Buffer pKa Impacts the Mechanism of Hydrogen Evolution Catalyzed by a Cobalt Porphyrin-Peptide
Buffer pKa Impacts the Mechanism of Hydrogen Evolution Catalyzed by a Cobalt Porphyrin-Peptide
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DOI：
10.1021/acs.inorgchem.0c00362
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发表时间：
2020-06-15
影响因子：
4.6
通讯作者：
Bren, Kara L.
中科院分区：
文献类型：
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作者：
Alvarez-Hernandez, Jose L.;Sopchak, Andrew E.;Bren, Kara L.
研究了pH值对钴卟啉肽（CoMP 11-Ac）催化电化学析氢机理的影响。向在水和KCl中的CoMP 11-Ac中加入缓冲剂导致催化电流相对于其在不存在缓冲剂的情况下的值增强高达200倍。两种不同的催化制度被确定为缓冲液pK（a）的函数。在存在pK（a）7.7的缓冲液的情况下，E-h = -1.42 V（建议反映Co（II/I）对）保持独立于缓冲液pk，与在这些条件下限制Co（III）-H形成的速率一致。我们得出结论，缓冲物质pK（a）影响催化电流和电位以及反应的速率决定步骤。
The effect of buffer pK(a) on the mechanism of electrochemical hydrogen evolution catalyzed by a cobalt porphyrin peptide (CoMP11-Ac) at constant pH is presented. The addition of buffer to CoMP11-Ac in water and KCl leads to an enhancement of the catalytic current of up to 200-fold relative to its value in the absence of a buffer. Two distinct catalytic regimes are identified as a function of the buffer pK(a). In the presence of buffers with pK(a) 7.7), an E-h = -1.42 V, proposed to reflect the Co(II/I) couple, is maintained independent of the buffer pk, consistent with rate-limiting Co(III)-H formation under these conditions. We conclude that the buffer species pK(a) impacts catalytic current and potential and the rate-determining step of the reaction.