Fabrication of 1D/2D CdS/CoSx direct Z-scheme photocatalyst with enhanced photocatalytic hydrogen evolution performance

In this work, we fabricate a 1D/2D heterojunction photocatalyst composed of n-type CdS nanorods and p-type CoS_x nanoflake. This photocatalyst achieves a hydrogen evolution rate of 9.47 mmol g^?1 h^?1, which is 13.7 times higher than that of pure CdS nanorods. Scanning Kelvin Probe, Mott-Schottky plots, UV–Vis absorption spectra and surface photocarrier orienting reaction results indicate that the enhanced photocatalytic performance of CdS/CoS_x is owing to the fabrication of direct Z-Scheme heterojunction system which greatly improves the utilization, migration and separation rate of photo-generated carriers. To the best of our knowledge, this work is the first time to describe a CdS/CoS_x direct Z-scheme system with 1D/2D nanostructure, which can expedite the transfer process of photogenerated carriers with strong redox energy to participate in photocatalytic reactions.     

Highly exposed (001) facets Ni(OH)2 induced formation of nickle phosphide over cadmium sulfide nanorods for efficient photocatalytic hydrogen evolution

An efficient Ni₂P–CdS photocatalyst for photocatalytic hydrogen evolution was synthesized by phosphorizing β-Ni(OH)₂ nanosheet with exposed (001) facets on CdS nanorods. The obtained Ni₂P–CdS composite displays an outstanding and stable photocatalytic hydrogen generation rate of 68.47 mmol g⁻¹ h⁻¹ in 10 vol% lactic acid under visible light irradiation, more than 17 times higher than that for pure CdS nanorods. The transient photocurrent response, EIS measurement, Mott-Schottky plots, acidic LSV measurement, and PL spectra have proved that Ni₂P loading can significantly improve the separation of photo-excited electron-hole pairs in CdS nanorods and enhance the hydrogen evolution capability for CdS. These improvements are achieved by features of Ni₂P such as the high capability of trapping photo-generated electrons from CdS, lifting the total Fermi level and lowering the hydrogen evolution overpotential of the composite. The results show that β-Ni(OH)₂ precursor with a high exposure degree of (001) facet is contributed to the epitaxial formation of (001)-facet-exposed Ni₂P co-catalyst on CdS nanorods, resulting in that the Fermi level and the hydrogen evolution overpotential of the composite can be further lifted and lowered. This study has provided a novel precursor-derived route to fabricate high-performance co-catalysts with highly exposed active facets on CdS nanorods for effective photocatalytic hydrogen evolution.     

In2O3:Sn/TiO2/CdS heterojunction nanowire array photoanode in photoelectrochemical cells

The design of photoanode with highly efficient light harvesting and charge collection properties is important in photoelectrochemical (PEC) cell performance for hydrogen production. Here, we report the hierarchical In₂O₃:Sn/TiO₂/CdS heterojunction nanowire array photoanode (ITO/TiO₂/CdS-nanowire array photoanode) as it provides a short travel distance for charge carrier and long light absorption pathway by scattering effect. In addition, optical properties and device performance of the ITO/TiO₂/CdS-nanowire array photoanode were compared with the TiO₂ nanoparticle/CdS photoanode. The photocatalytic properties for water splitting were measured in the presence of sacrificial agent such as SO₃²⁻ and S²⁻ ions. Under illumination (AM 1.5G, 100 mW/cm²), ITO/TiO₂/CdS-nanowire array photoanode exhibits a photocurrent density of 8.36 mA/cm² at 0 V versus Ag/AgCl, which is four times higher than the TiO₂ nanoparticle/CdS photoanode. The maximum applied bias photon-to-current efficiency for the ITO/TiO₂/CdS-nanowire array and the TiO₂ nanoparticle/CdS photoanode were 3.33% and 2.09%, respectively. The improved light harvesting and the charge collection properties due to the increased light absorption pathway and reduced electron travel distance by ITO nanowire lead to enhancement of PEC performance.     

