IrO(x)nH(2)O with lattice water-assisted oxygen exchange for high-performance proton exchange membrane water electrolyzers

The trade-off between activity and stability of oxygen evolution reaction (OER) catalysts in proton exchange membrane water electrolyzer (PEMWE) is challenging. Crystalline IrO2 displays good stability but exhibits poor activity; amorphous IrOx exhibits outstanding activity while sacrificing stability. Here, we combine the advantages of these two materials via a lattice water-incorporated iridium oxide (IrOx center dot nH(2)O) that has short-range ordered structure of hollandite-like framework. We confirm that IrOx center dot nH(2)O exhibits boosted activity and ultrahigh stability of >5700 hours (similar to 8 months) with a record-high stability number of 1.9 x 10(7) noxygen nIr(-1). We evidence that lattice water is active oxygen species in sustainable and rapid oxygen exchange. The lattice water-assisted modified OER mechanism contributes to improved activity and concurrent stability with no apparent structural degradation, which is different to the conventional adsorbate evolution mechanism and lattice oxygen mechanism. We demonstrate that a high-performance PEMWE with IrOx center dot nH(2)O as anode electrocatalyst delivers a cell voltage of 1.77 V at 1 A cm(-2) for 600 hours (60 degrees C).

Automated summary

The trade-off between activity and stability of oxygen evolution reaction (OER) catalysts in proton exchange membrane water electrolyzer (PEMWE) is challenging. We combine the advantages of crystalline IrO2 and amorphous IrOx to form a lattice water-incorporated iridium oxide (IrOx center dot nH(2)O) with a hollandite-like framework structure. This material exhibits boosted activity and ultrahigh stability, with a stability number of 1.9 x 10^7 noxygen nIr^-1. The lattice water-assisted modified OER mechanism contributes to improved activity and concurrent stability in the PEMWE.