Theoretical Study on the Electrochemical Properties of Ti-Modified Vanadium-Oxide Clusters

Density functional theory (DFT) calculations were employed to systematically investigate the electrochemical properties of a series of vanadium-oxide clusters, including Lindqvist-type polyoxovanadates (POVs), [V6O7(OCH3)12] (V6), [TiV5O6(OCH3)13]- (TiV5), and [Ti2V4O5(OCH3)14] (Ti2V4) as well as the cationic vanadium-oxide cluster [Ti3V3O4(OCH3)15]+ (Ti3V3). Analysis on the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) reveals that Ti modification shifts the electron-gaining center to Ti atoms, while V atoms remain the electron-losing centers. DFT calculations demonstrate that Ti modification effectively modulates the redox potentials of vanadium-oxide clusters and significantly broadens their electrochemical windows. However, root-mean-square deviation (RMSD) values and recombination energy calculations indicate that Ti modification adversely affects the structural stability of vanadium-oxide clusters. Notably, Ti modification substantially enhances the diffusion coefficients, with Ti2V4 exhibiting the most pronounced improvement. Additionally, solvation energy calculations show that Ti modification alters the surface charge distribution of vanadium-oxide clusters, strengthening hydrogen bonding interactions between vanadium-oxide clusters and acetonitrile (CH3CN), thereby significantly improving their solubility.