Two-dimensional g-C3N4 Research Articles

Remarkable photocatalytic activity enhancement of CO2 conversion over 2D/2D g-C3N4/BiVO4 Z-scheme heterojunction promoted by efficient interfacial charge transfer

In this study, a series of dual two-dimensional (2D/2D) Z-scheme g-C3N4/BiVO4 ultrathin nanosheets were successfully fabricated by coupling 2D g-C3N4 and 2D BiVO4 ultrathin nanosheets via a thermal-polymerization and subsequent hydrothermal method. The mass ratio between g-C3N4 and BiVO4 was optimized to improve the visible-light photocatalytic performance of CO2 reduction. Significantly, g-C3N4/BiVO4 (5:5) composite exhibited the optimal CO2 conversion efficiency towards CH4 (4.57 μmol g−1 h−1) and CO (5.19 μmol g−1 h−1), which were 4.8 and 4.4 folds higher than that of g-C3N4. The suitable band structures of single components induced the formed direct Z-scheme heterojunction, which efficiently suppressed the photoinduced carrier recombination and remained the strong redox capability. Moreover, the tight face-to-face interfacial contact between 2D g-C3N4 and 2D BiVO4 increased the transmission channels and accessible area for charges, and thereby facilitated charge transfer and provided abundant active sites for the photocatalytic reaction. Based on the trapping experiments, the photocatalytic mechanisms of g-C3N4/BiVO4 were reasonably proposed and validated by the photoluminescence spectra associated with time-resolved fluorescence decay. Furthermore, the repetitive photocatalytic experiments demonstrated the advantage of recyclability, which endowed 2D/2D Z-scheme g-C3N4/BiVO4 heterojunctions a promising application prospect.

Construction of g-C3N4/WO3/MoS2 ternary nanocomposite with enhanced charge separation and collection for efficient wastewater treatment under visible light

Graphitic carbon nitride (g-C3N4) has enormous potentials for photocatalysis, yet it only possesses moderate activity because of excitonic effects and sluggish charge transfer. Here, we develop a novel two-dimensional g-C3N4/WO3/MoS2 (CWM) ternary nanocomposite through a facile co-calcination and a hydrothermal process to reach a highly-efficient photocatalyst for organic pollutant elimination under visible light. The WO3 and MoS2 nanoparticles were dispersed on the ultra-thin g-C3N4 nanosheets, in which the electronegative g-C3N4 facilitates formation of oxygen vacancies in WO3. Compared to pure g-C3N4, WO3, and binary composites, CWM exhibited higher photocatalytic activities for various organic pollutants removal under visible light irradiation. For instance, the CWM showed a removal ratio of ∼99% for RhB after only 10 min irradiation of visible light (λ > 420 nm) and nearly 100% for ciprofloxacin after 2 h of operation. The results showed that OH radicals are the main active species for organic degradation, which suggests a direct Z-scheme heterojunction in CWM that improved spatial separation of charge carries. Furthermore, the collection of electrons is significantly enhanced by MoS2 for oxygen reduction reaction, and the increased oxygen vacancies of WO3 further enhanced the separation of electron-hole pairs; therefore, it led to an effective suppression of charge carriers recombination. The above synergistic effects of ternary photocatalyst result in higher photocatalytic oxidation performance for wastewater treatment compared with pure WO3, g-C3N4 and their binary composites.

Remarkable improvement in hydrogen storage capacities of two-dimensional carbon nitride (g-C3N4) nanosheets under selected transition metal doping

We have performed DFT simulations to quest for an optimal material for onboard hydrogen (H2) storage applications. Using first-principles calculations, we established that the selected transition metals (M: Sc, Ti, Ni, V) decorated two-dimensional (2D) g-C3N4 sheets as optimal materials with reversible and significantly high H2 gravimetric densities. By effectively avoiding metal-metal (M-M) clustering effect in case of mono doping, up to four molecules of H2 per dopant could be adsorbed with an average binding energy of around 0.30–0.6 eV/H2, which is ideal for practical applications. Decorating the g-C3N4 sheet with (M-M) dimers, the systems are found to be even more efficient for H2 binding than single dopant decoration. The stability of these M decorated g-C3N4 sheets have been confirmed with ab-initio molecular dynamics simulations. We have further calculated the H2 desorption temperatures of metal decorated g-C3N4 sheets, which confirms the practical application of these metal decorated sheets at ambient working conditions.

