Advanced materials for water splitting in a PEM electrolyser

Water electrolysis has recently increased in interest with the large diffusion of renewable energy sources and the perspective to producing high purity green hydrogen [1-3]. Hydrogen can be also used to store energy in grid-balancing services. A challenging problem to the development of advanced polymer electrolyte membrane water electrolysis systems is the long term stability of core components i.e. electrocatalysts, membranes, bipolar plates. High surface area nanostructured electro-catalysts and highly conductive membranes can substantially reduce such energy losses allowing to achieve efficient hydrogen production. However, proper stability characteristics should be demonstrated to promote large scale deployment. Nanosized IrRuOx anode catalysts [1] have been assessed in solid polymer membrane water electrolysers (PEMWEs) in combination with perfluorosulfonic electrolytes including novel short side chain membranes (Aquivion®) [3]. The physico-chemical properties before and after steady-state and accelerated stress tests have been investigated in-situ using electrochemical diagnostics (ac-impedance, cyclic voltammetry etc.) and ex-situ by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analysis. Particular efforts were addressed to correlate the modifications in terms of chemical, structural, morphological properties with the electrochemical stability for the water splitting process. Optimised membranes and electro-catalysts combinations have shown very low degradation rates and promising characteristics for application in advanced electrolysis systems [4].