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Chemistry of ternary monocarboxyterpyridine-bipyridine-trimercaptotriazine ruthenium complexes and application in dye sensitized solar cells
摘要： The synthesis of the [RuII(Hmctpy)(H2O)(Cl2)], [RuII(Hmctpy)(dmbpy)Cl]Cl and [RuII(Hmctpy)(dmbpy)(H3tmt)](PF6)2 complexes (mctpy = monocarboxyterpyridine, dmbpy = dimethylbipyridine, tmt = trimercaptotriazine) was carried out based on a vectorial design for energy transfer in dye sensitized solar cells (DSSC). The [RuII(mctpy)(dmbpy)(Hxtmt)]n complexes were fully characterized and the electrochemical and absorption/emission properties corroborated their potentially as TiO2 photosensitizing agents. However, the observed current density and open circuit voltage were rather small, imparting a low efficiency for the assembled DSSCs. The results indicated a unexpected contribution of the charge recombination effects at the electrode surface. Such effects increased with the number of deprotonated groups in the tmt ligand as they interact with the nanocrystalline TiO2 surface, capturing electrons from the conduction band.
关键词： Ruthenium dyes,Carboxypolyimine dyes,Photoelectrochemistry,Charge recombination,Trimercaptotriazine dyes
更新于2025-09-23 15:21:01
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Compositionally graded SnO2/TiO2 bi-layered compounds with dramatically enhanced charge transport efficiency for self-driven water purification applications
摘要： To maximize the advantages of thin-film-based TiO2 photoelectrodes for transparent self-driven photoelectrochemical (PEC) reactions, we artificially designed a compositionally graded bi-layer compounds consisting of SnO2 and TiO2. This structure exhibited a vigorous photocatalytic activity, sufficient photovoltage, and long-term stability. A compositionally graded SnO2/TiO2 interface (G-SnTiO) for improved charge transport efficiency and sufficient photovoltage was derived by a solution process using simultaneous sintering after sol-gel coating the SnO2/TiO2 layers; the structure was verified by various analysis methods, such as transmission electron microscopy, energy dispersive X-ray spectroscopy, and secondary ion mass spectrometry. The high performance from the G-SnTiO structure was attributed to an effective charge separation from the formation of a heterostructure interface with reduced defects, resulting in a sufficient photovoltage for self-driving. To construct self-driven and sustainable overall cells without an external potential and considerable reduction in transparency, two-electrode PEC cells with a G-SnTiO photoanode and Cu2O photocathode were fabricated with a regular hexahedron shape for a color degradation test of methylene-blue-incorporated electrolytes, and exhibited enhanced purification speed and robust durability.
关键词： Charge transport,Photoelectrochemistry,Water oxidation,Compositionally graded structure,Self-driven overall cell
更新于2025-09-23 15:21:01
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Pulsed Laser Deposition of Bismuth Vanadate Thin Filmsa??The Effect of Oxygen Pressure on the Morphology, Composition, and Photoelectrochemical Performance
摘要： Thin layers of bismuth vanadate were deposited using the pulsed laser deposition technique on commercially available FTO (fluorine-doped tin oxide) substrates. Films were sputtered from a sintered, monoclinic BiVO4 pellet, acting as the target, under various oxygen pressures (from 0.1 to 2 mbar), while the laser beam was perpendicular to the target surface and parallel to the FTO substrate. The oxygen pressure strongly affects the morphology and the composition of films observed as a Bi:V ratio gradient along the layer deposited on the substrate. Despite BiVO4, two other phases were detected using XRD (X-ray diffraction) and Raman spectroscopy—V2O5 and Bi4V2O11. The V-rich region of the samples deposited under low and intermediate oxygen pressures was covered by V2O5 longitudinal structures protruding from BiVO4 film. Higher oxygen pressure leads to the formation of Bi4V2O11@BiVO4 bulk heterojunction. The presented results suggest that the ablation of the target leads to the plasma formation, where Bi and V containing ions can be spatially separated due to the interactions with oxygen molecules. In order to study the phenomenon more thoroughly, laser-induced breakdown spectroscopy measurements were performed. Then, obtained electrodes were used as photoanodes for photoelectrochemical water splitting. The highest photocurrent was achieved for films deposited under 1 mbar O2 pressure and reached 1 mA cm?2 at about 0.8 V vs Ag/AgCl (3 M KCl). It was shown that V2O5 on the top of BiVO4 decreases its photoactivity, while the presence of a bulk Bi4V2O11@BiVO4 heterojunction is beneficial in water photooxidation.
