g-C3N4 Layer Research Articles

Fabrication of novel flower-like Sr3(VO4)2 anchored on g-C3N4: Visible-light-triggered degradation of organic contaminants

ABSTRACT Herein, designing of sustainable flower-like novel Sr3(VO4)2/g-C3N4 (SrVO/CN) nanocatalyst was successfully fabricated by easier hydrothermal method and utilised as a visible-light-driven for the degradation of methylene blue (MB) dye and ciprofloxacin (CF) antibiotic for the first time. The physicochemical behaviour of the nanocomposite was confirmed by various analytical techniques. These results confirm the successive development of flower-like Sr3(VO4)2 anchored on the g-C3N4 layer. The SrVO/CN can serve as an excellent catalyst for the decomposition of MB dyes and CF drugs under visible light irradiation. The results from UV-Vis spectroscopy evidently showed that the catalytic efficiency of SrVO/CN nanocomposite is higher than pure Sr3(VO4)2 nano-flowers. The SrVO/CN nanocomposite explores degradation efficiency of about 88.20% and 92.50% for MB and CF drug respectively. Furthermore, the stability and recycle behaviour of the SrVO/CN nanocomposites exhibit excellent effects. Hence, as prepared SrVO/CN behave as an example of the ‘Killing of two birds with one arrow’ approach.

Facile ball-milling synthesis of WO3/g-C3N4 heterojunction for photocatalytic degradation of Rhodamine B

Novel Z-scheme WO3/g-C3N4 heterojunction was prepared by hydrothermal method combining ball milling. The degradation of Rhodamine B dye was used to evaluate the photocatalytic activity. The results showed that WO3/g-C3N4 composites synthesized by ball milling method exhibited the highest degradation efficiency of 95.5% than pure WO3 (7.4%), bulk g-C3N4 (45.6%) and other WO3/g-C3N4 composites (53.0%). The enhancement of the photocatalytic activity may be attributed to the higher specific surface area caused by ball milling and the formation of the Z-scheme heterojunction between g-C3N4 layers and WO3 nanosheets which could promote the separation and transfer of photogenerated electron-hole pairs.

Enhanced photo-electrochemical response of screen-printed electrodes based on g-C3N4 hollow spheres and other morphologies for sensing applications

In this work, graphite-like carbon nitride (g-C3N4) materials were synthesized with different morphologies including bulk, fibers, sheets and hollow spheres, and their photo-electrocatalytic behaviors compared face-to-face. Thereafter, g-C3N4 materials were deposited on ITO substrates for the development of four photo-electrochemical sensing platforms. A systematic characterization evidenced the shape, surface area, crystal structure, composition, electronic structure, photophysical behavior and electrocatalytic activity contributions on an integral photo-electrochemical response. The voltammetric and amperometric results revealed a higher photo-electrocatalytic activity of the electrodes containing hollow spheres compared to other morphologies, with signals up to three orders of magnitude more intense when H2O2 was used as a molecule probe. Those electrodes also showed current responses up to 20-fold more intense under UV-light irradiation compared to measurements in darkness. The response intensification was attributed to a synergic contribution of i) superior adsorption and diffusion processes on the inner and outer faces of hollow spheres, ii) narrowed bandgap that allows extended absorption to the visible-light range with dramatically enhanced light-harvesting capability, iii) decreased recombination of the photogenerated electron-hole pairs, and iv) the presence of more abundant cyano (CN) functional groups which promotes interactions with small target analytes and catalyze some redox reactions. Thereby, morphology modulation resulted in a crucial strategy for improving the photo-electrochemical response of electrodes containing layered g-C3N4 materials. These results support the development of innovative substrates as signal-transducers for improved sensing applications.

Facile preparation of visible light-sensitive layered g-C3N4 for photocatalytic removal of organic pollutants

The graphite-phase carbon nitride (g-C3N4) photocatalytic materials were prepared by one-step calcination method to degrade methylene blue (MB) and potassium butyl xanthate (PBX) under visible light irradiation. The prepared g-C3N4 photocatalytic materials were investigated in detail by various characterizations, and the experiments showed that the graphitic phase carbon nitride photocatalytic materials were successfully prepared by the one-step calcination method. The material possesses excellent optical properties and strong visible light absorption, thus achieving photocatalytic degradation of MB and PBX. The catalyst dosage, pH, the initial concentration of pollutants have important effects on photocatalytic activity of MB and PBX. The photocatalytic degradation efficiency was 98.99% for MB and 96.83% for PBX under the optimal conditions (catalyst dosage, initial pollutant concentration and pH value were 500 mg L−1, 20 mg L−1 and 7, respevtively). The photocatalytic mechanisms on MB and PBX were elucidated. ·OH was the key specie for MB, while ·O2− was the key specie for PBX. This study advances the development of photocatalytic technology for mineral wastewater.

