Nano-metal diborides-supported anode catalyst with strongly coupled TaOx/IrO2 catalytic layer for low-iridium-loading proton exchange membrane electrolyzer

• Published in: Nature communications Vol. 14; no. 1; p. 5119
• Main Authors: Wang, Yuannan, Zhang, Mingcheng, Kang, Zhenye, Shi, Lei, Shen, Yucheng, Tian, Boyuan, Zou, Yongcun, Chen, Hui, Zou, Xiaoxin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23.08.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 140/146; 147/135; 147/143; 639/301/299/886; 639/638/77/886; Catalysts; Composite materials; Corrosion resistance; Electrical conductivity; Electrical resistivity; Entropy; Free energy; Gibbs free energy; Heterojunctions; Humanities and Social Sciences; Hydrogen production; Iridium; Membranes; multidisciplinary; Oxygen evolution reactions; Protons; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-40912-8

The sluggish kinetics of oxygen evolution reaction (OER) and high iridium loading in catalyst coated membrane (CCM) are the key challenges for practical proton exchange membrane water electrolyzer (PEMWE). Herein, we demonstrate high-surface-area nano-metal diborides as promising supports of iridium-based OER nanocatalysts for realizing efficient, low-iridium-loading PEMWE. Nano-metal diborides are prepared by a novel disulphide-to-diboride transition route, in which the entropy contribution to the Gibbs free energy by generation of gaseous sulfur-containing products plays a crucial role. The nano-metal diborides, TaB 2 in particular, are investigated as the support of IrO 2 nanocatalysts, which finally forms a TaO x /IrO 2 heterojunction catalytic layer on TaB 2 surface. Multiple advantageous properties are achieved simultaneously by the resulting composite material (denoted as IrO 2 @TaB 2 ), including high electrical conductivity, improved iridium mass activity and enhanced corrosion resistance. As a consequence, the IrO 2 @TaB 2 can be used to fabricate the membrane electrode with a low iridium loading of 0.15 mg cm −2 , and to give an excellent catalytic performance (3.06 A cm −2 @2.0 V@80 o C) in PEMWE―the one that is usually inaccessible by unsupported Ir-based nanocatalysts and the vast majority of existing supported Ir-based catalysts at such a low iridium loading. The extreme scarcity of Ir largely limits the wide application of proton exchange membrane water electrolyzer (PEMWE) for hydrogen production. Here, the authors report high-surface area nano-metal diboride as promising support of anode nanocatalyst IrO 2 for realizing efficient, low Ir loading PEMWE.