High-efficient precious-metal-free g-C3N4-Fe3O4/β-FeOOH photocatalyst based on double-heterojunction for visible-light-driven hydrogen evolution

The two-dimensional (2D) g-C3N4 has a wide application prospect in photocatalysis field due to its larger surface reactions, wider absorption of light and faster charge separation. However, the lack of active site of reduction leads to its poor hydrogen evolution reaction (HER) activity. In this work, the intermediate β-FeOOH was synthesized as a high-efficiency precious metal free co-catalyst in hydrogen production. Then, the g-C3N4-Fe3O4/β-FeOOH (CNFF-x,y, x = 1, 2 and 3, y denotes the reaction time (h)) photocatalyst based on p-n and Z-scheme heterojunction was constructed via a subsequent solvothermal process. The chemical composition, microtopography, crystallography, photochemical and electrochemical properties of the CNFF-x,y were analyzed by XRD, FI-IR, TEM, XPS and so on. The visible-light-driven (VLD) catalytic performance of CNFF-x,y heterojunction was evaluated by the hydrogen evolution reaction (HER). Results showed that CNFF-2,10 photocatalyst based on p-n (g-C3N4-Fe3O4) and Z-scheme (Fe3O4/β-FeOOH) heterojunction presented the highest VLD catalytic HER activity (33.25 μmol g−1 h−1) at the absence of Pt co-catalyst after illumination for 6 h. It indicated that the effective introduction of Fe3O4/β-FeOOH nanoparticles (NPs) into g-C3N4 to construct double-heterojunction (g-C3N4-Fe3O4/β-FeOOH) could greatly broaden the light response property and inhibit the recombination of photo-induced carriers, exhibiting enhanced HER activity. Meanwhile, this double-heterojunction photocatalyst presented robust photostability and reproducibility even been used several times. The findings of an intermediate β-FeOOH were put forward in this study will provide some new ideas for the research of HER.

Sharply increasing the visible photoreactivity of g-C3N4 by breaking the intralayered hydrogen bonds

Photocatalytic H2 production has attracted much attention using visible-light-responsive graphitic carbon nitride (g-C3N4) as photocatalyst. However, two-dimensional g-C3N4 has suffered from poor photocatalytic activity due to numerous intralayered hydrogen bonds and limited visible-light-responsive range. To solve this problem, in this paper, breaking the hydrogen bonds of g-C3N4 by S-doping is reported through poly-condensation of dicyandiamide (DCDA)-thioacetamide (TAA) mixture. The effects of TAA amount on the structure, property and photocatalytic performance of S-doped g-C3N4 are systematically studied. Among all the prepared photocatalysts, sample T0.6, exhibits the highest photoreactivity with a hydrogen production rate of 525.5 µmol g−1 h−1 under the visible light irradiation (λ > 420 nm), which is 7.7-times higher than that of bulk g-C3N4 (BCN). The enhanced photocatalytic hydrogen production is mainly attributed to substituting of sp2-hybridized N with S atoms, which breaks intralayered hydrogen bonds of g-C3N4, resulting in greatly enhanced visible-light-response ability and efficient migration and separation of photo-induced charge carriers by facilitating the n → π* electron transition. In addition, the porous structures of S-doped multi-layered g-C3N4 also provide more reactive sites for water-splitting, which also facilitates the hydrogen production. The present study provides new insights into the design of high efficient g-C3N4-based photocatalyst.

