Controlled synthesis of MnO2@TiO2 hybrid nanotube arrays with enhanced oxygen evolution reaction performance

A novel tube-in-tube nanostructure of MnO₂@ TiO₂ hybrid arrays has been obtained by a facile and controllable chemical bath deposition method. Scrutiny on the hybrid arrays indicates that the chemical bath deposition method favors the growth of the MnO₂ nanotubes with different diameter which can modulate the oxygen evolution reaction (OER) activity as well as bandgap width of the hybrid. In terms of OER activity, onset potential (E_s) shifts negatively from 0.698 V (vs.Ag/AgCl) of pristine titania nanotube arrays (TNAs) to 0.501 V of the hybrid loaded with 26.6%wt MnO₂, and the current density on the hybrid electrode can be significantly enhanced up to 20.87 mA/cm², almost 97 times higher than that on TNAs electrode (0.214 mA/cm²). Optical absorption measurement suggests that the bandgap width (E_g) can be tuned by loading MnO₂ onto the TNAs implying interaction between the MnO₂ and TNAs. The MnO₂@TiO₂ hybrid nanotube arrays may find promising potential in electrochemical water splitting, photocatalysis, thermocatalysis and other sustainable energy applications.     

Preparation of carbon dots/TiO2 electrodes and their photoelectrochemical activities for water splitting

Carbon dots with various functional groups can be employed as the potential sensitizer. In this study, carbon dots are obtained by electrochemical ablation of graphite rods in alkaline electrolyte. The better preparation condition is the applied potential of 40 V and the ablation time of 5 h. TiO₂ nanotube arrays and TiO₂ nanoparticles photoelectrodes are sensitized by the as-prepared carbon dots through using impregnation method. Carbon dots/TiO₂ nanotube arrays electrodes exhibit greater photoelectrochemical hydrogen production activities than carbon dots/TiO₂ nanoparticles electrodes. It is because more carbon dots can be well combined with TiO₂ nanotube arrays. Based on the IPCE values in visible light region, the role of carbon dots on TiO₂ nanotube arrays electrode depends on the up-converted PL behaviors from their surface states and the alkaline electrolyte. The results provide insight into carbon dots that serve as sensitizer of TiO₂ photoelectrode in water splitting system of alkaline solution.     

Efficient light harvesting by NiS/CdS/ZnS NPs incorporated in C,N-co-doped-TiO2 nanotube arrays as visible-light sensitive multilayer photoanode for solar applications

Here, we report a significant enhancement in photo-electrochemical activity of co-doped/modified TiO₂ nanotube arrays (TNAs). First, TiO₂ nanostructures were sensitized with nitrogen and carbon via a single step/low cost anodization process and then modified with Nis/CdS/ZnS nano particles (NPs) by the successive ionic layer adsorption and reaction (SILAR) method at room temperature. Photo-electrochemical properties and physical/chemical characteristics of the pure and sensitized/modified TNAs were investigated using field emission scanning electron microscopy (FESEM), XRD, XPS and EDX, comprehensively. Electrochemical measurements and UV–Vis DRS spectroscopy of the photo-electrodes showed that co-doping with anions and modification with different NPs result in the broadening of the absorption region of visible light and the reduction of band gap energy. The mechanism responsible for the enhanced photo-electrochemical activity of the C, N-co-doped/NiS, CdS, ZnS NPs modified TNAs for the water reduction reaction using aqueous solutions of Na₂S/Na₂SO₃ as sacrificial electrolyte under the whole spectrum of simulated solar light irradiation has been presented. The highest photocurrent in presence of sacrificial agent (Na₂S/Na₂SO₃) was obtained as 18.79 mA/cm², for the optimized SILAR loading cycles and dopants concentration. Furthermore, a high incident photon to current efficiency (IPCE) of about 82% for the optimum photo-anode had been achieved. These results confirm that the C, N-co-doped/NiS, CdS, ZnS NPs modified TNAs nanocomposite may offer a promising strategy to attain maximum efficiency in a variety of solar energy conversion systems, along with reduced photo-corrosion in the semiconductor-semiconductor heterojunction.     

