Rutile (IrTaSnReMn)Oₓ high-entropy oxide anode for durable acidic oxygen evolution toward water electrolysis

A durable low-Ir anode catalyst is required for efficient acidic oxygen evolution reaction (OER) in proton-exchange membrane water electrolysis. Here, a Ti-supported entropy-stabilized rutile (IrTaSnReMn)Oₓ high-entropy solid solution was fabricated by a thermal decomposition route. The near-equimolar multication design stabilizes a rutile-type oxide framework, modulates Ir local coordination, and creates Ir-M bridge environments. In 0.5 M H₂SO₄, the optimized (IrTaSnReMn)Oₓ electrode requires an overpotential of 160 mV to reach 10 mA cm⁻² and exhibits a Tafel slope of 25.53 mV dec⁻¹ . It also maintains stable operation at 200 mA cm⁻² for 500 h, while post-stability inductively coupled plasma mass spectrometry (ICP-MS) detects only trace Ir dissolution. Electrochemical active surface area (ECSA) normalized activity, Ir mass activity, and turnover frequency ( TOF ) analyses further indicate enhanced intrinsic activity and improved Ir utilization compared with IrO₂ and lower-component control oxides. Structural and spectroscopic analyses show homogeneous incorporation of Ir, Ta, Sn, Re, and Mn into a rutile-type multicomponent oxide and reveal modified Ir-O-M coordination. The density functional theory (DFT) calculations comparing different bridge configurations identify the Ir-Mn bridge as the most favorable site for balancing oxygen-intermediate adsorption and lowering the potential-determining step. This work provides a structure-guided strategy for designing low-Ir multicomponent rutile oxides for durable acidic water oxidation.