Crystalline g-C3N4 Research Articles

Preparation of High-efficient Donor-π-Acceptor System with Crystalline g-C3N4 as Charge Transfer Module for Enhanced Photocatalytic Hydrogen Evolution

Preparation of High-efficient Donor-π-Acceptor System with Crystalline g-C3N4 as Charge Transfer Module for Enhanced Photocatalytic Hydrogen Evolution

Enhancement of antifouling and separation properties of poly(m-phenylene isophthalamide) hybrid ultrafiltration membrane using highly crystalline poly(heptazine imide) nanosheets

A highly crystalline phase g-C3N4, namely poly (heptazine imide) (PHI) was synthesized using molten salts. A high-performance ultrafiltration membrane was prepared by blending PHI nanosheets with Poly(m-phenylene isophthalamide) (PMIA) to obtain casting solution, and further prepared by phase conversion method. Hybrid PMIA membranes were prepared by incorporating 0.02–0.10 wt% of PHI, which were further characterized by SEM, AFM, XRD, FTIR, XPS, TGA and surface zeta potential. The hydrophilicity, water flux, and rejection of bovine serum albumin (BSA) of the membrane significantly increased. For instance, the water permeability of M4 (264.6 Lm−2h−1bar−1) was about 2.3 times that of bare PMIA membrane (113.6 Lm−2h−1bar−1), while maintaining a BSA rejection of 94.7 % for a 1000 mgL−1 BSA feed solution. Moreover, the M4 membrane showed excellent antifouling performance with a flux recovery rate of up to 88.7 % and lower irreversible fouling of 11.3 %. This study may provide reference for the modulation of highly crystalline g-C3N4 structure and its application in membrane fabrication for water treatment.

Decorating nitrogen-deficient crystalline g-C3N4 with Ti3C2(OH)2 for photocatalytic CO2 reduction and RhB degradation enhancement

Visible light responding photocatalytic technology has shown great potential to mitigate the greenhouse effect and global pollution issues in recent years. Herein, alkalized titanium carbide Ti3C2Tx (TCOH) is combined with nitrogen-deficient g-C3N4 (CN-Nx) by simply mixing for photocatalytic CO2 reduction and RhB degradation. TCOH replaces noble metals as a co-catalyst for CN-Nx due to its full-spectrum absorption properties and excellent conductivity, which effectively enhances the overall light absorption capacity of CN-Nx. Additionally, a large Fermi energy level difference between TCOH and CN-Nx leads to a built-in electric field forming at their interface when combined. This built-in electric field can enhance the photogenerated electron-hole pair separation and reduce the recombination rate. So the visible light utilization ranges of optimized 2TCOH-30 %/CN-N0.02 expanded from 477 nm (CN-N0.02) to 481 nm, and the average lifetimes of the photogenerated carriers is 4.37 ns, which is 2.64 times longer than CN-N0.02. Moreover, the CO yield reaches 67.55 μmol/g during photocatalytic CO2 reduction of 2TCOH-30 %/CN-N0.02, which is 4.06 and 2.54 times than 2TCOH and CN-N0.02. During the RhB degradation, 2TCOH-30 %/CN-N0.02 can remove approximately 98.3 % of RhB in 15 min, which is1.6 and 1.4 times of 2TCOH and CN-N0.02. Also, 2TCOH-30 %/CN-N0.02 shows excellent stability, the photocatalytic capacity for CO2 reduction and RhB degradation has no significant degradation after six times circles.

Facilely tuning the triazine-heptazine ratios in crystalline g-C3N4 for efficient photo-degradation of tylosin

Intrinsically, g-C3N4 has high-density defects, insufficient efficiencies of photogenerated charge carrier separation and transfer, and inadequate photocatalytic ability against antibiotics. A facile crystallinity engineering on g-C3N4 assisted by molten-salts and simultaneously fine-tuning the triazine-heptazine ratio led to forming type-II homojunctions, without introducing foreign atoms and being metal-free. It was successfully achieved through modulating the calcination temperatures and using KCl-LiCl. The salts accelerated deamination reaction kinetics, tuned the unit ratio, and improved the degree of carbon nitride polymerization. At a triazine-heptazine ratio of 74:26 obtained at 450 °C, 10 mg/L of tylosin was completely mitigated within 9 min by the catalyst. Active radicals including O2− and OH were boosted from charge carriers under visible light, and the recombination of photogenerated excitons was relieved on the interfaces of the homojunctions. Breaking glycosidic bonds and dropping off deoxyglycosyl moieties are considered the main degradation mechanism. The cytotoxicity and acute toxicity of the degradation product are classified as harmless. In addition, 3D-molecular docking between the transformation products and target proteins (L4 and L22) in ribosome confirms toxicity reduction. This work paves a way for efficient and harmless photocatalytic degradation of tylosin by facilely modulating the unit ratio and enhancing the crystallinity of carbon nitride without introducing foreign atoms.

