Microdrop-confined synthesis and regulation of porous hollow Ir-based catalysts for the mass transfer-enhanced electrolysis of pure water

Maximally exploiting the active sites of iridium catalysts is essential for building low-cost proton exchange membrane (PEM) electrolyzers for green H 2 production. Herein, we report a novel microdrop-confined fusion/blasting (MCFB) strategy for fabricating porous hollow IrO 1− x microspheres (IrO 1− x -PHM) by introducing explosive gas mediators from a NaNO 3 /glucose mixture. Moreover, the developed MCFB strategy is demonstrated to be general for synthesizing a series of Ir-based composites, including Ir–Cu, Ir–Ru, Ir–Pt, Ir–Rh, Ir–Pd, and Ir–Cu–Pd and other noble metals such as Rh, Ru, and Pt. The hollow structures can be regulated using different organics with NaNO 3. The assembled PEM electrolyzer with IrO 1−x -PHM as the anode catalyst (0.5 mg/cm 2 ) displays an impressive polarization voltage of 1.593 and 1.726 V at current densities of 1 and 2 A/cm 2, respectively, outperforming commercial IrO x catalysts and most of the ever-reported iridium catalysts with such low catalyst loading. More importantly, the breakdown of the polarization loss indicates that the improved performance is due to the facilitated mass transport induced by the hollowness. This study offers a versatile platform for fabricating efficient Ir-based catalysts for PEM electrolyzers and beyond.