Enhanced photocatalytic H2 evolution over In2S3 via decoration with GO and Fe2P co-catalysts

In this study, GO and Fe₂P were used as co-catalysts to improve the separation efficiency of photogenerated electron-hole pairs in an In₂S₃ photocatalyst. The metallic character of Fe₂P provided a cheap substitute for traditional noble metal co-catalyst for H₂ production in aqueous media. The GO/Fe₂P/In₂S₃ composite demonstrated significantly enhanced photocatalytic activity compared to pure In₂S₃, delivering a H₂ production rate of 483.35 μmol h^?1 g^?1 and a quantum yield was 22.68% under visible light irradiation. The design of the photocatalyst was optimized using “Design Expert” software. The analysis showed that a GO loading of 1.18 wt%, a Fe loading of 5.36 wt%, and a calcination temperature of 180 °C were optimal.     

Enhancement of visible light photocatalytic hydrogen evolution by bio-mimetic C-doped graphitic carbon nitride

Bio-mimetic C-doped graphitic carbon nitride (g-C₃N₄) with mesoporous microtubular structure has been prepared by a simple chemical wet bio-template impregnation approach (direct impregnation and hydrothermal impregnation) using urea as a precursor and kapok fibre as bio-template and in-situ carbon dopant. Our finding indicated that the hydrothermal impregnation had induced more in-situ C-doping in g-C₃N₄ as compared to the direct impregnation approach. The introduction of in-situ C doping in the g-C₃N₄ and the mesoporous microtubular structure remarkably enhanced light-harvesting capability up to near infrared regions. The photocurrent measurement and electrochemical impedance spectroscopy (EIS) analysis suggested that the bio-template C-doped g-C₃N₄ exhibits a superior photoinduced electron-hole pairs separation efficiency due to C doping and mesoporous microtubular structure significantly promotes excellent conductivity and electron redistribution in the sample. C-doped graphitic carbon nitride sample prepared by the hydrothermal (HB/g-C₃N₄) approach exhibits excellent photocatalytic hydrogen production with an H₂ production rate of 216.8 μmol h⁻¹ g⁻¹ which was a 1.3 and 2.9 improvement over C-doped graphitic carbon nitride prepared by direct impregnation (DB/g-C₃N₄) and pristine g-C₃N_4, respectively. This study provides new insights into the development of low-cost and sustainable photocatalysts for photocatalytic hydrogen production.     

Preparation of direct Z-scheme Bi2WO6/TiO2 heterojunction by one-step solvothermal method and enhancement mechanism of photocatalytic H2 production

Direct Z-scheme Bi₂WO₆/TiO₂ heterojunction photocatalyst was prepared by one-step solvothermal method. The catalyst was characterized by XRD, TEM, XPS, UV–Vis DRS, photoluminescence spectroscopy and photoelectrochemical studies. The photocatalytic hydrogen production experiments show that Bi₂WO₆ did not generate H₂ and the H₂-production rate of TiO₂ is only 0.1 mmol⋅g⁻¹h⁻¹. The hydrogen production rate of the Bi₂WO₆/TiO₂ heterojunction photocatalyst reaches 12.9 mmol⋅g⁻¹h⁻¹, which is 129 times that of TiO₂. Compared with TiO₂, the enhanced H₂-production activity of the heterojunction catalyst can be attributed to the wider light absorption range and the efficient separation and migration of carriers at the close contact interface between Bi₂WO₆ and TiO₂. Based on the work functions of Bi₂WO₆, TiO₂ and their heterojunctions, combined with the results of electron paramagnetic resonance spectroscopy and Mott-Schottky measurements, the photocatalytic H₂ production mechanism of Z-scheme heterojunction Bi₂WO₆/TiO₂ was proposed. This work provides an easy and simple way to design a binary Z-scheme photocatalyst with efficient catalytic H₂-production activity without electron mediators.     

