The polymer electrolyte membrane (PEM) water electrolyzer is a game-changing technology with respect to renewable energy storage, enabling hydrogen to be produced at high efficiency [1]. However, due to harsh oxidizing conditions accelerated by high overpotential and low pH in the anode, highly corrosion resistance components or protective coatings are required. Therefore, titanium-based porous transport layers (PTLs) such as titanium felt, titanium mesh and sintered titanium powders are commonly used in the anode on the basis of their excellent chemical stability, electron conductivity and high corrosion resistivity. However, the critical passivation of titanium-based PTLs cannot be disregarded, as this affects the electrical resistivity of the surface and fatally decreases cell performance and durability [2-4]. In order to permit the use of titanium PTLs in PEM electrolyzers, platinum group metals (PGMs) such as platinum are typically used as a protective layer so that lifetimes of over 50,000 hours can be achieved [5].

In the present work, a very simple and scalable method is used to protect the titanium PTL from passivation by sputtering very thin layers of PGMs onto porous transport layers [6]. Compared to the cell without the coatings, the cell assembled with iridium and platinum coatings showed degradation rates close to zero, while the same cell performance was observed after 4000 hours with a cell voltage of 2V. These results demonstrate that iridium and platinum coatings on titanium-based PTLs are highly effective at protecting the PTL against passivation, ultimately improving cell performance and durability. The results of this work will provide useful information about the use of stable PTLs when accessing the performance and durability of other PEM electrolysis components such as electrodes and membranes [7].

References

1. Carmo, M., et al., A comprehensive review on PEM water electrolysis. International Journal of Hydrogen Energy, 2013. 38(12): p. 4901-4934.
2. Rakousky, C., et al., The stability challenge on the pathway to high-current-density polymer electrolyte membrane water electrolyzers. Electrochimica Acta, 2018. 278: p. 324-331.
3. Rakousky, C., et al., Polymer electrolyte membrane water electrolysis: Restraining degradation in the presence of fluctuating power. Journal of Power Sources, 2017. 342: p. 38-47.
4. Rakousky, C., et al., An analysis of degradation phenomena in polymer electrolyte membrane water electrolysis. Journal of Power Sources, 2016. 326: p. 120-128.
5. Ayers, K.E., et al., Research Advances towards Low Cost, High Efficiency PEM Electrolysis. ECS Transactions, 2010. 33(1): p. 3-15.
6. Liu, C., et al., Performance enhancement of PEM electrolyzers through iridium-coated titanium porous transport layers. Electrochemistry Communications, 2018. 97: p. 96-99.
7. Bender, G., et al., Initial approaches in benchmarking and round robin testing for proton exchange membrane water electrolyzers. International Journal of Hydrogen Energy, 2019. 44(18): p. 9174-9187.