A ruthenium single atom nanozyme-based antibiotic for the treatment of otitis media caused by Staphylococcus aureus.

Staphylococcus aureus (S. aureus) infection is a primary cause of otitis media (OM), the most common disease for which children are prescribed antibiotics. However, the abuse of antibiotics has led to a global increase in antimicrobial resistance (AMR). Nanozymes, as promising alternatives to traditional antibiotics, are being extensively utilized to combat AMR. Here, we synthesize a series of single-atom nanozymes (metal-C3N4 SANzymes) by loading four metals (Ag, Fe, Cu, Ru) with antibacterial properties onto a crystalline g-C3N4. These metal-C3N4 display a rob-like morphology and well-dispersed metal atoms. Among them, Ru-C3N4 demonstrates the optimal peroxidase-like activity (285.3 U mg-1), comparable to that of horseradish peroxidase (267.7 U mg-1). In vitro antibacterial assays reveal that Ru-C3N4 significantly inhibits S. aureus growth compared with other metal-C3N4 even at a low concentration (0.06mg mL-1). Notably, Ru-C3N4 acts as a narrow-spectrum nanoantibiotic with relative specificity against Gram-positive bacteria. Biofilms formed by S. aureus are easily degraded by Ru-C3N4 due to its high peroxidase-like activity. In vivo, Ru-C3N4 effectively eliminates S. aureus and relieves ear inflammation in OM mouse models. However, untreated OM mice eventually develop hearing impairment. Due to its low metal load, Ru-C3N4 does not exhibit significant toxicity to blood, liver, or kidney. In conclusion, this study presents a novel SANzyme-based antibiotic that can effectively eliminate S. aureus and treat S. aureus-induced OM.

Hydrothermal synthesis of CeVO4/g-C3N4 Z-scheme photocatalyst for removal of dyes under photocatalysis

Wastewater treatment emerged as the major concern as the water scarcity increases. Photocatalysis is the efficient way to reduce the pollutants from wastewater without causing destruction to environment. Herein, simplistic preparation of pristine and g-C3N4-CeVO4 nanocomposites for photocatalysis was explored. The structural, optical and vibrational study was confirmed by standard analysis. The samples possess good crystalline nature and g-C3N4 was corroborateed by XRD. The Raman modes were confirmed Ce-O and V-O bending and stretching bonds. The photocatalysts bandgap were narrow down on assisting g-C3N4 and the bandgap engineering was altered by g-C3N4 heterojunction. The morphology of CeVO4 and its composites showed the formation of ball-like structure and the sheets of g-C3N4 was also confirmed. Janus Green B (JG) dye was model pollutant and metal halide lamp was employed as light source. The prepared pure CeVO4 photocatalysts showed better efficiency. Nevertheless, g-C3N4 assisted sample shows good efficiency and greater rate constant. This was characteristic feature of proper heterojunction development amid g-C3N4 and CeVO4. CeVO4, 0.1 g g-C3N4-CeVO4 and 0.2 g g-C3N4- CeVO4 rate constant were 9.2 × 10-4, 1.1 × 10-2, 1.54 × 10-2 and 2 × 10-2 min−1. The photogenerated electrons and holes were enthusiastically break up and reactive species were generated which paved the path for enhanced photocatalytic removal of pollutants. Among various photocatalysts, 0.2 g g-C3N4-CeVO4 is prospective material for wastewater remediation process.

