Electrochemistry of Polymeric Cobaloxime-Containing Assemblies in Organic and Aqueous Solvents
Electrochemistry of Polymeric Cobaloxime-Containing Assemblies in Organic and Aqueous Solvents
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DOI：
10.1149/2162-8777/aba1ff
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发表时间：
2020-01
影响因子：
2.2
通讯作者：
Brian L. Wadsworth;Daiki Nishiori;Nghi P. Nguyen;Edgar A. Reyes Cruz;G. Moore
中科院分区：
文献类型：
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作者：
Brian L. Wadsworth;Daiki Nishiori;Nghi P. Nguyen;Edgar A. Reyes Cruz;G. Moore
我们报告了由分子钴肟催化剂通过中间聚乙烯吡啶表面涂层固定在石墨电极上组成的异质均质组件的结构和电化学性质。当这些修饰电极浸入有机溶剂（含有 0.1 M 四丁基高氯酸铵作为支持电解质的碳酸丙烯酯）或碱性水溶液（0.1 M NaOH）中时，循环伏安法测量可以确定嵌入聚合物结构中的钴肟的 Co III/II 峰值电位和 Co II/I 中点电位。此外，使用 pH 中性水溶液（0.1 M 磷酸盐缓冲液）记录的伏安法测量结果证实，固定化钴肟仍具有产氢催化活性，并且当相对于 H+/H 2 平衡电位以 –0.35 V 极化时，其转换频率为 1.6 s− 1。与固定化钴肟相关的氧化还原特征的波形分析表明，与碱性条件相比，pH 中性条件下聚合物膜内的排斥相互作用更强，这归因于较低 pH 值下吡啶鎓物质的比例增加。我们的测量还显示了在不同溶剂环境中测量时电化学活性位点数量的变化，这表明在非催化溶剂条件下确定的电活性负载不一定代表催化条件下的电活性负载，从而可能导致催化周转频率的误报。
We report on the structural and electrochemical properties of a heterogeneous-homogeneous assembly composed of molecular cobaloxime catalysts immobilized onto graphite electrodes via an intervening polyvinylpyridine surface coating. When these modified electrodes are immersed in an organic solvent (propylene carbonate containing 0.1 M tetrabutylammonium perchlorate as a supporting electrolyte) or basic aqueous solutions (0.1 M NaOH), cyclic voltammetry measurements enable determination of the Co III/II peak potentials and Co II/I midpoint potentials of cobaloximes embedded within the polymeric architectures. Additionally, voltammetry measurements recorded using pH neutral aqueous solutions (0.1 M phosphate buffer) confirm the immobilized cobaloximes remain catalytically active for hydrogen production and operate at a turnover frequency of 1.6 s− 1 when polarized at–0.35 V vs the H+/H 2 equilibrium potential. Waveform analysis of redox features associated with immobilized cobaloximes indicates more repulsive interactions within the polymer film at pH neutral vs basic conditions, which is attributed to the increased fraction of pyridinium species at lower pH values. Our measurements also show the number of electrochemically active sites changes when measured in different solvent environments, indicating that electroactive loadings determined under non-catalytic solvent conditions are not necessarily representative of those under catalytic conditions and could thereby lead to misrepresentations of catalytic turnover frequencies.