Hierarchical titanium nitride nanostructured thin film gas diffusion electrodes for next generation PEM fuel cells

• A mesoporous thin film comprising hierarchical titanium nitride nanostructures (HTNTF) was successfully grown and coated with Pt nanoparticles. • The Pt-HTNTF was successfully deposited on a commercial GDL with MPL, in a HTNTF-GDE design. • The HTNTF exceeds DOE stability targets both in rotating disk and fuel cell (in GDE configuration) accelerated stress tests (AST). • High performance achieved in the ionomer free membrane electrode assembly. Durability of the catalyst support in polymer electrolyte membrane fuel cell (PEMFC) is still one of the main obstacles to its full deployment. In fact, despite the high peak performances achieved by state of the art membrane electrode assemblies (MEA), the degradation of their performances is still a major issue. Since engineering solutions proposed to overcome this issue increase the complexity and the cost of the system, the development of a stable catalyst support capable to stabilize the Pt nanoparticles is a preferable strategy. For this reason, in this work a highly durable, high surface area support has been developed by growing an array of hierarchical nanostructures of an extremely oxidation resistant material, i.e. , titanium nitride (TiN) directly on the microporous layer of a commercial gas diffusion layer. Pt was successively deposited to obtain a hierarchical titanium nitride nanostructured thin film gas diffusion electrode (HTNTF-GDE). It resulted capable to withstand the harsh conditions of the accelerated stress tests (AST) with a degradation of the electrochemically active surface area (ECSA) of to 31% after 15,000 cycles in the rotating disk electrode (RDE) setup and of 34% degradation after 5000 cycles in a fuel cell set-up, exceeding in both cases the DOE target for support durability. Besides durability, we investigated the HTNTF-GDE also in an ionomer free catalyst layer configurations.