Boosting the efficiency of IrOx nanoparticles with micron-flower Nb4N5 support for oxygen evolution reaction in polymer electrolyte membrane water electrolyzer

Precious metal Ir is still the best oxygen evolution reaction (OER) catalyst for polymer electrolyte membrane water electrolysis (PEMWE). Developing suitable support materials to improve the utilization rate of Ir is therefore of great significance for the practical application of PEMWE. Herein, we report a unique spherical Nb4N5 µm-flower as an anode catalyst support for PEMWE. Through an organic colloidal method, a supported IrOx/Nb4N5 catalyst was successfully prepared. TEM analysis showed that the IrOx particles were uniformly dispersed on the surface of the Nb4N5 µm-flower, with a particle size of only about 1.8 nm. XPS revealed that Nb4N5 can effectively regulate the d-band center of Ir, thereby reducing the adsorption energy between oxygen molecules and improving the OER efficiency. Half-cell tests and actual PEMWE operation demonstrate that the performance of the IrOx/Nb4N5 catalyst is superior to commercial IrO2. The overpotential was 247 mV at 10 mA cm−2, and the Tafel slope was only 53.2 mV dec−1 when the IrO2 content was 40 wt %. Moreover, the mass activity was 857.6 A g–1IrO2 at 1.7 V, which is 4.7 times that of commercial IrO2. After an initial 150 h of PEMWE operation, the water decomposition voltage at 1 A cm−2 only increased by 5.5 %. These results suggest that the supported IrOx/Nb4N5 catalyst is a promising candidate for real PEMWE applications.