Enhancing the activity and durability of iridium electrocatalyst supported on boron carbide by tuning the chemical state of iridium for oxygen evolution reaction

The main challenge for the anode electrocatalyst in a polymer electrolyte membrane water electrolyzer (PEMWE) is to maintain activity and stability simultaneously under the corrosive environment. We report a highly active and durable iridium electrocatalyst supported on boron carbide for the oxygen evolution reaction. The physical and electrochemical properties of the catalyst are controlled by changing the synthetic reduction temperature from 30 °C to 100 °C. The prepared Ir/B₄C-100 °C catalyst shows two times higher mass activity than Ir/B₄C-30 °C, even outperforming two commercial catalysts. The improved activity can be correlated to the high concentration of Ir (III) and OH species on the surface and the well-dispersed iridium nanoparticles on the support. Controlling the reduction temperature is also found to enhance iridium stability by developing the interactions between iridium and B₄C. These metal-support interactions inhibit the oxidative dissolution of Ir (III) and the aggregation of iridium species. Ir/B₄C-100 °C also shows better single cell performance than those of two commercial catalysts when tested in a PEMWE. The cell with the synthesized catalyst of Ir/B₄C-100 °C shows a current density of 1.98 A/cm² at 1.8 V, whereas those with two commercial catalysts exhibit values of 1.36 and 0.692 A/cm² at 1.8 V, respectively.