474452 Platinum-Nickel Nanowires As Electrocatalysts in Alkaline Hydrogen Oxidation and Evolution
Catalyst development in AEM systems typically focuses on oxygen reduction and evolution, since the reactions are kinetically orders of magnitude slower than hydrogen oxidation and evolution. Alternatives, however, exist to PGMs in these reactions: silver in oxygen reduction; and nickel and cobalt in oxygen evolution.[3, 4] While hydrogen oxidation and evolution are kinetically faster reactions, they are roughly two orders of magnitude slower on Pt in base compared to acidic environments. Non-PGM catalyst options are also less clear, and generally struggle to justify the AEM cost benefit, producing activities orders of magnitude lower than PGMs at higher overpotentials.
Recently, advanced Pt electrocatalysts have been developed in an effort to thrift the amount of PGMs in AEM fuel cells and electrolyzers. Pt-nickel (Ni) nanowires, previously developed for acidic oxygen reduction, were studied for their activity in hydrogen oxidation and evolution. These materials were formed by spontaneous galvanic displacement, a process that occurs when a metal template contacts a nobler metal cation. At low levels of displacement, small amounts of Pt were deposited to produce high electrochemical surface areas. Subsequent post-synthesis processing was used to integrate the Pt-rich and Ni-rich zones, compressing the Pt lattice and improving its activity for hydrogen oxidation and evolution. Compared to carbon-supported Pt nanoparticles (Pt/HSC), Pt-Ni nanowires produced hydrogen oxidation/evolution exchange current densities 9 times greater.
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