Facile approach to synthesize g-PAN/g-C3N4 composites with enhanced photocatalytic H2 evolution activity

Enhanced photocatalytic activity of Ag/Ag2Ta4O11/g-C3N4 under wide-spectrum-light irradiation: H2 evolution from water reduction without co-catalyst

Designing a superior and stable catalyst toward H₂ evolution under solar light to solve the energy crisis has attracted wide concern. Herein, we have constructed a novel heterojunction photocatalyst Ag/Ag₂Ta₄O₁₁/g-C₃N₄ by in situ assembly, which can efficiently split water to generate H₂ by utilizing wide-spectrum-light irradiation. Optimal H₂ production reaches highly to 253.03 μmol g^-1 h^-1 under the simulated solar light. Moreover, the catalyst presented well stability by the retained 98% photocatalytic activity and invariable textural structure after five recycling tests. The mechanism of H₂ generation over the prepared material was carefully investigated through scanning electron microscope (SEM), transmission electron microscopy (TEM), UV-Vis absorption spectra (UV-Vis), photoluminescence analysis (PL), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectra (EPR), and several electrochemical measurements. It is proposed that the carriers are efficiently separated through Ag-mediated Z-scheme route in space, retaining their strong redox ability. Ag particles produced by in situ reduction from the component Ag₂Ta₄O₁₁ could devote to the quick electron migration as the bridge center, effective solar light harvesting due to their surface plasmon resonance, and excellent stability by inhibiting their agglomeration and elution. This research offers a new idea for constructing full solid Z-scheme photocatalysts under wide-spectrum-light irradiation.

Evaluation of dual layered photoanode for enhancement of visible-light-driven applications

Ternary structures consisting of hollow g-C₃N₄ nanofibers/MoS₂/sulfur, nitrogen-doped graphene and bulk g-C₃N₄ (TCN) were designed as a dual layered film and fabricated using a spin-coating method. The first ternary structures were spin-coated on fluorine-doped tin oxide (FTO) glass, followed by spin-coating of g-C₃N₄ film to form dual layers. We characterized the microstructural morphologies, chemical composition/bonding and optical properties of the dual layered film and observed significantly reduced recombination rates of photo-induced electron–hole pairs due to effective separation of the charge carriers. We tested methylene blue (MB) photodegradation and observed remarkable MB degradation by the dual layered film over 5 hours, with a kinetic rate constant of 1.24 × 10⁻³ min⁻¹, which is about four times faster than that of bare TCN film. Furthermore, we estimated the H₂ evolution of the dual layered film to be 44.9 μmol over 5 hours, and carried out stable recycling over 45 hours under visible irradiation. Due to the lower electrochemical impedance spectroscopy (EIS) resistance value of the dual layered film (∼50 ohm cm²) compared to the TCN film, the ternary structures and bulk g-C₃N₄ film were well-connected as a heterojunction, reducing the resistance at the interface between the film and the electrolyte. These results indicate that the effective separation of the photo-induced electron–hole pairs using the dual layered film dramatically improved its photo-response ability under visible light irradiation.

Ternary structures consisting of hollow g-C₃N₄ nanofibers/MoS₂/sulfur, nitrogen-doped graphene and bulk g-C₃N₄ (TCN) were designed as a dual layered film and fabricated using a spin-coating method.

Polymeric Donor-Acceptor Heterostructures for Enhanced Photocatalytic H2 Evolution without Using Pt Cocatalysts

Polymeric carbon nitride (CN) is a promising material for photocatalytic water splitting. However, CN in its pristine form tends to show moderate activity due to fast recombination of the charge carriers. The design of efficient photocatalytic system is therefore highly desired, but it still remains a great challenge in chemistry. In this work, a pyrene-based polymer able to serve as an electron donor to accelerate the interface charge carrier transfer of CN is presented. The construction of donor-acceptor (D-A) heterojunction was confirmed to significantly restrain the charge recombination and, thus, improve the proton reduction process. This study provides a promising strategy to achieve solar H₂ production in an efficient and low-cost manner.

