Ultrathin g-C3N4 Research Articles

Exfoliated Porous Carbon Nitride by Simultaneous Oxidation-Corrosion for Photocatalytic H2O2 Production and Organic Degradation.

Graphitic carbon nitride (g-C3N4) is a fascinating material with potential applications in photocatalysis due to its good chemical stability, high thermal stability, and relative ease of synthesis. In this work, ultrathin g-C3N4 is constructed using a hybridized method, which combines the advantages of thermal and liquid-phase stripping methods. This sample can improve performance in degrading organic pollutants several times, and the highest enhancement efficiency occurs in an alkaline environment. In addition, photocatalytic production of hydrogen peroxide can be increased to 2.6 times that of the bulk sample. These improved properties are due to the increase in specific surface area, the generation of free radicals, and adsorption capacity. This work presents a one-step exfoliation method for bulk g-C3N4 for more surface-active sites and strong redox capacity.

Engineering Dual Carbon and Nitrogen Vacancies in g-C3N4 for Enhanced Photodegradation of Tetracycline Hydrochloride.

Ultrathin g-C3N4 nanosheets with specific nitrogen vacancies and combined carbon and nitrogen dual vacancies were created by annealing g-C3N4 under different atmospheric conditions. The nanosheets with dual vacancies showed significant improvements in the photodegradation of tetracycline hydrochloride (TC-HCl) compared with both the pristine g-C3N4 and its nitrogen-deficient version. Various techniques, such as Raman spectroscopy, electron spin resonance (ESR), X-ray photoelectron spectroscopy, wavelength-dependent studies, electrochemical methods, and photoluminescence measurements, were used to identify vacancy defects, revealing that performance enhancement was particularly notable under visible light. Density functional theory calculations indicated that dual vacancies introduced a shallow defect state above the valence band, enhancing visible light absorption and reducing electron-hole pair recombination. Conversely, nitrogen vacancies alone formed a deep defect state, which extended light absorption but potentially trapped photoelectrons, limiting their contribution to photoreactions. Radical-scavenging experiments and ESR spin-trap spectra identified the superoxide radical (·O2-) as the primary reactive oxygen species responsible for TC-HCl degradation. A comprehensive degradation pathway for TC-HCl was proposed using liquid chromatography-mass spectrometry data. This research highlights a strategic approach to boost TC-HCl photodegradation by engineering the vacancies in g-C3N4.

Synergy of S doping and defect construction in holey ultra-thin g-C3N4 nanosheets for improved photocatalytic hydrogen production from water

Combining the advantages of multiple strategies including morphology control, atom doping, and defect construction, the photocatalytic hydrogen evolution reaction (HER) performance of graphitic carbon nitride (g-C3N4) may be boosted significantly. Herein, holey ultra-thin g-C3N4 nanosheets (CNS-x, x = H, O, N) modified with structural vacancies and sulfur (S) dopant are synthesized through a straightforward method involving the pyrolysis of thiocyanuric acid under various gas atmospheres. The textural properties, type and concentration of structural defect, and S doping level are significantly influenced by the gas atmosphere. Remarkably, CNS-H with C, N dual defects and S-dopant exhibits the HER rate of 46.59 mmol·g−1·h−1, which is 16.68 times higher than that of bulk g-C3N4. The corresponding apparent quantum yields are 17.24 % at 420 nm and 1.90 % at 520 nm. The enhanced HER performance of CNS-H can be attributed to the combined effect of improved charge separation, extended photoabsorption, and optimized properties of the platinum cocatalyst.

The effect of co-modification of ultrathin g-C3N4 nanosheets with Ag and S on photocatalytic hydrogen production

The technology of photocatalytic water splitting holds immense potential for hydrogen (H2) generation. However, its development is hindered by a lack of active sites and low efficiency of photogenerated carriers. In this study, Ag-S-CN ultrathin nanosheets were successfully fabricated by co-modification of graphitic carbon nitride (CN) with silver (Ag) and sulfur (S). S doping within the CN layers broadened light absorption and provided additional reaction sites, while the incorporation of Ag into the CN interlayers enhanced the migration rate of photogenerated carriers between adjacent layers via Ag-S bonds. Consequently, the 0.05 Ag-S-CN photocatalyst achieved a high H2 yield of 0.93 mmol g-1 h-1 without requiring any additional cocatalyst, which is approximately 23.25 and 10.33 times higher than that of CN and S-CN, respectively. This work presents an effective strategy for developing highly efficient photocatalysts.

Edge functionalized with benzenesulfonyl groups of g-C3N4 nanosheets as a highly efficient photocatalyst for water purification

Photocatalytic water purification is a promising method for environmental remediation, but it is greatly hindered by the rapid charge carrier recombination behavior of the photocatalysts. Herein, a simple wet-chemical method is developed for grafting electron-withdrawing benzenesulfonyl groups at the edges of g-C3N4 nanosheets. These exhibited a superior and versatile photocatalytic performance on the degradation of organic contaminant, as well as disinfected Escherichia coli (E. coli) bacteria under visible light illumination. Systematic studies reveal that the grafting of benzenesulfonyl groups led to the synergic effect in ultrathin g-C3N4 nanosheets of enhancing the photogenerated charge carrier separation on surface, improving light absorption, changing electronic band structure, and causing surface charge redistribution, all of which are beneficial for enhancing the photocatalytic performance. Notably, these edge-activated g-C3N4 photocatalysts also demonstrate remarkable photocatalytic activity in the real tap water and urban wastewater, indicating their promising potential for application in real wastewater treatment.

