An Investigation of Thin-Film Ni-Fe Oxide Catalysts for the Electrochemical Evolution of Oxygen
An Investigation of Thin-Film Ni-Fe Oxide Catalysts for the Electrochemical Evolution of Oxygen
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DOI：
10.1021/ja405351s
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发表时间：
2013-08-21
影响因子：
15
通讯作者：
Bell, Alexis T.
中科院分区：
文献类型：
--
作者：
Louie, Mary W.;Bell, Alexis T.
研究了电沉积Ni-Fe膜在碱性电解液中的析氧反应(OER)结构和电化学活性。体相和表面成分均为40%Fe的Ni-Fe膜表现出比新沉积的Ni膜高约2个数量级、比Fe膜高约3个数量级的OER活性。在电解液(KOH)中，新沉积的Ni膜的活性增加了20倍；然而，所有含Fe的膜在沉积时都是稳定的。Ni膜中Ni(OH)(2)氧化为NiOOH的电位低于OER起始电位。Fe的加入增加了Ni(OH)(2)/NiOOH氧化还原的电位，降低了Ni在NiOOH中的平均氧化态。Fe含量高达95%的混合Ni-Fe膜的Tafel斜率(40 mV dec(-1))和反应级数与时效Ni膜相同。在0.1M KOH溶液中，OER电位下的原位拉曼光谱显示出NiOOH的两个特征谱带。这些谱带的相对强度随Fe含量的不同而不同，表明Ni-O的局域环境发生了变化。当纯Ni膜老化时，观察到了类似的带相对强度的变化和OER活性的增加。这些观察结果表明，Ni-Fe薄膜中的Ni催化了OER，Fe的存在改变了Ni的氧化还原性质，导致了Ni(OH)(2)/NiOOH氧化还原发生的电位的正移，降低了Ni中心的平均氧化态，同时增加了Ni离子对OER的活性。
A detailed investigation has been carried out of the structure and electrochemical activity of electrodeposited Ni-Fe films for the oxygen evolution reaction (OER) in alkaline electrolytes. Ni-Fe films with a bulk and surface composition of 40% Fe exhibit OER activities that are roughly 2 orders of magnitude higher than that of a freshly deposited Ni film and about 3 orders of magnitude higher than that of an Fe film. The freshly deposited Ni film increases in activity by as much as 20-fold during exposure to the electrolyte (KOH); however, all films containing Fe are stable as deposited. The oxidation of Ni(OH)(2) to NiOOH in Ni films occurs at potentials below the onset of the OER. Incorporation of Fe into the film increases the potential at which Ni(OH)(2)/NiOOH redox occurs and decreases the average oxidation state of Ni in NiOOH. The Tafel slope (40 mV dec(-1)) and reaction order in OH- (1) for the mixed Ni-Fe films (containing up to 95% Fe) are the same as those for aged Ni films. In situ Raman spectra acquired in 0.1 M KOH at OER potentials show two bands characteristic of NiOOH. The relative intensities of these bands vary with Fe content, indicating a change in the local environment of Ni-O. Similar changes in the relative intensities of the bands and an increase in OER activity are observed when pure Ni films are aged. These observations suggest that the OER is catalyzed by Ni in Ni-Fe films and that the presence of Fe alters the redox properties of Ni, causing a positive shift in the potential at which Ni(OH)(2)/NiOOH redox occurs, a decrease in the average oxidation state of the Ni sites, and a concurrent increase in the activity of Ni cations for the OER.