Size optimization of IrOx nanoparticles synthesized by Br mediation for enhanced PEM water electrolysis

Abstract

We have creatively developed a hydrothermal approach to synthesize ultra-small IrOx nanoparticles with precise size control at 1.6 nm by carefully modulating KBr concentrations. Br ions are adsorbed onto the surface of IrOx and modulate the free energy through adsorption, thereby controlling the nanoparticle size to achieve ultra-small IrOx. The tailored IrOx nanoparticles are aimed to be high-performance electrocatalysts for efficient oxygen evolution reaction. The optimized nanoparticles exhibited an ultra-low overpotential of 230 mV to reach 10 mA/cm2 for oxygen evolution reaction in acid and showed negligible degradation after 50 h operation at 10 mA/cm2. When assembled in a proton exchange membrane electrolyzer, the catalyst enabled the device to reach 1 A/cm2 at only 1.69 V with excellent durability over 100 h at 1 A/cm2. Through detailed cost accounting, it was determined that 1 kg of hydrogen could be produced for a remarkably low, significantly below prevailing cost targets. This work not only develops an effective strategy to enhance oxygen evolution reaction efficiency by tailoring IrO2 particle size, but also shows the great potential for scalable application in industrial water electrolysis.