Nanostructured MoO3 for Efficient Energy and Environmental Catalysis

Abstract

This paper mainly focuses on the application of nanostructured MoO 3 materials in both energy and environmental catalysis fields. MoO 3 has wide tunability in bandgap, a unique semiconducting structure, and multiple valence states. Due to the natural advantage, it can be used as a high-activity metal oxide catalyst, can serve as an excellent support material, and provide opportunities to replace noble metal catalysts, thus having broad application prospects in catalysis. Herein, we comprehensively summarize the crystal structure and properties of nanostructured MoO 3 and highlight the recent significant research advancements in energy and environmental catalysis. Several current challenges and perspective research directions based on nanostructured MoO 3 are also discussed.Molecules 2020, 25, 18 2 of 26 applications in energy and environmental catalysis on account of their relatively low cost, high activity, and stability [9][10][11][12].Molybdenum oxide (MoO 3 ), a kind of transition metal oxide with a n-type semiconducting, nontoxic nature and high stability, has attracted a lot of attention. In particular, nanostructured MoO 3 has demonstrated superior properties to bulk MoO 3 , which is successfully employed in rechargeable batteries [13], capacitors [14], photocatalysis [15], electrocatalysis [16], gas sensors [17], and other applications [6]. The extended tunnels between the MoO 6 octahedra in MoO 3 are suitable for insert/de-insert mobile ions, such as H + and Li + , and multiple oxidation states can enable rich redox reactions. Moreover, the superiorities of low cost, chemical stability, high theoretical specific capacity (1117 mA·h/g), and the environmentally friendly nature make nanostructured MoO 3 exceptional electrode materials for rechargeable batteries capacitors [13,18]. MoO 3 has been investigated as the photocatalyst in terms of its anisotropic layered structure for absorbing UV, as well as visible light. Introducing a defect band by H + intercalation or oxygen vacancies can create defect state and decrease MoO 3 bandgap, which effectively increase the photocatalytic activity [15]. Each oxygen atom bonds to only one molybdenum atom of MoO 6 octahedra, and oxygen vacancy generates Mo dangling bond. MoO 3 favors the adsorption of water molecules in oxygen vacancies, which act as electron acceptors and consequently reduce the energy barrier make it highly reactive for electrocatalysis [2,19]. As a good gasochromic material, MoO 3 has efficient positive-ion accommodation and good charge transfer, and it can be used as an optical-based gas sensor. Moreover, relying on the change in the conductance of the oxide-on-gas adsorption/reaction, MoO 3 has been used for NO, NO 2 , CO, H 2 , NH 3 , and other gases [17]. The unique structure strongly affects the performances. Large efforts have been made to obtain nanostructured MoO 3 with appealing properties by engineering multiple synthetic strategies for the applications in various fields. A variety of methods have been developed, including hydrothermal met...

Stable α-MoO3 Electrode with a Widened Electrochemical Potential Window for Aqueous Electrochemical Capacitors

“…A high η value indicates a poor electroactivity toward water electrolysis. This can be attributed to the weak electrocatalytic activity of MoO 3 for both the HER and the OER, the electrochemical inertness of the graphite substrate, and the relatively high electrochemical stability window of the neutral aqueous electrolyte against water splitting. , Both electrodes exhibit the features of pseudocapacitive materials because of the observed broad redox peaks. , …”

How the Complex Network of Specklegram Deciphers Intra‐Film Thermal Induced Dynamics?

“…[7,30] The RF sputtering technique was selected because of its potential to produce low-cost, uniform, and good quality films with tailored stoichiometry. [31] The quality of the deposited films depend on various deposition parameters. The experimental conditions of thin-film preparation were: (i) sample: MoO 3 (Sigma-Aldrich, purity 99.99%), (ii) substrate: glass substrate, (iii) chamber base pressure: ≈10 −6 mbar, (iv) background argon pressure: 0.03 mbar, (v) magnetron power supply frequency: 13.56 MHz, (vi) RF power: 150 W, (vii) deposition time: 30 min, (viii) substrate-target distance: 5 cm, (ix) post-deposition annealing temperature and time: 400 °C, 1 h. The commercially available MoO 3 powder was ground in an agate mortar with a pestle and was used as the sputtering target.…”

“…The reason for selecting molybdenum oxide (MoO 3 ) was because of its extensive use in electronic industry being a type III electrochromic, n-type, wide bandgap material exhibiting photochromic and thermochromic behavior because of its different coordination number, oxidation states, and stoichiometry. [31] Deposition in an inert gas such as argon changes the kinetic energy distribution of particles and significantly influences the resputtering of the deposited materials. During coating, Argon ions collided with the target and ejected the neutral atoms to form the plasma state.…”

Advances in the designs and mechanisms of MoO3 nanostructures for gas sensors: a holistic review

“…This unique layered structure of α-MoO3 has increases content of pentavalent Mo 5+ ions, which possesses strong affinity to oxygen 49,50 . Since gas sensors function by the reaction between oxygen and adsorbed analyte gas molecules, the presence of Mo 5+ increases the adsorption effect, thus resulting in enhancing the gas sensor response 49,[51][52][53][54] . In recent times, the MoO3 based gas…”