Carbon dioxide reforming of methane over nickel catalysts supported on TiO2(001) nanosheets

As we all know, the critical problem of nickel catalysts for carbon dioxide reforming of methane is the deactivation of catalysts due to the carbon deposition and sintering of the active components under high temperature. It was reported that anatase TiO₂ nanosheets with high-energy (001) facets had strong interaction with nickel, which was probably beneficial to resist sintering of nickel nanoparticles and to eliminate deposited carbon via oxygen migration. In this study, Ni nanoparticles were supported on TiO2 nanosheets with exposed high-energy (001) facets. The Ni/TiO₂(001) catalysts were characterized by means of X-ray diffraction, transmission electron microscopy, physisorption of N₂, X-ray photoelectron spectroscopy and H₂ temperature-programmed reduction, and the spent catalysts were characterized by Roman and thermogravimetry analysis. The catalytic performance of Ni/TiO₂(001) catalysts were measured for carbon dioxide reforming of methane reaction. It was found that the prepared Ni/TiO₂(001) catalysts showed reasonably higher catalytic activity and stability compared with the nickel catalyst supported on commercial titanium oxide (P25). The high dispersion of nickel nanoparticles of Ni/TiO₂(001) catalysts was helpful to the resistance towards carbon deposition and the strong metal-support interaction was helpful to the resistance towards nickel sintering on account of the unusual surface properties of TiO₂(001).     

Cu2ZnSnS4 decorated CdS nanorods for enhanced visible-light-driven photocatalytic hydrogen production

Design and preparation of high performance photocatalysts are always the keys for photocatalytic hydrogen production by using green and unlimited solar energy. In this work, we present the synthesis of Cu₂ZnSnS₄ (CZTS) decorated CdS nanorods and their use for visible-light-driven photocatalytic hydrogen production. The as-synthesized CZTS decorated CdS nanorods exhibit much higher visible-light-driven photocatalytic hydrogen production performance than that of individual CdS nanorods and individual CZTS nanoparticles. Specifically, the hydrogen production rate of representative CZTS decorated CdS nanorods was 48-times and 165-times higher than that of individual CdS nanorods and individual CZTS nanoparticles. The enhanced photocatalytic hydrogen production performance may be contributed by the p-n heterojunction as well as the synergistic effect between CdS nanorods and CZTS particles. The present work not only reported new low-cost and highly efficient photocatalysts for visible-light-driven photocatalytic hydrogen production, but also provided new method for the design and preparation of high performance visible-light-driven heterostructured photocatalysts for photocatalytic hydrogen production.     

Enhanced hydrogen generation from methanol aqueous solutions over Pt/MoO3/TiO2 under ultraviolet light

The photocatalytic activity in hydrogen production from methanol reforming can be significantly enhanced by Pt/MoO₃/TiO₂ photocatalysts. Compared with Pt/P25, the photocatalytic activity of optimized Pt/MoO₃/TiO₂ shows an evolution rate of 169 μmol/h/g of hydrogen, which is almost two times higher than that of Pt/P25. XRD and Raman spectra show that MoO₃ are formed on the surface of TiO₂. It is found that with the bulk MoO₃ just formed, the catalyst shows the highest activity due to a large amount of heterojunctions and the high crystallinity of MoO₃. The HRTEM image showed a close contact between MoO₃ and TiO₂. It is proposed that the Z-scheme type of heterojunction between MoO₃ and TiO₂ is responsible for the improved photocatalytic activity. The heterojunction structure of MoO₃/TiO₂ does not only promote the charge separation, but also separates the reaction sites, where the oxidation (mainly on MoO₃) and reduction (on TiO₂) reactions occurred.     

Single crystalline TiO2 nanorods with enhanced visible light activity for solar hydrogen generation

Single crystalline TiO₂ nanorods and polycrystalline nanotubes were fabricated with same length to investigate the effects of their nanostructures on photocatalytic properties for splitting water. In order to enhance the visible light absorbance, TiO₂ nanorods and nanotubes were sensitized with semiconductor nanoparticles such as CdS, CdSe, and CdS/CdSe, and compared in viewpoint of solar hydrogen generation. It was observed that single-crystalline nanorods showed superior photocatalytic properties to polycrystalline nanotubes, and also the potential level of the nanorods with rutile phase was measured as lower than that of the nanotubes with mixture of anatase and rutile. Further improvement of photo-conversion efficiency was obtained by subsequent heat treatments of the sensitized photoelectrodes. It turns out that the improvement is attributed to the improved crystallinity and the increased size of the nanoparticles during the post-annealing treatments. It was demonstrated that TiO₂ nanorods with lower potential level and a single crystalline phase on FTO glass were advantageous for effective charge injection from the sensitized nanoparticles and transport without recombination lost at grain boundaries.     