Fabrication of a Perylene Tetracarboxylic Diimide-Graphitic Carbon Nitride Heterojunction Photocatalyst for Efficient Degradation of Aqueous Organic Pollutants

Metal-free g-C₃N₄ is a promising candidate for the next-generation visible light-responsive photocatalyst; however, high recombination probability of the photogenerated charge carriers on g-C₃N₄ limits its photocatalytic activity. To further increase the intrinsic photocatalytic activity of g-C₃N₄, here, perylene tetracarboxylic diimide-g-C₃N₄ (PDI/GCN) heterojunctions are prepared by one-step imidization reaction between perylene tetracarboxylic dianhydride (PTCDA) and g-C₃N₄ in aqueous solution. By the combination of various testing results, it is confirmed that the surface hybridization of PTCDA and g-C₃N₄ in the PDI/GCN heterojunctions via O═C-N-C═O covalent bonds occurs at lower PTCDA-to-g-C₃N₄ weight percentage. By selecting p-nitrophenol (PNP) and levofloxacin (LEV) as the target organic pollutants, the visible-light photocatalytic performance of the PDI/GCN heterojunctions is studied. It shows that the PDI/GCN heterojunction prepared at a PTCDA-to-g-C₃N₄ weight percentage of 1% exhibits remarkably higher visible-light photocatalytic degradation and mineralization ability toward aqueous target pollutants as compared with g-C₃N₄ and Degussa P25 TiO₂. On the basis of the experimental results including photoelectrochemistry, indirect chemical probe, and electron spin resonance spectroscopy, it is verified that the surface hybridization in the heterojunctions is responsible for this enhanced photocatalytic activity via accelerating the migration and separation of the photogenerated charge carriers, causing to produce more active species like ^•O₂^-, h_VB⁺, and ^•OH for deep oxidation of PNP or LEV to CO₂ and inorganic anions.

Photocatalytic activity of ZrO2 composites with graphitic carbon nitride for hydrogen production under visible light

The synthesized ZrO₂/g-C₃N₄ composites exhibit superior performance in water splitting for hydrogen production due to the effective electron–hole separation at the composite interface.

Graphitic carbon nitride/CoTPP type-II heterostructures with significantly enhanced photocatalytic hydrogen evolution

CoTPP inhibits the recombination of electron-hole pairs through extracting holes from g-C₃N₄ thus dramatically enhancing photocatalytic hydrogen production under visible light irradiation.

Synergistic effect between Cu–Cr bimetallic oxides supported on g-C3N4 for the selective oxidation of toluene to benzaldehyde

Supported Cu–Cr/g-C₃N₄ catalysts were prepared via an in situ heating treatment method for the selective oxidation of toluene to benzaldehyde.

Metal–organic framework assisted and in situ synthesis of hollow CdS nanostructures with highly efficient photocatalytic hydrogen evolution

Hollow CdS nanoboxes with a specific surface area of 153 m² g⁻¹ are synthesized through in situ sulfurizing Cd-MOF-47 with thiourea, which exhibit a greatly improved photocatalytic activity in water splitting to hydrogen (21 654 μmol g⁻¹ h⁻¹).

Nanostructured g-C3N4/AgI composites assembled by AgI nanoparticles-decorated g-C3N4 nanosheets for effective and mild photooxidation reaction

AgI nanoparticles-decorated g-C₃N₄ nanosheets with enhanced visible-light photocatalytic activity for the mild photooxidation of 1,4-DHP into its pyridine derivatives.

Mechanistic insights into N-hydroxyphthalimide modified graphitic carbon nitride boosted photocatalytic hydrogen production

N-Hydroxyphthalimide (NHPI) retards the recombination of electron–hole pairs through extracting holes from g-C₃N₄, dramatically improving photocatalytic hydrogen production.