Construction of Z-scheme and p-n heterostructure: Three-dimensional porous g-C3N4/graphene oxide-Ag/AgBr composite for high-efficient hydrogen evolution

Hydrogen is known as an alternative new energy for its advantages of non-pollution and high calorific value, and photocatalysis technology is regarded as one of the most effective means to produce hydrogen in recent years. In this topic, aiming at the poor photoresponse, fast combination of photo-induced carriers and unstable structure of traditional photocatalysts, the three-dimensional porous g-C3N4/graphene oxide framework was constructed by compounding two-dimensional graphene oxide and two-dimensional g-C3N4 via hard template (SiO2 nanoparticles) method and selective chemical etching. Then, silver bromide nanoparticles, a superior photosensitizer, were immobilized on the three-dimensional porous framework to construct the three-dimensional porous g-C3N4/graphene oxide-AgBr photocatalyst with Ag plasmas by solvothermal method. Research showed that this novel photocatalyst based on Z-scheme heterostructure (GO-AgBr), p-n heterostructure (g-C3N4-AgBr) and Ag plasmas presented high-efficient visible-light driven hydrogen evolution (3.69 mmol/g/h) at the absence of Pt co-catalyst, which is higher than the majority of existing catalysts, and it also possessed strong stability on its activity and structure. Accordingly, the enhanced hydrogen evolution and photostability were attributed to the highly ordered structure and fast interfacial electron conduction of three-dimensional porous framework, superior photosensitivity of AgBr and synergistic effect of Ag plasmas. Therefore, this study provided a potential method for exploitation of hydrogen energy.

The Z-scheme Ag2CO3@g-C3N4 core-shell structure for increased photoinduced charge separation and stable photocatalytic degradation

The core-shell Ag2CO3@g-C3N4 photocatalyst was prepared by coating two-dimensional nanosheet g-C3N4 on the surface of Ag2CO3, which could substantial improve the photo-degradation for MO (methyl orange), and the Ag2CO3@g-C3N4 (5 wt%) composite exhibited the best degradation efficiency, up to 96.7%. Meanwhile, the composites also have great degradation properties for MB (methylene blue), RhB (Rhodamine B) and phenol, the enhanced photocatalytic performance was due to the faster photogenerated carrier migration efficiency derived from core-shell structure and chemical bond hybridization effect arising from Ag2CO3 and g-C3N4. In addition, the Ag2CO3@g-C3N4 photocatalyst has great stability for MO degradation and the activity remains at 87.3% after five cycles, due to the Z-scheme structure formed by the Ag2CO3@g-C3N4 photoacatalyst, which effectively avoids the accumulation of photoinduced electrons in the Ag2CO3 and inhibits Ag+ photoreduction, which greatly improves the stability of Ag2CO3. This Ag2CO3@g-C3N4 core-shell photocatalyst with Z-scheme system not only promotes the photodegradability of Ag2CO3, but ensures its stability performance, which providing new ideas for designing new high-efficiency photocatalytic materials.

Sorbent and solvent co-enhanced direct analysis in real time-mass spectrometry for high-throughput determination of trace pollutants in water

A sorbent and solvent co-enhanced direct analysis in real-time mass spectrometry (SSE-DART-MS) method was developed for high-throughput determination of trace pollutants in water. The use of sorbent for preconcentration and solvents for assisting desorption and ionization synergistically enhanced the signals from the trace pollutants detected by DART-MS. Phthalic acid esters (PAEs) were used as model analytes to validate the SSE-DART-MS method. Graphitic carbon nitride (g–C3N4)–based materials with two morphologies and six organic solvents were used to systematically evaluate the enhancement effect by the sorbent and solvent. A better analytical performance was achieved with the two-dimensional (2D) g-C3N4, compared to three-dimensional (3D) g-C3N4/C, indicating that the morphologies of sorbents played a key role in SSE-DART-MS analysis. The MS signals of all the analytes were increased by 10–100 times for the two materials in the presence of the selected solvents. With the SSE-DART-MS method, concentration limits of detection for water samples in the range 0.07–0.94 ng L−1, and recovery in the range 82.8–119% using g-C3N4, were obtained for the PAEs. This work not only provides a reliable method for the coupling of solid phase extraction technique with DART-MS, but also presents valuable information for conducting other DART-MS analyses.

