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Comparison of Penta and Tetra-pyridyl Cobalt-based Catalysts for Water Reduction: H2 Production Cycle, Solvent Response and Reduction Free Energy.
ChemPhysChem ( IF 2.3 ) Pub Date : 2020-09-21 , DOI: 10.1002/cphc.202000600
Yeliz Gurdal 1 , Marcella Iannuzzi 2
Affiliation  

Understanding water reduction towards H2 generation is crucial to overcome today's renewable energy obstacles. Previous studies have shown the superior H2 production performances of Cobalt based penta‐pyridyl (CoaPPy) and tetra‐pyridyl (CoaTPy) complexes in solution. We investigate H2 production cycles of CoaPPy and CoaTPy complexes immersed in water solution by means of Ab‐initio Molecular Dynamics and Density Functional Theory. We monitor dynamic properties of the systems, solvent response and structural changes occurring in the catalysts, by simulating all intermediate steps of the H2 production cycle. Reduction free energies and reorganization energies are calculated. Our results show that, following the first electron injection, H2 production proceeds with the singlet spin state. Following the first electron insertion, we observe a significant rearrangement of the hydrogen bonding network in the first solvation shell. The cobalt center turns out to be more accessible for the surrounding water molecules in the case of CoaTPy at all the intermediate steps, which explains its higher catalytic performance over CoaPPy. Following the first reduction reaction, a larger gain in reduction free energy is estimated for CoaTPy with respect to CoaPPy, with a difference of 0.14 eV, in line with the experiments. For the second reduction, instead, CoaPPy shows more negative reduction potential, by 0.41 eV.

中文翻译:

五水和四吡啶基钴基减水催化剂的比较:H2生产周期,溶剂响应和还原自由能。

了解减少H 2产生的用水量对于克服当今的可再生能源障碍至关重要。先前的研究表明,溶液中钴基五吡啶基(CoaPPy)和四吡啶基(CoaTPy)配合物具有优异的H 2生产性能。我们通过从头算分子动力学和密度泛函理论研究了浸泡在水溶液中的CoaPPy和CoaTPy配合物的H 2生产周期。我们通过模拟H 2的所有中间步骤来监控系统的动态特性,溶剂响应和催化剂中发生的结构变化生产周期。计算还原自由能和重组能。我们的结果表明,在第一次电子注入之后,H 2生产以单重态自旋状态进行。第一次电子插入后,我们观察到第一个溶剂化壳中氢键网络的显着重排。在所有中间步骤中,在CoaTPy的情况下,钴中心对于周围的水分子来说更容易接近,这说明了它比CoaPPy具有更高的催化性能。在第一个还原反应之后,与实验一致,相对于CoaPPy,CoaTPy的还原自由能估计有较大的提高,相差0.14 eV。相反,对于第二次还原,CoaPPy显示出更大的负还原电位,为0.41 eV。
更新日期:2020-09-21
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