Journal
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
Volume 58, Issue 37, Pages 12999-13003Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201905501
Keywords
cations; electrocatalysis; nickel oxyhydroxide; oxygen evolution reaction (OER); Raman spectroscopy
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Funding
- European Union [732840-A-LEAF]
- Sao Paulo Research Foundation (FAPESP) [17/05040-1]
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [17/05040-1] Funding Source: FAPESP
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Herein, the effect of the alkali cation (Li+, Na+, K+, and Cs+) in alkaline electrolytes with and without Fe impurities is investigated for enhancing the activity of nickel oxyhydroxide (NiOOH) for the oxygen evolution reaction (OER). Cyclic voltammograms show that Fe impurities have a significant catalytic effect on OER activity; however, both under purified and unpurified conditions, the trend in OER activity is Cs+ > Na+ > K+ > Li+, suggesting an intrinsic cation effect of the OER activity on Fe-free Ni oxyhydroxide. In situ surface enhanced Raman spectroscopy (SERS), shows this cation dependence is related to the formation of superoxo OER intermediate (NiOO-). The electrochemically active surface area, evaluated by electrochemical impedance spectroscopy (EIS), is not influenced significantly by the cation. We postulate that the cations interact with the Ni-OO- species leading to the formation of NiOO--M+ species that is stabilized better by bigger cations (Cs+). This species would then act as the precursor to O-2 evolution, explaining the higher activity.
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