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Energy diagram analysis of photoelectrochemical water splitting process
摘要： Photoelectrochemical (PEC) water splitting process is thoroughly revisited based on the energy diagram to elucidate the experimental observations. The TiO2 nanorod structure is studied as the model system for the photoanode of the PEC cell due to its stability in both acidic and basic solutions. The photocurrents with the external bias are examined under the various electrolytes of H2SO4, NaCl, and NaOH. The energy diagrams of the whole PEC system related to the water splitting process are interactively constructed in three-electrode configuration with the vacuum level as the common reference. Electrode potentials and photocurrents measured with the external bias in dark and under light are systematically correlated with the energy diagram of the PEC system. The pH dependent flat-band potential is explained by applying the pH dependent Helmholtz layer potential at the interface. In addition, the distribution of the applied potential in the PEC system during the water splitting process is understood by in-depth understanding of the energy band diagram.
关键词： band analysis,TiO2 nanorod,photoelectrochemical water splitting
更新于2025-09-23 15:23:52
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Morphological effect of composite TiO2 nanorod-TiO2 nanoparticle/PEDOT:PSS electrodes on triiodide reduction
摘要： Composite electrodes consisting of TiO2 nanoparticles (NPs)-TiO2 nanorods (NRs) and poly (3,4-ethylene-dioxythiophene)-polystyrene sulfonate (PEDOT:PSS) were prepared on a conductive glass substrate. The presence of TiO2 in the composite structure was proved by X-ray diffraction (XRD) Raman and FTIR-ATR measurements. The surface morphologies of TiO2 NP-PEDOT:PSS, TiO2 NR-PEDOT:PSS and TiO2 NP-TiO2 NR-PEDOT:PSS electrodes were characterized by scanning electron microscopy (SEM). According to the cyclic voltammetry measurement (CV), the electrocatalytic activity of composite electrodes on the reduction of triiodide improved after TiO2 addition compared with pristine PEDOT:PSS and platinum (Pt) electrodes. Electrochemical impedance spectroscopy (EIS) showed that the charge transfer resistance (Rct) strongly depends on the morphologies (ratio between TiO2 NP and TiO2 NR) of the composite electrodes. It was found that Rct decreased by increasing the amount of TiO2 nanorod in the whole mixture of TiO2 nanoparticles and PEDOT:PSS.
关键词： nanomaterials,nanocomposites,EIS,TiO2 nanorod,PEDOT:PSS
更新于2025-09-23 15:21:01
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Influence of Surface Modifier Molecular Structures on the Photovoltaic Performance of Sb <sub/>2</sub> S <sub/>3</sub> Sensitized TiO <sub/>2</sub> Nanorod Array Solar Cells
摘要： In this paper, Sb2S3 sensitized TiO2 nanorod arrays are prepared by the pyrolysis of 1.2 M antimony-thiourea complex solution in DMF at 270 ℃ for 10 min. Various surface modifiers with different functional groups and carbon numbers of C10H21PO3H2, C12H25SO3Na, C3H7COOH, C5H11COOH, C7H15COOH, C11H23COOH, C13H27COOH, C15H31COOH and C17H35COOH are applied to modify Sb2S3 sensitized TiO2 nanorod arrays. The corresponding solar cells are fabricated, and their photovoltaic performances are evaluated. To the different functional group surface modifiers, the improvement of functional group on photovoltaic performance is the order of -COOH > -PO3H2 > -SO3Na. To the different carbon number (4-18) surface modifiers, RCOOH with carbon number range of 8-12 exhibit better photovoltaic performance. Moreover, the Sb2S3 sensitized TiO2 nanorod array solar cells with C11H23COOH achieve the best photoelectric conversion efficiency (PCE) of 5.37 % with the open-circuit voltage (Voc) of 0.53 V, short-circuit current density (Jsc) of 16.98 mA?cm-2, fill factor (FF) of 60.66 % and the average PCE of 5.11±0.21 % with the Voc of 0.52±0.01 V, Jsc of 16.65±0.24 mA?cm-2, FF of 58.93±1.21 %. The PCE of 5.37 % corresponding to the use of spiro-OMeTAD as the hole transporting material is a relatively high PCE for Sb2S3 solar cells.
