The transient covering of iridium species with ultrathin carbon shells via Joule-heating for robust acidic water oxidation

Abstract

Designing efficient and stable oxygen evolution reaction (OER) catalysts to boost the performance of proton exchange membrane water electrolyzers is of paramount significance for the development of green hydrogen. The establishment of a core–shell structure is a representative approach to promote the high efficiency and stability of active sites. This work presents a novel method for synthesizing catalysts by utilizing a reliable, low-cost, ultrafast Joule-heating method to construct carbon shells that evenly anchor and encapsulate iridium nanoparticles to carbon paper. The whole process of iridium-particle generation and carbon-shell evolution is successfully demonstrated, and a rapid high heat input and precise energy control are proven to be essential conditions for transient carbon coating engineering, which is further confirmed by systematically comparing the as-obtained samples with those prepared by conventional argon plasma bombardment and tube-furnace thermal treatment. When assembled in an electrolyzer, the CIr-RJH-30||Pt/C electrolyzer could stably operate at a constant current density of 100 mA cm⁻² for ∼400 h, while CIr-plasma||Pt/C, CIr-thermal||Pt/C, and IrO₂||Pt/C electrolyzers completely lost the capability for water electrolysis after 25.9 h, 21.1 h, and 45.5 h, respectively. These results demonstrate the effectiveness of the core–shell structure formed by the Joule-heating treatment in improving the performance of the catalyst.