Ultrasensitive electrochemiluminescence biosensing from Cobalt single atom embedded high crystalline g-carbon nitride nanorod

Here, cobalt single-atom (Co SA) was introduced into the structure of the crystalline g-C3N4 nanorod (cry-CNN), which showed rapid electron transfer rate and excellent redox activity, thereby resulting in high electrochemiluminescence (ECL) emission. Compared to bulk g-C3N4, the cry-CNN had higher ECL intensity due to increasing the crystallinity to change the charge transport of electrons in the layer. Besides, benefiting from the unique electronic structure and catalytic activity of Co SA, the obtained Co SA@cry-CNN represented enhanced ECL intensity at a lower negative potential than that of cry-CNN, owing to the Co SA not only accelerated the electron transfer of the cry-CCN in heptazine cavity, but also promoted the co-reactive S2O82- to produce more active intermediate SO4•–. Interestingly, the experimental results showed that the ECL emission of Co SA@cry-CNN was about 23 times higher than that of BCN, and was 5 times higher than that of cry-CNN. Furthermore, using Co SA@cry-CNN as luminophore, a compact and efficient HCR-link-CHA(HLC) cascade amplification strategy was designed to construct a biosensor for detection of microRNA-222, which converted a certain amount of target to a DNA nanonet with plenty of quencher via N cycle of HCR and CHA reaction. The constructed biosensor had good monitoring performance and the limit of detection was as low as 40.0 amol/L. The proposed strategy integrated luminous structural adjustment and co-reaction efficiency improvement could be effectively extended to exploration of other novel ECL materials, and also provided new ideas for the early diagnosis of diseases.

2D/2D homojunction-mediated charge separation: Synergistic effect of crystalline C3N5 and g-C3N4 via electrostatic self-assembly for photocatalytic hydrogen and benzaldehyde production

Homojunction engineering is a promising modification strategy to improve charge carrier separation and photocatalytic performance of carbon nitrides. Leveraging intrinsic heptazine/triazine phase and face-to-face contact, crystalline C3N5 (CC3N5) was combined with protonated g-C3N4 (pgCN) through electrostatic self-assembly to achieve robust 2D/2D homojunction interfaces. The highest photocatalytic performance was obtained through crystallinity and homojunction engineering, by controlling the pgCN:CC3N5 ratio. The 25:100 pgCN:CC3N5 homojunction (25CgCN) had the highest hydrogen production (1409.51 μmol h−1) and apparent quantum efficiency (25.04%, 420 nm), 8-fold and 180-fold higher than CC3N5 and pgCN, respectively. This photocatalytic homojunction improves benzaldehyde and hydrogen production activity, retaining 89% performance after 3 cycles (12 h) on a 3D-printed substrate. Electron paramagnetic resonance demonstrated higher ·OH−, ·O2− and hole production of irradiated 25CgCN, attributed to crystallinity and homojunction interaction. Thus, electrostatic self-assembly to couple CC3N5 and pgCN in a 2D/2D homojunction interface ameliorates the performance of multifunctional solar-driven applications.

Bandgap modulations and promoted carrier separation in crystalline g-C3N4 thin films via chemical vapor deposition

The preparation of high-quality graphite-like phase carbon nitride (g-C3N4) films is challenging, which limits the potential optoelectronic and photocatalytic applications. Here, we report the growth of crystalline g-C3N4 films with thicknesses of approximately 100–200 nm on the indium tin oxide substrates by chemical vapor deposition. The films show high crystalline quality and uniformity as suggested by the appearance of interference fringes in the transmission spectra and the existence of exciton peak. The optimized growth conditions for high-quality g-C3N4 films deposition have been obtained through combined optical characterizations and detailed electronic structure analyses using x-ray spectroscopies. The as-grown g-C3N4 films exhibit a bandgap value of 3.05 eV as well as an enhanced fluorescence lifetime of ∼12.43 ns. By adding thiourea to the melamine precursors, N vacancies have been formed in the main heptazine structure, achieving the modulation of the bandgap and the promoted carrier separation. This work provides guidelines for understanding the property–structure relationships during g-C3N4 film deposition. The deposition of high crystallinity g-C3N4 films therein further extends the applications in the fields of optoelectronic and photocatalytic devices.

