Oxygen Evolution Reaction Activity and Stability Benchmarks for Supported and Unsupported IrO_<i>x</i> Electrocatalysts

Advanced materials are needed to meet the requirements of devices designed for harvesting and storing renewable electricity. In particular, polymer electrolyte membrane water electrolyzers (PEMWEs) could benefit from a reduction in size iridium oxide (IrOx) particles used electrocatalyze sluggish oxygen evolution reaction (OER). To verify validity this approach, we built library 18 supported unsupported IrOx catalysts established their stability number (S-number) values using inductively coupled plasma mass spectrometry electrochemistry. Our results provide quantitative evidence that (i) nanocatalysts more active toward OER but less stable than micrometer-sized catalysts, example, commercial IrO2 or porous microparticles; (ii) tantalum-doped tin oxides (TaTO) as supports nanoparticles antimony-doped (ATO) carbon black (Vulcan XC72); (iii) thermal annealing under air atmosphere yields depreciated activity enhanced stability; (iv) beneficial effect holds both micro- nano-IrOx leads 1 order magnitude lower Ir atom dissolution rate with respect nonannealed catalysts; (v) best compromise between was obtained microparticles after at 450 °C. These insights guidance on which material classes strategies most likely increase sustainably efficiency while contributing diminish cost PEMWE devices.