Ag2Se nanoparticles anchored on S-g-C3N4 nanosheets towards efficient photocatalytic tetracycline hydrochloride removal and H2 generation

To improve the stability of Ag based co-catalysts and to increase the photocatalytic performance of graphitic carbon nitride (g-C3N4), Ag2Se nanoparticles were grown onto superior thin sulfur-doped g-C3N4 nanosheets which was fabricated via two-step thermal polymerization at high temperature. Ultrathin S-doped g-C3N4 nanosheets were prepared via two-step thermal polymerization using melamine and thiourea. The ratios of Ag2Se were adjusted to fabricate a series of Ag2Se/S-g-C3N4 (Ag2Se/SCN) composite samples by controlled solvothermal synthesis. S-doping plays an important role in mono-dispersion of Ag2Se nanoparticles on S-g-C3N4 nanosheets because of the control of growth sites. The photocatalytic removal of tetracycline hydrochloride test indicates that sample Ag2Se/SCN-3 with Ag2Se loading of 3 % reveals the best removal effect, in which tetracycline hydrochloride of 60 % is removed within 60 min. Photocatalytic hydrogen generation test results without co-catalyst addition demonstrate that sample Ag2Se/SCN-3 exhibits the best H2 evolution rate of 2116.35 μmol·g−1·h−1, which is 3.8 times of that of pure carbon nitride. The photocatalytic mechanism tests suggest that Schottky heterojunctions are formed in the Ag2Se/S-g-C3N4 composites. The formation of Schottky heterojunctions improved the separation efficiency of photogenerated charge carriers. The incorporation of Ag2Se nanoparticles (as the co-catalyst) on S-g-C3N4 nanosheets is the key for drastically improving the photocatalytic performance and eliminating the use of Pt co-catalyst during the photocatalytic processes.

Photocatalytic reduction of the uranium(Ⅵ) by ultra-thin porous g-C3N4 nanosheets synthesized via microwave-assisted

Graphitic carbon nitride (g-C3N4) has garnered significant attention in the realm of photocatalytic reduction of U(Ⅵ) from aqueous solutions owing to its favorable bandgap and visible light responsiveness. Nevertheless, conventionally prepared bulk g-C3N4 suffers from limitations such as a small specific surface area and high recombination of photo-generated charges, consequently impeding the efficiency of photocatalytic reactions and hampering practical applications. To address these shortcomings, this study presents a novel approach wherein ultra-thin porous g-C3N4 nanosheets were successfully synthesized through the microwave-assisted calcination of urea in a single step. The resulting g-C3N4 nanosheets exhibit a multi-hollow mesh structure with a significantly enlarged specific surface area, the specific surface area and pore size of MCN90 are 170 m²/g and 17 nm, respectively, which are 2.3 times and 8 times that of the bulk g-C3N4. Photocatalytic experiments revealed that these ultra-thin porous nanosheets demonstrate superior performance in the reduction of U(Ⅵ) to U(Ⅳ), achieving a reduction rate of 100 % within 20 minutes for the optimal sample, as opposed to 78 % in 40 minutes for bulk g-C3N4. This enhanced photocatalytic activity can be primarily attributed to the unique ultra-thin porous nanosheet structure, which facilitates increased specific surface areas, improve photoelectric properties, and substantially shortened electron migration distances which reduce the recombination efficiency of photogenerated electrons and holes pairs. Consequently, these findings not only offer insights into the optimization of g-C3N4 for U(Ⅵ) reduction but also provide a valuable reference for the preparation of other two-dimensional ultra-thin porous materials aimed at similar applications.

Vacancies engineering in ultrathin porous g-C3N4 tubes for enhanced photocatalytic PMS activation for imidacloprid degradation

Precise morphology and vacancy engineering is a promising strategy to enhance the degradation performance of refractory contaminants in photocatalysis coupling peroxymonosulfate activation (PC-PMS) systems. In this context, we developed ultrathin porous g-C3N4 tubes with three-coordinated nitrogen (Nb) vacancies between the heptazine units through hydrogen intercalated exfoliation and selective nitrogen removal at high temperatures. The ultrathin porous tubular architecture provides an ultrahigh-specific surface area with abundant exposed active sites, ensures effective mass transfer, and shortens the diffusion distance of photogenerated carriers. The Nb vacancies act as unsaturated sites, inhibiting the photogenerated carrier’s recombination and facilitating the adsorption/activation of O2 and its conversion to ∙O2– via photogenerated electrons. Then, the PMS is subsequently oxidated by photogenerated holes selectively producing 1O2. Together, these continuously released free radicals unlock the complete degradation of imidacloprid within 20 min in the PC-PMS system, with a degradation rate about 350 % higher than conventional g-C3N4 tubes and 10-fold that of pristine g-C3N4. This study provides a novel insight into the efficient utilization of photogenerated electron-hole pairs conversion to ∙O2– and 1O2 for the removal of pesticide contaminants through the rational design of photocatalysts in the PC-PMS system.

