Search Results (357)

Active semiconductor layers of TiO₂ were synthesized via pulsed laser deposition in He, N₂, O₂, or Ar to manufacture DSSC structures. As-prepared nanostructured TiO₂ coatings grown on FTO were photosensitized by the natural absorption of the N719 (Ruthenium 535-bis TBA) dye to fabricate photovoltaic structures. TiO₂ photoanode nanostructures with increased adsorption areas of the photosensitizer (a combination with voluminous media) were grown under different deposition conditions. Systematic SEM, AFM, and XRD investigations were carried out to study the morphological and structural characteristics of the TiO₂ nanostructures. It was shown that the gas nature acts as a key parameter of the architecture and the overall performance of the deposited films. The best electro-optical performance was reached for photovoltaic structures based on TiO₂ coatings grown in He, as was demonstrated by the short-circuit current (Isc) of 5.40 mA, which corresponds to the higher recorded roughness (of 44 ± 2.9 nm RMS). The higher roughness is thus reflected in a more efficient and deeper penetration of the dye inside the nanostructured TiO₂ coatings. The photovoltaic conversion efficiency (η) was 1.18 and 2.32% for the DSSCs when the TiO₂ coatings were deposited in O₂ and He, respectively. The results point to a direct correlation between the electro-optical performance of the prepared PV cells, the morphology of the TiO₂ deposited layers, and the crystallinity features, respectively. Full article

Nanocrystalline Bi₂S₃ shells were conformally deposited on ZnO nanowire arrays via a successive ionic layer adsorption and reaction approach. Microstructure, optical, and electric properties of the as-prepared ZnO/Bi₂S₃ core/shell nanowire heterostructures were thoroughly investigated using various characterization and electrochemical methods. Compared with the pristine ZnO photoanode (−734 mV and 0.57 mA·cm⁻²), the ZnO/Bi₂S₃ photoanode with a type-II heterojunction exhibited a more negative shift in the coupled open circuit potential (−862 mV) and a higher photocurrent density (2.92 mA·cm⁻²), achieving more effective photocathodic protections for the coupled 304 stainless steel under solar illumination. Full article

We report on the fabrication of sub-20 nm BiFeO₃ (BFO) nanoparticles using a solid-state approach and preferential leching process. The nanoparticles were subsequently used to deposit, through spray pyrolysis, BFO thin films in a rhombohedral (R3c) crystallographic structure. Then, systematic investigations of the optical and the photocatalytic properties were conducted to determine the effects of the particles size, the microstructure and the increased surface area on their catalytic performances. Especially, improved optical properties were observed, with an optical bandgap energy of 2.20 eV compared to reported 2.7 eV for the bulk system. In addition, high optical absorption was obtained in the UV–visible light region reaching up to 90% at 400 nm. The photoelectrochemical measurements revealed a high photocurrent density under visible light irradiation. Besides, density functional theory calculations were performed on both bulk and thin film BFO structures, revealing an interesting comparison of the electronic, magnetic, ferroelectric and optical properties for bulk and thin film BFO systems. Both theoretical and experimental findings show that the alignment of the band edges of BFO thin film is coherent with good photocatalytic water splitting potential, making them desirable photoanode materials. Full article

Dye-sensitized solar cells (DSSCs), a powerful system to convert solar energy into electrical energy, suffer from the high cost of the Pt counter electrode and photosensitizer. In this study, the dual application of waste grape skin is realized by employing the grape skin and its extract as the carbon source of the carbon-based counter electrode and photosensitizer, respectively. The ultraviolet–visible absorption and Fourier transform infrared spectroscopy verify the strong binding between the dye molecules (anthocyanins) in the extract and the TiO₂ nanostructure on the photoanode, contributing to a high open-circuit voltage (V_OC) value of 0.48 V for the assembled DSSC device. Moreover, the waste grape skin was subjected to pyrolysis and KOH activation and the resultant KOH-activated grape skin-derived carbon (KA-GSDC) possesses a large surface area (620.79 m² g⁻¹) and hierarchical porous structure, leading to a high short circuit current density (J_SC) value of 1.52 mA cm⁻². Additionally, the electrochemical impedance spectroscopy reveals the efficient electron transfer between the electrocatalyst and the redox couples and the slow recombination of electrolytic cations and the photo-induced electrons in the conduction band of TiO₂. These merits endow the DSSC with a high photovoltaic efficiency of 0.48%, which is 33% higher than that of a common Pt-based DSSC (0.36%). The efficiency is also competitive, compared with some congeneric DSSCs based on other natural dyes and Pt counter electrode. The result confirms the feasibility of achieving the high-value application of waste grape skin in DSSCs. Full article