Cu(OH)2-modified TiO2 nanotube arrays for efficient photocatalytic hydrogen production

Cu(OH)₂/TNAs photocatalyst was prepared by loading Cu(OH)₂ nanoparticles on TiO₂ nanotube arrays (TNAs) using a chemical bath deposition method. The amount of Cu(OH)₂ loaded on the arrays was controlled by the repeated deposition times. The prepared catalyst was used to generate hydrogen under simulated solar light irradiation, and the results demonstrated that the hydrogen yield of Cu(OH)₂/TNAs was 20.3 times that of the pure TNAs. Furthermore, the photocatalytic efficiency for hydrogen production decreased only 5.8% after five cycles, indicating that Cu(OH)₂/TNAs photocatalyst showed excellent stability and reusability. This work presents an applicable and facile method to fabricate a highly active and stable photocatalyst for hydrogen production.     

A comparative study of CuO deposition methods on titania nanotube arrays for photoelectrocatalytic ammonia degradation and hydrogen production

In this study, the deposition of CuO nanoparticles into titania nanotube arrays (TiNTAs) was prepared via two methods, i.e an in-situ anodization (AND) and a successive ionic layer adsorption reaction (SILAR). The two methods were compared in terms of their properties as efficient photoanodes in photoelectrocatalytic processes. FESEM and TEM imaging showed that the nanotubular structure was successfully generated. The bandgap energy was probed by UV-DRS analysis, revealing that CuO-TiNTAs SILAR had a lower bandgap than other samples. The photoelectrochemical responses of CuO-TiNTAs SILAR exhibit better activity compared to its counterpart. The maximum ammonia removal was achieved at 50.1% while as high as 235.7 μmol of hydrogen was generated over 120 min under Hg lamp illumination, by the use of CuO-TiNTAs SILAR. We thereby conclude that, for the given experimental conditions, CuO-TiNTAs SILAR is a better photoanode than CuO-TiNTAs AND concurrently eliminate ammonia and produce hydrogen in a photoelectrochemical setup.     

Improvement of photocatalytic hydrogen generation from CdSe/CdS/TiO2 nanotube-array coaxial heterogeneous structure

The fabrication and characterization of CdSe/CdS/TiO₂ nanotube-array coaxial heterogeneous structure that has potential applications in photocatalytic water splitting and toxic pollutants degradation are investigated. CdSe(top)/CdS(under) double-layer is conformally deposited onto TiO₂ nanotubes by successive ionic layer adsorption and reaction (SILAR) and electrochemical atomic layer deposition (ECALD), respectively, for the CdS under layer and the CdSe top layer. Such double sensitized TiO₂ nanotubular photoelectrode exhibits significant enhancements in photoconversion efficiency, visible light response, and efficient hydrogen generation. The detailed synthesis process and the surface morphology, phase structure, elemental analysis, and photoelectrochemical properties of the resulting films with the CdSe/CdS/TiO₂ nanotube-array coaxial heterogeneous structure are discussed. The photoconversion efficiency of 9.47% and hydrogen generation rate of 10.24 ml h⁻¹ cm⁻² were observed. Both values are a 7-fold enhancement compared with that of the pure TiO₂ nanotube. The as-prepared photoelectrode presents potential application for industrialized photocatalytic hydrogen generation in the future.     

Linker-free quantum dot sensitized TiO2 photoelectrochemical cells

Aerosol based techniques were used to characterize and deposit quantum dots (QDs). Using an electrospray-assisted characterization technique, the mobility diameter of CdSe QDs was successfully measured in real-time. The electrospray technique was also used to deposit CdSe QDs onto nanostructured TiO₂ films. Compared to conventional methodologies such as dip coating with linker-containing molecules or chemical bath deposition, an electrospray system enabled uniform deposition of QDs over the nanostructured TiO₂ surface in a short processing time. As-deposited films were annealed to enhance binding between the QDs and TiO₂ surface. These QD-decorated TiO₂ films were used in photoelectrochemical cells, for which the photoenergy conversion efficiencies were tested. Optimization of the deposition time of the QDs resulted in increased efficiencies. Multiple layers of QDs caused a decrease in energy-conversion efficiency, likely due to inhibition of the transportation of photogenerated electrons into the TiO₂ structure. The energy-conversion efficiency trends were supported by time-resolved photoluminescence decay data.     