Heterostructured d-Ti3 C2 /TiO2/ g-C3 N4 Nanocomposites with Enhanced Visible-Light Photocatalytic Hydrogen Production Activity

The construction of a 2D-2D heterostructured composite is an efficient method to improve the photocatalytic hydrogen generation capability under visible light. In this work, simple heat treatment of a mixture of g-C₃ N₄ and delaminated Ti₃ C₂ was used to prepare a series of d-Ti₃ C₂ /TiO₂ /g-C₃ N₄ nanocomposites. The d-Ti₃ C₂ not only acted as the support layer and resource to glue the anatase TiO₂ particles and g-C₃ N₄ layers together but also served as the fast electron transfer channel to improve the photogenerated charge carriers' separation efficiency. By tuning the g-C₃ N₄ /d-Ti₃ C₂ mass ratio, heating temperature and soaking time, the d-Ti₃ C₂ /TiO₂ /g-C₃ N₄ nanocomposite 4-1-350-1 achieved an excellent H₂ evolution rate of 1.62 mmol h^-1  g^-1 driven by a 300 W Xe lamp with a 420 nm cutoff filter. The heterostructured composite photocatalyst was stable even after 3 cycles, representing excellent potential for the practical application in solar energy conversion.

Effect of electron-hole separation in MoO3@Ni2P hybrid nanocomposite as highly efficient metal-free photocatalyst for H2 production

Effectiveness and stability of photocatalyst are of importance not only for improving H₂ evolution, but also for the realization of enhanced semiconductors property in practical applications. In this study, a novel MoO₃@Ni₂P hybrid nanostructure is successfully prepared by a two step strategy of one-pot pyrolysis followed by calcination method. The reasonable design and controllable preparation of MoO₃@Ni₂P make it exhibit much high photocatalytic activities for H₂ evolution with about 39.8 and 15.8 times compared to the pure MoO₃ and Ni₂P. This prominently increased effect is certified by results of various characterization such as SEM, TEM, XRD, XPS, BET, FT-IR, UV-vis DRS, transient photocurrent, steady-state fluorescence, transient-state fluorescence and Mott-Schottky studies etc. The investigation indicates that the assembly of Ni₂P nanoparticles and MoO₃ can provide more active sites and accelerate the transfer of electrons. Moreover, the possible mechanism of photocatalytic H₂ generation is proposed.

Carbon nitrides and metal nanoparticles: from controlled synthesis to design principles for improved photocatalysis

The use of sunlight to drive chemical reactions via photocatalysis is of paramount importance towards a sustainable future. Among several photocatalysts, earth-abundant polymeric carbon nitride (PCN, often wrongly named g-C3N4) has emerged as an attractive candidate due to its ability to absorb light efficiently in the visible and near-infrared ranges, chemical stability, non-toxicity, straightforward synthesis, and versatility as a platform for constructing hybrid materials. Especially, hybrids with metal nanoparticles offer the unique possibility of combining the catalytic, electronic, and optical properties of metal nanoparticles with PCN. Here, we provide a comprehensive overview of PCN materials and their hybrids, emphasizing heterostructures with metal nanoparticles. We focus on recent advances encompassing synthetic strategies, design principles, photocatalytic applications, and charge-transfer mechanisms. We also discuss how the localized surface plasmon resonance (LSPR) effect of some noble metals NPs (e.g. Au, Ag, and Cu), bimetallic compositions, and even non-noble metals NPs (e.g., Bi) synergistically contribute with PCN in light-driven transformations. Finally, we provide a perspective on the field, in which the understanding of the enhancement mechanisms combined with truly controlled synthesis can act as a powerful tool to the establishment of the design principles needed to take the field of photocatalysis with PCN to a new level, where the desired properties and performances can be planned in advance, and the target material synthesized accordingly.

