Platinum Nanoflowers: A New Class of Nanostructured Electrocatalysts for the Oxygen Reduction Reaction

Abstract

Platinum-based nanomaterials are currently one of the most effective options as proton exchange membrane fuel cell (PEMFC) cathode catalysts for the oxygen reduction reaction (ORR). Throughout the last decade, advancements in catalyst morphologies have shifted from 2 to 3 nm nanoparticles towards complex shaped nanostructures (such as octahedra, nanowires, nanoframes...etc.) supported on carbon blacks.1 These advanced nanostructures take advantage of electronic and structural effects that allow for activity improvements of over 30 times when compared to traditional platinum nanoparticles in liquid electrolyte.2 We synthesized and explored a novel class of materials (platinum nanoflowers) for the oxygen reduction reaction which display a high level of crystallinity and porosity.3 The nanostructures form rapidly in solution when utilizing the microwave heating technique of an adapted polyol synthesis procedure and forms due to the altered kinetics of nanoparticle growth with the addition of iodine ions to allow for the overgrowth towards nanoflower structures. The nanoflowers appear monomorphic (similar size and shape), maintains its crystalline structure from petal to petal, and displays deep consistent pores throughout its structure. The platinum nanoflowers display a similar mass activity (~300 A/g at 0.90V vs. RHE) and a factor of 4 enhancement in specific activity (~1800 µA/cm2 at 0.90V vs. RHE) for the oxygen reduction reaction compared to a commercial platinum-carbon catalyst. Ly, A., Asset, T. & Atanassov, P. J. Power Sources 478, 228516 (2020).Chen, C. et al. Science 343, 1339–1343 (2014).Yin, J., Wang, J., Li, M., Jin, C. & Zhang, T. Chem. Mater. 24, 2645–2654 (2012). Figure 1