Wu Yueshen, Jiang Jianbing, Weng Zhe, Wang Maoyu, Broere Daniël L J, Zhong Yiren, Brudvig Gary W, Feng Zhenxing, Wang Hailiang
Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.
Energy Sciences Institute, Yale University, West Haven, Connecticut 06516, United States.
ACS Cent Sci. 2017 Aug 23;3(8):847-852. doi: 10.1021/acscentsci.7b00160. Epub 2017 Jul 26.
Transition-metal-based molecular complexes are a class of catalyst materials for electrochemical CO reduction to CO that can be rationally designed to deliver high catalytic performance. One common mechanistic feature of these electrocatalysts developed thus far is an electrogenerated reduced metal center associated with catalytic CO reduction. Here we report a heterogenized zinc-porphyrin complex (zinc(II) 5,10,15,20-tetramesitylporphyrin) as an electrocatalyst that delivers a turnover frequency as high as 14.4 site s and a Faradaic efficiency as high as 95% for CO electroreduction to CO at -1.7 V vs the standard hydrogen electrode in an organic/water mixed electrolyte. While the Zn center is critical to the observed catalysis, in situ and operando X-ray absorption spectroscopic studies reveal that it is redox-innocent throughout the potential range. Cyclic voltammetry indicates that the porphyrin ligand may act as a redox mediator. Chemical reduction of the zinc-porphyrin complex further confirms that the reduction is ligand-based and the reduced species can react with CO. This represents the first example of a transition-metal complex for CO electroreduction catalysis with its metal center being redox-innocent under working conditions.
基于过渡金属的分子配合物是一类用于电化学将CO还原为CO的催化剂材料，其可以经过合理设计以实现高催化性能。迄今为止开发的这些电催化剂的一个常见机理特征是与催化CO还原相关的电生成还原金属中心。在此，我们报道了一种异质化的锌卟啉配合物（锌（II）5,10,15,20-四甲基卟啉）作为一种电催化剂，在有机/水混合电解质中，相对于标准氢电极在-1.7 V时，其对于将CO电还原为CO的周转频率高达14.4 s⁻¹，法拉第效率高达95%。虽然锌中心对于观察到的催化作用至关重要，但原位和操作X射线吸收光谱研究表明，在整个电位范围内它是无氧化还原活性的。循环伏安法表明卟啉配体可能充当氧化还原介质。锌卟啉配合物的化学还原进一步证实还原是基于配体的，并且还原产物可以与CO反应。这代表了过渡金属配合物用于CO电还原催化的首个实例，其金属中心在工作条件下是无氧化还原活性的。
