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Aerogels; Antimony compounds; Catalysts; Electrodes; Electrolytic cells; Iridium; Mass spectrometry; Metal nanoparticles; Nanocomposites; Oxygen evolution reaction; Photoelectrons; Photons; Tin oxides; X ray photoelectron spectroscopy, Ambient-pressure x-ray photoelectron spectroscopies; Antimony-doped tin oxide; Electrocatalytic activity and stability; Ir nanoparticles; Membrane electrode assemblies; Operando; Proton exchange membranes; Reaction mechanism, Iridium compounds
Abstract:
The use of high amounts of iridium in industrial proton exchange membrane water electrolyzers (PEMWE) could hinder their widespread use for the decarbonization of society with hydrogen. Nonthermally oxidized Ir nanoparticles supported on antimony-doped tin oxide (SnO2:Sb, ATO) aerogel allow decreasing the use of the precious metal by more than 70 while enhancing the electrocatalytic activity and stability. To date, the origin of these benefits remains unknown. Here, we present clear evidence of the mechanisms that lead to the enhancement of the electrochemical properties of the catalyst. Operando near-ambient pressure X-ray photoelectron spectroscopy on membrane electrode assemblies reveals a low degree of Ir oxidation, attributed to the oxygen spill-over from Ir to SnO2:Sb. Furthermore, the formation of highly unstable Ir(III) species is mitigated, while the decrease of Ir dissolution in Ir/SnO2:Sb is confirmed by inductively coupled plasma mass spectrometry. The mechanisms that lead to the high activity and stability of Ir catalysts supported on SnO2:Sb aerogel for PEMWE are thus unveiled. Copyright © 2020 American Chemical Society.