Branched multiphase TiO2 with enhanced photoelectrochemical water splitting activity

An efficient hierarchical structure, nano-branch containing anatase TiO₂ nanofibers and rutile nanorods, was prepared via the combination of the electrospinning and hydrothermal processes. This novel configuration of TiO₂ multiphase possessed higher surface area, roughness, and fill factors compared with each single phase component prepared in the same condition, which significantly enhanced its light absorption. Our experimental results showed that within the interface of multiphase TiO₂, the heterojunction promoted the charge separation and improved the charge transfer rate, leading to higher efficiency for photoelectrochemical water splitting. The photocurrent density of the nano-branched TiO₂ electrode could reach 0.95 mA/cm², which was almost twice as large as that of the pristine TiO₂ nanorod. Our work provides a simple and feasible routine to synthesize complex TiO₂ nanoarchitectures, which lays a foundation for improving energy storage and conversion efficiency of TiO₂-based photoelectrodes.     

Efficient interfacial charge transfer of 2D/2D CoP/CdS heterojunction for extremely boosted photocatalytic H2 evolution performance

Constructing 2D/2D heterojunction photocatalysts has attracted great attentions due to their inherent advantages such as larger interfacial contact areas, short transfer distance of charges and abundant reaction active sites. Herein, 2D/2D CoP/CdS heterojunctions were successfully fabricated and employed in photocatalytic H₂ evolution using lactic acid as sacrificial reagents. The multiple characteristic techniques were adopted to investigate the crystalline phases, morphologies, optical properties and textual structures of heterojunctions. It was found that integrating 2D CoP nanosheets as cocatalysts with 2D CdS nanosheets by Co–S chemical bonds would significantly boost the photocatalytic H₂ evolution performances, and the 7 wt% 2D/2D CoP/CdS heterojunction possessed the maximal H₂ evolution rate of 92.54 mmol g^?1 h^?1, approximately 31 times higher than that of bare 2D CdS nanosheets. Photoelectrochemical, steady photoluminescence (PL) and time-resolved photoluminescence (TRPL) measurements indicated that there existed an effective charge separation and migration over 2D/2D CoP/CdS heterojunction, which then markedly lengthened the photoinduced electrons average lifetimes, retarded the recombination of charge carriers, and caused the dramatically boosted photocatalytic H₂ evolution activity. Moreover, the density functional theory (DFT) calculation further corroborated that the efficient charge transfer occurred at the interfaces of CoP/CdS heterojunction. This present research puts forward a promising strategy to engineer the 2D/2D heterojunction photocatalysts endowed with an appealing photocatalytic H₂ evolution performance.     

Photodeposition of amorphous MoSx cocatalyst on TiO2 nanosheets with {001} facets exposed for highly efficient photocatalytic hydrogen evolution

Semiconductor-based photocatalytic hydrogen production is a promising approach to convert solar energy to renewable and clean hydrogen energy. However, development of cheap and efficient hydrogen evolution cocatalyst to replace noble metal based cocatalysts remains a challenge. Here, we report a MoS_x/TiO₂ nanohybrid prepared by a facile photo-assisted deposition method. The amorphous MoS_x grows intimately on the single-crystalline TiO₂ nanosheet with {001} facets exposed to form a heterojunction, which can not only facilitate the charge separation and transfer, but also provide plenty of active sites for hydrogen evolution reaction owing to abundant unsaturated S atoms on amorphous MoS_x. As a result, the MoS_x/TiO₂ nanohybrid shows a remarkable enhancement in photocatalytic hydrogen evolution performance in comparison to bare TiO₂ nanosheet. The best 0.5%-MoS_x/TiO₂ nanohybrid exhibits a hydrogen production rate at 1835.7 μmol g^?1 h^?1 under Xenon light irradiation, which is about 177 times higher than that of bare TiO₂ nanosheet. This work paves a way for the design and construction of low-cost and noble-metal-free photocatalysts for efficient photocatalytic hydrogen evolution.     