Interstitial carbon doped of setaria viridis-like Znln2S4 hollow tubes for efficient the performance of photocatalytic hydrogen production

In the photocatalytic water splitting hydrogen production system, the key to efficient use of solar energy is to choose a suitable photocatalyst. As an important ternary sulfide, ZnIn₂S₄ (ZIS) has attracted wide attention because of its narrow band gap (E_g = 2.3–2.8 eV) and wide light absorption range. However, further modification was still needed. Therefore, in this work, the unique C/ZIS hollow tubes with nano-flakes were prepared by a simple solvothermal method. To a large extent, this unique structure increased the utilization of light and active sites. Moreover, the dissolution of PAN during the solvothermal process caused the carbon element to be uniformly doped into the hollow tube framework. After a series of characterization results, C/ZIS-3.0 has the best hydrogen release rate (1241.94 μmol g⁻¹ h⁻¹) and good cyclability under visible light irradiation (λ ≥ 420 nm). And its unique morphology and possible catalytic mechanism were further discussed.     

Highly efficient white-LED-light-driven photocatalytic hydrogen production using highly crystalline ZnFe2O4/MoS2 nanocomposites

Designing efficient photocatalytic systems for hydrogen evolution is extremely important from the viewpoint of the energy crisis. Highly crystalline heterostructure catalysts have been established, considering their interface electric field effect and structural features, which can help improve their photocatalytic hydrogen-production activity. In this study, we fabricated a highly crystalline heterojunction consisting of ZnFe₂O₄ nanobricks anchored onto 2D molybdenum disulfide (MoS₂) nanosheets (i.e., ZnFe₂O₄/MoS₂) via a hydrothermal approach. The optimized ZnFe₂O₄/MoS₂ photocatalyst, with a ZnFe₂O₄ content of 7.5 wt%, exhibited a high hydrogen-production rate of 142.1 μmol h⁻¹ g⁻¹, which was 10.3 times greater than that for the pristine ZnFe₂O₄ under identical conditions. The photoelectrochemical results revealed that the ZnFe₂O₄/MoS₂ heterojunction considerably diminished the recombination of electrons and holes and promoted efficient charge transfer. Subsequently, the plausible Z-scheme mechanism for photocatalytic hydrogen production under white-LED light irradiation was discussed. Additionally, the influence of cocatalysts on the photocatalytic hydrogen evolution for the ZnFe₂O₄/MoS₂ heterostructure was investigated. This work has demonstrated a simplified coupling of one-dimensional or zero-dimensional structures with 2D nanosheets for improving the photocatalytic hydrogen production activity as well as confirmed that MoS₂ is a viable substitute for precious metal-free photocatalysis.     

Modification of twin crystal Cd0.5Zn0.5S photocatalyst with up-conversion nanoparticles for efficient photocatalytic H2-production

The photocatalytic H₂-production by solar light has been considered a promising technology to converse solar energy into carbon-free hydrogen. The development of efficient and stable catalysts is the most urgent problem in this technology. Up to now, twin crystal Cd_0.5Zn_0.5S solid solution has been regarded as the best efficient pristine sulphide catalysts for visible-light-driven hydrogen production. Its catalytic activity can be remarkably improved further by loading suitable co-catalyst, such as PdP_~0.33S_~1.67, noble metal Pt, and NiS_x. However, these twin crystal Cd_0.5Zn_0.5S-based nanocomposites can only response to partial (wavelength less than 520 nm) visible light irradiation. Large amount of visible light and near infrared light (NIR) in solar spectrum can not be absorbed by Cd_0.5Zn_0.5S and, therefore, do not contribute to the H₂ production. In this work, β-NaYF₄:Yb³⁺,Tm³⁺,Er³⁺ up-conversion nanoparticles (UPNs) are prepared by a hydrothermal process and the corresponding nanocomposite photocatalyst (twin crystal Cd_0.5Zn_0.5S/β-NaYF₄:Yb³⁺,Tm³⁺,Er³⁺ (T-CZS/UPNs)) based on this kind of up-conversion nanoparticles and twin crystal Cd_0.5Zn_0.5S nanocrystal is successfully prepared for the first time. The compositions, morphologies, and optical properties of the T-CZS/UPNs are investigated using XRD, SEM, HRTEM, UV–vis–NIR absorption spectra and photoluminescence (PL) spectrum. The photocatalytic hydrogen evolution experiments are performed under the irradiation of visible light, NIR light or simulated solar light, respectively. The H₂ production rate over T-CZS/UPNs-15 nanocomposite under the irradiation of simulated solar light in the presence of Na₂S/Na₂SO₃ as sacrificial agent is measured to be 159.3 mmol/h/g, which is 3.4 times higher than that of pristine T-CZS nanocrystals. In particular, this nanocomposite exhibits also significant photocatalytic hydrogen production rate (0.497 mmol/g/h) under NIR light irradiation (λ > 800 nm), reveals the contribution of NIR light to H₂ production via an photon-up-conversion process. This work gives an innovative vision in constructing efficient photocatalysts to make the efficient use of NIR solar light.     

