Interfacial Titanium Diffusion Self-Adapting Layer in Ultrathin Epitaxial MnO₂/TiO₂ Heterostructures

Abstract

The electrochemical performance of supercapacitors is suppressed by a large number of defects in the interface of heterostructure due to lattice mismatch. In this paper, the (001) oriented rutile MnO 2 thin films with different thicknesses were grown on rutile TiO 2 substrates. The lattice mismatch between film and substrate was minimized through a Ti diffusion self-adapting layer. The energy-dispersive spectroscopy mappings were used to measure the diffusion range of Ti. The results of high-resolution X-ray diffraction confirmed that the dependence of the out-of-plane lattice parameter on the thickness was consistent with the self-adapting interface model, indicating that Ti diffusion can indeed alleviate the lattice mismatch. In addition, the results of the synchrotron soft X-ray absorption spectrum indicated that the capacitance of the thin films with a large proportion of Ti diffusion increased with electrons involved in the reaction. Although the decrease of carrier density and conductivity of the thinner films depressed the electrochemical activity, it is worth mentioning that the film we designed still has considerable specific capacitance even when it is very thin, which can provide a new idea for the development of thinner and larger capacity potential microsupercapacitors.

Physicochemical properties of different crystal forms of manganese dioxide prepared by a liquid phase method and their quantitative evaluation in capacitor and battery materials

“…[46][47][48] In order to improve the conductivity of manganese dioxide, graphene and carbon nanotubes can be added into it, or MnO 2 can be loaded onto a conductive substrate to create more contact interfaces, so as to improve charge transfer efficiency. [49][50][51][52] Doping different atoms and materials, [53][54][55][56] forming heterostructures between different crystal forms, [57][58][59] and intercalating ions between layers can modify the manganese dioxide crystal structure, [60][61][62] which can improve the conductivity and increase the layer spacing, thus improving the electrochemical performance. The existence of oxygen vacancy promotes charge transfer in the local electric eld and improves the surface redox reaction kinetics and the conductivity, thus improving the electrochemical performance.…”