Papers by Keyword: Photoelectrochemical

Abstract: Cu (OH)₂@TiO₂ nanowire arrays (NWAs) on the Fluorine-doped tin oxide (FTO) substrates had been fabricated via an simple and facile deposition method. The as-prepared Cu (OH)₂@TiO₂ NWAs were subsequently characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffraction (XRD), UVVis diffuse reflectance spectra (DRS), X-ray photoelectron spectrometer (XPS) and photoelectrochemical measurements. This results suggested that the Cu (OH)₂@TiO₂ NWAs efficiently impeded the recombination between photoelectrons and holes. Therefore, this approach would afford a simple, effective, facile and low-cost method for preparation photoanode, which would enhance the hydrogen generating capability of TiO₂ from water splitting.

Abstract: Ferrites have been predicted to be potential material for photo catalytic and photo electrochemical (PEC) hydrogen generation under visible light photons. The article briefly reviews, as well as compares the supremacy of ferrites over titanates and sulfides with respect to their photo-electro catalytic hydrogen producing ability. It shows that though the band energetic of a material plays a vital role to induce the photo-splitting of water; but its optical structure, at the first instance is very important to utilize it to absorb the visible light photons. Among all the PEC materials, the low-band gap ferrites (Fe-d orbital) favor absorption of visible light photons; at the same time offer an advantage of being an eco-friendly material system. A specific focus is given to the single phase, nanostructure and composite forms of typical ZnFe₂O₄ system. Though a concise report, but also throws light on the importance and tunability of PEC properties.

Abstract: Mononuclearmolybdenum complex with the general formula [MoTp*(NO)I(X)], where Tp* =tris(3,5-dimethylpyrazolyl)hidroborate and X =1,4-bis(pyridin-4-ylethynyl)benzene) was found to exhibit the required chemical and physical properties as a photosensitiser in photoelectrochemical cell. The complex was structurally characterised by infrared, UV-Vis and electrochemical analysis. TiO₂ electrode films were prepared by paste technique and characterised by SEM and XRD. Photoelectrochemical properties of [MoTp*(NO)I(X)]-sensitisedTiO₂ photoelectrode were carried out in 1.0 M NaOH electrolyte with a SCE reference electrode and a platinum counter electrode. The [MoTp*(NO)I(X)]-sensitised TiO₂ photoelectrode showed positive photoinduced current compared to unsensitised TiO₂ photoelectrode.

Abstract: CuZnSnSe thin films were deposited by thermal vacuum evaporation with and without argon gas stream at room temperature. Effect of argon gas on surface morphology and on photoelectrochemical (PEC) characteristics of the films was studied. The electrodes prepared under argon gas showed better enhanced characteristics, due to slower nucleation and growth due to dilution effect of the inert gas. While both electrodes showed soundly good PEC behaviors in a hexacyanoferrate(III)/hexacyanoferrate(II) redox couple, the electrode with argon gas showed 20 fold enhancement in photoactivity, compared to the one without argon gas. The results manifested thin film electrode performance can be enhanced simply by inclusion of argon inert gas inside the preparation chamber, with no need for other procedures such as annealing.

Abstract: This article presents a comparative study on the synthesis and characterization of the binary and ternary ferrites for photocatalytic and photoelectrochemical applications. The importance and role of ferrite photocatalysts is discussed in context to the visible-light active photocatalyst application viz. for hydrogen production via. water-splitting. It also demonstrates that computational-exploration of any material system is key to identify, and achieve visible-light active photocatalysts.

Abstract: The crystallization of anatase from amorphous TiO₂ nanotube arrays (TNTs) has been carried out by annealing in air and hydrothermal treatment in water. The morphology and crystalline phase of obtained TNTs membranes were detailedly characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The surface electronic structure and photoelectrochemical properties (PEC) of TNTs obtained by different crystallization methods were investigated. The results show that the TNTs electrode crystallized by hydrothermal treatment method demonstrate a broader surface photovoltage response range and higher photoelectrochemical properties than that of TNTs electrode directly annealed in air due to effective Ti³⁺ sites.

Abstract: We have developed a chemical process for atomic planarization of gallium nitride (GaN) using a platinum catalyst and ultraviolet (UV) light irradiation. The process is mediated by a hydrolysis reaction catalyzed by platinum as a solid catalyst. Because the reaction occurs selectively from the step edges, a flat surface composed of a straight step-and-terrace structure is obtained. In the absence of UV light, owing to the low step edge density, the removal rate is quite slow, approximately 1 nm/h. In contrast, under UV light, etch pits are formed on the terraces by photo-electrochemical etching causing an increase in the step edge density. We achieved surface planarization with a removal rate of 9.6 nm/h assisted by irradiation with UV light.

Abstract: TiO_2, transition metal oxide nanotubes were successfully grown by anodizing of titanium foil (Ti) in ethylene glycol electrolyte containing 5wt % hydrogen peroxide and 5wt % ammonium fluoride for 60 minutes at 60V. It was found such electrochemical condition resulted in the formation of nanotube with average diameter of 90nm and length of 6.6 µm. These samples were used to study the effect of W loading by RF sputtering on TiO₂ nanotubes. Amorphous TiO₂ nanotube substrate leads to enhance incorporation of W instead of anatase. Therefore for the entire study, W was sputtered on amorphous TiO₂ nanotube substrate. TiO₂ nanotube sputtered below 1 minute resulted in the formation of W-O-Ti while beyond this point; it accumulates to form a self-independent structure of WO₃ on the surface of the nanotubes. TiO₂ nanotube sputtered for 1minute at 100W and annealed at 450°C exhibited best photocurrent density (1.4 mA/cm²) with photoconversion efficiency of 2.5%. The reason for such behavior is attributed to W⁶⁺ ions allows for electron traps that suppress electron-hole recombination and exploit the lower band gap of material to produce a water splitting process by increasing the charge separation and extending the energy range of photoexcitation for the system.

Abstract: We have fabricated columnar nano-porous SiC by photo-electrochemical etching on the C-face of n-type 6H SiC at constant voltage. SEM images reveal that the pores are long, straight and parallel with diameters of about 20 nm. We have produced such layers up to 250 μm thick. The pore morphologies for both Si and C-face SiC samples are compared and discussed as a part of the effort to understand the growth mechanism. It is found that the constant voltage etching condition on C-face SiC is crucial for this nano-columnar pore formation.

Abstract: The effects of initial surface morphology on the early stages of porous SiC formation under highly biased photoelectrochemical etching conditions are discussed. We etched both Si-face and C-face polished n-type 6H SiC with different surface finishes prepared either by mechanical polishing or by chemical mechanical polishing at NOVASiC. For both Si-face and C-face porous SiC samples, a variety of surface and cross sectional porous morphologies, due to different surface finishes, are observed. The proposed explanation is based on the spatial distribution of holes at the interface of the SiC and electrolyte inside the semiconductor.