In- situ solid-phase fabrication of Ag/AgX (X=Cl,Br, I)/g-C3N4 composites for enhanced visible-light hydrogen evolution

In this work, a series of Ag/AgX (X = Cl, Br, I)/g-C₃N₄ (Ag/AgX/CN) composites were successfully fabricated by an in-situ solid phase method. The morphology and structure, photoluminescence and photoelectrochemical properties of composites were investigated in detail. The as-prepared Ag/AgX/CN composites were used as H₂ evolution photocatalysts under visible-light irradiation with a sacrificial agent. The experimental results revealed that Ag/AgI/CN-4 composite possesses highest-H₂ evolution rate (up to 59.22 μmol g⁻¹ h⁻¹) which are approximately 31 times higher than that of pure g-C₃N₄ (1.94 μmol g⁻¹ h⁻¹). In addition, Ag/AgCl/CN-4 and Ag/AgBr/CN-4 composites also present high photocatalytic activities yielding, 26.39 and 18.05 μmol_H2 g⁻¹ h⁻¹_, respectively. The enhanced photocatalytic activities of Ag/AgI/CN-4 composite might be attributed to the synergistic effect between Ag/AgI nanoparticles and g-C₃N₄ and the localized surface plasmon resonance effect of metallic Ag. Moreover, Ag/AgI/CN-4 composite showed excellent recyclability and stability after five cycling photocatalytic tests (about 25 h). Furthermore, the possible photocatalytic mechanism of Ag/AgI/CN composites is proposed.     

In situ loading amorphous CoSx on N-doped g-C3N4 through light assisted synthesis for enhanced photocatalytic hydrogen generation

Loading co-catalysts are an effective strategy to break the confinement of bulk carbon nitride in photocatalysis. Employing this strategy, N-doped g-C₃N₄ decorated with CoS_x was successfully prepared through a photochemical synthesis route. The optimum hydrogen evolution performance of N-CN-CoS_x-4 was 1757 μmol g⁻¹ h⁻¹ under visible light irradiation. Superior interfacial carrier transfer properties and improved light absorption of N-CN-CoS_x-4 could elucidate its better photocatalytic activity. This research offers a reference for the construction of high-efficiency, stable and low-priced photocatalysts.     

One-step preparation of halogenated aminobenzonitrile modified g-C3N4 via copolymerization and in situ halogen doping for highly enhanced visible light hydrogen evolution

A series of halogenated aminobenzonitrile modified graphitic carbon nitride (g-C₃N₄) was prepared by a one-step calcination of dicyandiamide and 2-amino-5-halogen-benzonitriles (X-ABN, X = F, Cl, Br or I, 1.67 wt% of dicyandiamide) together, and named as X-ABN-CN. The resulting X-ABN-CN photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflection spectroscopy, and photoluminescence spectroscopy. The characterization results indicated that X-ABN-CN have been successfully prepared, and the π-conjugated system and electronic structure of X-ABN-CN could be improved via copolymerization, Ullmann reaction and in situ halogen doping. Under visible light irradiation (λ > 400 nm), the photocatalytic activity of X-ABN-CN were much higher than that of pure g-C₃N₄ and increase with the increase of halogen atomic number. The hydrogen evolution rate of I-ABN-CN (131.4 μmol h⁻¹) was 7.4 times that of g-C₃N₄ (17.7 μmol h⁻¹). Furthermore, the corresponding mesoporous X-ABN-CN (X-ABN-MCN, X = F, Cl, Br or I) were prepared by using SiO₂ nanoparticles as template. As expected, I-ABN-MCN showed the highest photocatalytic activity in all mesoporous samples, which is about 8.8 times that of g-C₃N₄. The results manifest that the copolymerization, Ullmann reaction, in situ halogen doping and mesoporous structure could be integrated together to modify g-C₃N₄ by a simple one-step calcination process.     