Simultaneously efficient light absorption and charge transport of CdS/TiO2 nanotube array toward improved photoelectrochemical performance

CdS has been widely used to modify TiO₂-based photoanodes for photoelectrochemical (PEC) water splitting. Due to the poor interface contact between chalcogenides and oxides, however, such CdS modified TiO₂ materials usually exhibit inefficient separation and transport of charges, leading to an unsatisfactory efficiency during the PEC water splitting process. Addressing this issue, we herein report a CdS/TiO₂ nanotube array (CdS/TNA) photoanode that was fabricated through a successive ion layer absorption and reaction (SILAR) method with an additional subsequent annealing. This post-annealing process is essential to enhance the interface contact between the CdS and the TNAs, resulting in an accelerated transfer of photogenerated electrons from the CdS to the TNAs. In addition, the post-annealing also improves the light absorption capability of the CdS/TNA photoanode. The simultaneous enhancement of charge transport and light absorption provided by the post-annealing is essential for improving the PEC performance of the CdS/TNA photoanode. The CdS/TNA photoanode obtained by this strategy exhibits a much enhanced PEC performance in water splitting, and its photocurrent density and solar-to-hydrogen conversion efficiency could reach 4.56 mA cm⁻² at 1.23 V vs. reversible hydrogen electrode and 5.61%, respectively. This simple but effective route can provide a general strategy for obtaining high-performance oxide-based photoelectrodes.     

Enhancement of photoelectrochemical activity of Fe2O3 nanowires decorated with carbon quantum dots

Owing to its up-conversion photoluminescence, photo-induced electron transfer property, and excellent conductivity, carbon quantum dots (CQDs) have been established as effective sensitizers in combination with Fe₂O₃ nanowires for enhancing the catalytic activity of photoelectrochemical water oxidation. In comparison to pristine Fe₂O₃ nanowires, Fe₂O₃ nanowires decorated with CQDs demonstrate 27 orders of magnitude increase in photocurrent density at 0.23 V vs. Ag/AgCl. The mechanism of enhanced photoelectrochemical activity of CQDs/Fe₂O₃ composite was also investigated. Thereby, it is confirmed that the enhanced optical absorption, accelerated interfacial charge carrier transfer and effective separation of photogenerated electron-hole pairs induced by CQDs decoration account for the enhancement of CQDs/Fe₂O₃ nanowire arrays in photoelectrochemical application.     

In situ synthesis of MoO3/Ag/TiO2 nanotube arrays for enhancement of visible-light photoelectrochemical performance

A ternary composites of MoO₃/Ag/TiO₂ nanotube arrays were synthesized by in-situ annealing of TiO₂ nanotube arrays impregnated with AgNO₃ over MoO₃ powders. During the annealing process, the crystallization of the TiO₂ nanotubes, the thermo-decomposition of AgNO₃ to Ag nanoparticles, and the sublimation of MoO₃ occur jointly. The photoelectrochemical measurements of the resultants indicate that MoO₃/Ag/TiO₂ nanotube arrays present better photoelectrochemical properties compared with Ag/TiO₂ nanotube arrays and pristine TiO₂ nanotube arrays. Especially, the highest photocurrent and open circuit voltage are up to 21.29 μA/cm² and 0.058 V under visible light irradiation, whereas 1.77 and 3.87 times larger than those of TiO₂ nanotube arrays, respectively. Superior photoelectrochemical stability and larger photo-conversion efficiency of the ternary composites are also demonstrated. The improved photoelectrochemical properties are related to the close interfacial contact among MoO₃, Ag, and TiO₂ as well as the surface plasma resonance of Ag in the ternary composites, which broaden the range of light response and enhance the efficiency of charge separation. This study provides a skillful solution to construct TiO₂-based composite materials and demonstrates it is an unique architecture to promote the visible light driven photocatalytic application of TiO₂.     

Enhanced photoelectrochemical-response in highly ordered TiO2 nanotube-arrays anodized in boric acid containing electrolyte

We examine the photoelectrochemical properties of highly ordered titanium dioxide nanotube-array photoanodes, fabricated by anodization of titanium in a nitric acid/hydrofluoric acid electrolyte, with and without the addition of boric acid. Under UV–Vis illumination the photocurrent densities achieved with TiO₂ nanotube-arrays fabricated in the H₃BO₃–HNO₃–HF electrolyte are a factor of seven greater than the TiO₂ nanotube-array samples obtained in the commonly used HNO₃–HF electrolyte, indicating the ability to control the photoelectrochemical response of the highly ordered nanotube arrays by tailoring the electrolyte composition. For 560 nm long boric-acid fabricated nanotube arrays, a photoconversion efficiency of 7.9% is achieved upon a 320–400 nm illumination at an intensity of 98 mW/cm², with hydrogen generated by water photoelectrolysis at the power-time normalized rate of 1708-μmol/h W (42 ml/h W). The resulting nanotube-arrays demonstrate excellent photocorrosion stability, with no detectable degradation in photoconversion properties over 6 months of testing. While the titania bandgap is not suitable for high visible spectrum efficiencies, the high photoconversion efficiency achieved under UV illumination indicates the suitability of the highly ordered nanotube-array architecture for hydrogen generation by water photoelectrolysis.     