关键词： spiro-OMeTAD,Sb2S3 sensitized TiO2 nanorod array,solar cell,surface modifier
更新于2025-09-23 15:19:57
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Niobium doped TiO2 nanorod arrays as efficient electron transport materials in photovoltaic
摘要： One-dimensional (1-D) rutile TiO2 nanorod arrays (NRAs) synthesized by a hydrothermal method suffer from low electrical conductivity and large amounts of surface defects, hindering their further applications. Nb doping is thus introduced to modify their electronic properties. Results indicate that light Nb doping reduces rod nanosizes, increases electron concentrations, decreases surface defective oxides and lowers conduction band of the TiO2 NRAs, while heavy doping induces transformations of morphologies and crystalline orientations as well as occurrences of compositional deviations and low oxidative states of Ti3t. After 0.1 mol% and 1 mol% Nb incorporations, device efficiencies are substantially improved by ~16% and ~33% for the model perovskite and dye-sensitized solar cells, respectively, which are ascribed to reduced recombination at the perovskite/TiO2 interfaces (e.g. charge lifetime increasing from 62 μs to 107 μs) and improved electron transport through the photoanode of TiO2 NRAs (e.g. electron diffusion length increasing from ~14 μm to ~50 μm). Our study verifies that Nb doped 1-D TiO2 NRAs are versatile electron transporting materials in different kinds of emerging solar cells, and are also potential for other fields including photocatalysis, sensors and batteries etc.
关键词： TiO2 nanorod array,Dye-sensitized solar cell,Niobium doping,Charge transport,Perovskite solar cell,Recombination
更新于2025-09-19 17:13:59
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Efficient Nanorod Arrays Perovskite Solar Cells: A Suitable Structure for High Strontium-Substitution in a Nature Environment
摘要： Organic-inorganic hybrid perovskite solar cells (PSCs) have become a research hotspot because of their excellent power conversion efficiency (PCE), but the presence of toxic lead (Pb) in perovskite film has significantly limited their commercial application. In this study, using a TiO2 nanorod arrays (TNRAs) as the electron transport layer (ETL), strontium chloride (SrCl2) was chosen to fabricate lead-less PSCs in air environment (relative humidity, RH=50%) by a simple two-step spin-coating method. The influence of introduced strontium (Sr) on the perovskite films and cell properties was systematically investigated by various characterization methods. With increasing Sr substitution amount from 0 to 15 mol%, the formed perovskite films with a compact structure and a large crystalline size essentially remained invariable, while residual PbI2 was reduced, which is beneficial for the cell performance. The optimal PCE of 16.08% (average PCE = 15.37%) was obtained for the 5 mol% Sr-substituted PSCs because of the enhanced charge extraction from the perovskite film to the TNRAs and the suppressed charge recombination in the PSC. Both the humidity and thermal stability of the Sr-substituted PSCs were improved. More importantly, the 15 mol% Sr-substituted PSCs still exhibited a PCE of 15.09% in air (RH = 50%), maintaining 99% of the cell efficiency of the pristine (0 mol% Sr) PSC (15.27%), suggesting that the TNRAs structure is suitable for synthesis of high Sr-substituted lead-less PSCs.
关键词： Lead-less perovskite solar cells,TiO2 nanorod arrays,Defect density,Strontium substitution,Recombination
更新于2025-09-19 17:13:59
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Sol–gel approach for the growth of vertically aligned 3D-TiO2 nanorod arrays as an efficient photoanode for high-performance dye-sensitized solar cells
摘要： In this study, a facile, low cost, and scalable sol–gel method has been proposed for the coating of ultra-thin layer of TiO2 on FTO substrate as a seed layer for the growth of 3D-TiO2 nanorod (3D-TiO2-NR) arrays on FTO. Then, the two-step hydrothermal process including nanorod growth and the chemical etching treatment was proceeded for the fabrication of FTO/3D-TiO2-NR photoanodes. The thickness of the deposited TiO2 in FTO/TiO2-sg samples was measured with small-angle X-ray scattering technique, and it was obtained to be 21.3 nm. FE-SEM and TEM techniques were used for the morphological characterization of 3D-TiO2-NR, and it was obtained that the tightly adhered film of vertically aligned 3D-TiO2-NR with two-layer nanostructuring is formed with a cubic base and a nanorods head. Finally, DSSCs with iodine-based and cobalt(II/III) tris(2,2′-bipyridine) complex-based electrolytes with two different photoanodes including 3D-TiO2-NR and TiO2-NP were assembled and their photovoltaic characteristics were investigated. For [Co(bpy)3]2+/3+ shuttle-based DSSC, the obtained power conversion efficiency (η) was about 3.5% with Jsc of 9.36 mA cm?2 in 3D-TiO2-NR-based DSSC, while η of TiO2-NP-based DSSC was about 1.4%. The results showed that employing 3D-TiO2-NR-based photoanode in DSSCs with bulky electron shuttles remarkably improves the photovoltaic characteristics of DSSCs. Electrochemical impedance spectroscopic studies also showed the lower charge transfer resistances for DSSCs with nanorod-based photoanode building blocks.