Novel ReS2/g-C3N4 heterojunction photocatalyst formed by electrostatic self-assembly with increased H2 production

Binary heterostructures (named as CN@Re) composed of ReS₂ nanospheres and g-C₃N₄ nanosheets are constructed by electrostatic self-assembly method. The ReS₂ nanospheres were prepared by hydrothermal method and the g-C₃N₄ nanosheets were treated with surface charge modification. Hydrogen production efficiency of modified CN and CN@Re nanostructures was evaluated in a simulated solar environment. To our surprise, CN5@Re5% exhibits the highest H₂ production up to 1823 μmol g^?1h^?1 of CN5@Rey, which is 3.2 times as high as CN. The improvement of the photocatalytic hydrogen production efficiency of modified CN is attributed to its interaction with the hole sacrificing agent lactic acid, while the improvement of the photocatalytic activity of CN@Re nanostructure is attributed to the efficient electron transfer efficiency between CN and ReS₂ and the enhanced light absorption capacity brought by ReS₂. In addition, the photocatalytic stability of CN5@Re5% has been studied, which can maintain a stable rate of hydrogen production over four cycles. The apparent quantum efficiency is as high as 4.10% at 365 nm and 2.82% at 420 nm.     

A systematic study of photocatalytic H2 production from propionic acid solution over Pt/TiO2 photocatalyst

The propionic acid (HPr) is one of the main by‐products during fermentative H₂ process. To efficiently convert HPr to H₂ gas, photocatalytic H₂ production from HPr solution with the use of Pt/TiO₂ photocatalyst under ultraviolet light has been studied in this research. The Pt/TiO₂ photocatalyst has been prepared by the sol–gel method and further characterized by X‐ray diffraction, TEM and XPS. Effects of Pt loading amount, HPr concentration, initial pH value on photocatalytic H₂ production have been investigated in detail. From practical point of view, the H₂ evolution from HPr solution under UV irradiation for prolonged time has been studied as well. The Langmuir model can be able to describe the relationship between HPr concentration with the maximum rate of H₂ production. The apparent quantum efficiency and apparent energy conversion efficiency are found to 1.65 and 0.72%, respectively. To better understand the photocatalytic H₂ process over Pt/TiO₂, a possible mechanism for the degradation of HPr has been proposed as well. Based on our results, an efficient route for hydrogen production from renewable biomass can be established by coupling biological H₂ production process with photocatalytic H₂ production process. Copyright © 2010 John Wiley & Sons, Ltd.     

One-pot synthesis of non-noble metal WS2/g-C3N4 photocatalysts with enhanced photocatalytic hydrogen production

As an increasing number of photocatalysis are developed, non-noble metal photocatalysts that can be synthesized from earth-abundant and low-cost materials have received a great deal of attention. In this study, non-noble metal WS₂/g-C₃N₄ photocatalysts were prepared by a facile one-pot synthesis. Varying masses of tungsten disulfide (WS₂) were successfully loaded onto g-C₃N₄ and characterized by X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). These results indicated that the WS₂ was successfully synthesized and immobilized closely on the surface of g-C₃N₄ to form a sheet-like nanostructure. The H₂ generation results showed that the optimal photocatalyst was 0.3-WCN because it had the highest photocatalytic H₂ production of 154 μmol h⁻¹g⁻¹, which is 34 times higher than bare g-C₃N₄ and even higher than 0.3 wt% platinum-loaded g-C₃N₄. Additionally, the possible mechanism of the photocatalyst was studied by photoluminescence (PL), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoelectrochemical tests, which showed that the WS₂ played a key role in improving the efficiency of separation and migration of the photogenerated carriers in g-C₃N₄.     

