High Mass Activity of Co-Sputtered Ir−Ru Thin Films on TiC for Acidic Oxygen Evolution Reaction

Abstract Reducing the precious metal loading while maintaining high activity remains a main challenge for acidic oxygen evolution reaction (OER) anodes in proton exchange membrane water electrolysis. Herein, we report ultralow-loading, uniformly dispersed Ir−Ru thin-film electrodes fabricated via precursor-free physical vapor deposition (PVD) on conductive TiC substrates. By employing RF magnetron cosputtering, we prepared ultrathin (∼3 nm) composition-controlled Ir−Ru films with a total platinum group metal (PGM) loading of ∼4 μg cm−2, achieving uniform dispersion that overcomes the limitations of conventional solution-based methods. In addition, the TiC substrate improved the activity−stability factor of the Ir−Ru films, possibly by mitigating excessive surface oxidation and lattice-oxygen-associated degradation. As a result, the cosputtered Ir69Ru31 thin-film electrode delivers extraordinary mass activities of 3.11 and 23.5 A mgPGM−1 at 1.53 and 1.70 V vs RHE, respectively, exceeding conventional Ir-based benchmarks by over two orders of magnitude. These results demonstrate that PVD-derived thin films can serve as a scalable platform for improving precious-metal utilization in acidic OER.