Growth of anatase and rutile TiO2@Sb:SnO2 heterostructures and their application in photoelectrochemical water splitting

We report three-dimensional (3D) nanostructures based on shape- and phase-controlled TiO₂ coated transparent conducting oxide (TCO) nanowire array. Core-shell and branched nanostructures were obtained using an aqueous chemical bath deposition (CBD) method at room temperature. Adjusting the pH of a TiCl₄ solution is a key factor that determines the morphology of the nanostructure. Spherical TiO₂ anatase covered a Sb-doped SnO₂ (ATO) nanowire when pH was maintained at a high level. In contrast, branched nanostructures with TiO₂ rutile nanorods were synthesized by keeping a TiCl₄ solution going down to a low pH. Nanorods were grown epitaxially along the [001] direction on ATO nanowires. Morphological and structural analysis indicates that phases and shapes of the 3D hybrid nanostructure are determined by the pH of the solution and the reaction time. A two-fold higher photoconversion efficiency of rutile TiO₂ rod@ATO was obtained under simulated solar illumination compared to that of the anatase TiO₂ nanoshell@ATO. These 3D hybrid nanostructures can offer (i) a large surface area and efficient charge transport in the TiO₂ nanostructure, and (ii) an effective charge collection path through one-dimensional TCO, which is promising for various areas, including photoelectrochemical water splitting, as well as for application in electronic and photonic nanodevices.     

Excellent photocatalytic and photoelectrochemical activities from 1D/2D FeSe2/SnSe heterojunction photocatalysts constructed by FeSe2 nanorods and SnSe nanosheets

In this work, FeSe₂ nanorods have been employed to be loaded on SnSe nanosheets to develop 1D/2D FeSe₂/SnSe heterojunction photocatalysts. These test results of XRD, SEM, HRTEM and XPS fully confirm the successful construction of FeSe₂/SnSe heterojunction. These results of photocatalytic and photoelectrochemical test further reveal that FeSe₂/SnSe heterojunction photocatalysts have excellent photocatalytic and photoelectrochemical activities. In comparison to the SnSe, the highest photocurrent density of the 1D/2D FeSe₂/SnSe heterojunction photocatalyst is 19.2 μA/cm², which has 123% promotion. Besides, the biggest degradation rates k of the 1D/2D FeSe₂/SnSe heterojunction photocatalyst is 0.00612 nearly 297% enhancement than the SnSe. Further analysis indicated that as for 1D/2D FeSe₂/SnSe heterojunction photocatalyst, its internal resistance was largely reduced and carrier separation efficiency was significantly improved with the recombination of FeSe₂. This work confirmed that FeSe₂/SnSe is an ideal composite system with great potential in photocatalysis.     

Enhanced photocatalytic performance of hollow spherical CdS QDs@ZrO2–TiO2 composites with double Z-scheme heterostructures

In this paper, CdS QDs@ZrO₂–TiO₂ hollow spherical composites with double Z-scheme heterostructure modified by CdS QDs were prepared by the sol–gel method and vacuum impregnation method using polystyrene (PS) microspheres synthesized by the self-assembly technique as templates. A series of characterization results show that CdS QDs@ZrO₂–TiO₂ composites treated by PS microspheres have the structure of hollow spheres with uniform size and orderly arrangement. Moreover, the double Z-scheme heterojunction formed between CdS QDs, ZrO₂, and TiO₂ in the composite can optimize the charge transfer path and improve the charge separation efficiency. Results of the photodegradation and the photo-splitting water of CdS QDs@ZrO₂–TiO₂ composites show that, compared with other systems, CdS QDs@ZrO₂–TiO₂ composites have the highest photocatalytic degradation rate of crystal violet, and meanwhile, the photocatalytic hydrogen production rate of the composite under simulated sunlight is more than 100 times that of TiO₂. The good absorption of visible light, the successful construction of double Z-scheme heterojunction, and the unique hollow sphere structure of CdS QDs@ZrO₂–TiO₂ composites are the key factors for enhanced photocatalytic performance.     

