Evaluating corrosion resistance and in-situ performance of copper bipolar plates with protective Nb and Ti-coatings for proton exchange membrane water electrolysis

To reduce the cost of proton exchange membrane water electrolysis (PEMWE), this study proposes replacing bulk titanium bipolar plates (BPPs) with copper substrates protected by vacuum plasma-sprayed Nb or Ti coatings. Performance was evaluated via ex situ electrochemical tests in simulated anodic environments and in situ validation in a five-cell electrolyzer stack. Results demonstrate that Nb coatings provide superior protection, with corrosion current densities (1.7 × 10 −8 A cm −2 ) lower than those of Ti coatings (2.3 × 10 −6 A cm −2 ). Additionally, Nb coatings exhibit lower interfacial contact resistance than Ti coatings, leading to improved cell performance, evidenced by lower operating voltages during in situ stack testing. Beyond performance comparison, this study demonstrates that tailored protective coatings enable the use of cost-effective, highly conductive copper substrates in aggressive PEMWE environments.