Preparation of boron-carbide-supported iridium nanoclusters for the oxygen evolution reaction.

• Iridium nanoclusters supported on boron carbide are proposed as a catalyst for the oxygen evolution reaction. • A simple chemical reduction method was used to synthesize grape-like iridium nanoclusters supported on B 4 C. • Iridium nanoclusters supported on B 4 C showed better oxygen evolution activity than a commercial iridium oxide catalyst. Reducing the iridium loading for the oxygen evolution reaction (OER) is one of the main challenges of polymer electrolyte membrane water electrolysis (PEMWE). This study introduces grape-like iridium nanoclusters supported on boron carbide (B 4 C) which increase iridium utilization compared to a non-supported iridium catalyst. A simple chemical reduction method with NaBH 4 as a reducing agent was used to synthesize iridium nanoclusters on B 4 C. TEM images indicated that grape-like iridium nanoclusters were successfully dispersed on the B 4 C support. The catalytic performance of Ir/B 4 C was better than that of a commercial catalyst. To reach a current density of 10 mA/cm2, the overpotential of Ir/B 4 C was less than that of the commercial catalyst by 32 mV. Ir/B 4 C also has a mass activity 2.55 times higher than that of the commercial catalyst at 1.55 V. These improvements are attributed to the high electrochemical active surface area, the weak adsorption strength of oxygen, and the presence of Ir(OH) 4 on the surface. The durability of Ir/B 4 C is comparable to that of the commercial catalyst at 1 mA/cm2 for 15 h and higher at 10 mA/cm2 for 3 h. B 4 C may weaken the oxidative dissolution of iridium by transferring electrons even though the high electrochemical surface area of iridium in Ir/B 4 C may reduce its durability. [ABSTRACT FROM AUTHOR]