Spatially separated HOMO-LUMO sites in highly intra- and inter-plane crystalline g-C3N4 photocatalyst for exceptional H2 generation

Spatially separated HOMO-LUMO sites in the highly crystalline g-C3N4 can vastly facilitate the rapid transfer and separation of photogenerated charges to greatly improve its photocatalytic performance, which remains a great challenge to be achieved. In this study, the highly intra- and inter-plane crystalline g-C3N4 (c-CN) with the spatially separated HOMO-LUMO sites is explicitly produced through a moderate Na-modulated strategy to efficiently promote the directional transfer and separation of photoinduced charges. As a result, the optimized c-CN1.0 photocatalyst exhibits exceptional H2-evolution performance (313.5 μmol h−1, AQE = 13.38 %), which is ca. 14.3 times of the bulk g-C3N4. The excellent hydrogen-generation efficiency of c-CN photocatalyst is mainly ascribed to the synergism of high intra- and inter-layer crystallization of g-C3N4 and spatially separated HOMO-LUMO sites, which can vastly boost the directional transfer and effective separation of photoexcited electrons and holes. This research may open novel avenues to construct other photocatalysts with high efficiency.

Harnessing the Power of Light: The Synergistic Effects of Crystalline Carbon Nitride and Ti3C2Tx MXene in Photocatalytic Hydrogen Production.

Photocatalytic hydrogen evolution is an environmentally friendly means of energy generation. Although g-C3N4 possesses fascinating features, its inherent shortcomings limit its photocatalytic applications. Therefore, modifying the intrinsic properties of g-C3N4 and introducing cocatalysts are essential to ameliorate the photocatalytic efficiency. To achieve this, metal-like Ti3C2Tx is integrated with crystalline g-C3N4 via a combined salt-assisted and freeze-drying approach to form crystalline g-C3N4/Ti3C2Tx (CCN/TCT) hybrids with different Ti3C2Tx loading amounts (0, 0.2, 0.3, 0.4, 0.5, 1, 5, 10 wt.%). Benefiting from the crystallization of CN, as evidenced by the XRD graph, and the marvelous conductivity of Ti3C2Tx supported by EIS plots, CCN/TCT/Pt loaded with 0.5 wt.% Ti3C2Tx displays an elevated H2 (2) should be subscripted evolution rate of 2651.93µmol g-1 h-1 and a high apparent quantum efficiency of 7.26% (420nm), outperforming CN/Pt, CCN/Pt, and other CCN/TCT/Pt hybrids. The enhanced performance is attributed to the synergistic effect of the highly crystalline structure of CCN that enables fleet charge transport and the efficient dual cocatalysts, Ti3C2Tx and Pt, that foster charge separation and provide plentiful active sites. This work demonstrates the potential of CCN/TCT as a promising material for hydrogen production, suggesting a significant advancement in the design of CCN heterostructures for effective photocatalytic systems.

A novel all-organic S-scheme heterojunction with rapid interfacial charges migration for efficient photocatalytic H2 production

Poly (triazine imide), as a kind of highly crystalline g-C3N4, exhibits a promising potential for photocatalytic hydrogen production, however, some drawbacks still limit its photocatalytic performance. The strategy of constructing S-scheme heterojunction with different semiconductor photocatalysts enables the effective separation of photogenerated electrons and holes, and the strong oxidative and reductive properties of the original photocatalysts could be retained, which will significantly improve the photocatalytic activity. In this work, we synthesized the organic-organic S-scheme heterojunction between PTI and organic small molecule poly (barbituric acid) (PBA) by hydrogen bond self-assembly method, which results in a significant enhancement of photocatalytic H2 production activity. The H2 production rate of the optimum PBA/PTI-2 sample under visible light irradiation is about 0.92 mmol g–1, which is 5.5 times higher than that of PTI and 14.4 times higher than that of PBA. This excellent photocatalytic performance is attributed to the successful construction of S-scheme heterojunction between PTI and PBA, which effectively accelerates carrier transport and spatial segregation by the formation of a built-in electric field and band bending at the interface. In addition, the S-scheme heterojunction could also reserve the maximum redox capability and enhance the light absorption of the prepared photocatalytic system. This work provides a new strategy and understanding for the design and development of organic-organic S-scheme heterojunction photocatalysts.

Isotype heterojunction: tuning the heptazine/triazine phase of crystalline nitrogen-rich C3N5 towards multifunctional photocatalytic applications.