Naphthalimide-porphyrin hybridized graphitic carbon nitride for enhanced photocatalytic hydrogen production

A series of NP/g-C3N4 hybrids of graphitic carbon nitride (g-C3N4) with naphthalimide-porphyrin (NP) are developed for photocatalytic hydrogen production. Planar naphthalimide-porphyrins are facilely adsorbed onto flexible two-dimensional g-C3N4 through π–π stacking. Except for its function as photosensitizer, NP in the hybrid could efficient inhibit the charge recombination by electron transfer from the lowest unoccupied molecular orbital (LUMO) of NP to conduction band of g-C3N4, meanwhile facilitate Förster energy transfer from g-C3N4 donor to NP acceptor for the efficient overlap of absorption spectrum of NP and emission of g-C3N4. As a result, the hybrid 2%NP/g-C3N4 containing 2% weight ratio of NP exhibits an impressive photocatalytic hydrogen production rate (HPR) of 2297 μmol g−1 h−1, while pristine g-C3N4 shows a HPR of 698 μmol g−1 h−1. Specifically, the performance of 2%NP/g-C3N4 is far superior compared with the hybrids of g-C3N4 with Zn(II)-tetrakis(4-carboxylphenyl)porphyrin (ZnTCPP) and Zn(II)-tetrakis(4-phenyl)porphyrin (ZnTPP) in photocatalytic hydrogen production under the same conditions.

In Situ Growing Triethanolamine-Functionalized Metal-Organic Frameworks on Two-Dimensional Carbon Nanosheets for Electrochemiluminescent Immunoassay.

A facile strategy for in situ growing triethanolamine (TEOA)-functionalized metal-organic framework (TEOA@MOF) on the two-dimensional graphene oxide (GO) or g-C3N4 nanosheets via the self-assembly technique was introduced. In this method, Zn2+ was first attached on the carbon nanosheets by electrostatic interaction; then, trimesic acid (H3btc) acted as the complex agent and TEOA as a base for the deprotonation of H3btc and a template, which leads to in situ growing the MOF on the carbon nanosheets obtaining a sandwich-like structure. Different types of surface analysis techniques were employed to characterize the GO-TEOA@MOFs and g-C3N4-TEOA@MOFs nanomaterials fabricated. The GO-TEOA@MOFs or g-C3N4-TEOA@MOFs nanomaterial-modified electrode brings out obviously enhanced electrochemiluminescence (ECL) behaviors due to numerous TEOA in the framework structures. Specifically, both TEOA and GO can serve as the co-reactants for the ECL system of Ru(bpy)32+ and have the synergic effect of enhancing the signal. Based on the GO-TEOA@MOFs modified electrodes, we developed a sensitive and rapid label-free ECL immunoassay strategy for human copeptin, and the linear range was 5 pg mL-1 to 500 ng mL-1 as well as the limit of detection was 360 fg mL-1. This work exhibits excellent specificity and good stability of the prepared immunosensor in the practical sample determination, demonstrating it can serve as a very promising method for the clinical diagnostics of acute myocardial infarction disease.

Construction of Ti3C2 MXene/O-doped g-C3N4 2D-2D Schottky-junction for enhanced photocatalytic hydrogen evolution

construction of the Schottky-junction is considered to be a valid route to boost the spatial charge separation and transfer of the photocatalytic system. Herein, two-dimensional (2D) O-doped g-C3N4 nanosheets were prepared by an annealing route, and then a 2D/2D Ti3C2 MXene/O-doped g-C3N4 Schottky-junction was fabricated using an in-situ electrostatic assembly of negatively charged Ti3C2 MXene and positively charged O-doped g-C3N4 nanosheets. The as-prepared Ti3C2 MXene/O-doped g-C3N4 Schottky-junction exhibited almost two times enhanced hydrogen evolution (25124 μmol/g/h) in comparison to pristine O-doped g-C3N4 (13745 μmol/g/h) and Ti3C2 MXene/pristine C3N4 (15573 μmol/g/h). Based on fully characterizations and theory calculation, the enhanced photocatalytic performance could be attributed to the synergy effect of intimate 2D/2D interfacial contact and the construction of Schottky-junction, which result in the short charge transport distance from HCN to Ti3C2 MXene and efficient separation of the photo-generated charge. This study will provide new insight into developing 2D/2D Schottky-junction photocatalysts for the solution of the energy crisis.