Surface Coating of NCM-811 Cathode Materials with g-C3N4 for Enhanced Electrochemical Performance.

Li(Ni0.8, Co0.1, Mn0.1)O2 (NCM-811) cathode materials have been commercialized recently, aiming to increase the specific capacity and specific energy of the lithium-ion battery for practical applications in electric vehicles. The surface coating has been proved to be an effective approach for the stabilization of NCM-based cathodes, which could reduce the structural instability and prevent surface reactions between the cathode materials and electrolytes. Herein, we demonstrate the facile synthesis of graphitic carbon nitride (g-C3N4)-coated NCM cathodes with both the sonication-assisted liquid exfoliation method (g-C3N4NS@NCM-811) and chemical vapor-assisted coating method (g-C3N4@NCM-811). It is discovered that coating with a thin g-C3N4 layer could reduce the impedance of the NCM-811 cathode material, as well as increase the cycle stability of the cathode material, leading to increased capacity retention from 130 mA h/g (for the pristine sample) to 140 mA h/g after 225 cycles. While the coating of thick g-C3N4 nanosheets could hinder the lithium intercalation, resulting in significant loss of specific capacity. This study paves the way toward practical applications of the g-C3N4-coated NCM-811 cathode materials.

Enhanced boron modified graphitic carbon nitride for the selective photocatalytic production of benzaldehyde

Graphitic carbon nitride is a non-metal photocatalyst easily prepared from nitrogen organic compounds through green synthesis processes that do not require the use of solvents. This work proposes the use of boron to modify the layered g-C3N4 structure by incorporating B to induce defects aimed at the enhancement of the photocatalytic activity. Boron-modified graphitic carbon has been obtained using elemental B and NaBH4 as precursors. The XRD and FTIR characterization results suggest that the C and N positions of g-C3N4 can be replaced by B, resulting in a layered modified structure in which the tri-s-triazine units are altered. The exchange of B atoms differed from the boron precursor according to the analysis of the chemical properties of the surface. Thus, the elemental B had a preference to exchange positions with N atoms, whereas the use of NaBH4 led to the substitution of B into the C positions. This difference considerably affected the photocatalytic activity during the selective oxidation of benzyl alcohol. The sample modified with NaBH4 led to the highest oxidation rate and selectivity linked to a lesser recombination effect than the other samples according to photoluminescence tests. This work provides evidence about the convenience of the selection of precursors during the modification of g-C3N4. The photon absorbance rate was determined for the estimation of the quantum yield. Although the photon absorbance rate was quite similar in all the cases, the different registered kinetics led to a maximum quantum efficiency of 0.15% for NaBCN.

LDHs-based bifunctional electrocatalyst for effective tunable syngas generation via CO2 reduction

Electrocatalytic reduction of CO2 into syngas (CO and H2) has been recognized to be a promising approach to achieve carbon neutrality. However, producing syngas with tunable H2/CO ratios in a wide range is still challenging. Herein, nitrogen doped graphene aerogel (GA) supported both single-atomic Ni and Ni nanoparticles (NPs) with a surface atomic ratio of 1.11 were constructed by using layered double hydroxide (LDHs) and g-C3N4 as Ni and N precursors, respectively. H2 and CO are the only products of CO2 electroreduction and the ratio of H2/CO can be tuned from 0.4 to 2.5 by changing applied potentials. In addition, the catalyst exhibits a large CO Faradaic efficiency (74%) and good long-term stability (12 h) at a relatively small potential (−0.67 V vs. RHE). This study will shed a new light on the construction of bifunctional catalysts for efficient tunable syngas generation via electroreduction of CO2.

