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

Abstract

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 (B4C) which increase iridium utilization compared to a non-supported iridium catalyst. A simple chemical reduction method with NaBH4 as a reducing agent was used to synthesize iridium nanoclusters on B4C. TEM images indicated that grape-like iridium nanoclusters were successfully dispersed on the B4C support. The catalytic performance of Ir/B4C was better than that of a commercial catalyst. To reach a current density of 10 mA/cm2, the overpotential of Ir/B4C was less than that of the commercial catalyst by 32 mV. Ir/B4C 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/B4C is comparable to that of the commercial catalyst at 1 mA/cm2 for 15 h and higher at 10 mA/cm2 for 3 h. B4C may weaken the oxidative dissolution of iridium by transferring electrons even though the high electrochemical surface area of iridium in Ir/B4C may reduce its durability.