Template Electrochemical Growth and Properties of Mo Oxide Nanostructures

Abstract

This work is aimed at studying the growing process of nanostructures electrodeposited from molybdate aqueous solutions at different pH values into pores of polycarbonate membrane templates. The challenging issue was the opportunity to investigate a rather complex deposition process in a confined ambient, where electrochemical conditions are quite different from those usually established for deposition on a flat substrate. Nanostructures were grown from a bath containing Mo 7 O 24 6− (NH 4 ) 6 Mo 7 O 24 •4H 2 O) at different concentrations (50−100 g/L), at a constant cathodic current density of 2 mA/cm 2 (electrodeposition area ∼8 cm 2 ). Nanostructured deposit was characterized by XRD, EDS, Raman, XPS, and photoelectrochemical spectroscopy. Several parameters have been investigated, such as electrodeposition time, concentration of Mo precursor, and pH. These parameters do not influence the nature of deposit that always consists of mixed valence molybdenum oxides, whereas the nanostructure morphology changes with pH. Nanostructures were found amorphous and consisting mainly of MoO 2 underneath α-MoO 3 . Photoelectrochemical spectroscopy revealed n-type conductivity and two linear regions in the (I ph •hν) 0.5 vs hν plot, giving optical gaps of 2.5 and 3.2 eV, typical of MoO 2 and α-MoO 3 , respectively. To our best knowledge, this is the first paper dealing with the fabrication of a uniform array of MoO 2 /MoO 3 core−shell nanowires by template electrosynthesis.

Amorphous oxygen-rich molybdenum oxysulfide Decorated p-type silicon microwire Arrays for efficient photoelectrochemical water reduction

“…The Raman spectrum shown in Figure S11a confirms the presence of bridged oxygen and bridged sulfur bonds (i.e., Mo-O-Mo and Mo-S-Mo) as well as the O-Mo-S bonds [54]; while the FTIR spectrum verifies the presence of terminal oxygen (i.e., Mo= O, Figure S11b, SI) [55]. Notably, both Raman and FTIR spectra are distinctly different from those of MoO 3 [56][57][58], MoO 2 [58,59], and MoS 2 [60,61] reported in the literature, showing some unique characteristics of reduced oxysulfide [54]. This indicates that the deposited MoO x S y is not a simple blend of Mo oxides and sulfides.…”

Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite

“…Most notable feature is the fact that the evolved Mo 3d scan is rather broad in nature, which is due to Mo ions existing in multiple valence states. 39 Note that the Mo chemistry is complex due its ability to take chemical valence states ranging from 2+ to 6+. [35][36][37][38][39]…”

“…The observed x-a trend in CFMO indicates the continuous increase in lattice parameter with Mo content. It is obvious that when some of Fe 3+ ions are substituted by Mo y+ ions (y=3,4, 5 and 6), the lattice is subjected to distortion resulting in an increase or decrease in the lattice parameter.Note that the chemistry i.e., the chemical state of Mo, is always complex due to the possibility of Mo ions exist in variable chemical valence states, namely Mo 3+ , Mo 4+ , Mo 5+ , Mo 6+ [35][36][37][38][39]. Therefore, the lattice parameter increase or decrease or a reasonable compromise is due to the net result of two effects.…”

Metal-Oxide Based Nanomaterials: Synthesis, Characterization and Their Applications in Electrical and Electrochemical Sensors

“…Apart from the carbon based and metal nanomaterials, metal oxides (MOX) attracted great attention, due to their chemical characteristics and functional properties [ 3 , 4 , 5 ], for the development of chemical sensors [ 6 , 7 ] applied to achieve a safer working environment. In compliance with government regulations such as Control of Substances Hazardous to Health (COSHH) and Occupational Safety and Health Administration (OSHA) regulations, MOX based sensors have been recently adopted to efficiently reveal the presence of toxic and combustible gases (i.e., hydrogen sulfide, carbon monoxide) to withstand high humidity and temperature.…”