Coupled reaction pathways and microenvironment engineering in IrOx/Nb2O5 for efficient water electrolysis

Recent efforts in proton-exchange membrane water electrolysis (PEMWE) focus on developing superior catalysts and membrane electrode assemblies (MEAs) to achieve efficient expression of performance low-IrO x -loaded PEMWE systems. Herein, we report an infusive result that, through anchoring amorphous IrO x clusters onto Nb 2 O 5 support, we were able to switch the reaction pathway and optimize the MEA microenvironment. Specifically, the near-ideal Ir–Ir atomic configuration and the strong coupling strength of the *O and *OH species on adjacent iridium atoms in IrO x /Nb 2 O 5 facilitate direct O*–O* radical coupling to form an intermediate O*–O*–Ir configuration during acidic OER without generating OOH* species. This configuration significantly enhances the OER Ir mass activity from 23.1 to 424.2 A g Ir −1 at 1.5 V, while reducing the overpotential (@10 mA cm −2 ) from 339 to below 190 mV compared to IrO 2 . Furthermore, the IrO x /Nb 2 O 5 catalyst also addresses the electron and proton transport issues in low-Ir-loaded MEA, through tuning the band structure and wettability of the low-Ir-loaded catalyst layer and Ti porous transport layer interface. The resulting catalysts achieve ultra-low overpotentials in a PEMWE system, with cell voltages of 1.57 and 1.83 V at current densities of 1 and 3 A cm −2 and stable operation under industrial conditions for 1000 h.