2D MOFs enriched g-C3N4 nanosheets for highly efficient charge separation and photocatalytic hydrogen evolution from water

Here we report a 2D-2D heterostructure of g-C₃N₄/UMOFNs photocatalysts via mechanical grinding two kinds of two-dimensional nanosheets of g-C₃N₄ nanosheets and UMOFNs, which exhibits enhanced H₂ evolution from water with simulated solar irradiation. g-C₃N₄ nanosheets are in close contact with UMOFNs, and there is a certain interaction between them, showing the effect of superimposition on the two-dimensional layer. The 2D-2D heterostructure offers a maximal photocatalytic hydrogen production activity of 1909.02 μmol g⁻¹ h⁻¹ with 3 wt% of UMOFNs, which is 3-fold higher than that of g-C₃N₄ nanosheets (628.76 μmol g⁻¹ h⁻¹) and 15-flod higher than that of bulk g-C₃N₄ (124.30 μmol g⁻¹ h⁻¹). The significant increasement of photocatalysis is due to 2D-2D heterostructure possessing a short charge transfer distance and large contact area between g-C₃N₄ and UMOFNs. The highly dispersed NiO, CoO and π-π bonds in UMOFNs of 2D-2D structure also promote charge transfer and enhance the photocatalytic activity.     

The heterojunction construction of hybrid B-doped g-C3N4 nanosheets and ZIF67 by simple mechanical grinding for improved photocatalytic hydrogen evolution

In this study, B-doped g-C₃N₄ nanosheets (BCN) were prepared using a thermal-oxidative etching method, resulting in a semiconductor with a large specific surface area. The B-doping enhances the light absorption of graphitic carbon nitride(g-C₃N₄) and improves the photogenerated carrier lifetime. The optimal B-containing amount resuled in a hydrogen production rate of 1297 μmol g⁻¹ h⁻¹ for g-C₃N₄ nanosheets. Furthermore, zeolitic imidazolate framework (ZIF)67/BCN heterostructures were successfully obtained through simple mechanical grinding approaches. The BCN provided abundant active sites and contributed to excellent encapsulation on the surface of ZIF67. The obtained ZIF67/BCN photocatalyst displayed an H₂ evolution rate of 3392 μmol g⁻¹ h⁻¹, attributed to forming type-II heterojunctions between ZIF67 and BCN. Moreover, the BCN exhibited a higher conduction band (CB) potential with ZIF67 than CN, resulting in more efficient light-driven charge separation between ZIF67 and BCN and enhanced photocatalytic performance. This work provides a meaningful reference for improving the activity of g-C₃N₄ photocatalysts.     

Mo incorporated Ni nanosheet as high-efficiency co-catalyst for enhancing the photocatalytic hydrogen production of g-C3N4

The design and development of noble metal-free, low-cost and stable co-catalyst are of great significance to the practical application of photocatalysts. In this work, the Mo incorporated Ni nanosheets (MoNi NSs) are successfully prepared and loaded onto g-C₃N₄ via a simple and controllable method. The controlled loading of MoNi NSs with an optimal Mo intake can greatly enhance the photocatalytic H₂-evolution property of g-C₃N₄ (Mo_0.25Ni_0.75/CN5). Specifically, the Mo_0.25Ni_0.75/CN5 exhibits the highest photocatalytic H₂-evolution rate of 273.2 μmol h⁻¹ (5464 μmol h⁻¹ g⁻¹), which is the highest rate under one-solar light in the g-C₃N₄ systems coupled with noble-metal-free co-catalysts. The greatly enhanced photocatalytic H₂-evolution activity of MoNi/g-C₃N₄ is attributed to the role of MoNi as an outstanding co-catalyst to promote the carriers’ separation and transfer, and accelerate the surface H₂ evolution reaction (HER).     

The charge transfer pathway of g-C3N4 decorated Au/Bi(VO4) composites for highly efficient photocatalytic hydrogen evolution

In this report, a novel g-C₃N₄/Au/BiVO₄ photocatalyst has been prepared successfully by assembling gold nanoparticles on the interface of super-thin porous g-C₃N₄ and BiVO₄, which exhibits outstanding photocatalytic performance toward hydrogen evolution and durable stability in the absence of cocatalyst. FESEM micrograph analysis suggested that the intimate contact between Au, BiVO₄, and g-C₃N₄ in the as-developed photocatalyst allows a smooth migration and separation of photogenerated charge carriers. In addition, the XRD, EDX and XPS analysis further confirmed the successful formation of the as-prepared g-C₃N₄/Au/BiVO₄ photocatalyst. The photocatalytic hydrogen production activity of the developed photocatalyst was evaluated under visible-light irradiation (λ > 420 nm) using methanol as a sacrificial reagent. By optimizing the 5-CN/Au/BiVO₄ composite shows the highest H₂ evolution rate (2986 μmolg⁻¹h⁻¹), which is 15 times higher than that of g-C₃N₄ (199 μmolg⁻¹h⁻¹) and 10 time better than bare BiVO₄ (297 μmolg⁻¹h⁻¹). The enhancement in photocatalytic activity is attributed to efficient separation of the photoexcited charges due to the anisotropic junction in the g-C₃N₄/Au/BiVO₄ system. The enhancement in photocatalytic activity is attributed to efficient separation of the photoexcited charges due to the anisotropic junction in the g-C₃N₄/Au/BiVO₄ system.     

