Redox Potentials of Polyoxometalates from an Implicit Solvent Model and QM/MM Molecular Dynamics
Redox Potentials of Polyoxometalates from an Implicit Solvent Model and QM/MM Molecular Dynamics
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DOI：
10.1021/acs.jpcc.0c04169
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发表时间：
2020-07-16
影响因子：
3.7
通讯作者：
Penfold, T. J.
中科院分区：
文献类型：
--
作者：
Falbo, E.;Penfold, T. J.
电化学储存能量的能力对于将风能和太阳能等间歇性可再生能源整合到现代能源网络中至关重要。在众多可能的解决方案中，氧化还原液流电池（rfb）尤其具有吸引力，因为其能量含量和功率输出可以独立缩放，具有高度的灵活性。对于rbb来说，多金属氧酸盐（pom）非常有吸引力，因为这些过渡金属氧化物纳米团簇表现出以可逆方式存储多个电子的能力。然而，尽管人们对POM的性质很感兴趣，但POM结构与其氧化还原性质之间的联系仍不清楚。在这篇论文中，我们使用许多不同的理论方法研究了[SiW12O40](4-) （SiW12）和[PV14O42](9-) （PV14）的氧化还原电位。我们首先采用热力学循环方法结合量子化学和隐式溶剂化来估计氧化还原电位。随后，我们使用分子动力学来促进溶剂环境的明确描述。隐式溶剂化模型是半定量的，当存在强溶质-溶剂相互作用时，问题就出现了。通过热力学积分法和分数电子法两种方法，我们表明，明确地包括溶剂环境可以改善计算出的强溶质-溶剂相互作用的氧化还原电位，并为其性质及其在还原时的变化提供重要的原子性见解。我们的研究结果说明了这些方法在解决模拟POMs氧化还原电位这一具有挑战性的问题方面的性能，并为更详细地了解存在的结构-性质关系提供了框架。
The ability to electrochemically store energy is crucial for the integration of intermittent renewable energy sources such as wind and solar power into modern energy grids. Among a wide variety of possible solutions, redox flow batteries (RFBs) are especially attractive as their energy content and power output can be scaled independently, offering a high degree of flexibility. For RFBs, polyoxometalates (POMs) are very appealing as these transition metal oxide nanoclusters exhibit the ability to store multiple electrons in a reversible manner. However, despite the interest in their properties, the link between the POM structure and its redox properties remains unclear. In this contribution, we study the redox potentials of [SiW12O40](4-) (SiW12) and [PV14O42](9-) (PV14) using a number of different theoretical methods. We first adopt the thermodynamic cycle approach combined with quantum chemistry and implicit solvation to estimate the redox potentials. Subsequently, we use molecular dynamics to facilitate an explicit description of the solvent environment. The implicit solvation model is semiquantitative, and problems arise when strong solute-solvent interactions are present. Using two approaches, thermodynamic integration and fractional number of electrons methods, we show that explicitly including the solvent environment can improve the calculated redox potentials for strong solute-solvent interactions and also gives important atomistic insights into its nature and how it changes upon reduction. Our results illustrate the performance of these approaches for addressing the challenging problem of simulating the redox potentials in POMs and provides the framework to develop a more detailed understanding of the structure-property relationships that exist.