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Potential and Buffer Dependent Catalyst Decomposition during Nickel-based Water Oxidation Catalysis.
ChemSusChem ( IF 8.4 ) Pub Date : 2020-09-22 , DOI: 10.1002/cssc.202001428
Joeri Hessels 1 , Fengshou Yu 1 , Remko J Detz 2 , Joost N H Reek 1
Affiliation  

The production of hydrogen by water electrolysis benefits from the development of water oxidation catalysts. This development process can be aided by the postulation of design rules for catalytic systems. The analysis of the reactivity of molecular complexes can be complicated by their decomposition under catalytic conditions into nanoparticles that may also be active. Such a misinterpretation can lead to incorrect design rules. In this study, the nickel‐based water oxidation catalyst [NiII(meso‐L)](ClO4)2, which was previously thought to operate as a molecular catalyst, is found to decompose to form a NiOx layer in a pH 7.0 phosphate buffer under prolonged catalytic conditions, as indicated by controlled potential electrolysis, electrochemical quartz crystal microbalance, and X‐ray photoelectron spectroscopy measurements. Interestingly, the formed NiOx layer desorbs from the surface of the electrode under less anodic potentials. Therefore, no nickel species can be detected on the electrode after electrolysis. Catalyst decomposition is strongly dependent on the pH and buffer, as there is no indication of NiOx layer formation at pH 6.5 in phosphate buffer nor in a pH 7.0 acetate buffer. Under these conditions, the activity stems from a molecular species, but currents are much lower. This study demonstrates the importance of in situ characterization methods for catalyst decomposition and metal oxide layer formation, and previously proposed design elements for nickel‐based catalysts need to be revised.

中文翻译:

镍基水氧化催化过程中潜在的和取决于缓冲剂的催化剂分解。

通过水电解生产氢得益于水氧化催化剂的开发。催化系统的设计规则可以为该开发过程提供帮助。分子配合物的反应性分析可能会由于其在催化条件下分解成可能具有活性的纳米粒子而变得复杂。这样的误解会导致错误的设计规则。在这项研究中,发现以前认为镍可以用作分子催化剂的镍基水氧化催化剂[Ni II(meso-L)](ClO 42分解形成NiO x受控的电位电解,电化学石英晶体微量天平和X射线光电子能谱测量表明,在长时间的催化条件下,pH 7.0磷酸盐缓冲液中的有机层会沉积。有趣的是,形成的NiO x层在较少的阳极电势下从电极表面解吸。因此,电解后在电极上无法检测到镍。催化剂的分解强烈依赖于pH和缓冲液,因为没有迹象表明在磷酸盐缓冲液或pH 7.0乙酸盐缓冲液中在pH 6.5会形成NiO x层。在这些条件下,活性源自分子种类,但电流要低得多。这项研究证明了就地的重要性 催化剂分解和金属氧化物层形成的表征方法,以及以前建议的镍基催化剂设计元素都需要修改。
更新日期:2020-11-09
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