Efficient Electrocatalytic Water Oxidation at Neutral and High pH by Adventitious Nickel at Nanomolar Concentrations.
Efficient Electrocatalytic Water Oxidation at Neutral and High pH by Adventitious Nickel at Nanomolar Concentrations.
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DOI：
10.1021/jacs.5b08139
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发表时间：
2015-10
影响因子：
15
通讯作者：
Isolda Roger;M. Symes
中科院分区：
文献类型：
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作者：
Isolda Roger;M. Symes
利用地球上丰富的元素进行电解水氧化是开发廉价、大表面积太阳能-氢转换阵列的关键挑战。近年来在这一领域进行了大量的研究，但仍有必要证明目前报告的密度确实是由于所考虑的物种，而不是由于低水平的外来（但可能是高度活跃的）污染物的存在。本研究表明，浓度低至17 nM的不定式镍可以在轻度碱性水溶液中作为水氧化催化剂，在过电位低至540 mV （pH 9.2）和400 mV （pH 13）时实现稳定（数十小时）电流密度为1 mA cm（-2）。这种镍不是故意添加到电解液中，但通过ICP-MS发现它作为杂质存在于电解质中。通过长时间体电解实验，用XPS证实了阳极上镍的存在。在表明如此低水平的镍可以在与许多最近报道的水氧化催化剂相当的过电位下进行水氧化时，这项工作增加了该领域新材料所需的举证负担：必须排除微量负载下外来金属离子的污染，这是任何观察到的水氧化活性的可能原因。
Electrolytic water oxidation using earth-abundant elements is a key challenge in the quest to develop cheap, large surface area arrays for solar-to-hydrogen conversion. There have been numerous studies in this area in recent years, but there remains an imperative to demonstrate that the current densities reported are indeed due to the species under consideration and not due to the presence of adventitious (yet possibly highly active) contaminants at low levels. Herein, we show that adventitious nickel at concentrations as low as 17 nM can act as a water oxidation catalyst in mildly basic aqueous solutions, achieving stable (tens of hours) current densities of 1 mA cm(-2) at overpotentials as low as 540 mV at pH 9.2 and 400 mV at pH 13. This nickel was not added to the electrolysis baths deliberately, but it was found to be present in the electrolytes as an impurity by ICP-MS. The presence of nickel on anodes from extended-time bulk electrolysis experiments was confirmed by XPS. In showing that such low levels of nickel can perform water oxidation at overpotentials comparable to many recently reported water oxidation catalysts, this work serves to raise the burden of proof required of new materials in this field: contamination by adventitious metal ions at trace loadings must be excluded as a possible cause of any observed water oxidation activity.