Extended-Surface Thin-Film Platinum Electrocatalysts with Tunable Nanostructured Morphologies

[Image: see text] Reducing platinum group metal (PGM) loadings in fuel cells and electrolyzers is paramount for cost reductions and getting hydrogen to scale to help decarbonize the global economy. Conventional PGM nanoparticle-based ink-cast electrocatalysts lose performance at high current densities owing to mass transport resistances that arise due to the use of ionomer binders. Herein, we report the development of binder-free extended-surface thin-film platinum electrocatalysts with tunable nanoscale morphology and periodic spacing. The electrocatalysts are prepared by sputtering various loadings of platinum on Al(2)O(3) nanostructures templated from self-assembled block copolymer (BCP) thin films on glassy carbon substrates. Testing for oxygen reduction on a rotating disk electrode setup with ultralow PGM loadings (5.8 μg(Pt) cm(–2)) demonstrates electrocatalyst performance that rivals commercial platinum electrocatalysts in terms of mass activity (380 mA mg(Pt)(–1) at 0.9 V vs RHE) while surpassing commercial catalysts in terms of stability (mass activity loss: 11–13% after 20,000 potential cycles). Moreover, catalyst performance probed as a function of nanoscale feature size and morphology reveals an inverse correlation between feature size and electroactivity, as well as the superiority of cylindrical morphologies over lamellae, presenting BCP templating as a fabrication pathway toward stable, tunable catalyst geometries.