Journal
CHEMISTRY OF MATERIALS
Volume 27, Issue 23, Pages 8011-8020Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.chemmater.5b03404
Keywords
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Funding
- National Science Foundation (NSF) through a GOALI
- Proton OnSite [CHE-1301461]
- China Scholar Council
- W. M. Keck Foundation
- M. J. Murdock Charitable Trust
- ONAMI
- Air Force Research Laboratory [FA86500515041]
- National Science Foundation [0923577, 0421086]
- University of Oregon
- Research Corporation for Science Advancement
- Sloan Foundation
- Camille and Henry Dreyfus Foundation
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [0421086] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [0923577] Funding Source: National Science Foundation
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [1301461] Funding Source: National Science Foundation
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Fe cations dramatically enhance oxygen evolution reaction (OER) activity when incorporated substitutionally into Ni or Co (oxy)hydroxides, serving as possible OER active sites. Pure Fe (oxy)hydroxides, however, are typically thought to be poor OER catalysts and are not well-understood. Here, we report a systematic investigation of Fe (oxy)hydroxide OER catalysis in alkaline media. At low overpotentials of 350 mV, the catalyst dissolution rate is low, the activity is dramatically enhanced by an AuOx/Au substrate, and the geometric OER current density is largely independent of mass loading. At higher overpotentials of similar to 450 mV, the dissolution rate is high, the activity is largely independent of substrate choice, and the geometric current density depends linearly on loading. These observations, along with previously reported in situ conductivity measurements, suggest a new model for OER catalysis on Fe (oxy)hydroxide. At low overpotentials, only the first monolayer of the electrolyte-permeable Fe (oxy)hydroxide, which is in direct contact with the conductive support, is OER-active due to electrical conductivity limitations. On Au substrates, Fe cations interact with AuOx after redox cycling, leading to enhanced intrinsic activity over FeOOH on Pt substrates. At higher overpotentials, the conductivity of Fe (oxy)hydroxide increases, leading to a larger fraction of the electrolyte-permeable catalyst film participating in catalysis. Comparing the apparent activity of the putative Fe active sites in/on different hosts/surfaces supports a possible connection between OER activity and local structure.
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