Joint Center for Artificial Photosynthesis, Materials Science Division, Lawrence Berkeley National Laboratory, California 94720, USA.
J Am Chem Soc. 2013 Aug 21;135(33):12329-37. doi: 10.1021/ja405351s. Epub 2013 Aug 12.
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.
已经对碱性电解质中析氧反应（OER）的电沉积 Ni-Fe 薄膜的结构和电化学活性进行了详细研究。具有 40%Fe 体相和表面组成的 Ni-Fe 薄膜表现出的 OER 活性大约比新沉积的 Ni 薄膜高 2 个数量级，比 Fe 薄膜高 3 个数量级。在电解质（KOH）中暴露时，新沉积的 Ni 薄膜的活性最多可增加 20 倍；然而，所有含 Fe 的薄膜在沉积时都是稳定的。Ni 薄膜中 Ni(OH)2 氧化为 NiOOH 的过程发生在 OER 起始电位以下。Fe 掺入薄膜会增加 Ni(OH)2/NiOOH 氧化还原发生的电位，并降低 NiOOH 中 Ni 的平均氧化态。混合 Ni-Fe 薄膜（含高达 95%Fe）的 Tafel 斜率（40 mV dec(-1))和 OH(-)反应级数（1）与老化 Ni 薄膜相同。在 OER 电位下在 0.1 M KOH 中获得的原位拉曼光谱显示出 NiOOH 的两个特征带。这些带的相对强度随 Fe 含量而变化，表明 Ni-O 的局部环境发生了变化。当纯 Ni 薄膜老化时，观察到这些带的相对强度的相似变化和 OER 活性的增加。这些观察表明，OER 在 Ni-Fe 薄膜中由 Ni 催化，Fe 的存在改变了 Ni 的氧化还原性质，导致 Ni(OH)2/NiOOH 氧化还原发生的电位正移，Ni 位的平均氧化态降低，同时 OER 中 Ni 阳离子的活性增加。
