Antimony-doped tin oxide as a promising support for low-loading iridium electrodes in proton exchange membrane electrolysis

Proton exchange membrane (PEM) water electrolysis is a key technology for producing green hydrogen. However, its widespread adoption is limited by the reliance on platinum group metals, particularly iridium, for the kinetically sluggish oxygen evolution reaction (OER). Enhancing the overall efficiency of PEM electrolysis requires the development of active, stable, and low-Ir loading catalysts for the OER. To achieve this, using a support material to anchor iridium nanoparticles is crucial for enhancing both catalytic activity and stability. Iridium oxide supported on antimony-doped tin oxide (IrO x /ATO) has emerged as a promising alternative due to its excellent electrocatalytic performance, enabling rapid and efficient oxygen evolution. The support structure also reduces iridium loading, which is crucial for lowering costs and improving scalability. This study presents the synthesis and electrochemical characterization of an IrO x /ATO catalyst containing approximately 22 wt% of iridium oxide, produced using a combination of cost-effective and scalable methods. The catalyst demonstrated outstanding OER activity, achieving 241 mA mg Ir −1 @ 1.55 V RHE , and exhibited excellent stability in 0.1 M HClO 4 under a degradation test protocol. In single-cell electrolysis tests, it achieved 1.65 V @ 1 A cm −2 and demonstrated 400 h of stable operation at 2.3 A cm −2 with 0.2 mg Ir cm −2 . These results highlight the potential of IrO x /ATO as a highly efficient and durable anode catalyst, making it a strong candidate for large-scale PEM electrolyzer deployment. • IrO x /ATO (ca. 22 wt% of Ir) was synthesized to effectively conduct the acidic OER; • IrO x /ATO was prepared using a combination of low-cost and easily scalable methods; • The IrO x /ATO activity and stability are superior to the commercial benchmark; • 400 h of stable operation at 2.3 A cm −2 were obtained with 0.2 mg Ir cm −2 ; • IrO x /ATO is a strong candidate for large-scale PEM electrolyzer deployment.