Three dimensional hierarchical heterostructures of g-C3N4 nanosheets/TiO2 nanofibers: Controllable growth via gas-solid reaction and enhanced photocatalytic activity under visible light

Graphitic C₃N₄ nanosheets were uniformly grown on electrospun TiO₂ nanofibers with three-dimensional nanofibrous networks via a facial gas-solid reaction. The mass loading of g-C₃N₄ nanosheets could be easily controlled by adjusting the mass ratios of gaseous precursors (urea) to TiO₂ NFs. The three-dimensional hierarchical heterostructures of g-C₃N₄ nanosheets/TiO₂ nanofibers could be obtained with excellent distribution and high specific surface area of 121.5m²g^-1, when the mass loading of g-C₃N₄ was 59.8wt.%. Under visible light irradiation, the degradation rate constant (rhodamine B) and the H₂ evolution rate of the heterostructures were about 4.6 and 1.6 times of pure g-C₃N₄, while 23 and 167.8 times of TiO₂ nanofibers, respectively. Their enhanced performance could be attributed to the effective charge separation and electron transfer process. Our work provides an attractive strategy to construct various three-dimensional hierarchical heterostructures of g-C₃N₄ nanosheets for environmental and energy applications.

Bioinspired Mesoporous Chiral Nematic Graphitic Carbon Nitride Photocatalysts modulated by Polarized Light

Endowing materials with chirality and exploring the responses of the material under circularly polarized light (CPL) can enable further insight into the physical and chemical properties of the semiconductors to be gained, thus expanding on optoelectronic applications. Herein a bioinspired mesoporous chiral nematic graphitic carbon nitride (g-C₃ N₄ ) for efficient hydrogen evolution with polarized light modulation based on chiral nematic cellulose nanocrystal films prepared through silica templating is described. The mesoporous nematic chiral g-C₃ N₄ exhibits an ultrahigh hydrogen evolution rate of 219.9 μmol h^-1 (for 20 mg catalyst), corresponding to a high enhancement factor of 55 when compared to the bulk g-C₃ N₄ under λ>420 nm irradiation. Furthermore, the chiral g-C₃ N₄ material exhibits unique photocatalytic activity modulated by CPL within the absorption region. This CPL-assisted photocatalytic regulation strategy holds great promise for a wide range of applications including optical devices, asymmetric photocatalysis, and chiral recognition/separation.

Noble-metal-free Ni3N/g-C3N4 photocatalysts with enhanced hydrogen production under visible light irradiation

Noble-metal-free Ni₃N/g-C₃N₄ heterojunctions that show high photocatalytic hydrogen evolution activity comparable to platinized g-C₃N₄ were successfully synthesized.

Large enhanced photocatalytic activity of g-C3N4 by fabrication of a nanocomposite with introducing upconversion nanocrystal and Ag nanoparticles

A novel heterostructured nanocomposite UCNPs@SiO₂@Ag/g-C₃N₄ was developed for the first time to substantially boost the solar-light driven photocatalytic activity of g-C₃N₄. Its photocatalytic properties and photocatalytic mechanism were investigated. The as-synthesized photocatalyst with excellent improvement in the solar absorption and separation efficiency of photoinduced electron–hole pairs exhibited optimum solar-induced photocatalytic activity in dye degradation and hydrogen production. The experimental results showed that the rates of degradation of Rhodamine B (RhB) and hydrogen evolution were about 10 and 12 times higher than that of pristine g-C₃N₄, respectively. The excellent photocatalytic activity was attributed to the synergetic effect of upconversion nanoparticles (UCNPs) and Ag nanoparticles (NPs) on the modification of the photocatalytic properties of g-C₃N₄, resulting in a broad light response range for g-C₃N₄ as well as the fast separation and slow recombination of photoinduced electron–hole pairs. This study provides new insight into the fabrication of g-C₃N₄-based nanocomposite photocatalysts with high catalytic efficiency through the artful assembly of UCNPs, Ag NPs and g-C₃N₄ into a hetero-composite nanostructure. The prominent improvement in photocatalytic activity enables the potential application of g-C₃N₄ in the photocatalytic degradation of organic pollutants and hydrogen production utilizing solar energy.