High-efficiency photoreduction of CO2 to solar fuel on alkali intercalated Ultra-thin g-C3N4 nanosheets and enhancement mechanism investigation

The visible-light photocatalytic reduction of CO2 becomes a vital breakthrough to alleviate the greenhouse effect and achieve carbon neutrality. In this paper, ultrathin g-C3N4 nanosheets of 1.74 nm were constructed, and K+ was successfully doped between layers. The yields of CO and CH4 are 1.65 μmol·g−1·h−1 and 0.15 μmol·g−1·h−1, which are 4.70 and 7.27 times higher than the original g-C3N4, respectively. The ultra-thin nano-lamellar structure shortens the carrier transmission distance, and the intercalation of K+ not only promotes the electron transport between g-C3N4 layers but also changes the original hybrid mode of the catalytic system, thus shortening the band gap and adjusting the energy band structure.In addition, the CO2 adsorption center of the K+ intercalated g-C3N4 is transferred from the coordinated carbon atom to the center of the triazine unit, and the binding energy is obviously increased, which strengthens the CO2 adsorption. Finally, through in-situ DRIFT characterization, it is speculated that the reaction enhancement mechanism is that the modified catalyst promotes the adsorption and activation of CO2, resulting in the production of more intermediates, especially more hydrocarbon intermediates, which is more conducive to the photocatalytic reduction of CO2.

CsPbBr3 perovskite based tandem device for CO2 photoreduction

The design of efficient photocatalytic devices is of great significance to achieve low-cost carbon dioxide reduction into solar fuels. Herein, directional charge-carrier migration is realized by introducing a CO2 reduction device with a tandem structure made up of g-C3N4 and an inorganic lead-perovskite (CsPbBr3). This photocatalytic device shows a significantly increased CO2 photoreduction rate in a humid gaseous CO2 system when compared to the parental g-C3N4 layer. This “full artificial photosynthesis” thereby generates fuel molecules and oxygen from water and CO2, only, without any co-catalysts or sacrificial agents. To our surprise, the device maintains greater than 90% of the CO production yield after 5 days continuous irradiation. The existence of internal electric field is confirmed, which drive the directional movement of photogenerated charge-carriers with the perovskite being reductive, while the carbon nitride with its enormous oxidation stability is covering the oxidation processes. This represents a promising possibility for the practical application of CO2 photoreduction with scalable devices.

An efficient and robust chain-mail electrocatalyst Ni2P @ g-C3N4 for oxygen evolution in alkaline solution

The development of an efficient, durable and inexpensive catalyst for electrocatalytic water splitting is a daunting challenge and has attracted the interest of a large number of researchers. In this study, a novel oxygen evolution reaction (OER) electrocatalyst based on graphitic carbon nitride (g-C3N4) layers encapsulated with Ni2P nanoflowers (Ni2P @ g-C3N4) is synthesized, which exhibits low overpotentials of 237 mV for OER at 10 mA cm−2 and remarkable stability. The combination of the reactive Ni2P core and the chain-mail material is an important reason for the excellent electrocatalytic performance. The robust g-C3N4 chain-mail protects the internal transition metal phosphides (TMPs) core from the harsh reaction environment, and well balances the catalytic activity and stability. As the core of the catalyst, the encapsulated Ni2P nanoflower core can transport electrons to the surface of the chain-mail layer. Our work demonstrates an efficient and robust Ni-based chain-mail electrocatalyst and provides a novel prospect for the development of the electrocatalyst.

A Highly Efficient Photocatalyst Based on Layered g-C3N4/SnS2 Composites

Background: In this report, the layered g-C3N4/SnS2 composite was successfully fabricated by a facile hydrothermal route. Methods: The ultraviolet-visible spectroscopy data presented that such layered g-C3N4/SnS2 catalysts showed a remarkable visible-light absorption, hence significantly enhancing the catalytic activity. Particularly, the g-C3N4/SnS2 catalysts showed an outstanding catalytic performance for the degradation of methylene blue (~ 98.1%) under visible light irradiation that is much better than that of pure SnS2 (~ 86.7%) and pure g-C3N4 (~ 67.3%). Results: The remarkable photocatalytic performance is ascribed to its layer structure resulting in a large surface area, which not only improves the ion transfer rate but also provides abundant surface reaction sites. Conclusion: Our work demonstrates that the layered g-C3N4/SnS2 can be considered as an exceptional candidate for a highly-efficient photocatalyst.

