Novel Metastable Hexagonal MoO₃ Nanobelts: Synthesis, Photochromic, and Electrochromic Properties

Abstract

In this work, we report the crystalline structure, morphology, and optical properties of novel metastable hexagonal phase MoO3 (h-MoO3) nanobelts prepared by a simple hydrothermal route from peroxomolybdate solution with the presence of sodium nitrate as a mineralizer. During the reaction process, NaNO3 has been proposed to influence the deoxidation, condensation, and further dehydration of the water-soluble peroxomolybdate precursor for connecting the [MoO6] octahedra with vertex sharing and edge sharing arrangements on determining the generation of metastable phase. The present work comparatively investigates the photochromic and electrochromic behaviors of the resultant hexagonal h-MoO3 nanobelts and the common thermodynamically stable orthorhombic α-MoO3 nanobelts. The performances concerning photochromism on two types of MoO3 nanobelt suspensions show that the photochemical efficiency of h-MoO3 is more excellent than that of α-MoO3 under UV light irradiation based on a remarkable coloration phenomenon. And the as-obtained h-MoO3 nanobelt coated film exhibits a steady electrochromic property in quick response to electrical impulse. Higher structure openness degree in the tunnel structure of h-MoO3, which could lead to an efficient electron−hole separation and provid larger spatial locations for cation insertion/extraction and diffusion, is suggested to be responsible for its enhanced coloration properties.