Papers by Keyword: Photoelectrochemistry

Abstract: The perovskite CsPbBr₃ possesses good photoelectrochemical properties, making it a potential candidate for use as a photoanode. The commonly used photoanode is the FTO/TiO₂/CsPbBr₃ photoanode in water splitting applications. However, there has been no research conducted on the FTO/TiO₂/CsPbBr₃ photoanode for the oxidation of glucose derived from abundant biomass sources. This study aims to analyze the influence of heat treatment and glucose concentration on the performance of glucose oxidation, as well as the efficiency of glucose conversion and electricity production. First, CsPbBr₃ solution is prepared under vacuum conditions using the Ligand Assisted Reprecipitation (LARP) method. Subsequently, the fabrication process of the FTO/TiO₂/CsPbBr₃ photoanode is carried out with variations including no heat treatment, heat treatment at a temperature of 110°C, and variations in glucose solution concentrations of 0.2 M and 0.5 M. XRD and SEM tests are conducted to determine the formed phases and morphology of CsPbBr₃. The XRD and SEM results confirm the presence of CsPbBr₃ phase and the formation of CsPb₂Br₅ phase due to the heat treatment process. The EIS testing reveals that the heat treatment process induces an oxidation process in the CsPbBr₃ perovskite, which can decrease the glucose oxidation performance of the FTO/TiO₂/CsPbBr₃ photoanode. Based on HPLC analysis, the highest conversion efficiency of glucose is 97.37%, respectively under 110 oC heat treatment and with 0.5 M glucose.

Abstract: This chapter aims at reviewing the characterisation techniques that are commonly used for high temperature oxidation study, especially on stainless steels. In addition, the experimental studies about the high temperature oxidation i.e. thermogravimetric method and chromium volatilisation measurement are explained. The various kinds of characterisation techniques for physico-chemical and electronic properties of thermal oxide scales are reviewed, starting from optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), focused ion beam coupled with scanning electron microscope (FIB/SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (RS), and photoelectrochemical characterisation (PEC). The review focuses on the basic concepts and shows how the characterising tools can be applied to thermal oxide characterisation.

Abstract: Several earth-abundant transition-metal oxides (e.g. Fe₂O₃, CoO, and Cu₂O) possessing suitable band gaps for solar water splitting exist, but energy level alignment is often sub-optimal, i.e. the conduction and valence bands do not straddle the water oxidation and reduction potentials. Here, using a nanocrystalline-TiO₂-based photoelectrochemical cell as a model system, we investigate the effect of tuning the semiconductor energy levels by adding Li⁺ ions to the electrolyte. The effect of LiClO₄ addition on band edges, interfacial recombination resistance, electron diffusion length, and charge-separation efficiency were quantified by impedance spectroscopy and analysis of incident photon-to-current efficiency spectra. We find that the TiO₂ band edges are shifted toward positive potentials by the addition of Li⁺, and that this increases the apparent electron diffusion length without affecting the charge-separation efficiency, most likely due to a change in the driving force for O₂ reduction. These results should prove useful in the modeling and optimization of solar water splitting cells employing metal oxide photoelectrodes.

Abstract: Nickel based alloys are well considered materials for uses in high temperature applications. Inconel 690 is the one of outstanding candidate with the superior properties. The aim of this report is to present the influence of water vapor on thermal oxide film. Inconel 690 was oxidized under dry and wet atmosphere at 900°C for 30 hours. The oxidized samples were characterized by SEM/EDS, Raman spectroscopy, and photoelectrochemical technique. The results illustrated that typical thermal oxides grown on alloy composed of Cr, Fe, Ni, in forms of Cr₂O₃, NiFe₂O₄, NiCr₂O₄, Fe₂O₃, Fe_2–xCr_xO₃ and/or solid solution of NiFe₂O₄−NiCr₂O₄. The presence of water vapor affected on oxide morphology, its stoichiometry, and also semiconducting behavior. Oxide film grown under water vapor atmosphere show the homogeneity. Water vapor promoted the predominated oxide of Cr₂O₃ with n−type semiconducting. Moreover the characterization revealed the effect of surface orientation on oxidation mechanism in case of sample which oxidized in oxygen atmosphere.