An electrochemiluminescence immunosensor for the N-terminal brain natriuretic peptide based on the high quenching ability of polydopamine.

A sandwich-type electrochemiluminescence (ECL) immunosensor for the N-terminal brain natriuretic peptide (NT-proBNP) is described. The assay is based on the quenching of the ECL of graphite-like carbon nitride (g-C3N4) by polydopamine (PDA). Two-dimensional g-C3N4 is grown in-situ on titanium dioxide nanoflowers (TiO2 NFs). The macroporous structure of the NFs enhances the interfacial stability of g-C3N4, and also promotes the ECL reaction of g-C3N4 with the co-reactant. The introduction of gold nanoparticles into the matrix further enhances the ECL and facilitates the immobilization of capture antibodies. The nanoquencher used to label the secondary antibody is synthesized by catalytic polymerization of dopamine in the presence of bimetallic NiPd nanoparticles. The nanoquencher preserves the high reactivity of polydopamine and quenches the ECL of the g-C3N4/TiO2 system. Compared to other methods, the detection limit for NT-proBNP is decreased to 50fg∙mL-1. Graphical abstract Schematic presentation of the electrochemiluminescence (ECL) process of the immunosensor: titanium dioxide nanoflowers@graphite-like carbon nitride-gold nanoparticles (TiO2 NFs@g-C3N4-Au) as luminophor, and polydopamine (PDA) as nanoquencher.

Hydrogen evolution by catalyzing water splitting on two-dimensional g-C3N4-Ag/AgBr heterostructure

Due to the increasing pressure of social environment and the increasing demand of human for energy, it is urgent to seek a sustainable and pollution-free new energy. Hydrogen is considered as a new type of energy because of its high calorific value, no environmental pollution and low cost of raw materials. In this experiment, to improve the visible-light driven catalytic activity of two-dimensional g-C3N4, g-C3N4 and Ag/AgBr nanoparticles (NPs) were used as the carrier and cocatalyst, and the g-C3N4/Ag/AgBr (CNAA-α, α = 1, 2 and 3) heterojunction photocatalysts with different amounts of Ag/AgBr were synthesized via solvothermal technology. The morphology, composition, structure, photochemical and electrochemical characteristics of the samples were analyzed through XRD, FTIR, TEM, XPS and a series of photoelectrochemical characterizations, and the visible-light driven catalytic hydrogen evolution activities of the samples were studied by catalyzing water splitting. Research showed that the CNAA-2 exhibited the smallest overvoltage (86.5 mV vs RHE) and Tafel slope (61.0 mV·dec−1), so that the highest photocatalytic activity (47.84 μmol·g−1·h−1) for hydrogen evolution was obtained at the absence of Pt co-catalyst. Furthermore, this heterojunction photocatalyst exhibited good photostability and could be recycled several times with no significant decrease of its activity. This indicated that the addition of Ag/AgBr NPs to the two-dimensional g-C3N4 nanosheets to construct an effective p-n heterojunction system at their interfaces could promote the conduction of photo-induced carriers and inhibit their combination, so that it would significantly improve the photoresponse ability and catalytic activity of two-dimensional g-C3N4 nanosheets.

Graphitic Carbon Nitride Nanosheets Decorated Flower-like NiO Composites for High-Performance Triethylamine Detection.

The graphitic carbon nitride (g-C3N4) nanosheets decorated three-dimensional hierarchical flower-like nickel oxide (NiO) composites (NiO/g-C3N4, Ni/CN) were synthesized via a facile hydrothermal method combined with a subsequent annealing process. The structure and morphology of the as-prepared Ni/CN composites were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen absorption. The gas-sensing experiments reveal that the composites with 10 wt % two-dimensional g-C3N4 (Ni/CN-10) not only exhibits the highest response of 20.03 that is almost 3 times higher than pristine NiO to 500 ppm triethylamine (TEA) at the optimal operating temperature of 280 °C but also shows a good selectivity toward TEA. The gas-sensitivity promotion mechanism is attributed to the internal charge transfer within the p–n heterojunction. Furthermore, the high specific surface area of the Ni/CN composites promotes adequate contact and reaction between the composites and triethylamine molecules. Therefore, the Ni/CN sensor has a great potential application in detecting TEA.

