Journal
ACS NANO
Volume 13, Issue 11, Pages 13225-13234Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.9b06244
Keywords
rhodium-ridium alloy; oxygen evolution reaction; acidic electrolyte; microwave synthesis; ensemble effect
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Funding
- National Science Foundation [CHE-1807847]
- Welch Foundation [F-1841, F-1731]
- U.S. Department of Energy, Office of Science, Basic Energy Sciences [DE-SC0019019]
- Alfred P. Sloan Foundation
- Camille Dreyfus Teacher-Scholar Award
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The oxygen evolution reaction (OER) is pivotal for renewable energy conversion and storage devices, such as water electrolyzers and rechargeable metal-air batteries. However, the rational design of electrocatalysts with suitably high efficiencies and stabilities in strongly acidic electrolytes remains a significant challenge. Here, we show the demonstration of sub-10 nm, composition-tunable Rh-Ir alloy nanoparticles (NPs) prepared using a scalable microwave-assisted method as superior acidic OER catalysts. The OER activities showed a volcano-shaped dependence on Ir composition, with Ir-rich NPs (Ir >= 51%) achieving better OER performance than pure Ir NPs, as reflected by lower overpotentials and higher mass activities. Most significantly, Rh22Ir78 NPs achieved a maximum mass activity of 1.17 A mg(Ir)(-1) at a 300 mV overpotential in 0.5 M H2SO4, which corresponds to a 3-fold enhancement relative to pure Ir NPs, making it one of the most active reported OER catalysts under acidic conditions. Density functional theory calculations reveal that owing to the synergy of ensemble and electronic effects by alloying a small amount of Rh with Ir, the binding energy difference of the O and OOH intermediates is reduced, leading to faster kinetics and enhanced OER activity. Furthermore, Rh-Ir alloy NPs demonstrated excellent durability in strongly acidic electrolyte. This work not only provides fundamental understandings relating to composition-electrochemical performance relationships but also represents the rational design of highly efficient OER electrocatalysts for applications in acidic media.
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