oxygen evolution reaction (OER) in acidic media is of paramount importance. This work reports that Sr-doped solid solution structural ultrafine IrMnO₂ nanoparticles (NPs) (≈1.56 nm) on the carbon nanotubes (Sr-IrMnO₂/CNTs) are efficient catalysts for the acidic OER. Even with the Ir use dosage 3.5 times lower than that of the commercial IrO₂, the Sr-IrMnO₂/CNTs only need an overpotential of 236.0 mV to drive 10.0 mA cm⁻² and show outstanding stability for >400.0 h. Its Ir mass activity is 39.6 times higher than that of the IrO₂ at 1.53 V. The solid solution and Sr-doping structure of Sr-IrMnO₂ are the main origin of the high catalytic activity and excellent stability of the Sr-IrMnO₂/CNTs. The density function theory calculations indicate that the solid solution structure can promote strong electronic coupling between Ir and Mn, lowering the energy barrier of the OER rate-determining step. The Sr-doping can enhance the stability of Ir against the chemical corrosion and demetallation. Water electrolyzers and proton exchange membrane water electrolyzers assembled with the Sr-IrMnO₂/CNTs show superb performance and excellent durability in the acid media.