Detailed atomistic understanding of the vanadium redox reactions taking place at electrode/water interfaces is key for improvement of the power density of vanadium redox flow batteries. In this work, we employ ab initio molecular dynamics-based metadynamics simulations to examine V²⁺/V³⁺ and VO₂⁺/VO²⁺ redox reactions at the oxygen-functionalized graphite (112̅0) surface contrasting the behavior of O–C═O and C═O groups. By evaluating free-energy barriers, we reveal that the kinetics of adsorption and desorption processes for every vanadium ion is more favorable in the case of O–C═O. We also find that interfacial VO₂⁺/VO²⁺ transformations should be more rapid than those observed for the V²⁺/V³⁺ couple, with the V³⁺ desorption being the rate-limiting step of the overall process. The obtained results suggest that increasing the content of O–C═O groups on carbon-based electrodes should help enhance the power density of vanadium redox flow batteries.

中文翻译：

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从自由能计算中，氧官能化碳电极对钒氧化还原液流电池的电催化活性

对电极/水界面处发生的钒氧化还原反应的详细原子了解是提高钒氧化还原液流电池功率密度的关键。在这项工作中，我们采用从头算分子动力学的元动力学模拟方法，研究了氧官能化石墨（112̅0）表面上的V ²⁺ / V ³⁺和VO ₂ ⁺ / VO ²⁺氧化还原反应，以对比O–C的行为。 ═O和C═O组。通过评估自由能垒，我们发现在O–C═O的情况下，每种钒离子的吸附和解吸过程动力学更为有利。我们还发现界面VO ₂ ⁺ / VO ²⁺转变应比对V ²⁺ / V ³⁺对观察到的转变更快，其中V ³⁺解吸是整个过程的限速步骤。获得的结果表明，增加碳基电极上O–C═O的含量应有助于提高钒氧化还原液流电池的功率密度。