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

• A Nb 4 N 5 micro-flower was developed to support IrO x as anode catalyst for PEMWE. • The IrO x /Nb 4 N 5 catalyst outperformed commercial IrO 2. • The catalyst-support interaction improved OER performance. • Superior performance and good stability were achieved for practical PEMWE operation. 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 Nb 4 N 5 µm-flower as an anode catalyst support for PEMWE. Through an organic colloidal method, a supported IrO x /Nb 4 N 5 catalyst was successfully prepared. TEM analysis showed that the IrO x particles were uniformly dispersed on the surface of the Nb 4 N 5 µm-flower, with a particle size of only about 1.8 nm. XPS revealed that Nb 4 N 5 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 IrO x /Nb 4 N 5 catalyst is superior to commercial IrO 2. The overpotential was 247 mV at 10 mA cm−2, and the Tafel slope was only 53.2 mV dec−1 when the IrO 2 content was 40 wt %. Moreover, the mass activity was 857.6 A g –1 IrO2 at 1.7 V, which is 4.7 times that of commercial IrO 2. 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 IrO x /Nb 4 N 5 catalyst is a promising candidate for real PEMWE applications. [Display omitted] [ABSTRACT FROM AUTHOR]