Formation of single-crystalline rutile TiO2 splitting microspheres for dye-sensitized solar cells

The morphological evolution of specimen taken out after the different duration in TiCl₃ solution was investigated by field emission scanning electron microscopy (FE-SEM). The rutile TiO₂ splitting microspheres may be formed by the splitting crystal growth mechanism through the multistep process. The microsphere composed of the 20 nm width nanorods was in the range of 1.5–2.5 μm in the diameter. The dye-sensitized solar cell (DSC) based on the microspheres received 3.57% conversion efficiency under simulated AM 1.5 (100 mW/cm²) solar illumination, which exhibited remarkably higher charge collection efficiency and light scattering compared to that of P25. Electrochemical impedance spectroscopy (EIS) measurement revealed that impedance resistance at the surface of single-crystalline rutile TiO₂ splitting microspheres was 6 times larger than that of P25 nanoparticles, indicating electron recombination was significantly retarded.     

Chemical bath deposition synthesis of TiO2/Cu2O core/shell nanowire arrays with enhanced photoelectrochemical water splitting for H2 evolution and photostability

In this study, we have developed a facile chemical bath deposition (CBD) method to grow p-type Cu₂O nanoparticles on n-type TiO₂ nanowire arrays (TiO₂ NWAs) to fabricate TiO₂/Cu₂O core/shell heterojunction nanowire arrays (TiO₂/Cu₂O core/shell NWAs). When used as photoelectrode, the fabricated TiO₂/Cu₂O core/shell NWAs show improved photoelectrochemical (PEC) water splitting activity to pure TiO₂ NWAs. The effects of the CBD cycle times on the PEC activities have been studied. The TiO₂/Cu₂O core/shell heterojunction nanowire array photoelectrode prepared by cycling 5 times in the CBD process achieves the highest photocurrent of 2.5 mA cm^?2, which is 2.5 times higher than that of pure TiO₂ NWAs. In addition, the H₂ generation rate of this photoelectrode reaches to 32 μmol h^?1 cm^?2, 1.7 times higher than that of pure TiO₂ NWAs. Furthermore, the TiO₂/Cu₂O core/shell heterojunction nanowire array photoelectrode shows excellent photostability and achieves a stable photocurrent of over 2.3 mA cm^?2 during long light illumination time of 5 h. The enhanced photocatalytic activity of TiO₂/Cu₂O core/shell heterojunction nanowire array photoelectrode is attributed to the synergistic actions of TiO₂ and Cu₂O for improving visible light harvesting, and efficient transfer and separation of photogenerated electrons and holes.     

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.     

In-situ Raman study of relation between microstructure and photoactivity of CdS@TiO2 core-shell nanostructures

In the present study, the CdS@TiO₂ core-shell nanostructure was fabricated by the interface assembly of TiO₂ nanoparticles on the surface of CdS. All the samples were characterized by XRD, SEM, TEM and BET. Hydrogen production demonstrates that CdS@TiO₂ core-shell nanocomposites exhibited much higher photocatalytic activity than bare CdS. Raman and in-situ Raman techniques were used to identify the presence of TiO₂ ultrathin shell on the surface of CdS. It was found that the lattice strain of CdS@TiO₂ and CdS nanospheres increased linearly with the time in photocatalytic reaction. Except for the innitial point at t = 0, the ratio of the peak intensity for 2LO and 1LO (I_2LO/I_1LO) for CdS@TiO₂ is always lower than that of CdS. For CdS@TiO₂ composites, the increasement for the I_2LO/I_1LO ratio with time is basically unchanged, while that of the CdS nanospheres shows a general increase, with a significant fluctuation at t = 30min. It was also found that the electron phonon coupling for the cubic phase of CdS is much lower than the hexagonal CdS, which is mainly due to the difference of 1LO phonon symmetry. The above results suggested that the interaction between electron and phonon is a function of reaction time, which can be a good indicator of the status of the photocatalyst, even for such complex core-shell nanostrucures, during the reaction process. The in-situ Raman results directly proves that the ultra-thin TiO₂ shell can effectively protect the CdS core and avoid to be photocorrosion. Ultrathin TiO₂ film absorbs ultraviolet light, while it is transparent for visible light, the CdS can respond to the visible light, in this way the CdS@TiO₂ can achieve the efficient utilization for the solar energy.     