关键词： Adhesion,Electron shuttle,TiO2 nanorod arrays,DSSC,Cobalt(II/III) tris(2,2′-bipyridine) complexes,Sol–gel
更新于2025-09-12 10:27:22
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Ag-Ag2S quantum-dots modified TiO2 nanorod arrays with enhanced photoelectrochemical and photocatalytic properties
摘要： In this paper, highly ordered titanium dioxide nanorod (TNR) arrays decorated with Ag-Ag2S quantum-dots (QDs) were synthesized on FTO substrate through hydrothermal treatment and in-situ vulcanization. The content of Ag2S QDs on Ag/TNR was controlled by changing the immersion time of Ag/TNR in the N-N-dimethyl formamide (DMF) solution containing dissolved sulfur element. The morphology, structure, composition and optical, photoelectric and photocatalytic properties of QDs/TNR arrays were studied in detail. In the visible range, the QDs/TNR array with a soaking time of 12 h exhibits the maximal photocurrent density (0.082 mA/cm2) and photodegradation rate (62.2%), which is 5.5 and 1.85 times higher than that of pure TNR. The improvement of these properties could be attributed to synergy effect between Ag and Ag2S materials. That is, Ag QDs can stably capture and transmit photo-generated electrons from the TNR surface, whereas the Ag2S promoter is regarded as the interface active sites to enhance photocatalytic reactions. Therefore, the synergistic effect of Ag-Ag2S can significantly enhance the photoelectrochemical and photocatalytic propertise of the TNR arrays.
关键词： Ag-Ag2S quantum-dots,photoelectrochemical and photocatalytic properties,synergistic effect,TiO2 nanorod arrays
更新于2025-09-10 09:29:36
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NH2-MIL-125(Ti)/TiO2 Nanorod Heterojunction Photoanodes for Efficient Photoelectrochemical Water Splitting
摘要： A photoactive amine-functionalized Ti metal-organic framework (MOF) (MIL(125)-NH2(Ti)) layer is uniformly coated on vertically ordered TiO2 nanorods (NRs) via a facile hydrothermal reaction, and the performance of the heterojunction photoanode in photoelectrochemical (PEC) water splitting is studied. The photocurrent density of the MIL(125)-NH2/TiO2 NRs reaches 1.63 mA/cm2 at 1.23 V vs. a reversible hydrogen electrode under AM 1.5 G simulated sunlight illumination, which is ~2.7 times higher than that of pristine TiO2 NRs. The incident photon-to-electron conversion efficiency of the MIL(125)-NH2/TiO2 NRs improves significantly at λmax = 340 nm, implying the promotion of water oxidation through efficient light absorption and charge separation. The enhancement of the PEC activity in the TiO2 NRs caused by an MIL(125)-NH2 coating is discussed in relation to the surface area and elongated configuration of the TiO2 NRs, the band gap of MIL(125)-NH2(Ti), and the type (II) heterojunction. This study demonstrates the rational design of heterojunctions between the semiconductor and the MOF, which paves the way for new facile and general approaches to achieve a high efficiency in water splitting.
关键词： TiO2 nanorod,Photoelectrochemical water splitting,Photoanode,MIL(125)-NH2,Hydrothermal reaction
更新于2025-09-09 09:28:46