Flower-like titanium dioxide as novel co-reaction accelerator for ultrasensitive “off–on” electrochemiluminescence aptasensor construction based on 2D g-C3N4 layer for thrombin detection

Flower-like titanium dioxide as novel co-reaction accelerator for ultrasensitive “off–on” electrochemiluminescence aptasensor construction based on 2D g-C3N4 layer for thrombin detection

In situ-grown ZnO particles on g-C3N4 layers: a direct Z-scheme-driven photocatalyst for the degradation of dye and pharmaceutical pollutants under solar irradiation

In situ-grown ZnO particles on g-C3N4 layers: a direct Z-scheme-driven photocatalyst for the degradation of dye and pharmaceutical pollutants under solar irradiation

Cooperative effects of zinc–nickel sulfides as a dual cocatalyst for the enhanced photocatalytic hydrogen evolution activity of g-C3N4

ZnS−NiS2/g-C3N4 ternary composites were synthesized via a thermal polymerization and post co-deposition−sulfidation method. The decoration of g-C3N4 layers with ZnS−NiS2 nanoparticles extended visible light absorption and promoted the separation and transfer of photo-generated charge carriers. The photocatalytic performance of the ZnS−NiS2/g-C3N4 composites was evaluated by the visible-light-driven hydrogen evolution. Briefly, compared to g-C3N4, ZnS/g-C3N4, and NiS2/g-C3N4, the hydrogen evolution rate on ZnS−NiS2/CN(0.4) was separately increased by 31, 31, and 1 times, highlighting the synergistic effect of ZnS and NiS2. The interface between ZnS and g-C3N4 modified the charge separation and transfer process. Meanwhile, NiS2 with a Pt-like behavior acted as an electron acceptor to facilitate transfer photoelectrons and to provide active sites for proton reduction. This work will offer new insight into improving g-C3N4-based photocatalysts with mixed metal sulfides for efficient hydrogen evolution.

Continuous g-C3N4 layer-coated porous TiO2 fibers with enhanced photocatalytic activity toward H2 evolution and dye degradation.

TiO2/g-C3N4 composite photocatalysts with various merits, including low-cost, non-toxic, and environment friendliness, have potential application for producing clean energy and removing organic pollutants to deal with the global energy shortage and environmental contamination. Coating a continuous g-C3N4 layer on TiO2 fibers to form a core/shell structure that could improve the separation and transit efficiency of photo-induced carriers in photocatalytic reactions is still a challenge. In this work, porous TiO2 (P-TiO2)@g-C3N4 fibers were prepared by a hard template-assisted electrospinning method together with the g-C3N4 precursor in an immersing and calcination process. The continuous g-C3N4 layer was fully packed around the P-TiO2 fibers tightly to form a TiO2@g-C3N4 core/shell composite with a strong TiO2/g-C3N4 heterojunction, which greatly enhanced the separation efficiency of photo-induced electrons and holes. Moreover, the great length–diameter ratio configuration of the fiber catalyst was favorable for the recycling of the catalyst. The P-TiO2@g-C3N4 core/shell composite exhibited a significantly enhanced photocatalytic performance both in H2 generation and dye degradation reactions under visible light irradiation, owing to the specific P-TiO2@g-C3N4 core/shell structure and the high-quality TiO2/g-C3N4 heterojunction in the photocatalyst. This work offers a promising strategy to produce photocatalysts with high efficiency in visible light through a rational structure design.

An insight into the bridging role of Co3O4 in MOF-derived binary metal oxide modified sheet-like g-C3N4 for photo-assisted peroxymonosulfate activation

Structurally complementary MOF-derived binary metal oxide modified layered g-C3N4 is synthesized by hydrothermal treatment and co-pyrolysis. This article focuses on exploring the synergy of photocatalysis and PMS activation mediated by Co3O4.

Developing controllable mesoporous CoTiO3/C3N4 heterostructures for enhanced photocatalytic performances

Excellent charge carrier kinetics and high light absorption capability are key factors in increasing photocatalytic efficiency. Here, novel mesoporous CoTiO3/g-C3N4 heterostructures at varying CoTiO3 percentages were synthesized utilizing an easy soft and hard template approach for the degradation of acridine orange (AO) under visible light exposure. The TEM images exhibited irregular nanocrystals containing stacked g-C3N4 layers with crimped nanosheets, and spherical CoTiO3 NPs (10 nm) were uniformly distributed throughout the g-C3N4 layers. The results indicated that the mesoporous 3%CoTiO3/g-C3N4 heterostructure exhibited the highest degradation of AO dye (100%) within 60 min compared to g-C3N4 (10%) and CoTiO3 (18%). Furthermore, the 3% CoTiO3/g-C3N4 heterostructure had a better degradation rate, approximately 10.75- and 6.93-fold larger than those of g-C3N4 and CoTiO3 NPs, respectively. The enhanced mesoporous CoTiO3/g-C3N4 exhibited effective photoinduced carrier separation, a widened light harvesting range, and synergistic effects. Additionally, the 3% CoTiO3/g-C3N4 heterostructure revealed superior photocatalytic stability in AO dye recycling degradation for long-life regeneration. A direct Z-scheme mechanism was suggested for the degradation of AO dye over mesoporous CoTiO3/g-C3N4, and it was further supported by photoluminescence (PL) spectroscopy and photoelectrochemical responses. The present work demonstrates new insight and an approach to synthesizing mesoporous CoTiO3/g-C3N4 heterostructures for various potential applications.