Photoelectrochemical study on charge separation mechanisms of Bi2WO6 quantum dots decorated g-C3N4

In this paper, the Bi₂WO₆ quantum dots (QDs) decorated g-C₃N₄ nanoplates were successfully synthesized via a one-step hydrothermal method. The morphology of the Bi₂WO₆ could be tuned from regular nanoplates to quantum dots. Remarkably, the Bi₂WO₆ QDs coupled with g-C₃N₄ not only prevented the aggregation, but also decreased the size of Bi₂WO₆ QDs about 3.5 nm. Meanwhile, the charge separation mechanisms of Bi₂WO₆ QDs/g-C₃N₄ photocatalyst were investigated by electrochemical impedance spectra, Mott-Schottky and linear voltammetry scans. As a result, the photoelectrochemical (PEC) experiments provided forceful evidence for the charge separation mechanism of the Bi₂WO₆ QDs/g-C₃N₄ Z-scheme. The Z-scheme system not only accelerated the separation efficiency of charge, but also improved the ability of PEC water splitting at measured 1.23 V vs. RHE.     

Hierarchical NiS decorated CuO@ZnFe2O4 nanoarrays as advanced photocathodes for hydrogen evolution reaction

Rationally designed architecture and smart components of catalysts can greatly accelerate the hydrogen evolution reaction in photoelectrochemical water splitting. Herein, hierarchical NiS quantum dots decorated CuO nanowires@ZnFe₂O₄ nanosheets core/shell nanoarrays were prepared by a viable multi-step synthesis approach. First, CuO nanowire arrays were prepared through the thermal treatment of copper mesh. Then, CuO@ZnO core/shell nanowire arrays were prepared via an impregnation-calcination process. Next, the CuO nanowire arrays with different ZnFe₂O₄ nanosheet contents were prepared through wet chemical reaction and subsequent thermal treatment. The further NiS quantum dots decoration was realized through a chemical bath deposition. The CuO nanowire arrays covered with ZnFe₂O₄ porous nanosheets not only offer abundant active sites to react with the electrolyte but also improve visible light utilization. Moreover, the hierarchical nanoarray structure provides a direct electron transport pathway with a graded interface for better charge flow. As a result, remarkably enhanced photoelectrochemical performance and excellent cycling stability were obtained for the CuO@ZnFe₂O₄ nanoarray photocathodes due to the synergistic effects of ideal components and hierarchical nanoarray structure. Additionally, the further NiS decoration makes CuO@ZnFe₂O₄ exhibit a significantly enhanced photocathodic current density.     

Highly efficient photocatalytic conversion of gas phase CO2 by TiO2 nanotube array sensitized with CdS/ZnS quantum dots under visible light

With the massive consumption of fossil fuels, energy crisis and effectively reducing CO₂ to curb global warming have become urgent and severe problems in the world. Photocatalytic conversion of CO₂ technology which can convert CO₂ into combustible compounds by using solar energy can solve both of the problems mentioned above. However, the photocatalytic conversion of CO₂ exhibits too low efficiency, especially under visible light. So, in order to improve the photocatalytic efficiency, the composite photocatalysts of TiO₂ nanotube array (TNTA) sensitized by CdS/ZnS quantum dots (QDs) were successfully prepared by anodization method and successive ionic layer adsorption and reaction (SILAR) method in this work. And the composite photocatalysts exhibited a high performance for photocatalytic conversion of gas-phase CO₂ to methanol under visible light. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), and X-ray photoelectric spectroscopy (XPS) were employed to characterize the ingredients and morphologies of the synthesized photocatalysts. And, UV–vis diffuse reflectance spectra (UV–Vis DRS) revealed that CdS/ZnS QDs enhanced the photo-absorption of composite photocatalyst in the visible light region. The main product methanol yield of CdS/ZnS-TNTA under visible light was 2.73 times that of bare TNTA when TNTA was treated by 10 SILAR cycles. Meanwhile, the product yield first increased before decreasing with the increase of the CO₂ flow rate. And the greatest product yield reached up to 255.49 nmol/(cm²-cat·h) with the increase of light intensity. The reaction mechanism was discussed in this paper. This high performance for photocatalytic reduction of CO₂ was primarily attributed to the CdS/ZnS QDs sensitization, which widens the response wavelength range of the catalyst to include visible light and partly inhibits the recombination of electron-hole pairs.     

