In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity
In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity
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DOI：
10.1021/jacs.5b06814
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发表时间：
2015-12-09
影响因子：
15
通讯作者：
Smith, Wilson A.
中科院分区：
文献类型：
--
作者：
Trzesniewski, Bartek J.;Diaz-Morales, Oscar;Smith, Wilson A.
镍基析氧催化剂（OECs）是具有成本效益且非常活性的材料，其可潜在地用于高效的太阳能-燃料转换过程以实现可持续能源产生。我们提出了一个系统的光谱电化学表征的两个含铁的镍基OECs，即硼酸镍（Ni（Fe）-Bi）和羟基氧化镍（Ni（Fe）OOH）。我们的拉曼和X-射线吸收光谱的结果表明，这两个OEC的化学性质相似，硼酸根阴离子不发挥明显的作用，在pH值为13的催化过程。此外，我们显示的光谱证据，在这两个带负电荷的网站，OECs（NiO-），这可以被描述为吸附的“活性氧”的产生。我们的数据最终将镍基OEC的OER活性与OEC表面上这些位点的产生联系起来。两种OECs的OER活性强烈依赖于pH，这可以归因于Ni基OECs的去质子化过程，导致形成带负电荷的表面位点，其充当OER前体。这项工作强调了电解质效应的相关性，以获得催化活性相在镍基OECs，除了铁杂质的关键作用。在开发用于在中等pH下催化OER的镍基化合物时，应仔细考虑这种效应。补充地，UV-vis光谱测量显示这些催化剂在催化活性状态下强烈变暗。这种着色效应与镍的氧化直接相关，并且可能是限制利用Ni基OEC的太阳能驱动装置的效率的重要因素。
Ni-based oxygen evolution catalysts (OECs) are cost-effective and very active materials that can be potentially used for efficient solar-to-fuel conversion process toward sustainable energy generation. We present a systematic spectroelectrochemical characterization of two Fe-containing Ni-based OECs, namely nickel borate (Ni(Fe)-Bi) and nickel oxyhydroxide (Ni(Fe)OOH). Our Raman and X-ray absorption spectroscopy results show that both OECs are chemically similar, and that the borate anions do not play an apparent role in the catalytic process at pH 13. Furthermore, we show spectroscopic evidence for the generation of negatively charged sites in both , OECs (NiOO-), which can be described as adsorbed "active oxygen". Our data conclusively links the OER activity of the Ni-based OECs with the generation of those sites on the surface of the OECs. The OER activity of both OECs is strongly pH dependent, which can be attributed to a deprotonation process of the Ni-based OECs, leading to the formation of the negatively charged surface sites that act as OER precursors. This work emphasizes the relevance of the electrolyte effect to obtain catalytically active phases in Ni-based OECs, in addition to the key role of the Fe impurities. This effect should be carefully considered in the development of Ni-based compounds meant to catalyze the OER at moderate pHs. Complementarily, UV-vis spectroscopy measurements show strong darkening of those catalysts in the catalytically active state. This coloration effect is directly related to the oxidation of nickel and can be an important factor limiting the efficiency of solar-driven devices utilizing Ni-based OECs.