Photocatalytic technology has been well studied as a means to achieve sustainable energy generation through water splitting or chemical synthesis. Recently, a low C/N atomic ratio carbon nitride allotrope, C3N5, has been found to be highly prospective due to its excellent electronic properties and ample N-active sites compared to g-C3N4. Tangentially, crystalline g-C3N4 has also been a prospective candidate due to its improved electron transport and extended π-conjugated system. For the first time, our group successfully employed a one-step molten salt calcination method to prepare novel N-rich crystalline C3N5 and elucidate the effect of calcination temperature on the heptazine/triazine phase. Calcination temperatures of 500 °C (CC3N5-500) and 550 °C (CC3N5-550) lead to crystalline carbon nitride with both heptazine and triazine phases, forming an intimate isotype heterojunction for robust interfacial charge separation. An excellent photocatalytic hydrogen evolution rate (359.97 μmol h-1; apparent quantum efficiency (AQE): 12.86% at 420 nm) was achieved using CC3N5-500, which was 15-fold higher than that of pristine C3N5. Furthermore, CC3N5-500 exhibited improved activity for simultaneous benzyl alcohol oxidation and hydrogen production, as well as H2O2 production (AQE: 9.49% at 420 nm), signifying its multitudinous photoredox capabilities. Moreover, the recyclability tests of the optimal CC3N5-500 on a 3D-printed substrate also showed a 92% performance retention after 4 cycles (16 h). This highlights that crystalline C3N5 significantly augmented the reaction performance for diverse multifunctional solar-driven applications. As such, these results serve as a guide toward the structural tuning of 2D metal-free carbon nanomaterials with tunable crystallinity toward achieving boosted photocatalysis.

W18O49/crystalline g-C3N4 layered heterostructures with full solar energy harvesting towards efficient H2O2 generation and NO conversion

The photocatalytic performance of graphitic carbon nitride (g-C3N4) heterostructures related to the charge carrier separation and transport efficiency is often governed by the interfaces. Herein, in-situ growth of W18O49 nanobelts is attained on amorphous and crystalline g-C3N4 nanosheets to study the effects of the interfaces on photocatalytic oxidation activities. The horizontal growth of W18O49 on g-C3N4 nanosheets is the key in formation of two dimensional (2D)/2D W18O49/g-C3N4 heterostructures. The growth of W18O49 nanobelts on crystalline g-C3N4 nanosheets shows well-developed interfaces (sample W18O49-CCN) in comparison with heterostructures constructed using amorphous g-C3N4 base (sample W18O49-ACN). Characterizations on the structure, components, and properties of the samples demonstrate that these heterostructures reveal extended photo-absorption in visible to near infrared region, with sample W18O49-CCN showing much higher photogenerated charge carrier separation and transport efficiency. A H2O2 evolution rate of 5550 µMg−1h−1 is observed for sample W18O49-CCN under full solar-spectrum illumination (and 398 µMg−1h−1 observed for pristine crystalline g-C3N4), which is ∼ 2.4 times of that of sample W18O49-ACN prepared using amorphous g-C3N4. In addition, a NO removal rate of 72.1% is observed for sample W18O49-CCN with a NO2 selectivity of 6.2%. These results provide inspiration for construction of g-C3N4 homojunctions for practical photo-redox reaction applications.

Highly intra- and inter-plane crystalline ReSx/g-C3N4: Facile synthesis and boosted photocatalytic H2 evolution

Improving the crystallinity of g-C3N4 is regarded as a desirable pathway to boost its photocatalytic activity. However, the current highly crystalline g-C3N4 photocatalysts are mainly emphasized on increasing their inter-plane crystallinity through ordered stacking layers while their intra-plane crystallinity has been seldomly concerned, causing the finitely enhanced photocatalytic performance. In this work, the high intra- and inter-plane crystallinity of g-C3N4 accompanied by the deposition of amorphous ReSx cocatalyst are simultaneously realized through a facile strategy, causing the successful formation of highly intra- and inter-plane crystalline ReSx/g-C3N4 (ReSx/c-CN) photocatalysts. In this case, the mixture of melamine and NaCl is initially calcined to prepare highly intra-plane crystalline g-C3N4 (i-CN). Subsequently, the i-CN is further treated by HCl to improve its inter-plane crystallinity, which can simultaneously realize the deposition of amorphous ReSx cocatalyst on g-C3N4 surface to finally produce ReSx/c-CN photocatalysts. Consequently, the high intra- and inter-plane crystallinity of g-C3N4 can effectively boost the separation and migration of photogenerated carriers, while the amorphous ReSx cocatalyst can supply abundant active sites for interfacial H2-evolution reaction. Thus, the optimized ReSx/c-CN(3.0 wt%) photocatalyst exhibit remarkably improved H2-generation activity (23.4 μmol h−1), which is about 8.4-fold of the ReSx/bulk g-C3N4(3.0 wt%) photocatalyst. This work may supply new ideas for exploring other highly efficient photocatalysts in various applications.

