First-principles molecular dynamics simulation study on Ti/Mn ions in aqueous sulfuric acid for use in redox flow battery

• Published in: Journal of energy storage Vol. 72; p. 108398
• Main Authors: Choe, Yoong-Kee, Tsuchida, Eiji, Tokuda, Kazuya, Otsuka, Jun, Saito, Yoshihiro
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 20.11.2023
• Subjects: Flow battery; Molecular dynamics simulation; Ti/Mn ions; Flow battery; Molecular dynamics simulation; Ti/Mn ions
• ISSN: 2352-152X; 2352-1538
• DOI: 10.1016/j.est.2023.108398

The effect of the Ti4+ ion on the structural and chemical features of the Mn3+ ion in aqueous sulfuric acid was investigated using first-principles molecular dynamics (FPMD) simulation and second-order perturbation theory (CASPT2) with a complete active space self-consistent field (CASSCF) reference function. The focus was on the role of the Ti ion in the MnO2 formation reaction from the Mn3+ ion. The simulations showed that Mn3+ forms two types of complexes, [Mn(H2O)4(SO4)2]1− and [Mn(H2O)6]3+ in aqueous sulfuric acid with Ti ions where the population of the former was found to be higher than that of the latter. We found that when the HSO4− ion was coordinated to a Ti4+ ion, it released one proton, which increases proton concentration in the solution. Detailed quantum chemical calculations on the isolated Mn complexes show that if the Mn complexes interact with a hydronium ion, the stability of Mn3+ ion is increased to a large extent. Such a result implies that the increased local proton concentration due to Ti4+ ions hinders formation of MnO2 particle. •The effect of the Ti4+ ion on the structural and chemical features of the Mn3+ ion in aqueous sulfuric acid.•The role of the Ti ion in the MnO2 formation reaction from the Mn3+ ion in aqueous sulfuric acid solutions for use in redox flow battery.