Negative-Valent Palladium-Stabilized CoPdN Thin Films as a Catalyst for the Oxygen Evolution Reaction

The urgent global demand for sustainable energy drives the search for durable and efficient electrocatalysts for water splitting. Cobalt mononitride (CoN) stands out due to its earth abundance, high conductivity, and corrosion resistance, but its thermodynamic instability often results in cobalt-rich secondary phases. Here, we report a scalable reactive cosputtering approach for the controlled synthesis of CoN thin films, along with palladium (Pd) incorporation to enhance activity and stability. Pd doping induces a negative valence state and promotes electron transfer from nitrogen to Pd sites, thereby refining the microstructure, redistributing charge, and shifting the d-band center away from the Fermi level. These synergistic effects reduce the overpotential from 470 to 360 mV at 10 mA·cm–2 in a sample coated on the ITO substrate and deliver markedly improved long-term OER stability with increased catalytically active sites. The turnover frequency showed nearly twice the intrinsic activity with Pd doping. This work establishes Pd-doped CoN as a high-performance, durable electrocatalyst, offering a scalable pathway toward efficient water splitting technologies.