High-efficiency of novel hierarchical 3D macroporous g-C3N4 material on solar-driven photocatalytic water-splitting for hydrogen evolution

The use of multi-pore nanostructured g-C₃N₄ photocatalysts is an efficient approach to separate photogenerated charge carriers and increase visible light photocatalytic performance. Recent progress has yielded nanostructured material through hard templating, which limits potential applications. Integrating the 2D building block into multidimensional porous structures remains a significant challenge in scalable production. Herein, a novel technique based on P407 bubble clusters templating and fixation by freezing is described for the first time to fabricate a 3D opened-up macroporous g-C₃N₄ nanostructures for photocatalytic H₂ evolution. Three-dimensional hierarchical nanostructures provide more contact active sites and synergistically promote the creation of heterogeneous catalytic interfaces. This feature is very useful for understanding the transfer path of photoinduced charges as well as the origins of the high charge separation efficiency in photocatalytic reactions, thus yielding a remarkable visible light-induced H₂ evolution rate of 4213.6 μmol h⁻¹ g⁻¹, which is nearly 5.6 times (716 μmol h⁻¹ g⁻¹) higher than that of lamellar bulk g-C₃N₄. This newly developed approach offers a promising alternative to synthesize broad-spectral response 3D hierarchal g-C₃N₄ nanostructures and can be extended to assemble other functional nanomaterials as building blocks into macroscopic configurations coupled with electronic modulation strategy simultaneously.     

CaH2-assisted structural engineering of porous defective graphitic carbon nitride (g-C3N4) for enhanced photocatalytic hydrogen evolution

The practical applications of graphitic carbon nitride (g-C₃N₄) for photocatalytic hydrogen evolution is strictly hindered by the low surface area, poor light harvesting capability and detrimental recombination of photoexcited charge carriers. Herein, using melamine as precursor and metal hydride (i.e., CaH₂) as active agent, we facilely incorporate various types of defects (i.e., nitrogen (N) vacancies (V_N), cyano groups (CN) and surface absorbed oxygen species(O_abs)) into g-C₃N₄ within a single step. The as-prepared material (denoted as MM-H) exhibits narrowed bandgap, promoted photoexcited electron-hole separation rate and facilitated charge transfer kinetics with enlarged BET surface area and massive porosity. As a result, a prominently enhanced photocatalytic H₂ productivity efficiency (1305.9 μmol h⁻¹g⁻¹) is shown on MM-H. This performance is better than that of g-C₃N₄ with CaH₂ post-treatment (617.3 μmol h⁻¹g⁻¹) and raw bulk-C₃N₄ (178.2 μmol h⁻¹g⁻¹). This work opens up a new dimension for designing high performance g–C₃N₄–based catalysts targeting various photocatalytic processes.     

K and halogen binary-doped graphitic carbon nitride (g-C3N4) toward enhanced visible light hydrogen evolution

Water splitting driven by solar energy to produce hydrogen, which is highly dependent on the designing of semiconductor photocatalyst, is an efficient technology to address energy shortage problems and environment issues simultaneously. Here, the halogen and potassium binary-doped graphitic carbon nitride (named as X-K-C₃N₄, X = F, Cl, Br, I) photocatalysts were synthetized via simply one pot thermal polymerization method, which shown optimized band structure, enhanced optical absorption, higher separation rate of photogenerated carriers, and thus improved photocatalytic performance under visible light irradiation. As result, F–K–C₃N₄ is demonstrated to be highly efficient in the separation and transfer of carriers owing to the existence of C–F bond, CN triple bond and K junction. The F–K–C₃N₄ shows a highest H₂ evolution rate of 1039 μmol g⁻¹ h⁻¹ and a remarkable stability under visible light irradiation (λ ≥ 420 nm), which is about 8.5 times higher than that of pristine g-C₃N₄.     

