期刊
ACS CATALYSIS
卷 5, 期 11, 页码 6680-6689出版社
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.5b01551
关键词
loading dependence; thickness dependence; electrochemically active surface area; turnover frequency; nickel iron oxyhydroxide; double-layer capacitance; conductivity; pulsed deposition
资金
- National Science Foundation [CHE-1301461, 0923577, 0421086]
- United States Air Force
- United States Air Force Academy faculty pipeline program
- W. M. Keck Foundation
- M. J. Murdock Charitable Trust
- ONAMI
- Air Force Research Laboratory [FA8650-05-1-5041]
- University of Oregon
- Sloan Foundation
- Research Corporation for Science Advancement
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [0421086, 0923577] Funding Source: National Science Foundation
- Division Of Chemistry
- Direct For Mathematical & Physical Scien [1301461] Funding Source: National Science Foundation
One practical metric for electrocatalyst performance is current per geometric area at a given applied overpotential. An obvious route to increase performance is to increase the catalyst mass loading-as long as the intrinsic performance (i.e., specific activity or turnover frequency) of the catalyst is independent of loading, and other electrical, ionic, or masstransfer resistances are not severe. Here we report the geometric and intrinsic oxygen evolution reaction (OER) activities of Ni(Fe)OOH films, the fastest known water oxidation catalyst in basic media, as a function of mass loading from 0 to similar to 100 mu g cm(-2). We discuss practices for measuring and reporting intrinsic activities, highlighting experimental conditions where the film activity on a per-metal-cation basis can be accurately measured and where capacitance measurements of electrochemically active surface area fail. We find that the electrochemical reversibility of the (nominally) Ni2+/3+ redox wave correlates with the apparent intrinsic activity as a function of loading. We report a pulsed-electrodeposition method that dramatically improves the catalyst reversibility and performance at high loading compared to continuous electrodeposition, which we attribute to improved connectivity in the micro/nanostructure and better composition control. Pulse electrodeposited films are shown to have geometric performance similar to a number of advanced composite electrocatalyst structures and to maintain effective per-metal turnover frequencies of >0.4 s(-1) at 300 mV overpotential, even for loadings of similar to 100 mu g cm(-2).
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