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.     

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.     

Facile synthesis of CeO2/g-C3N4 nanocomposites with significantly improved visible-light photocatalytic activity for hydrogen evolution

Ceria dioxide supported on graphitic carbon nitride (CeO₂/g-C₃N₄) composites were facilely synthesized to be application for photocatalytic hydrogen (H₂) generation in this present work. The physical and chemical properties of CeO₂/g-C₃N₄ nanocomposites were determined via a series of characterizations. The CeO₂/g-C₃N₄ composites prepared by facile thermal annealing and rotation-evaporation method exhibit excellent photocatalytic H₂ evolution with visible-light illumination. The best hydrogen generation rate of CeO₂/g-C₃N₄ composite with 1.5 wt% Pt is 0.83 mmol h⁻¹ g⁻¹, which is almost same as that of composite with 3 wt% Pt prepared by simple physical mixing method. The significantly developed photocatalytic activity of CeO₂/g-C₃N₄ composite is majorly ascribed to the stronger interfacial effects with the more visible-light absorbance and faster electron transfer. This work reveals that construction of the CeO₂/g-C₃N₄ composite with high disperse and close knit by the facile thermal annealing and rotation-evaporation method could be an effective method to achieve excellent photocatalytic hydrogen evolution performance.     

Effect of nonmetal element dopants on photo- and electro-chemistry performance of ultrathin g-C3N4 nanosheets

Increased charge transfer and light absorption as well as large specific surface area are effective ways to improve the catalytic efficiency of photocatalysts. In this paper, barbituric acid, urea and thiourea were separately freeze-dried to form a homogeneous precursor with melamine, followed by thermal polymerization at 750 °C, g-C₃N₄ was doped successfully with C, N and S. Among them, C-doped g-C₃N₄ revealed well photocatalytic hydrogen production which reached to 2.45 mmol g⁻¹ h⁻¹. N-doped g-C₃N₄ exhibited enhanced photocatalytic degradation properties for organic dye (RhB) which is completely degraded within 8 min while the performance S-doped sample is not satisfied. The introduction of C resulted in planarized sample which has a larger specific surface area and provides more active sites. N doping makes the valence band position moving in the direction of high energy. Thus, holes have stronger oxidizing ability. Accordingly, the effect of C and N ratios in g-C₃N₄ photocatalysis was fully discussed for more comprehensive understanding of g-C₃N₄.     

In situ metal–organic framework-derived c-doped Ni3S4/Ni2P hybrid co-catalysts for photocatalytic H2 production over g-C3N4 via dye sensitization

Controlled integration of metal-based sulfides with phosphides possessing strong coupling effects is a promising way to accelerate electron transfer by modulating the electronic structures of the host species. In this work, a c-doped Ni₃S₄/Ni₂P (C@Ni₃S₄/Ni₂P) hybrid co-catalyst produced by in situ sulfuration and phosphidation of Ni-MOF was decorated on g-C₃N₄ and subsequently used for photocatalytic H₂ evolution under visible-light irradiation. Among the prepared composites tested herein, the optimized g-C₃N₄/C@Ni₃S₄/Ni₂P-30 composite showed the highest H₂ evolution rate (14.49 mmol g⁻¹ h⁻¹) with 1.0 mmol L⁻¹ of Eosin Y (EY)-sensitization, which is 10 times higher than that of pristine g-C₃N₄ (1.33 mmol g⁻¹ h⁻¹). The enhanced photocatalytic activity of this composite can be attributed to: (i) electronic interactions between Ni₂P and Ni₃S₄ (which synergistically increased the electron transfer rate) and (ii) staggered band alignment of excited-stated EY, g-C₃N₄, Ni₃S₄, and Ni₂P. This work may provide some perspectives for utilization of MOF-derived hybrid co-catalysts as substitutes of noble metals for effective photocatalytic H₂ evolution.     

In-situ growth of CdS quantum dots on g-C3N4 nanosheets for highly efficient photocatalytic hydrogen generation under visible light irradiation

Well dispersed CdS quantum dots were successfully grown in-situ on g-C₃N₄ nanosheets through a solvothermal method involving dimethyl sulfoxide. The resultant CdS–C₃N₄ nanocomposites exhibit remarkably higher efficiency for photocatalytic hydrogen evolution under visible light irradiation as compared to pure g-C₃N₄. The optimal composite with 12 wt% CdS showed a hydrogen evolution rate of 4.494 mmol h⁻¹ g⁻¹, which is more than 115 times higher than that of pure g-C₃N₄. The enhanced photocatalytic activity induced by the in-situ grown CdS quantum dots is attributed to the interfacial transfer of photogenerated electrons and holes between g-C₃N₄ and CdS, which leads to effective charge separation on both parts.     