In situ oxidation of ultrathin Ti3C2Tx MXene modified with crystalline g-C3N4 nanosheets for photocatalytic H2 evolution

With photoconductor being transferred and separated, interface contact plays a crucial role in developing composites photocatalyst. In the present work, 2D crystalline g-C₃N₄ (called as CCN) with 2D TiO₂ nanosheets (called as TO) obtained in situ oxidized single-layered Ti₃C₂T_x MXene is designed by an electrostatic self-assembly technology. This CCN/TO nanosheets system with a few TiO₂ nanosheets distributed to the surface is not only prolonging lifetime of photoelectron but also stimulating photogenerated carriers transferred in contact interface. The electron transfer mechanism of CCN/TO is further proved by Pt photo-deposition method. Therein, the optimal CCN-TO-0.6 exhibits excellent performance of H₂ generation compared with single photocatalyst of CCN. The result shows that the crystalline g-C₃N₄ photocatalysts introduced TiO₂ with interfacial effect favorably reduce H⁺ to H₂ and enhance photocatalytic activity.     

Construct organic/inorganic heterojunction photocatalyst of benzene-ring-grafted g-C3N4/CdSe for photocatalytic H2 evolution

Photocatalytic water splitting to produce hydrogen is a vital research direction for alleviating the energy crisis. Herein, benzene-ring grafted g-C₃N₄ nanotubes (Ph-g-C₃N₄) were prepared skillfully and coupled with CdSe nanoparticles which was realized efficiently hydrogen production. The addition of CdSe nanoparticles enhanced the stability of the catalytic system dispersion in water, and the absorbance of the composites catalyst CdSe/Ph-g-C₃N₄ (CPG) was enhanced. In addition, the CPG had been characterized to have low resistance and efficient photogenerated electron separation efficiency. The Ph-g-C₃N₄ nanotubes with a three-dimensional structure can provide an anchoring platform for CdSe nanoparticles and effectively prevent the agglomeration of CdSe. The constructed composites catalyst achieved the efficient transfer of photogenerated electrons as known from photoluminescence spectroscopy test analysis. When CdSe nanoparticles were anchored to Ph-g-C₃N₄, the electron transfer rate of the constructed composite was about twice that of the Ph-g-C₃N₄, which facilitates the hydrogen evolution reaction. The character and electron transfer pathways of the photocatalysts were investigated theoretically by performing density functional calculations. The finding provides a new idea for the doping of photocatalysts and the design of organic/inorganic heterojunction composites photocatalyst to achieve an efficient hydrogen production system.     

Manganese dioxides with different exposed crystal plane supported on g-C3N4 for photocatalytic H2 evolution from water splitting

A series of MnO₂/g-C₃N₄ composites with different exposed crystal plane were successfully prepared by different synthesized method. UV–Vis, PL, ESR and electrochemical results suggest that the visible-light absorbance, photoexcited electron-separation efficiency and oxygen defects are greatly dependent on the exposed crystal-faceted MnO₂ supported on g-C₃N₄. The experimental results display that the exposed crystal plane of MnO₂ have great influences on the photocatalytic hydrogen evolution performance, and the m-MnOCN composite with exposed (111) crystal plane exhibits superior photocatalytic performance for the release of H₂ under visible light irradiation, followed by the order of b-MnOCN [002]> p-MnOCN [110]. Moreover, Mechanism studies have shown that the possible mechanism of photocatalytic hydrogen evolution reaction is Z-scheme mechanism.     

Mesoporous composite NiCr2O4/Al-MCM-41: A novel photocatalyst for enhanced hydrogen production

A novel photocatalyst NiCr₂O₄/Al-MCM-41, using Al-MCM-41 zeolite as a support loaded with NiCr₂O₄ was successfully prepared by a facile sol-gel method and followed by calcination at 700 °C. The photocatalytic hydrogen production through water splitting was tested under visible-light irradiation for 3 h. According to the results of hydrogen evolution, the NiCr₂O₄/Al-MCM-41 hybrid composite displayed higher hydrogen production compared with individual NiCr₂O₄ or Al-MCM-41. This revealed that NiCr₂O₄ incorporated into the Al-MCM-41 zeolite effectively facilitated the photocatalytic activity. The highest hydrogen generation was obtained from 50%NiCr₂O₄/Al-MCM-41, whose hydrogen generation (8.92 mmol/g) was enhanced up to 2.4 times as much as individual NiCr₂O₄ (3.75 mmol/g). The main reason for the enhanced photocatalytic activity of the hybrid photocatalysts was ascribed to the excellent synergistic effect of NiCr₂O₄ and Al-MCM-41 zeolite. The mesoporous Al-MCM-41 catalyst support increased the dispersion of NiCr₂O₄ with more active sites. In addition, Al-MCM-41 zeolite promoted the charge transfer and inhibited the rapid recombination of photo-generated electrons-holes as electron acceptor and donor.     

