Journal
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
Volume 140, Issue 36, Pages 11286-11292Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jacs.8b05294
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Funding
- National Natural Science Foundation of China [11575280, 11775296, 11305250, 11405252, U1232117]
- Youth Innovation Promotion Association of the Chinese Academy of Sciences [2015212, 2017310]
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Developing highly efficient oxygen evolution reaction (OER) catalysts and understanding their activity are pivotal for electrochemical conversion technologies. Here, we report NiFe Prussian blue analogue (PBA) as a promising electrocatalyst for OER in alkaline conditions. This material has an impressively low overpotential of 258 mV that reaches a current density of 10 mA cm(-2). Post-mortem characterization showed that the as-prepared catalyst is entirely transformed into amorphous nickel hydroxide after the electrochemical treatment, and Ni(OH)(2) acts as the active species. Operando X-ray spectroscopic studies further found that this in situ generated Ni(OH)(2) displays an unique feature that allows deprotonation under applied potential creating NiOOH2-x that contains Ni4+ ions. The deprotonation reaction is reversible and potential-dependent, i.e., the amount of Ni4+ increases with increasing applied potential. Theoretical calculations were used to show that the role of Ni4+ is to trigger oxidized oxygen ions as electrophilic centers with the subsequent activation of anion redox reactions for OER.
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