Electrochemical Preparation of Molybdenum Trioxide Thin Films:  Effect of Sintering on Electrochromic and Electroinsertion Properties

Abstract

Molybdenum trioxide (MoO3) thin films prepared by cathodic electrodeposition on indium-tin-oxide coated glass substrates from aqueous peroxo-polymolybdate solutions have been studied as a function of sintering temperature (25-450 °C). Cyclic voltammetry, chronopotentiometry, chronoamperometry, and spectroelectrochemical measurements performed with MoO 3 thin films in 1 M LiClO4/propylene carbonate demonstrate that the electrochemical behavior (Li + insertion/extraction and coloration) is strongly dependent upon thermally induced changes in micro-/nanocrystallinity, which directly influence measured Li + diffusion properties as well as electroinsertion and electrochromic reversibilities. Structural analysis using X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy indicate that films heat treated at 100 °C or less exist as amorphous oxide-hydrates of molybdenum; whereas films heated to 250 °C exist as disordered, mixed-phase materials comprising monoclinic β-MoO 3 and orthorhombic R-MoO3. Crystallization to the more thermodynamically stable orthorhombic R-MoO3 occurs at 350 °C and above. The mixed-phase material exhibits inhomogeneous electrochemical activity, evidenced by the existence of complicated voltammetric and chronoamperometric responses. The effects of sintering temperature on ion insertion and electrocoloration properties are discussed.

Hydrothermal synthesis and electrochemical properties of α-MoO3 nanobelts used as cathode materials for Li-ion batteries

“…The present material has high specific capacities of 252 and 227 mA h g −1 for the initiation of charge-discharge process, respectively. Its capacities were decreased to 158 and 124 mA h g −1 after 30 cycles due to the irreversible capacity associated with the decomposition of the electrolytic solution and the solid-electrolyte interface (SEI) formation [25][26][27]. They were constant at 160 and 119 mA h g −1 afterwards.…”

Structurally and mechanically tunable molybdenum oxide films and patterned submicrometer structures by electrodeposition

“…The influence of bath formulation and growth conditions on the oxidation state of molybdenum oxide films has been studied in detail in the past [3]. McEvoy and Stevenson described the cathodic electrodeposition of MoO 3 from acidic peroxo-polymolybdate solutions onto indium-doped tin oxide (ITO) electrode [27]. The same authors deeply investigated the mechanism of molybdenum oxides deposition using different tools, namely chronocoulometry and quartz crystal microbalance techniques [28,29].…”

“…It was found that the sweep rate in cyclic voltammetry experiments determined the formation of either α-or -MoO 3 [24]. Remarkably, X-ray diffraction analyses indicate that the films are typically amorphous (or poorly crystalline) in the as-deposited state [11,24,27]. Therefore, annealing at temperatures equal to (or beyond) 250 ºC is typically required to achieve fully crystalline films [11,27].…”

“…Remarkably, X-ray diffraction analyses indicate that the films are typically amorphous (or poorly crystalline) in the as-deposited state [11,24,27]. Therefore, annealing at temperatures equal to (or beyond) 250 ºC is typically required to achieve fully crystalline films [11,27]. Guerfi et al [32] showed that an increase in crystallinity of the as-deposited molybdenum oxide is possible after heat-treating the films in air at 260 ºC and that complete crystallization occurs at 300ºC.…”

Facile synthesis of a green metastable MoO3 for the selective oxidation of methanol to formaldehyde

“…This method consumes a lot of water and also has very low yield as reported by Mizushima et al [15] that the Mo content in the final solution was reported only 3.3 % of the initial value. Some research groups tried to synthesize b-MoO 3 from other molybdenum sources, such as peroxo-polymolybdate [16], commercial a-MoO 3 [17] or sodium molybdate solution [18] but these efforts were unsuccessful. The thermodynamically stable a-MoO 3 was usually detected in the final product.…”