A direct one-step synthesis of ultrathin g-C3N4 nanosheets from thiourea for boosting solar photocatalytic H2 evolution

Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) nanosheets, as the promising photocatalyst with fascinating properties, have become a “rising star” in the field of photocatalysis. Although g-C₃N₄ nanosheets exfoliated from the bulk g-C₃N₄ powders are extensively emerged, developing a simple synthetic approach is still full of challenge. To this end, here we report a direct polymerization strategy to fabricate the ultrathin g-C₃N₄ nanosheets, that is only heating treatment of thiourea in air without addition of any template. The photocatalytic activities of as-prepared samples were evaluated by photoreduction of water to hydrogen (H₂) using triethanolamine as sacrificial agent and Pt as co-catalyst under visible-light irradiation (λ > 420 nm). As a result, our few-layered g-C₃N₄ nanosheets with an average thickness of 3.5 nm exhibit a superior visible-light photocatalytic H₂ evolution rate (HER) of 1391 μmol g⁻¹ h⁻¹ and a remarkable apparent quantum efficiency of 6.6% at 420 nm. Eventually, the HER of as-fabricated ultrathin g-C₃N₄ nanosheets is not only much higher than the dicyandiamide-derived g-C₃N₄ or melamine-derived g-C₃N₄, but also greater than the thermal-oxidation etched g-C₃N₄ nanosheets under the same condition.     

Montmorillonite-hybridized g-C3N4 composite modified by NiCoP cocatalyst for efficient visible-light-driven photocatalytic hydrogen evolution by dye-sensitization

The photocatalytic hydrogen evolution performance of g-C₃N₄ was enhanced via the hybridization with montmorillonite (MMT) and using NiCoP as cocatalyst. The highest hydrogen-evolution rate from water splitting under visible-light irradiation observed over MMT/g-C₃N₄/15%NiCoP was 12.50 mmol g⁻¹ h⁻¹ under 1.0 mmol L⁻¹ of Eosin Y-sensitization at pH of 11, which was ∼26.0 and 1.6 times higher than that of MMT/g-C₃N₄ (0.48 mmol g⁻¹ h⁻¹) and g-C₃N₄/15%NiCoP (7.69 mmol g⁻¹ h⁻¹). The apparent quantum yield at 420 nm reached 40.3%. The remarkably improved photocatalytic activity can be ascribed to the increased dispersion of g-C₃N₄ layers, staggered conduction band potentials between g-C₃N₄ and NiCoP, as well as the electrostatic repulsion originated from negatively charged MMT. This work demonstrates that MMT can be an outstanding support for the deposition of catalytically active components for photocatalytic hydrogen production.     

Heterostructured boron doped nanodiamonds@g-C3N4 nanocomposites with enhanced photocatalytic capability under visible light irradiation

Boron doped nanodiamonds (BDND) were coupled with graphitic carbon nitride (g-C₃N₄) nanosheets to form a heterojunction via a facile pyrolysis approach. The BDND@g-C₃N₄ heterojunction exhibits enhanced visible-light absorbance, improved charge generation/separation efficiency and prolonged lifetime of carriers, which lead to the enhanced photocatalytic activities for the hydrogen evolution and organic pollution under visible-light irradiation. The optimal H₂ evolution rate and apparent quantum efficiency at 420 nm of the BDND@g-C₃N₄ heterojunction is 96.3 μmol h⁻¹ and 6.91%, which is about 5 and 2 times higher than those of pristine g-C₃N₄ nanosheets (18.2 μmol h⁻¹ and 3.92%). No obvious decrease in hydrogen generation rate is observed in the recycling experiment due to the high photo-stabilization of the BDND@g-C₃N₄ composite. The degradation kinetic rate constant of organic pollution of the BDND@g-C₃N₄ structure is 0.1075 min⁻¹, which is 3 times higher compared to pristine g-C₃N₄. This work may provide a promising route to construct highly efficient non-metal photocatalysts for hydrogen evolution and organic pollution degradation under visible light irradiation.     

Chloroplast-granum-inspired porous nanorods composed of g-C3N4 ultrathin nanosheets as visible light photocatalysts for highly enhanced hydrogen production

Metal-free photocatalysts have attracted great attention in hydrogen production under visible light due to their low cost and abundance. Inspired by the structure of chloroplast-granum, here we prepare a new porous nanorod composed of F-doped g-C₃N₄ ultrathin nanosheet for photocatalytic hydrogen evolution. The obtained g-C₃N₄ (FCN-PNRs) show layer-by-layer stacked structure for highly efficient light hasting, exhibit F-doping for highly charge separation efficiency, and display porous structure for exposing a large amount of photocatalytic activity sites. These findings have been studied by various characterizations, such as Brunauer-Emmett-Teller, and Photoluminescence. As a result, the hydrogen production performance for the optimized FCN-PNRs photocatalyst reaches 2600 μmol h⁻¹ g⁻¹ under visible light, which is almost 16 times higher than bulk g-C₃N₄. This study not only reports a new chloroplast-granum-inspired g-C₃N₄ photocatalyst, but also provides new views to the fabrication and design of nature-inspired metal-free structures for catalysis applications.     