A novel heterostructured nanocomposite UCNPs@SiO₂@Ag/g-C₃N₄ was developed for the first time to substantially boost the solar-light driven photocatalytic activity of g-C₃N₄.

An amorphous/crystalline g-C3N4 homojunction for visible light photocatalysis reactions with superior activity

An amorphous/crystalline g-C₃N₄ homojunction was prepared for the first time at high temperature, in which the ratio of crystalline g-C₃N₄ in the homojunction was optimized.

Facile construction of leaf-like WO3 nanoflakes decorated on g-C3N4 towards efficient oxidation of alcohols under mild conditions

Selective oxidation of aryl and alkyl alcohols with H₂O₂ in aqueous media catalyzed by a well-defined WO₃/g-C₃N₄ composite.

Dye-sensitized photocatalyst for effective water splitting catalyst

Renewable hydrogen production is a sustainable method for the development of next-generation energy technologies. Utilising solar energy and photocatalysts to split water is an ideal method to produce hydrogen. In this review, the fundamental principles and recent progress of hydrogen production by artificial photosynthesis are reviewed, focusing on hydrogen production from photocatalytic water splitting using organic-inorganic composite-based photocatalysts.

Molecular Design of Polymer Heterojunctions for Efficient Solar-Hydrogen Conversion

Semiconducting photocatalytic solar-hydrogen conversion (SHC) from water is a great challenge for renewable fuel production. Organic semiconductors hold great promise for SHC in an economical and environmentally benign manner. However, organic semiconductors available for SHC are scarce and less efficient than most inorganic ones, largely due to their intrinsic Frenkel excitons with high binding energy. In this study the authors report polymer heterojunction (PHJ) photocatalysts consisting of polyfluorene family polymers and graphitic carbon nitride (g-C₃ N₄ ) for efficient SHC. A molecular design strategy is executed to further promote the exciton dissociation or light harvesting ability of these PHJs via alternative approaches. It is revealed that copolymerizing electron-donating carbazole unit into the poly(9,9-dioctylfluorene) backbone promotes exciton dissociation within the poly(N-decanyl-2,7-carbazole-alt-9,9-dioctylfluorene) (PCzF)/g-C₃ N₄ PHJ, achieving an enhanced apparent quantum yield (AQY) of 27% at 440 nm over PCzF/g-C₃ N₄ . Alternatively, copolymerizing electron-accepting benzothiadiazole unit extended the visible light response of the obtained poly(9,9-dioctylfluorene-alt-benzothiadiazole)/g-C₃ N₄ PHJ, leading to an AQY of 13% at 500 nm. The present study highlights that constructing PHJs and adapting a rational molecular design of PHJs are effective strategies to exploit more of the potential of organic semiconductors for efficient solar energy conversion.

Facile synthesis of mesoporous detonation nanodiamond-modified layers of graphitic carbon nitride as photocatalysts for the hydrogen evolution reaction

The hydrogen evolution reaction (HER) may contribute substantially to energy resources in the future through solar energy conversion.

Facile synthesis of mesoporous carbon nitride and titanium dioxide nanocomposites with enhanced visible light photocatalytic activity

C₃N₄–TiO₂ nanocomposites with a large surface area and strong visible light response were fabricated via a rapid solution combustion method.

Highly efficient visible light induced photocatalytic activity of a novel in situ synthesized conjugated microporous poly(benzothiadiazole)–C3N4 composite

Highly efficient visible light-driven heterojunction BBT–C₃N₄ exhibits superior redox ability for sulfathiazole and Cr(vi) removal.

Graphitic carbon nitride nanosheets obtained by liquid stripping as efficient photocatalysts under visible light

Well-scattered g-C₃N₄ nanosheets obtained using a liquid stripping possess much higher photocatalytic performance than bulk g-C₃N₄.