Electrostatic Self-Assembled Synthesis of Amorphous/Crystalline g-C3N4 Homo-Junction for Efficient Photocatalytic H2 Production with Simultaneous Antibiotic Degradation.

g-C3N4 has been regarded as a promising photocatalyst for photo-reforming antibiotics for H2 production but still suffers from its high charge recombination, which has been proven to be solvable by constructing a g-C3N4 homo-junction. However, those reported methods based on uncontrollable calcination for preparing a g-C3N4 homo-junction are difficult to reproduce. Herein, an amorphous/crystalline g-C3N4 homo-junction (ACN/CCN) was successfully synthesized via the electrostatic self-assembly attachment of negatively charged crystalline g-C3N4 nanorods (CCN) on positively charged amorphous g-C3N4 sheets (ACN). All the ACN/CCN samples displayed much higher photo-reforming of antibiotics for H2 production ability than that of pristine ACN and CCN. In particular, ACN/CCN-2 with the optimal ratio exhibited the best photocatalytic performance, with a H2 evolution rate of 162.5 μmol·g-1·h-1 and simultaneous consecutive ciprofloxacin (CIP) degradation under light irradiation for 4 h. The UV-vis diffuse reflectance spectra (DRS), photoluminescence (PL), and electrochemical results revealed that a homo-junction is formed in ACN/CCN due to the difference in the band arrangement of ACN and CCN, which effectively suppressed the charge recombination and then led to those above significantly enhanced photocatalytic activity. Moreover, H2 was generated from the water reduction reaction with a photogenerated electron (e-), and CIP was degraded via a photogenerated hole (h+). ACN/CCN exhibited adequate photostability and reusability for photocatalytic H2 production with simultaneous CIP degradation. This work provides a new idea for rationally designing and preparing homo-junction photocatalysts to achieve the dual purpose of chemical energy production and environmental treatment.

Molten salt-assisted anti-defect engineering to tailor ordered, highly crystalline g-C3N4 nanorods for efficient photocatalytic H2O2 production

Graphite carbon nitride (g-C3N4) is widely recognized as one of the most popular catalysts for photocatalytic hydrogen peroxide (H2O2) production. However, it is often overlooked that general g-C3N4 materials contain numerous dangling bonds and defects, which serve as recombination centers for photogenerated carriers and significantly hinder their catalytic activity. Herein, we present a novel approach to address this issue by rationally tailoring well-ordered g-C3N4 nanorods (CNR) through molten salt-assisted anti-defect engineering. The resulting highly crystalline CNR demonstrates high efficiency in the artificial photosynthesis of H2O2. Experimental results indicate that enhancing the crystallinity of g-C3N4 while reducing the defect concentration effectively promotes charge separation and transport. As a result, it exhibits a remarkable H2O2 generation rate of 1.58 mmol g-1h−1 using air as the oxygen source, accompanied by an apparent quantum yield of 18.00 % (λ = 400 nm). The excellent photocatalytic performance of CNR surpasses that of all previously reported pristine g-C3N4 materials. This work sheds light on the effectiveness of molten salt-assisted anti-defect engineering in improving catalyst activity, with potential applications in solar cells, sensor devices and other catalytic systems.