Construction of carbon dots modified hollow g-C3N4 spheres via in situ calcination of cyanamide and glucose for highly enhanced visible light photocatalytic hydrogen evolution

In this work, a series of carbon dots (CDs) modified hollow g-C₃N₄ spheres (HCNS-C_x) were constructed via a double in situ approach using cyanamide and glucose as precursors, respectively. As HCNS-C_x was synthesized by one-step in situ thermal polymerization of two precursors, which could make CDs and g-C₃N₄ keep tight connection and increase the separation of the photogenerated electron-hole pairs. The average diameter and wall thickness of the HCNS-C_x are about 355 nm and 55 nm, respectively. Under the visible light irradiation, the H₂ evolution rate (HER) of HCNS-C_1.0 (2322 μmol g^?1 h^?1) was 19 times that of bulk g-C₃N₄ (122 μmol g^?1 h^?1) and 1.8 times that of HCNS without CDs modification (1289 μmol g^?1 h^?1), respectively. And its apparent quantum efficiency is 17.93% at 420 nm. The specific surface area, light absorption capacity, and charge carrier mobility of HCNS-C_x could be dramatically improved due to the introduction of CDs and hollow structures of g-C₃N₄ spheres, resulting in a significant improvement of photocatalytic activity.     

In-situ synthesis of Pd nanocrystals with exposed surface-active facets on g-C3N4 for photocatalytic hydrogen generation

Engineering surface-active facets of metal cocatalysts is one of the most widely explored strategies to develop advanced photocatalysts and promote photocatalytic solar energy conversion. Here, the surface-active facets of Pd nanocrystals in Pd/g-C₃N₄ photocatalyst was related to the injection flow rate of PdCl₂. When PdCl₂ was injected at a low flow rate of 7.5 mL/h (7.5-Pd/g-C₃N₄), the Pd nanocrystals were uniformly dispersed onto the g-C₃N₄ with exposed low-index {100} and {111} surface-active facets. However, increasing the injection flow rate to 150 mL/h (150-Pd/g-C₃N₄) formed Pd nanocrystals where only the {100} surface-active facet was exposed. Under visible light irradiation, the 7.5-Pd/g-C₃N₄ nanocomposite exhibited excellent water splitting activity for hydrogen production (7.61 mmol g⁻¹ h⁻¹), which was significantly better than with the 150-Pd/g-C₃N₄ nanocomposite (3.3 mmol g⁻¹ h⁻¹). Theoretical calculations and experimental results confirm the importance of the {111} surface-active facets in the 7.5-Pd/g-C₃N₄ nanocomposite for promoting photocatalytic activity.     

Fabrication of hollow g-C3N4@α-Fe2O3/Co-Pi heterojunction spheres with enhanced visible-light photocatalytic water splitting activity

For the first time, g-C₃N₄@α-Fe₂O₃/Co-Pi heterojunctional hollow spheres were successfully fabricated via thermal condensation method followed by solvothermal and photo-deposition treatment, which showed excellent photocatalytical property. Except for the Z-scheme charge transfer between α-Fe₂O₃ and g-C₃N₄, the Co-Pi could further reduce the combination of photogenerated electrons and holes as a hole storage agent, resulting in remarkably enhanced visible-light photocatalytic water splitting activity with the H₂ production rate of 450 μmol h⁻¹g⁻¹, which is 15.7 times higher than that of g-C₃N₄. Moreover, the photocatalytic activity of the prepared ternary hollow photocatalysts showed almost no significant weakness after five cycles, which indicated their good performance stability. The as-prepared g-C₃N₄@α-Fe₂O₃/Co-Pi also possessed good activity for overall water splitting with the hydrogen production rate reaching 9.8 μmol h⁻¹g⁻¹. This synthesized g-C₃N₄@α-Fe₂O₃/Co-Pi composite is expected to be a promising candidate for water splitting.     

