Résumé
The high investment cost of proton-exchange membrane water electrolyzers (PEMWEs) is partly due to the expense of their constituent materials. (1) In this context, research efforts aim to minimize the use of iridium oxide (IrOx) in electrocatalyzing the oxygen evolution reaction (OER) at the anode. This strategy is also advantageous from an ecological standpoint, as it helps mitigate the geological scarcity of Ir, which is 40 times rarer than gold and 10 times rarer than platinum. Minimizing the size of IrOx particles is an appealing strategy in this pursuit; however, the Gibbs-Thomson effect, which governs the electrochemical stability of nanomaterials, casts doubt on the viability of this approach.In this contribution, I will summarize the research efforts of the scientific community, including our own, in comparing the electrocatalytic properties and stability of supported and unsupported IrOx particles. (2) I will show that supported IrOx nanocatalysts are typically more active towards the OER but less stable than unsupported micrometer-sized catalysts. Much of this instability arises from the metal oxide support, which, through degradation, leads to the detachment or electrical disconnection of IrOx nanoparticles (loss of doping elements). (3, 4) I will then present our recent advances in the synthesis of self-standing IrO2 nanostructures, (5) and demonstrate how they can be used to advance our understanding of intrinsic OER activity and stability, both at the rotating disk electrode and in membrane electrode assembly configuration. The benefits of advanced in situ or operando techniques, including inductively coupled plasma mass spectrometry, near-ambient pressure X-ray photoelectron spectroscopy and wide-angle X-ray scattering, will also be highlighted. Finally, I will introduce the next challenges to be addressed before PEMWE are widely deployed, including recycling of precious metals. (6)This work was supported by the “France 2030” government investment plan managed by the French National Research Agency, under the reference “ANR-22-PEHY-0011”, in the frame of the MATHYLDE project.