Unveiling the Failure Mechanism of Pt Coating on Ti Porous Transport Layer in Simulated PEMEC Environment

Pt coating has been considered a promising strategy to protect the Ti porous transport layer substrate in a proton exchange membrane electrolyzer from corrosion. However, despite significant advancements in understanding the composition, process, and structure of Pt coatings, the underlying causes of coating failure remains unclear. Here, we systematically investigate the failure processes of magnetron-sputtered Pt coatings on Ti substrates through ex situ electrochemical tests that simulate anode operational conditions. Three different thicknesses of thin Pt coatings were prepared on Ti substrates by controlling the sputtering time. As the polarization time increases, the coating gradually fails and the failure time is directly related to the thickness of the coating. Experimental results indicate that Pt coatings approximately 6 nm thick begin to fail after 24 h of operation, with interfacial contact resistance reaching 220.61 mΩ cm² after 48 h, which is significantly higher than that of bare Ti at 28.39 mΩ cm². Further analysis reveals the role of oxygen in the coating failure: oxygen atoms generated from electrolyzed water first diffuse from the coating surface into the interface between the coating and the substrate, and eventually, the gradual buildup of oxygen pressure results in the detachment of the coating. A deeper understanding of the failure mechanism of coatings can enhance the efficiency and durability of water electrolysis for hydrogen production by guiding the design of more durable coatings.