Regulating interfacial coupling of 1D crystalline g-C3N4 nanorods with 2D Ti3C2Tx MXene for boosting photocatalytic CO2 reduction

Two-dimensional (2D) layered photocatalysts coupled with 2D Ti3C2Tx (T = OH, O, or F) MXene cocatalysts in 2D/2D configuration have been extensively studied for use in artificial photosynthesis. Unfortunately, the overall photoreaction efficiency of these cocatalysts is often limited by weak 2D/2D interfacial van der Waals interactions, high interfacial electrostatic barriers, and slow interfacial charge transfer. In this study, 1D crystalline g-C3N4 (CCN) nanorods are grown along the c-axis using the molten-salt method and assembled onto a 2D Ti3C2Tx substrate by freeze-drying-assisted interfacial coupling, forming a unique Schottky junction photocatalyst in a 1D/2D configuration with interfacial hydrogen bonds. Transfer of photoelectrons in the CCN nanorods could along the radial π-conjugated plane to the hydrogen-bonded 2D Ti3C2Tx in the 1D/2D configuration is more efficient than the slow interlayer charge transfer in catalysts with a conventional 2D/2D configuration. Consequently, the optimized 1D-CCN/2D-Ti3C2Tx hybrid photocatalyst assembled by freeze-drying (TC/CCN-FD) exhibited an outstanding photocatalytic CO2 reduction activity at a rate of 2.13 μmol g1 h1, being 5.6 and 8.9 times more efficient than the pristine 1D CCN and 2D bulk g-C3N4 counterparts, respectively. Moreover, the selectivity towards the multielectron reduction product (CH4) was significantly enhanced over TC/CCN-FD owing to the faster interfacial charge transfer across the CCN/Ti3C2Tx interface and the higher density of photoelectrons on the Ti3C2Tx cocatalysts. This work will inspire further studies on suppressing the interfacial charge transfer barrier by matching the interfacial crystal orientation and strengthening the interfacial interactions.

Preparation of high-crystalline and non-metal modified g-C3N4 for improving ultrasound-accelerated white-LED-light-driven photocatalytic performances

As a non-metallic organic semiconductor, graphitic carbon nitride (g-C3N4) has received much attention due to its unique physicochemical properties. However, the photocatalytic activity of this semiconductor faces challenges due to factors such as low electronic conductivity and limited active sites provided on its surface. The morphology and structure of g-C3N4, including macro/micro morphology, crystal structure and electronic structure can affect its catalytic activity. Non-metallic heteroatom doping is considered as an effective method to tune the optical, electronic and other physicochemical properties of g-C3N4. Here, we synthesized non-metal-doped highly crystalline g-C3N4 by one-pot calcination method, which enhanced the photocatalytic activity of g-C3N4 such as mesoporous nature, reduced band gap, wide-range photousability, improved charge carrier recombination, and the electrical conductivity was improved. Hence, the use of low-power white-LED-light illumination (λ ≥ 420 nm) and ultrasound (US) irradiation synergistically engendered the Methylene Blue (MB) mineralization efficiency elevated to 100% within 120 min by following the pseudo-first-order mechanism under the following condition (i.e., pH 11, 0.75 g L−1 of O-doped g-C3N4 and S-doped g-C3N4, 20 mg L−1 MB, 0.25 ml s−1 O2, and spontaneous raising temperature). In addition, the rapid removal of MB by sonophotocatalysis was 4 times higher than that of primary photocatalysis. And radical scavenging experiments showed that the maximum distribution of active species corresponds to superoxide radical {mathrm{O}}_{2}^{cdot-}. More importantly, the sonophotocatalytic degradation ability of O-doped g-C3N4 and S-doped g-C3N4 was remarkably sustained even after the sixth consecutive run.

P, K doped crystalline g-C3N4 grafted with cyano groups for efficient visible-light-driven H2O2 evolution

Graphitic carbon nitride (g-C3N4), especially in heptazine forms, has long been considered as a promising non-toxic, benign and sustainable photocatalyst for producing the important chemical and potential green energy H2O2. However, bulk g-C3N4 shows moderate activity originated from its intrinsic drawbacks such as restricted visible-light harvesting ability and sluggish charge separation. Herein, a co-modified crystalline g-C3N4 by P, K ions and cyano group was successfully synthesized via co-thermal polymerization of precursors followed by molten salt treatment. The advanced g-C3N4 exhibits an outstanding photocatalytic H2O2 generation yield of 4424 μmol g−1h−1, more than 81-fold of the pristine counterpart, also superior than that of g-C3N4 processed by single modification treatment. This superior photocatalytic H2O2 evolution efficiency is attributed to the rational design of crystalline g-C3N4, enabling super visible photons capture, more efficient charge carries separation and substantially reduced charge recombination. The current work may furnish an integratable strategy for solar fuel production.