Self-sacrificing template synthesis of CdS quantum dots/Cd-Hap composite photocatalysts for excellent H2 production under visible light

Well dispersive CdS quantum dots (QDs) were successfully in-situ grown on cadmium hydroxyapatite (Cd₅(PO₄)₃OH, Cd-Hap) assembled rods through a self-sacrificing hydrothermal method. No any nocuous organic ligands were used in such self-sacrificing route, allowing for a green approach to prepare CdS QDs with clean surfaces and enough active sites. The deposition of CdS QDs onto Cd-Hap surfaces led to a dramatically enhanced performance in H₂ production under visible light irradiation as compared to bulk CdS nanoparticles. The optimal CdS QDs/Cd-Hap composite displayed a H₂ evolution rate of 14.1 μmol h^?1 without using any noble metal cocatalyst, which was about 4.2 times higher than that of pristine CdS. The apparent quantum efficiency for CdS QDs/Cd-Hap composite was up to 18%. It was also found that CdS QDs/Cd-Hap composite can continuously generate H₂ from water in the presence of electron donors for more than 125 h. The enhanced photocatalytic performance of CdS QDs/Cd-Hap composites could be attributed to the high charge separation efficiency resulting from the efficient capture of photoinduced electrons by oxygen vacancies in Cd-Hap rods and the quantum confinement effect of CdS QDs with strong redox capacity as well as the increased active sites.     

Efficient conjugated polymer-ZnSe and -PbSe nanocrystals hybrid photovoltaic cells through full solar spectrum utilization

Type-II heterojunction poly[(2-methoxy,5-octoxy)-1,4-phenylenevinylene] (MOPPV)-ZnSe nanocomposites synthesized by in situ polymerization method are studied with and without incorporation of PbSe quantum dots (QDs) active layer in the novel hybrid photovoltaic device architecture for full solar spectrum utilization. The performance of the device improves significantly by incorporated PbSe QDs active layer. The power conversion efficiency, open-circuit voltage, short-circuit density and fill factor of the device with PbSe QDs are 0.14%, 0.806 V, 0.309 mA and 34%, respectively. It is expected that PbSe QDs active layer provides wider interface and surface areas for efficient exciton dissociation and charge transport, as well as more photon capture and exciton generation by absorption in near infrared spectrum region.     

Towards activation of amorphous MoSx via Cobalt doping for enhanced electrocatalytic hydrogen evolution reaction

Amorphous molybdenum sulfide (a-MoS_x) has been shown as one of the most promising catalysts in acidic electrolytes towards hydrogen evolution reaction (HER). Its intrinsic electrocatalytic activity can be further enhanced via doping and cropping the electronic structure.In this study, one-step electro-deposition was employed to fabricate MoS_xCo_y/TNAs hybrid electrodes using TiO₂ nanotube arrays as support. The microstructure and chemical composition of the samples were characterized via X-ray diffraction (XRD), scanning electron microscope (SEM), tunneling electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). The electrochemical properties of the samples were investigated through linear sweep voltammetry (LSV), cyclic voltammetry (CV), Tafel curves, and electrochemical impedance spectroscopy (EIS). According to experimental results, MoSCo structure was formed after Co²⁺ was incorporated into MoS_x, resulting in increases in both unsaturated Mo and S atoms acting as the active sites that lead to enhancement of intrinsic electrocatalytic activity. The pseudo-capacitance of MoS_xCo_y/TNAs (x = 1.70, y = 0.25) reached 46 mF cm^?2, a 31.4% improvement over 35 mF cm^?2 of MoS_x/TNAs. The onset hydrogen evolution potential, overpotentials at current densities of ?10 mA cm^?2 and –20 mA cm^?2 were recorded at ?92 mV, ?173 mV, and ?209 mV, respectively, reduction of 30 mV, 24 mV, and 28 mV than ?112 mV, ?197 mV, and ?237 mV of MoS_x/TNAs, respectively. This electrode was subjected to 1000-cycle testing and demonstrated stable electrochemical activity, illustrating excellent stability.     

