*Lucia Mendizabal¹, Sigrid Laedre², Alejandro Oyarce², Nuria Rojas^3
1TEKNIKER, Eibar, Spain; ² SINTEF, Trondheim, Norway; ³ Centro Nacional del Hidrogeno CNH₂, Puertollano, Spain
Green hydrogen production by polymer electrolyte membrane water electrolysis (PEMWE) from surplus intermittent renewable energy sources (RES) and water is currently one of the main suitable alternatives for large and long-term energy storage known as Power-to-H₂, that can later be re-converted back to electricity by a polymer electrolyte membrane fuel cells (PEMFC) closing the loop of power-to-power (PtP). Even if not the most efficient solution of PtP sector, the conversion of electricity into H₂ by water electrolysis is expected to emerge as a promising solution for energy storage beyond PtP, since H₂ can act as a cross energy vector for sector coupling, enabling large amounts of renewable energy to be transfer from power sector to end-use sectors (transport, industry, buildings…) further contributing to decarbonization. PEM water electrolysers are today a technological reality at small scale, but to become a relevant technology for energy storage further developments are a must in terms of enhanced performance and durability and cost reduction. Bipolar plates (BPPs) are the most expensive PEMWE stack components, accounting for > 40% of the total costs, depending on the selected cell design. Titanium is currently considered the best BPP material for PEMWE, particularly on the anode side where high overpotential (1.6-2.0 V) are combined with low pH (2-5) in an oxidizing atmosphere. However, passivation (ICR increase and cell efficiency reduction) of titanium on the anode side and hydrogen embrittlement (mechanical degradation) on the cathode side severely reduced the durability and performance of the PEMWE stack. In order to avoid this, BPPs have commonly been coated with PGM or Au coatings, which further increases BPP costs. This presentation will describe current different coating solutions for BPPs for PEM water electrolyser and discuss about the recent developments of non-precious metal coatings by magnetron sputtering and HIPIMS techniques as a cost-effective and sustainable alternative for bipolar plates.