Iridium Oxide Supported on Bimetallic Nitrides as Anodic Catalysts in Acidic and Seawater Environments

The oxygen evolution reaction (OER) remains the principal bottleneck in electrochemical water splitting, particularly under acidic and seawater-relevant conditions where gains in the OER activity often compromise stability and selectivity. Overcoming this trade-off requires catalyst architectures that simultaneously enhance kinetics, durability, and OER selectivity. To address these challenges, we developed IrO x supported on monometallic TiN and bimetallic TiTaN and TiZrN as tunable platforms for selective and durable OER catalysis in 0.1 M HClO 4 and 0.6 M NaCl electrolytes. In acidic media, IrO x /TiZrN achieves 10 mA cm −2 at an overpotential of 280 mV vs RHE and exhibits stable operation for more than 100 h, outperforming commercial IrO 2 (C-IrO 2 ) and IrO x /TiN. Similar advantages extend to seawater-relevant conditions, with IrO x /TiZrN achieving a mass activity of 485 A g Ir −1 at 1.80 V vs RHE, compared to 193 A g Ir −1 for C-IrO 2, and demonstrating higher stability numbers that indicate suppressed Ir dissolution. At 1.85 V vs RHE, the Faradaic efficiency toward O 2 increases from 25% for C-IrO 2 to 62% for IrO x /TiZrN, consistent with in situ surface-enhanced Raman spectroscopy (SERS) measurements, which reveal a delayed onset of vibrational modes associated with chlorine-related intermediates (ν(Cl−Cl) and ν(O−Cl)). Density functional theory calculations show that Ta or Zr incorporation into TiN induces tensile strain, tuning adsorption energetics of key intermediates to favor OER over chlorine species evolution, consistent with the experimental observations. Together, these results illustrate a catalyst design strategy that enhances activity, stability, and oxygen selectivity in acidic and seawater electrolysis.