Synergy of sub-nano iridium clusters and cucurbit[6]uril-derived carbon boosts acidic water splitting

Acidic water splitting, essential for sustainable hydrogen production, is limited by the sluggish oxygen evolution reaction (OER). This study presents a series of iridium-based sub-nanocluster electrocatalysts supported on a porous carbon matrix (CBC-Ir-T, T = 300, 400, and 500 °C) for efficient overall water splitting. Impressively, CBC-Ir-400, with an ultralow Ir loading of 1.4 µg·cm⁻², exhibits exceptional bifunctional activity, achieving 10 mA·cm⁻² at overpotentials of only 240 mV for OER and 30 mV for hydrogen evolution reaction (HER). In practical acidic water splitting, it delivers a cell voltage of 1.53 V at 10 mA·cm⁻², outperforming the commercial Ir/C||Pt/C system. Comprehensive characterization reveals that the cucurbit[6]uril-derived porous carbon matrix, rich in defects and high specific surface area, promotes the formation of uniformly dispersed sub-nano Ir clusters. This optimizes the iridium electronic structure for enhanced intermediate adsorption, while strong electrical coupling with carbon support boosts charge transfer and mass transport. This synergy drives its superior performance. Our findings offer a scalable strategy for designing high-performance, ultralow-loading iridium sub-nanocluster catalysts, paving the way for cost-effective and sustainable hydrogen production via water electrolysis.