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.     

Direct Z-scheme CoS/g-C3N4 heterojunction with NiS co-catalyst for efficient photocatalytic hydrogen generation

Facilitating the separation of photoexcited electron-hole pairs and enhancing the migration of photogenerated carriers are essential in photocatalytic reaction. CoS/g-C₃N₄/NiS ternary photocatalyst was prepared by hydrothermal and physical stirring methods. The optimized ternary composite achieved a hydrogen yield of 1.93 mmol g^?1 h^?1, 12.8 times that of bare g-C₃N₄, with an AQE of 16.4% at 420 nm. The enhanced photocatalytic activity of CoS/g-C₃N₄/NiS was mainly ascribed to the synergistic interaction between the Z-scheme heterojunction constructed by CoS and g-C₃N₄ and the NiS co-catalyst featuring a large amount of hydrogen precipitation sites, which realized the efficient separation and migration of photogenerated carriers. In addition, the CoS/g-C₃N₄/NiS heterojunction-co-catalyst system exhibited excellent photocatalytic stability and recyclability.     

Photo-assisted splitting of water into hydrogen using visible-light activated silver doped g-C3N4 & CNTs hybrids

Herein, highly efficient and cost effective solar photocatalytic water splitting for hydrogen (H₂) generation was achieved by modified g-C₃N₄. Visible light absorption of g-C₃N₄ was enhanced by decorating g-C₃N₄ matrix with silver nanoparticles (Ag). Moreover, incorporation of carbon nanotubes (CNTs) in Ag/g-C₃N₄ facilitated photocatalytic performance through efficient separation and transfer of photogenerated e-h pairs (charges) in Ag/g-C₃N₄ that consequently generated very pure and significant H₂. Among several tested ratios (wt. %) of Ag/g-C₃N₄/CNTs, 1.82 (Ag/g-C₃N₄) and 2.00 (and Ag/g-C₃N₄/CNTs) were found to be highly efficient that harvested maximum visible-light and produced H₂ @1.48 mmol h⁻¹ and 1.78 mmol h⁻¹. We witnessed distinctive role of CNTs as an electron collector and carrier to separate photogenerated e-h pairs to facilitate photocatalysis for H₂ generation together with possible utility of Ag and CNTs doped materials with regard to energy transformation.     

In-situ synthesis of PdAg/g-C3N4 composite photocatalyst for highly efficient photocatalytic H2 generation under visible light irradiation

Novel PdAg bimetallic alloy nanoparticle modified graphitic carbon nitride (g-C₃N₄) nanosheet was designed and prepared by an in situ chemical reduction procedure. By optimizing the loading content of the PdAg alloy NPs, the PdAg/g-C₃N₄ composite photocatalyst showed a champion photocatalytic hydrogen generation rate of 3.43 mmol h⁻¹ g⁻¹, and the apparent quantum yield (AQY) was determined to be 8.43% at 420 nm. Moreover, the photoluminescence and photoelectrochemical experimental results suggest that a higher separation efficiency of photo-induced charge carriers (e^- and h⁺) was obtained after loading PdAg alloy NPs on g-C₃N₄. The experimental outcomes indicate that there is a synergistic effect formed between PdAg and g-C₃N₄, which could significantly promote the charge transfer photo-induced charge carriers in the hybrid sample. A reasonable catalytic mechanism for the enhanced photocatalytic performance of the composite photocatalyst was proposed and verified by TRPL measurement, which could be taken as a guidance for the development of novel high performance catalytic system.     

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.     

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.     

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.     

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.     

Construction of Cu7.2S4/g-C3N4 photocatalyst for efficient NIR photocatalysis of H2 production

Graphite-like carbon nitride (g-C₃N₄) has been regarded as a promising photocatalyst for solar-to-chemical conversion. Nevertheless, the narrow absorption of light extremely limited its photocatalytic performance under near-infrared (NIR) irradiation. Herein, the Cu₇.₂S₄ with outstanding NIR absorption was successfully introduced to g-C₃N₄ nanosheets through a simple in-situ growth procedure. As expected, the constructed Cu_7.2S₄/g-C₃N₄ (CSCN) photocatalysts exhibit superior H₂ production activity of 82 μmol g⁻¹ h⁻¹ under NIR light irradiation (λ > 800 nm), which outperforms currently reported g–C₃N₄–based NIR-driven H₂ production systems. Especially, the optimal sample CSCN-5 displays a robust activity of 66 μmol g⁻¹ h⁻¹ at λ = 850 nm monochromatic light irradiation. The excellent photocatalytic performance is linked to the extended optical absorption as well as the efficient separation efficiency of photoinduced carriers, which are evidenced by the UV-visible absorption spectroscopy and photoelectrochemical test. This work provides an effective approach for constructing a Cu_7.2S₄/g-C₃N₄ photocatalytic system for the transformation of NIR solar energy into hydrogen.     