In this study, zinc-doped ($\alpha$-Fe${}_2$O${}_3$:Zn), silver-doped ($\alpha$-Fe${}_2$O${}_3$:Ag) and zinc/silver co-doped hematite ($\alpha$-Fe${}_2$O${}_3$:Zn/Ag) nanostructures were synthesized by spray pyrolysis. The synthesized nanostructures were used as photoanodes in the photoelectrochemical (PEC) cell for water-splitting. A significant improvement in photocurrent density of 0.470 mAcm${}^{-2}$ at 1.23 V vs. reversible hydrogen electrode (RHE) was recorded for $\alpha$-Fe${}_2$O${}_3$:Zn/Ag. The $\alpha$-Fe${}_2$O${}_3$:Ag, $\alpha$-Fe${}_2$O${}_3$:Zn and pristine hematite samples produced photocurrent densities of 0.270, 0.160, and 0.033 mAcm${}^{-2}$, respectively. Mott–Schottky analysis showed that $\alpha$-Fe${}_2$O${}_3$:Zn/Ag had the highest free carrier density of 8.75 × 10${}^{20}$ cm${}^{-3}$, while pristine $\alpha$-Fe${}_2$O${}_3$, $\alpha$-Fe${}_2$O${}_3$:Zn, $\alpha$-Fe${}_2$O${}_3$:Ag had carrier densities of 1.57 × 10${}^{19}$, 5.63 × 10${}^{20}$, and 6.91 × 10${}^{20}$ cm${}^{-3}$, respectively. Electrochemical impedance spectra revealed a low impedance for $\alpha$-Fe${}_2$O${}_3$:Zn/Ag. X-ray diffraction confirmed the rhombohedral corundum structure of hematite. Scanning electron microscopy micrographs, on the other hand, showed uniformly distributed grains with an average size of <30 nm. The films were absorbing in the visible region with an absorption onset ranging from 652 to 590 nm, corresponding to a bandgap range of 1.9 to 2.1 eV. Global analysis of ultrafast transient absorption spectroscopy data revealed four decay lifetimes, with a reduction in the electron-hole recombination rate of the doped samples on a timescale of tens of picoseconds. Full article

One of the effective ways of utilizing marine environments is to generate energy, power, and hydrogen via the effect of photocatalysts in the seawater. Since the ocean is vast, we are able to use its large area, but the power generation system must be of low cost and have high durability against both force and corrosion. In order to meet those requirements, this study focuses on the fabrication of a novel marine wet solar cell composed of a titanium dioxide photoanode and a copper oxide photocathode. These electrodes were deposited on type 329J4L stainless steel, which possesses relative durability in marine environments. This study focuses on the characterization of the photocatalytic properties of electrodes in seawater. Low-cost manufacturing processes of screen-printing and vacuum vapor deposition were applied to produce the titanium dioxide and copper oxides electrodes, respectively. We investigated the photopotential of the electrodes, along with the electrochemical properties and cell voltage properties of the cell. X-ray diffraction spectroscopy (XRD) of the copper oxides electrode was analyzed in association with the loss of photocatalytic effect in the copper oxides electrode. Although the conversion efficiency of the wet cell was less than 1%, it showed promising potential for use in marine environments with low-cost production. Electrochemical impedance spectroscopy (EIS) of the cell was also conducted, from which impedance values regarding the electrical properties of electrodes and their interfaces of charge-transfer processes were obtained. This study focuses on the early phase of the marine wet solar cell, which should be further studied for long-term stability and in actual marine environmental applications. Full article