The critical role of surface area optimization in carbon quantum dots modified g-C3N4 for photocatalytic enhancement

G-C3N4 has shown great potential in photocatalytic degradation. However, the layered structure of g-C3N4 may prevent the contaminant adhesion in the interlayers, which greatly limited its active surface area for photocatalysis. Herein, a simple and fast hydrothermal process was optimized: with appropriate synthesis temperature, carbon dots dispersed into the interlayer of g-C3N4 without destroying the frame structure, opened the layer distance of g-C3N4, enlarged its surface area by 3.56 times, and enhanced its photoresponse and photoredox capacity significantly. Excellent photocatalytic activities were observed towards organic dyes Rhodamine B (RhB). This work provides a new approach to optimize the layered g-C3N4 via surface area modification, which enhanced the design and fabrication of a g-C3N4-based photocatalyst.

Phosphate group-mediated carriers transfer and energy band over carbon nitride for efficient photocatalytic H2 production and removal of rhodamine B

The development of effective methods that simultaneously regulate energy bands and electron transfer to realize high photocatalytic performance of graphitic carbon nitride (g-C3N4) remains a major challenge. Herein, we developed a novel strategy to construct a phosphate-group-intercalated g-C3N4 nanosheet photocatalyst that is driven by visible light. A series of characterizations confirmed that phosphate groups were inserted between the g-C3N4 layers and formed a vertical channel. A porous ultrathin nanosheet structure was formed. The synergistic effect of the phosphate-group intercalation and porous ultrathin nanosheet structure endowed this material with controllable electronic structures and upshifted the conduction bands, while facilitating photogenerated charge transfer and providing numerous active reactive sites. As a result, the g-C3N4 intercalated with phosphate groups photocatalyst exhibited high photocatalytic activity for H2 evolution and degradation of a coloured dye rhodamine B (RhB) under visible light. The maximum H2 production rate and degradation rate constant of the phosphate-group-intercalated g-C3N4 nanosheets (CNP-5) were 17-fold and 6-fold higher than those of primal g-C3N4, respectively. This study provides new insights for the incorporating atomic groups with modification effects and represents a giant leap in the construction of two-dimensional (2D) materials.

Bismuth-doped g-C3N4/ZIF-8 heterojunction photocatalysts with enhanced photocatalytic performance under visible light illumination

ABSTRACT In this work, g-C3N4/ZIF-8 heterojunction photocatalysts were synthesised by the process by which the metal-organic framework ZIF-8 nanoparticles were grown onto the g-C3N4 layer in situ. Bismuth element was doped into the as-prepared g-C3N4/ZIF-8 material and a new type of Bi@g-C3N4/ZIF-8 composite photocatalysts was manufactured, in which the doping element acts in adjusting the bandgap in the photocatalysts. The prepared photocatalysts were characterised by XRD, FESEM, TEM, FTIR, XPS, UV–VIS DRS, photoluminescence and photo-electrochemical experiments. The results show that the ZIF-8 nanoparticles grown in situ were well-formed onto the g-C3N4 layer, and bismuth was evenly doped into the gaps of the g-C3N4/ZIF-8 framework. The degradation rate of methylene blue by CNZ-1.5(Bi)-12, which was a photocatalyst composed of 12% Bi-doped with g-C3N4/ZIF-8 material (the mass ratio of g-C3N4: ZIF-8 = 1:1.5), reached 86.6% under visible light irradiation within 60 min. The free radical scavenging experiment and electron spin resonance spectroscopy showed that was the main active substance. Bismuth doping into the photocatalytic system promotes the excitation of electrons from the valence band to the conduction band and provides a good channel for the transmission of photogenerated carriers as well. It is achieved that intensive visible light absorption, the enhanced separation efficiency of photogenerated carriers, and excellent thermal stability and high recyclability in the novel composite photocatalyst, owing to the synergistic effect of the introduced bismuth with the heterostructure of g-C3N4/ZIF-8. Therefore, the synthesised Bi@g-C3N4/ZIF-8 heterojunction photocatalysts may be used as a good photocatalyst for purifying and degrading organic matter in sewage.