Dimensional transformation and morphological control of graphitic carbon nitride from water-based supramolecular assembly for photocatalytic hydrogen evolution: from 3D to 2D and 1D nanostructures

Geometric dimensionality and morphology largely affect the properties and functionalities of materials; however, simultaneously regulating them to realize synergic effects is a formidable scientific and technological challenge. Here we demonstrate an effective strategy to control the dimensionality and morphology of graphitic carbon nitride (g-C3N4) through heat treatment the melamine-cyanuric acid supramolecular precursors formed in water as a “green” solvent. By varying heat treatments, the three-dimensional (3D) hexagonal prism precursors could be transformed to 3D g-C3N4 loofah-like (CNl) architectures, ultrathin two-dimensional (2D) g-C3N4 nanosheets (CNs), and ordered one-dimensional (1D) g-C3N4 nanotube (CNt) array, respectively. The adsorbed melamine molecules on the surface of precursor and atmosphere in the transformation process, play a key role in determining the morphology of products. The resulting ultrathin 2D CNs have a porous structure, a small thickness (1.6 nm), a large surface area (208.8 m2·g−1), and high conductivity, thus exhibiting higher hydrogen evolution rate (23.9 μmol h−1) by 17.3 times than the bulk g-C3N4 (CN) under visible light irradiation. This strategy results in high-quality, ultrathin CNs at yields of ∼10 wt% from raw material, much higher than those of previous reports (∼6 wt% from bulk CN). This work not only enriches our understanding of the relationship between geometric dimensionality, morphology and properties of photocatalytic nanomaterials, but also could be potentially useful for the design and growth of 1D or 2D flexible polymers for energy-related applications and beyond.

High-performance carbon monoxide gas sensor based on palladium/tin oxide/porous graphitic carbon nitride nanocomposite

The palladium (Pd)/tin oxide (SnO2)/porous graphitic carbon nitride (g-C3N4) nanocomposites with different Pd and g-C3N4 contents were synthesized by a facile hydrothermal route and their applications as efficient carbon monoxide (CO) gas sensors were investigated. These nanocomposites were characterized in detail by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), micrograph techniques (FESEM and TEM), and energy dispersive X-ray spectroscopy (EDS), in order to evaluate their structural and morphological properties. On the basis of the FESEM and TEM analysis, two-dimensional porous g-C3N4 nanosheets provided a large surface area suitable for growth of SnO2 nanoparticles and formation of a heterogeneous nanocomposite. Among different weight ratios of the components of Pd/SnO2/g-C3N4 nanocomposites, 5%Pd/SnO2/5%g-C3N4 exhibited excellent CO sensing characteristics such as high response, short response/recovery times, good selectivity and stability at lower operating temperature of 125 °C. The outstanding gas sensing performance of these nanocomposites could be attributed to the high surface area of porous g-C3N4, the strong spillover effect of Pd nanoparticles as well as the formation of g-C3N4/SnO2 heterojunction.

Construction of g-C3N4/BCN two-dimensional heterojunction photoanode for enhanced photoelectrochemical water splitting

Two-dimensional heterojunction g-C3N4/BCN was constructed via thermal polymerization process. The formed two-dimensional heterostructure could enhance the interfacial contact area between BCN and porous g-C3N4 as well as shorten the photogenerated charge carriers transfer time and distance. The two-dimensional g-C3N4/BCN heterojunction photoanode shows enhanced photoelectrochemical (PEC) performance for water splitting under visible-light irradiation, which primarily originates from the improved charge transfer and separation, and prolonged lifetime of electrons. Under the visible light irradiation, the g-C3N4/BCN heterojunction sample yields a photocurrent density of ∼0.62 mA cm−2 at 1.23 V vs. RHE, which is about eight times as many as that of CN (0.08 mA cm−2) electrode at the same conditions. In addition, the possible electron transfer model and mechanism of PEC water splitting for H2 evolution have been discussed.