关键词： photoelectrochemistry,pulsed laser deposition,bismuth vanadate
更新于2025-09-23 15:19:57
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Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide
摘要： Nanostructured TiO2 and graphene-based materials constitute components of actual interest in devices related to solar energy conversion and storage. In this work, we show that a thin layer of electrochemically reduced graphene oxide (ECrGO), covering nanostructured TiO2 photoelectrodes, can significantly improve the photoactivity. In order to understand the working principle, ECrGO/TiO2 photoelectrodes with different ECrGO thicknesses were prepared and studied by a set of photoelectrochemical measurements. Methanol in alkaline conditions was employed as effective hole acceptor probe to elucidate the electronic phenomena in the electrode layers and interfaces. These studies underline the hole accepting properties of ECrGO and reveal the formation of a p-n junction at the interface between ECrGO and TiO2. It is shown for the first time that the resulting space charge region of about 10 nm defines the operational functionality of the ECrGO layer. Films thinner than the space charge region act as hole transport layer (HTL), which efficiently transfers holes to the liquid interface thus leading to enhanced photoactivity. Thicker films however act as hole blocking layer (HBL), resulting in a systematic decrease of the photoactivity. The finding of a thickness dependent threshold value for the operation of ECrGO as HTL and HBL is of general interest for the fabrication of optoelectronic devices with improved performance.
关键词： reduced graphene oxide,photoelectrodes,titanium dioxide,photoelectrochemistry,hole-transport layer
更新于2025-09-23 15:19:57
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Transparent Ta3N5 Photoanodes for Efficient Oxygen Evolution toward the Development of Tandem Cells
摘要： Photoelectrochemical water splitting is regarded as a promising approach to the production of hydrogen, and the development of efficient photoelectrodes is one aspect of realizing practical systems. In this work, transparent Ta3N5 photoanodes were fabricated on n-type GaN/sapphire substrates to promote O2 evolution in tandem with a photocathode, to realize overall water splitting. Following the incorporation of an underlying GaN layer, a photocurrent of 6.3 mA cm-2 was achieved at 1.23 V vs. a reversible hydrogen electrode. The transparency of Ta3N5 to wavelengths longer than 600 nm allowed incoming solar light to be transmitted to a CuInSe2 (CIS), which absorbs up to 1100 nm. A stand-alone tandem cell with a serially-connected dual-CIS unit terminated with a Pt/Ni electrode was thus constructed for H2 evolution. This tandem cell exhibited a solar-to-hydrogen energy conversion efficiency greater than 7% at the initial stage of the reaction.
关键词： (oxy)nitrides,photoelectrochemistry,water splitting,photoelectrochemical tandem cell,solar energy conversion
更新于2025-09-23 15:19:57
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On the Theoretical and Experimental Control of Defect Chemistry, Electrical and Photoelectrochemical Properties of Hematite Nanostructures
摘要： Hematite (α-Fe2O3) is regarded as one of the most promising cost-effective and stable anode materials in photoelectrochemical applications, and its performance, like other transition metal oxides, depends strongly on its electrical and defect properties. In this work, the electrical and thermo-mechanical properties of undoped and Sn-doped α-Fe2O3 nanoscale powders were characterized in-situ under controlled temperatures (T = 250 to 400oC) and atmospheres (pO2 = 10-4 to 1 atm O2) to investigate their transport and defect properties. Frequency-dependent complex impedance spectra show that interfacial resistance between particles is negligible in comparison with particle resistance. Detailed defect models predicting the dependence of electron, hole, iron and oxygen vacancy concentrations on temperature and oxygen partial pressures for undoped and doped α-Fe2O3 were derived. Using these defect equilibria models, the operative defect regimes were established and the bandgap energy of undoped α-Fe2O3 and oxidation enthalpy of Sn-doped α-Fe2O3 were obtained from the analysis of the temperature and pO2 dependence of the electrical conductivity. Based on these results, we are able to explain the surprisingly weak impact of donor doping on the electrical conductivity of α-Fe2O3. Furthermore, experimental means based on the results of this study are given for successfully tuning hematite to enhance its photocatalytic activity for the water oxidation reaction.
关键词： dilatometry,α-Fe2O3,defect chemistry,photoelectrochemistry,electrical conductivity
更新于2025-09-23 15:19:57
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Influence of Substrates on the Long-Range Order of Photoelectrodeposited Se-Te Nanostructures
摘要： The long-range order of anisotropic phototropic Se-Te films grown electrochemically at room temperature under uniform intensity, polarized, incoherent near-IR illumination has been investigated using crystalline (111)-oriented Si substrates doped degenerately with either p- or n-type dopants. Fourier-transform (FT) analysis was performed on large-area images obtained with a scanning electron microscope, and peak shapes in the FT spectra were used to determine the pattern fidelity in the deposited Se-Te films. Under nominally identical illumination conditions, phototropic films grown on p+-Si(111) exhibited a higher degree of anisotropy and a more well-defined pattern period than phototropic films grown on n+-Si(111). Similar differences in the phototropic Se-Te deposit morphology and pattern fidelity on p+-Si vs. n+-Si were observed when the deposition rate and current densities were controlled for by adjusting the deposition parameters and illumination conditions. The doping-related effects of the Si substrate on the pattern fidelity of the phototropic Se-Te deposits is ascribable to an electrical effect produced by the different interfacial junction energetics between Se-Te and p+-Si vs n+-Si that influences the dynamic behavior during phototropic growth at the Se-Te/Si interface.