Abstract: A transient photoelectrochemical analysis method is improved to investigate the semiconductor properties of oxide films on stainless steel 316L oxidized in high-temperature water. A minute amount of ZnO was added to the high-temperature water environment to alter the semiconductor properties of the oxide film deposited on stainless steel 316L. Characteristic phases in the oxide were investigated using the improved photoelectrochemical analysis method, and the semiconductor properties of the oxide film on stainless steel 316L suggested the presence of an n-type semiconductor. The photoelectrochemical dephasing angle showed movement of the flat band potential in the negative direction after ZnO addition.

Abstract: The nanoporous titania dispersion system are prepared under hydrothermal conditions by employing various amount β-cyclodextrin(CD) as the porogent.Then, different microsructure nanoporous TiO₂ electrodes are fabricated by Doctor-blade mehod, using the above synthesis of titanium dioxide materials.The photoelectrochemical properties of dye-sensitized nanoporous TiO₂ electrodes are studied with transient photocurrent spectrum ,electrochemical impedence spectra (EIS) and photocurrent action spectra. The results indicate that the current response signals of dye-sensitized porous TiO₂ electrodes are stable. In addition,the impedence arc radius decreases gradually and light current increases gradually with the addition of β–CD. Meanwhile, the dye-sensitized porous electrodes with β-CD/TiO₂ ＝40 wt% showes the best photoelectrochemical properties.

Abstract: Optical and photoelectrochemical properties of polybithiophene Poly (bTh) films electrochemically synthesized and modified with incorporation of silicon nanoparticles (n-Si or p-Si) dispersed in the electrolytic during polymerization were studied. The characterisation of these modified surface electrodes by Poly (bTh)+n-Si or Poly (bTh)+p-Si, was carried out by using the photocurrent measurements and UV-visible spectroscopy. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been used to investigate the electrochemical behaviour of the resulting materials. The results show that the photosensitive composite materials have good photoelectrochemical and optical properties, and it can be used as material for the photovoltaic cells applications.

Abstract: In order to improve the visible light response in titania photocatalysts, CuO/TiO₂ heterojunction nanostructures (CuO-TNT) were proposed and fabricated via the electrochemical process. TiO₂ nanotubes array (TNT) was first fabricated by secondary anodization, after that the CuO was doped by the electrodeposition. The thin film was characterized by X-ray diffraction (XRD), diffuse reflection spectra (DRS) and field emission scanning electron microscopy (FESEM). Besides, its photoelectrochemical properties were measured in 0.1 M Na2SO₃ solution. By comparing the results under different conditions of deposition, it was found that the deposition current density was a crucial parameter for controlling the morphology and the photoelectrochemical properties of the samples.

Abstract: Recent studies on the molecular mechanism of water photooxidation (or oxygen photoevolution) reaction on TiO2 and related metal oxides or oxynitrides are reviewed. It is shown that a lot of experimental and theoretical studies give definite support to our recently proposed new mechanism, called “nucleophilic attack of H2O” or “Lewis acid-base” mechanism. The new mechanism has the prominent features that it possesses energetic and kinetics different from the conventional electron-transfer mechanism and can explain water photooxidation reaction on visible-light responsive metal oxides or oxynitrides, contrary to the conventional one. The result indicates that the new mechanism is useful for searching for new efficient visible-light responsive materials for solar water splitting.

Abstract: Chromia scales grown on several chromia-forming metallic substrates in various conditions were characterised by photoelectrochemistry (PEC), highlighting the presence of two semiconductor phases signed by their respective bandgaps (3.0 and 3.5 eV) with variations of semiconduction type (n, p and insulator, more or less doped). The protective character of the scale was clearly demonstrated when the highest bandgap phase (3.5 eV), identified as the external subscale was close to an insulator.