Effect of anodization voltage on performance of TiO2 nanotube arrays for hydrogen generation in a two-compartment photoelectrochemical cell

Highly ordered TiO₂ nanotube arrays were prepared by anodic oxidation of Ti foil under different anodization voltages in ethylene glycol electrolyte. The morphology and photoelectrochemical performance of the TiO₂ nanotubes (NTs) samples were characterized by FESEM and electrochemical working station. Hydrogen production was measured by splitting water in the two-compartment photoelectrochemical (PEC) cell without any external applied voltage or sacrificial agent. The results indicated that anodization voltage significantly affects morphology structures, photoelectrochemical properties and hydrogen production of TiO₂ NTs. The pore diameter and layer thickness of TiO₂ samples increased linearly with the anodization voltage, which led to the enhancement of active surface area. Accordingly, the photocurrent response, photoconversion efficiency and hydrogen production of TiO₂ nanotubes were also linearly correlated with the anodization voltage.     

Band gap reduction of (Mo+N) co-doped TiO2 nanotube arrays with a significant enhancement in visible light photo-conversion: A combination of experimental and theoretical study

The present research aimed to evaluate the effects of co-doping TiO₂ nanotube aligned arrays (TNAs) with molybdenum and nitrogen on photocatalytic activity/performance under visible light irradiation. The surface morphology, electronic and optical properties of the pure and modified TNAs based on experimental characterization and theoretical calculations are reported. Both, pure and doped/modified TNAs were synthesized using a single step/low cost anodization method. Titanium sheets were immersed in ethylene glycol-based electrolytes containing NH₄F and NH₄F + K₂MoO₄ to fabricate highly ordered TNAs and Mo-doped TNAs, respectively. Mo–N-doped TNAs were fabricated by a thermal annealing process of Mo-doped samples in nitrogen environment (N₂-gas flow rate of 400 cc/min) for 2hr at 520 °C. Physical/chemical characteristics, structural and photo-electrochemical/electronic properties of the photo-electrodes were observed using several techniques including, field emission scanning electron microscopy (FESEM), Energy Dispersive X-Ray Spectroscopy (EDX), XRD, X-ray photoelectron spectroscopy (XPS), Raman and UV–Vis spectroscopy. We further used a full potential density functional theory (DFT) method to estimate the morphological and electronic structure of the synthesized photo-anodes and also observed a good agreement between theoretical calculations and characterization results. The characterization techniques confirm that Mo and N atoms have been incorporated into the lattice of anodized TNAs and molybdenum atoms partially substituted titanium atoms in the structure of TNAs. UV–Vis DRS spectroscopy experiments and theoretical results reveal that (Mo + N) co-doping creates a positive synergic effect on the band structure of TNAs which can enhance photo-conversion activity, compared to the single Mo/N-doped TNAs samples. In presence of sacrificial agent/electrolyte (aqueous solution of Na₂S/Na₂SO₃) and visible light irradiation, average photocurrent density of the co-doped TNAs photo-anode is 14 times greater than that of the undoped TNAs.     

Efficient and robust visible light photocatalytic H2 production based on CdSe quantum dots sensitized titania

In this work, cadmium selenide quantum dots (CdSe QDs) with different sizes were synthesized and employed as visible light sensitizers of titania, in comparison with other organic molecules based sensitizers, including the well-known ruthenium complex sensitizer, tris(4,4-dicarboxy-2,2-bipyridyl)ruthenium(II) chloride, phenolic-formaldehyde resin and poly (4-vinylphenol). The different sensitizers are linked to titania via different molecular linkages through self-assemble processes. CdSe QDs adsorbed onto titania via stabilization ligand (mercaptopropionic acid) are more stable and efficient in terms of photocatalytic H₂ generation and photocurrent generation. The CdSe QDs with a diameter of 2.5 nm exhibits a strong absorption peak centred at 500 nm (CdSe500) and shows the best photocatalytic performance than other QDs with larger size and organic sensitizers. The turnover number of CdSe500 QDs for H₂ generation reaches ca. 9000 after 96 h reaction, with a 0.6% quantum yield under irradiation at 450 nm (light intensity = 35 mW/cm²). During the initial 3.0 h reaction, the turnover numbers of different types of sensitizers are estimated about 4.3, 52.5, 323.2 and 16.5 for phenolic-formaldehyde resin, poly (4-vinylphenol), CdSe500 QDs and ruthenium complex, respectively. These results highlights the advantages of utilizing CdSe QDs as stable visible light sensitizers for solar energy conversion.