Two-dimensional mesoporous g-C3N4 nanosheets coupled with nonstoichiometric Zn-Cu-In-S nanocrystals for enhancing activity of photocatalytic water splitting

Graphitic carbon nitride (g-C3N4) is the most stable allotrope of carbon nitride with a conjugated, two-dimensional polymer of s-triazine, which is considered as a promising photocatalyst in sustainable chemistry. The low surface area and quantum efficiency and fast electron-hole recombination of g-C3N4 restrict its practical application. The formation of two-dimensional mesoporous structure and the construction of proper semiconductor composites are two approaches to promote the effective separation of photogenerated exciton and reduce the charge transfer resistance, which is beneficial to restrain the recombination of exciton and improve photocatalytic hydrogen performance. In this work, two-dimensional mesoporous g-C3N4 nanosheets (MCNS) coupled with nonstoichiometric Zn-Cu-In-S (ZCIS) nanocrystals were synthesized by a hydrothermal method. The constructed ZCIS/MCNS composites possessed highly photocatalytic hydrogen evolution performance under visible light irradiation without any noble metal cocatalysts. The EIS spectra and transient photocurrent responses corroborated ZCIS/MCNS had higher separation and transportation efficiency of photogenerated electron and hole. The incorporation of ZCIS into MCNS reduced the charge transfer resistance and enhanced the charge transfer efficiency. As the result, the photocatalytic hydrogen evolution rate of ZCIS/MCNS was higher than those of pure ZCIS and MCNS. 10-0.2ZCIS/MCNS showed a highest H2 production rate of 12.3 μmol h−1 over 100 mg photocatalyst without cocatalysts. This work supplied a feasible strategy to construct ZCIS/MCNS composites for the exploitation of solar energy.

2D–2D Heterostructured UNiMOF/g-C3N4 for Enhanced Photocatalytic H2 Production under Visible-Light Irradiation

On the basis of ultrathin two-dimensional (2D) nickel metal organic framework (UNiMOF) nanoflakes and 2D g-C3N4 nanoflakes, fresh visible-light-driven 2D/2D heterostructure catalysts were designed, which were assembled with a simplistic electrostatic self-assembly process. The photocatalytic performance of UNiMOF/g-C3N4 for H2 production was evaluated in visible light. The hydrogen evolution of 25.0% UNiMOF/g-C3N4 (UNG-25.0) heterojunction was 20.03 μmol h–1, which was greater than that of pure g-C3N4. In addition, the UNG composites also presented more excellent photocatalytic activity than that of bulk NiMOF/g-C3N4 (BNG) hybrid. This enhanced performance may depend on cooperative potentiation between UNiMOF and g-C3N4 efficiently lowering recombination of carriers. This work showed that constructing 2D–2D heterojunctions provides a feasible approach to obtain highly capable catalysts for photocatalytic decomposition of water.

Two-dimensional g-C3N4/TiO2 nanocomposites as vertical Z-scheme heterojunction for improved photocatalytic water disinfection

Developing highly active photocatalysts towards effective microorganism inactivation is a green and energy-smart strategy in response to the growing demands to water quality under the background of the water crisis. Here, a vertical face-to-face heterojunction is fabricated by horizontally assembling TiO2 nanosheets with {001} facets exposed on graphitic carbon nitride (g-C3N4) sheets through a facile hydrothermal driving coupling. The vertical heterojunction could almost completely disinfect 103 CFU/mL E. coli within 30 min under solar light, which is more efficient than the physically mixed composite and pure g-C3N4 and TiO2. The two-dimensional (2D) morphology provides ample surface area in forming the vertical heterojunction and enables intimate contact which is advantageous to charge transfer between g-C3N4 and TiO2. A Z-scheme charge transportation mechanism is confirmed through band structure analysis and reactive species (RSs) probing and trapping experiments. In comparison with physically mixed composite and the single-phase counterparts, the nanocomposite based on a Z-scheme electron transfer mode effectively prompts charge pair dissociation and subsequently encourages bacterial inactivation by boosting the generation of RSs. The constructing vertical Z-scheme heterojunction highlights the potential of 2D nanomaterials for accelerated water sterilization.