Extended-surface thin film platinum electrocatalysts with tunable nanostructured morphologies.

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 Al2O3 nanostructures templated from block copolymer (BCP) thin films self-assembled on glassy carbon substrates via sequential infiltration synthesis. Testing for oxygen reduction on a rotating disk electrode setup with ultra-low PGM loadings (5.8 µgPt cm-2) demonstrates electrocatalyst performance that rivals commercial platinum electrocatalysts in terms of mass activity (380 mA mgPt-1 at 0.9 V vs RHE), whilst surpassing commercial catalysts in terms of stability (mass activity loss: 11.45% at after 20,000 potential cycles). Moreover, catalyst performance probed as a function of nanoscale feature size and morphology reveals an inverse correlation between particle size and electroactivity, as well as the superiority of cylindrical morphologies over lamellae, presenting BCP templating as a fabrication pathway towards stable, tunable catalyst geometries.