MoS2/Ti3C2 heterostructure for efficient visible-light photocatalytic hydrogen generation

The MoS₂/Ti₃C₂ catalyst with a unique sphere/sheet structure were prepared by hydrothermal method. The MoS₂/Ti₃C₂ heterostructure loading 30% Ti₃C₂ has a maximum hydrogen production rate of 6144.7  μmol g⁻¹ h⁻¹, which are 2.3 times higher than those of the pure MoS₂. The heterostructure maintains a high catalytic activity within 4 cycles. The heterostructure not only effectively reduce the recombination of photogenerated electrons and holes, but also provide more activation sites, which promotes the photocatalytic hydrogen evolution reaction (HER). These works can provide reference for the development of efficient catalysts in photocatalytic hydrogen evolution.     

Realizing efficient exciton dissociation in an all-organic heterojunction photocatalyst for highly improved photocatalytic H2 evolution

Although graphitic carbon nitride is a promising photocatalyst in the field of energy conversion and environmental purification, the intrinsic properties like excitonic effects and sluggish charge transfer restrict further photocatalytic applications. To circumvent these limitations, the novel all-organic heterojunction photocatalysts were constructed by anchoring organic carbon dots (O-dots) on porous graphitic carbon nitride nanosheets (O-dots/CNS). Results demonstrated that excitons can be e?ectively dissociated into electrons and holes at the interface of O-dots/CNS heterojunction, followed by holes injected to O-dots and electrons accumulated in CNS to realize efficient charge separation. Consequently, the O-dots/CNS with the optimized hydrogen (H₂) evolution performance could be reached 1564.5 μmol h^?1g^?1 under the visible light irradiation. This work not only presents new ideas for rational design photocatalytic reaction system from exciton and charge carrier, but also broaden the applications of this new kind of organic dots in the field of energy conversion.     

The 2D RGO-NiS2 dual co-catalyst synergistic modified g-C3N4 aerogel towards enhanced photocatalytic hydrogen production

The two-dimension RGO (reduced graphene oxide)-NiS₂ dual co-catalyst synergistic modified g-C₃N₄ nanosheets aerogel is synthesized via the continuous thermal oxidation etching-hydrothermal method-freeze drying process. The results of scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) imply that the RGO-NiS₂ dual co-catalyst is introduced into the aerogel system successfully. The photocatalytic activity of the RGO-NiS₂ synergistic modified g-C₃N₄ aerogel remarkably exhibits an enhancement of 67 times than that of simplicial g-C₃N₄. Further, the photocatalytic process and the mechanism of the photocatalytic hydrogen production enhancement are studied, which is ascribed to RGO-NiS₂ dual co-catalyst synergistic modification, including the Pt-like behavior of the NiS₂ and the high conductivity and large specific surface area of the RGO.     

Facile preparation and photocatalytic hydrogen production of WS2 and its composites

Two-dimensional transition metal dichalcogenides, MoS₂ and WS₂ have been widely considered as promising materials for photocatalytic hydrogen production. However, compared with the widely investigated MoS₂, researches on WS₂ are much less. Besides, for the synthesis of WS₂, methods suitable for large-scale preparation are still rare. Then in this paper, a facile method for the preparation of WS₂ was developed based on the liquid-phase precipitation-calcination method reported previously. In specific, thiourea was introduced in the calcination process to realize the in-situ conversion of impurity WO₃ to WS₂. As a result, WS₂ was successfully prepared. More interestingly, a series of photocatalysts with different compositions and performances were easily obtained only through changing the thiourea amount. When no thiourea was used, a WS₂/WO₃ heterostructure was constructed, while when excessive thiourea was introduced, an efficient WS₂/g-C₃N₄ heterostructure (g-C₃N₄ = graphitic carbon nitride) was fabricated. Moreover, their hydrogen production performances were investigated with Erythrosine B (ErB) and triethanolamine (TEOA) as photosensitizer and sacrificial agent, respectively. The results showed that the as-obtained WS₂ has a comparable H₂-evolving activity (1686.3 μmol h^?1 g^?1) to the WS₂/WO₃ (1637.8 μmol h^?1 g^?1), and the WS₂/g-C₃N₄ owns the highest performance (2428.7 μmol h^?1 g^?1). This work provides a facile and feasible route for the preparation of efficient WS₂-based photocatalysts.     