Highly efficient hydrogen evolution catalysis based on MoS2/CdS/TiO2 porous composites

Efficient production of hydrogen through visible-light-driven water splitting mechanism using semiconductor-based composites has been identified as a promising strategy for converting light into clean H₂ fuel. However, researchers are facing lots of challenges such as light absorption and electron-hole pair recombination and so on. Here, new sheet-shaped MoS₂ and pyramid-shaped CdS in-situ co-grown on porous TiO₂ photocatalysts (MoS₂CdSTiO₂) are successfully obtained via mild sulfuration of MoO₃ and CdO coexisted inside porous TiO₂ monolith by a hydrothermal route. The scanning electron microscopy and transmission electron microscopy results exhibit that the MoS₂CdSTiO₂ composites have average pore size about 500 nm. The 3%MoS₂10%CdSTiO₂ demonstrated excellent photocatalytic activity and high stability for a hydrogen production with a high H₂-generation rate of 4146 μmol h^?1 g^?1 under visible light irradiation even without noble-metal co-catalysts. The super photocatalytic performance of the visible-light-driven hydrogen evolution is predominantly attributed to the synergistic effect. The conduction band of MoS₂ facilitates in transporting excited electrons from visible-light on CdS to the porous TiO₂ for catalytic hydrogen production, and holes to MoS₂ for inhibiting the photocorrosion of CdS, respectively, leading to enhancing the efficient separation of electrons and holes.     

Low-temperature preparation of AgIn5S8/TiO2 heterojunction nanocomposite with efficient visible-light-driven hydrogen production

AgIn₅S₈ and AgIn₅S₈/TiO₂ heterojunction nanocomposite with efficient photoactivity for H₂ production were prepared by a low-temperature water bath deposition process. The resultant AgIn₅S₈ shows an absorption edge at ∼720 nm, corresponding to a bandgap of ∼1.72 eV, and its visible-light-driven photoactivity (100.1 μmol h⁻¹) for H₂ evolution is 9 times higher than that (11 μmol h⁻¹) of the product derived from a hydrothermal process, while the obtained AgIn₅S₈/TiO₂ heterojunction nanocomposites prepared by using commercially available TiO₂ nanoparticles (P25) as TiO₂ source exhibit remarkably improved photoactivity as compared to the pristine AgIn₅S₈, and the AgIn₅S₈/TiO₂ nanocomposite with molar ratio of 1:10 shows a maximum photocatalytic H₂ evolution rate (371.1 μmol h⁻¹), which is 4.3 times higher than that (85 μmol h⁻¹) of the corresponding AgIn₅S₈/TiO₂ nanocomposite derived from a hydrothermal method. This significant enhancement in the photocatativity of the present AgIn₅S₈/TiO₂ nanocomposite can be ascribed to the better dispersion of the AgIn₅S₈ formed on TiO₂ nanoparticle surfaces and the more intimate AgIn₅S₈/TiO₂ heterojunction structure during the water bath deposition process under continuously stirring as compared to the corresponding nanocomposite derived from a hydrothermal method. This configuration of nanocomposite results in fast diffusion of the photogenerated carriers in AgIn₅S₈ towards TiO₂, which is beneficial for separating spatially the photogenerated carriers and improving the photoactivity. The present findings shed light on the tuning strategy of spectral responsive region and photoactivity of photocatalysts for efficient light-to-energy conversion.     

CuCr2O4/TiO2 heterojunction for photocatalytic H2 evolution under simulated sunlight irradiation

CuCr₂O₄/TiO₂ heterojunction has been successfully synthesized via a facile citric acid (CA)-assisted sol-gel method. Techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectrum (UV-vis DRS) have been employed to characterize the as-synthesized nanocomposites. Furthermore, photocatalytic activities of the as-obtained nanocomposites have been evaluated based on the H₂ evolution from oxalic acid solution under simulated sunlight irradiation. Factors such as CuCr₂O₄ to TiO₂ molar ratio in the composites, calcination temperature, photocatalyst mass concentration, and initial oxalic acid concentration affecting the photocatalytic hydrogen producing have been studied in detail. The results showed that the nanocomposite of CuCr₂O₄/TiO₂ is more efficient than their single part of CuCr₂O₄ or TiO₂ in producing hydrogen. The optimized composition of the nanocomposites has been found to be CuCr₂O₄·0.7TiO₂. And the optimized calcination temperature and photocatalyst mass concentration are 500 °C and 0.8 g l⁻¹, respectively. The influence of initial oxalic acid concentration is consistent with the Langmuir model.