关键词： interface,photodeposition,chalcogenide,Electrodeposition,photoelectrochemistry,nanopatterning
更新于2025-09-19 17:15:36
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Selective and Sensitive Visible-Light-Prompt Photoelectrochemical Sensor of Cu2+ Based on CdS Nanorods Modified with Au and Graphene Quantum Dots
摘要： Nowadays, increasing the risk for copper leaching into the drinking water in homes, hotels and schools has become unresolved issues all around the countries such as Canada, the United States, and Malaysia. The leaching of copper in tap water is due to a combination of acidic water, damaged pipes, and corroded plumbing fixtures. To remedy this global problem, a triple interconnected structure of CdS/Au/GQDs was designed as a photo-to-electron conversion medium for a real time and selective visible-light-prompt photoelectrochemical (PEC) sensor for Cu2+ ions in real water samples. The synergistic interaction of the CdS/Au/GQDs enabled the smooth transportation of charge carriers to the charge collector and provided a channel to inhibit the charge recombination reaction. Thus, a detection limit of 2.27 nM was obtained, which is 10,000 fold lower than that of WHO’s Guidelines for Drinking-water Quality (~30 μM). The photocurrent reduction was negligible after 30 days of storage under ambient conditions, suggesting the high stability of photoelectrode. Moreover, the real-time monitoring of Cu2+ ions in real samples was performed with satisfactory results, confirming the capability of the investigated photoelectrode as the most practical detector for trace amounts of Cu2+ ions.
关键词： Copper sensing,Photo-to-electron conversion,High stability,Photoelectrochemistry,CdS/Au/GQDs
更新于2025-09-19 17:13:59
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Interactions of plasmonic silver nanoparticles with high energy sites on multi‐faceted rutile TiO? photoanodes
摘要： The plasmonic interactions between silver nanoparticles and various rutile TiO2 facets are studied by correlating Advanced Electron Microscopy and Electrochemical Impedance Spectroscopy (EIS) to help design a route towards an optimised polycrystalline film fabrication. By using an Electron Backscatter Diffraction (EBSD) detector, it was determined that using HF as directing agent during the hydrothermal growth of TiO2 promotes the formation of high-angle grain boundaries. Silver photodeposition occurs preferentially at these boundaries, consistent with the presence of high energy sites on the (100)-oriented rutile TiO2 nanorods. Further EIS study showed an increase in the photoelectrochemical activity in the visible range of the solar spectrum for the samples consisting of silver nanoparticles deposited on these grain boundaries.
关键词： Water Splitting,Photoelectrochemistry,Plasmonic enhancement,Electron Microscopy,Grain Boundaries
更新于2025-09-19 17:13:59
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Annealed Polycrystalline TiO <sub/>2</sub> Interlayer of the n-Si/TiO <sub/>2</sub> /Ni Photoanode for Efficient Photoelectrochemical Water Splitting
摘要： High photovoltage generation from a photoelectrode is important for efficient solar-driven water splitting. Here, we report a thermal treatment process that greatly enhances photovoltage generation from an n-Si/TiO2/Ni photoanode. By selectively annealing the TiO2 interlayer, the photoanode generates a high photovoltage of 570 mV, which is very competitive as compared with photovoltages produced using other similar metal?insulator?semiconductor structures with earth-abundant metal catalysts. Different annealing conditions and junction layer thicknesses were systematically investigated. It is found that the optimal annealing temperature occurs between 500 and 600 °C. Within this temperature range, the deposited amorphous Ti is converted into polycrystalline anatase phase TiO2. The optimal annealing time scales linearly with TiO2 thickness and inversely with annealing temperature. The large photovoltage generation is attributed to the reduced defect states and improved junction barrier height by the annealed TiO2 interlayer. This study demonstrates that thermal annealing offers an attractive approach to modify the TiO2 interlayer material’s properties for photovoltage optimization.
关键词： photovoltage,photoanode,water splitting,thermal annealing,photoelectrochemistry,junction interlayer
更新于2025-09-19 17:13:59