Lei Haitao, Han Ali, Li Fengwang, Zhang Meining, Han Yongzhen, Du Pingwu, Lai Wenzhen, Cao Rui
Department of Chemistry & Beijing Key Laboratory of Opto-electronic Functional Materials and Micro-nano Devices, Renmin University of China, Beijing, 100872, China.
Phys Chem Chem Phys. 2014 Feb 7;16(5):1883-93. doi: 10.1039/c3cp54361g.
Six cobalt and manganese corrole complexes were synthesized and examined as single-site catalysts for water splitting. The simple cobalt corrole [Co(tpfc)(py)2] (1, tpfc = 5,10,15-tris(pentafluorophenyl)corrole, py = pyridine) catalyzed both water oxidation and proton reduction efficiently. By coating complex 1 onto indium tin oxide (ITO) electrodes, the turnover frequency for electrocatalytic water oxidation was 0.20 s(−1) at 1.4 V (vs. Ag/AgCl, pH = 7), and it was 1010 s(−1) for proton reduction at −1.0 V (vs. Ag/AgCl, pH = 0.5). The stability of 1 for catalytic oxygen evolution and hydrogen production was evaluated by electrochemical, UV-vis and mass measurements, scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), which confirmed that 1 was the real molecular catalyst. Titration and UV-vis experiments showed that the pyridine group on Co dissociated at the beginning of catalysis, which was critical to subsequent activation of water. A proton-coupled electron transfer process was involved based on the pH dependence of the water oxidation reaction catalyzed by 1. As for manganese corroles 2–6, although their oxidizing powers were comparable to that of 1, they were not as stable as 1 and underwent decomposition at the electrode. Density functional theory (DFT) calculations indicated that water oxidation by 1 was feasible through a proposed catalytic cycle. The formation of an O–O bond was suggested to be the rate-determining step, and the calculated activation barrier of 18.1 kcal mol(−1) was in good agreement with that obtained from experiments.
合成了六种钴和锰的卟啉配合物，并将其作为水分解的单中心催化剂进行了研究。简单的钴卟啉[Co(tpfc)(py)₂]（1，tpfc = 5,10,15-三(五氟苯基)卟啉，py = 吡啶）能高效催化水氧化和质子还原。通过将配合物1涂覆在氧化铟锡（ITO）电极上，在1.4 V（相对于Ag/AgCl，pH = 7）下电催化水氧化的周转频率为0.20 s⁻¹，在 -1.0 V（相对于Ag/AgCl，pH = 0.5）下质子还原的周转频率为10¹⁰ s⁻¹。通过电化学、紫外可见光谱和质谱测量、扫描电子显微镜（SEM）和能量色散X射线光谱（EDX）对1催化析氧和产氢的稳定性进行了评估，证实1是真正的分子催化剂。滴定和紫外可见光谱实验表明，Co上的吡啶基团在催化开始时解离，这对随后水的活化至关重要。基于1催化的水氧化反应对pH的依赖性，涉及质子耦合电子转移过程。至于锰卟啉2 - 6，尽管它们的氧化能力与1相当，但它们不如1稳定，在电极上会发生分解。密度泛函理论（DFT）计算表明，通过提出的催化循环，1催化水氧化是可行的。O - O键的形成被认为是速率决定步骤，计算得到的18.1 kcal mol⁻¹的活化能垒与实验结果吻合良好。