Hybridization of g-C3N4 quantum dots with 1D branched TiO2 fiber for efficient visible light-driven photocatalytic hydrogen generation

The hybrid 1D branched TiO₂ loaded with g-C₃N₄ QDs was successfully fabricated that plays a significant role in photocatalysis. The 1D branched TiO₂ prepared by electrospinning followed by alkali-hydrothermal process, and g-C₃N₄ QDs were grafted over it by a chemical vapor deposition method. The composite display enhancement in photocatalytic hydrogen evolution is about 10.57 mmol. g⁻¹.h⁻¹ in comparison to the g-C₃N₄ sample that only produces 0.32 mmol. g⁻¹.h⁻¹ while the HBTiO₂ sample evolved a negligible amount of hydrogen under visible light. The composite sample shows quantum efficiency for HER at 420 nm light is 18.6% that is much higher than the other two samples. The specific surface area of the composite sample is 92.39 m²g^-1 that is about 13 times more than bulk g-C₃N_4. The bandgap of HBTiO₂/g-C₃N₄ QDs, g-C₃N₄, and HBTiO₂ samples calculated as 2.71 eV, 2.67eV, and 3.24eV, respectively. The TRPL spectra imply that the duration of the lifetime of composite becomes longer which effectually overwhelm the electron-hole recombination. The 1D branched TiO₂ fiber reduces the charge recombination by fast transfer of electron while g-C₃N₄ QDs facilitate the visible light absorption by improving the optical properties. The formation of the type II heterostructure system remarkably promotes the separation and transfer of electron holes and facilitates the photo-reduction reaction.     

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.     

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.     

Bimetallic PtNi alloy modified 2D g-C3N4 nanosheets as an efficient cocatalyst for enhancing photocatalytic hydrogen evolution

Platinum-based alloy materials as effective cocatalysts in improving the performance of photocatalytic H₂ production have raised great interest. Herein, a facile strategy of chemical reduction is established to synthesize bimetallic PtNi nanoparticles on 2D g-C₃N₄ nanosheets with excellent photocatalytic activity. The addition of PtNi nanoparticles can provide new H⁺ reduction sites and increase more active sites of the material. The synergistic effect between PtNi alloy nanoparticles and 2D g-C₃N₄ nanosheets can regulate electronic structure, narrow the band, accelerate charge transfer efficiency and inhabit the recombination of photo-induced electron (e⁻) and hole pairs (h⁺), contributing to the improvement of hydrogen evolution activity. The optimal hydrogen evolution rate of Pt_0.6Ni_0.4/CN shows higher hydrogen evolution rate (9528 μmol·g⁻¹·h⁻¹), which is 13.1 times than that of pure g-C₃N₄ nanosheets. Besides, a possible mechanism of photocatalytic hydrogen generation has been brought up according to a series of physical and chemical characterization. This work also provides a potential idea of developing cocatalysts integrating metal alloys with 2D g-C₃N₄ nanosheets for promoting photocatalytic hydrogen evolution.     

One-pot calcination preparation of graphene/g–C3N4–Co photocatalysts with enhanced visible light photocatalytic activity

Photocatalytic technology for hydrogen evolution from water splitting and pollutant degradation is one of the most sustainable methods. Here, the graphene/g–C₃N₄–Co composite materials have been prepared by one-pot calcination method. The results show that g-C₃N₄ grow on the surface of graphene and form a sandwich structure, meanwhile, the introduction of Co increases the active sites, which promotes the photocatalytic performance. The influences of graphene and Co content on photocatalytic activity were also studied by UV–visible spectrophotometry (DRS), photoluminescence spectroscopy (PL), photocurrent, degradation MB, and hydrogen production. The apparent reaction rate constant k of graphene/g–C₃N₄–Co (3%) is 0.946 h⁻¹, which is 4.90 and 2.18 times faster than g-C₃N₄ and graphene/g-C₃N₄, respectively. And the hydrogen production rate of graphene/g–C₃N₄–Co (3%) (892.3 μmol h⁻¹ g⁻¹) is 3.53 and 1.61 times higher than g-C₃N₄ and graphene/g-C₃N₄, respectively.