Melamine-phytic acid derived supramolecular synthesis of g-C3N4 for enhanced solar hydrogen evolution

It is an effective approach to regulate the structure of photocatalysts by introducing the heteroatoms into the lattice for extended light absorption and enhanced charge separation. In this work, the P atoms were introduced to substitute the corner C atoms of g-C₃N₄ by calcinating the melamine-phytic acid derived supramolecular with high-density phosphate groups, which is synthesized by hydrothermal method. The intermediate state produced by the introduction of P atoms leads to the enhanced light absorption of P–CN_(7.2g-IP6) with a negative shifted conduction band position, which benefits the photocatalytic hydrogen reaction kinetically. Moreover, the electron transferred from P atom to the surrounding N atoms results in the positively charged P center, which could act as Lewis acid site. Such formed Lewis acid site at positively charged P center together with the Lewis base sites, such as amine or imine groups in P–CN, makes it easier to separate photogenerated charges, thus enabling the P–CN_(7.2g-IP6) to exhibit an enhanced photocatalytic hydrogen rate of 2.743 mmol·g⁻¹·h⁻¹, which is about 6.77 times that of pristine g-C₃N₄ (0.405 mmol·g⁻¹·h⁻¹). This work provides an alternative approach to regulating the structure of photocatalysts.     

A facile one-step strategy to construct 0D/2D SnO2/g-C3N4 heterojunction photocatalyst for high-efficiency hydrogen production performance from water splitting

Fabricating 0D/2D heterojunctions is considered to be an efficient mean to improve the photocatalytic activity of g-C₃N₄, whereas their applications are usually restricted by complex preparation process. Here, the 0D/2D SnO₂/g-C₃N₄ heterojunction photocatalyst is prepared by a simple one-step polymerization strategy, in which SnO₂ nanodots in-situ grow on the surface of g-C₃N₄ nanosheets. It shows the outstanding photocatalytic H₂ production activity relative to g-C₃N₄ under the visible light, which is due to the formation of 0D/2D heterojunction significantly contributing to the separation of photogenerated charge carriers. In particular, the H₂ production rate over the optimal SnO₂/g–C₃N₄–1 sample is 1389.2 μmol h⁻¹ g⁻¹, which is 6.06 times higher than that of g-C₃N₄ (230.8 μmol h⁻¹ g⁻¹). Meanwhile, the AQE value of H₂ production over the SnO₂/g–C₃N₄–1 sample reaches up to a maximum of 4.5% at 420 nm. This work develops a simple approach to design and fabricate g–C₃N₄–based 0D/2D heterojunctions for the high-efficiency H₂ production from water splitting.     

Rationally designed ternary CdSe/WS2/g-C3N4 hybrid photocatalysts with significantly enhanced hydrogen evolution activity and mechanism insight

Excellent light harvest, efficient charge separation and sufficiently exposed surface active sites are crucial for a given photocatalyst to obtain excellent photocatalytic performances. The construction of two-dimensional/two-dimensional (2D/2D) or zero-dimensional/2D (0D/2D) binary heterojunctions is one of the effective ways to address these crucial issues. Herein, a ternary CdSe/WS₂/g-C₃N₄ composite photocatalyst through decorating WS₂/g-C₃N₄ 2D/2D nanosheets (NSs) with CdSe quantum dots (QDs) was developed to further increase the light harvest and accelerate the separation and migration of photogenerated electron-hole pairs and thus enhance the solar to hydrogen conversion efficiency. As expected, a remarkably enhanced photocatalytic hydrogen evolution rate of 1.29 mmol g⁻¹ h⁻¹ was obtained for such a specially designed CdSe/WS₂/g-C₃N₄ composite photocatalyst, which was about 3.0, 1.7 and 1.3 times greater than those of the pristine g-C₃N₄ NSs (0.43 mmol g⁻¹ h⁻¹), WS₂/g-C₃N₄ 2D/2D NSs (0.74 mmol g⁻¹ h⁻¹) and CdSe/g-C₃N₄ 0D/2D composites (0.96 mmol g⁻¹ h⁻¹), respectively. The superior photocatalytic performance of the prepared ternary CdSe/WS₂/g-C₃N₄ composite could be mainly attributed to the effective charge separation and migration as well as the suppressed photogenerated charge recombination induced by the constructed type-II/type-II heterojunction at the interfaces between g-C₃N₄ NSs, CdSe QDs and WS₂ NSs. Thus, the developed 0D/2D/2D ternary type-II/type-II heterojunction in this work opens up a new insight in designing novel heterogeneous photocatalysts for highly efficient photocatalytic hydrogen evolution.