Facile synthesis of MoS2 QDs/TiO2 nanosheets via a self-assembly strategy for enhanced photocatalytic hydrogen production

The MoS₂ quantum dots (QDs) were interspersed on anatase TiO₂ nanosheets with exposed (001) facets by a facile self-assembly strategy. As expected, the MoS₂ QDs/TiO₂ nanosheets display an excellent photocatalytic performance for hydrogen production, and its hydrogen evolution rate is 139 μmol/h/g. More importantly, the hydrogen evolution rate of MoS₂ QDs/TiO₂ nanosheets is almost 4-fold in comparison to that of nude TiO₂ nanosheets. Based on the detailed characterizations, it can be obtained that the improved photocatalytic activity for hydrogen production can be ascribed to the particular characteristics of MoS₂ QDs, which can intensify the photo-absorption efficiency of TiO₂ nanosheets and enhance the separation and transfer efficiency of photo-excited charge carriers. It is anticipated that this work provides a novel paradigm to fabricate the highly-efficient photocatalysts for hydrogen evolution.     

Interfacial optimization of CeO2 nanoparticles loaded two-dimensional graphite carbon nitride toward synergistic enhancement of visible-light-driven photoelectric and photocatalytic hydrogen evolution

A novel series of CeO₂ nanoparticles (CeNP) loaded two-dimensional (2D) graphite carbon nitride nanosheet (CeNP/g-C₃N₄) composites which possess heterojunction are prepared with different proportions of CeNP by a reliable and straightforward method. The samples were employed to degrade the rhodamine B (RhB) and produce hydrogen. The microstructure, morphology, composition and surface chemical states of the samples are analyzed, and the ability of the photoelectric response is characterized. The characterization ensures uniform loading of CeNP over the g-C₃N₄ surface and a co-existence of Ce³⁺/Ce⁴⁺ in the CeNP/g-C₃N₄ composite. The FT-IR spectra have revealed the changes in the local dipole moment of amino groups, vibration mode of the constituent functional group and electronegativity, indicating the electric interaction between CeNP and g-C₃N₄. The photocatalytic hydrogen evolution efficiency of the CeNP/g-C₃N₄ increased initially and then decreased with the increasing of loaded CeNP. The CeNP/g–C₃N₄–C with 20 mg of CeNP was found to be the optimum proportion, which exhibited outstanding separation efficiency of the photo-generated carriers. The electron spin-resonance (ESR) spectra exhibit that the production of superoxide free radicals (?O₂^?) was much higher than that of hydroxyl free radicals (?OH) indicating that ?O₂^? species play a predominant role in the photocatalytic action. The mechanism for enhanced photocatalytic activity of the CeNP/g-C₃N₄ is attributed to the interfacial optimization, which improved the photo-generated carrier separation.     

A green one-pot approach for mesoporous g-C3N4 nanosheets with in situ sodium doping for enhanced photocatalytic hydrogen evolution

Synchronous nano-structuring and element-doping of g-C₃N₄ were realized via a green one-pot approach to improve its photocatalytic activity. Na-doped mesoporous g-C₃N₄ nanosheets of ∼5 nm in thickness were facilely synthesized by calcining a mixture of dicyandiamide and sodium chloride. NaCl not only serves as a confining-reactor to confine the growth of g-C₃N₄ into mesoporous nanosheets, but also acts as a sodium source for Na-doping. The nanosheets own greater specific surface area, stronger optical absorption and lower recombination of photo-induced electron-hole pairs than bulk g-C₃N₄, and exhibit an excellent visible-light photocatalytic hydrogen evolution efficiency which is about 13 times that of bulk g-C₃N₄. Moreover, the thermostable and hydrosoluble NaCl is simply removed and recycled by water and then directly reused in a new synthesis, making the process to be environmental-friendly and sustainable.