Piezoelectric assisted boosting photocatalytic hydrogen evolution over a finely prepared Pt/TiO2/g-C3N4 composite system using lactic acid as sacrificial agent

A one-step calcination method was employed to fabricate a new TiO2/g-C3N4(TCN) composite catalyst. The therein TiO2 nanoparticles with good dispersion were synthesized through a sol-gel method and followed by additional heat treatment. The ultra-thin and flat g-C3N4(CN) nanosheets were synthesized by calcining a mixture of urea and melamine. The obtained TCN exhibited significantly excellent performance, especially when 3 wt% Pt was added and lactic acid (HL) was used as a sacrificial agent, achieving a rate of 32.5 mmol/h/g. This improvement can be attributed to the uniform dispersion of nano TiO2 particles on g-C3N4, the flat ultra-thin layer structure of CN, and the constructed heterojunctions between two, which promote the separation of photogenerated electron-hole pairs. Measurements of PL and photocurrent response confirmed enhanced efficiency in interface charge separation and transfer. Additionally, it demonstrated lower internal resistance in EIS tests. Notably, owing to the piezoelectric properties of CN, when the reaction liquid was subjected to additional ultrasonic treatment, the hydrogen production rate further increased to 43.57 mmol/h/g and 2.9 mmol/h/g, respectively, in simulated sunlight and visible light response. The piezoelectric effect of CN induced by ultrasound regulated the bandgap width of the catalysts, broadening their response to visible light.

Potassium/cyano group co-incorporation promotes 2e− ORR selectivity in porous ultrathin carbon nitride for photocatalytic H2O2 production

Photocatalysis is a promising strategy for the production of H2O2, but the promotion of 2e− ORR selectivity remains a challenging goal in this field. Herein, Potassium (K+), cyano groups (-C≡N) and porous ultrathin structures were introduced into g-C3N4 simultaneously by the hyphenated technique of gas template method and molten salt-assisted method. The K+ and -C≡N can broaden the light absorption range, improve the reduction ability and promote electron transfer of the catalyst. Additionally, the presence of a permeable ultrathin structure plays a crucial role in improving the specificity of the 2e− oxygen reduction reaction (ORR). Benefiting from the multiple advantages, the H2O2 yield of K+ intercalated cyano-rich porous ultrathin g-C3N4 (KUCN) reached 781.39 μM with an extraordinary 2e− ORR selectivity of 94.5% (0.30 V vs. RHE). Overall, this study presents a practical approach for designing catalysts based on g-C3N4 that exhibit a high selectivity for the 2e− ORR reaction.

Metal Doped-MoS2/g-C3N4 Nanocomposites for Antibiotics Degradation with Photo-Fenton Reaction Process: Defect Engineering, Synergistic Effects, and Degradation Mechanisms

Currently, the energy crisis and environmental pollutions due to the growth of industrialization and urbanization become gradually a prominent and serious issue. Due to these reasons, we aimed to design photoactive metal-doped MoS2/g-C3N4 nanocomposites photocatalysts for the degradation of antibiotics. The degradation of organic pollutants with photocatalysis is considered as green, ecofriendly, economical, and promising methods. Herein, ultrathin g-C3N4 was prepared with simple method and combined with metal-doped MoS2 (Mg-doped MoS2) with varying the amounts of dopants. The prepared photocatalyst materials were tested for the degradation of ciprofloxacin in the photo-Fenton reaction process. The optimum amount of metal-doped MoS2/g-C3N4 nanocomposites photocatalysts showed enhanced catalytic performance and degrades 72% of ciprofloxacin while 52 and 48 % of degradations were achieved with MoS2 and g-C3N4 catalysts, respectively. Here, the key significant problems of the individual components were solved via synergistic effects in the photocatalytic degradation system. The results also offer an opportunity to enhance the electronic structures of the crystalline materials. Moreover, the metal-doping will also create defects on the MoS2 and improves the charge transfer ability of the photocatalyst. The results proved that the metal-doped MoS2/g-C3N4 nanocomposites photocatalysts could be a promising photo-Fenton catalyst system in the environmental remediation.

Synergistic Modulation of π-π* and n-π* Transitions by In Situ Phenol-Like Structure Integration for Efficiently Wide-Spectrum Hydrogen Production of Ultrathin Carbon Nitride.

2D carbon nitride nanosheets, exemplified by g-C3N4, offers significant structural benefits and enhanced photocatalytic activity. Nonetheless, the quantum confinement effect prevalent in nanoscale photocatalysts would result in an enlarged bandgap, potentially restricting the spectral absorption range and impeding improvements in photocatalytic efficiency. Here, a high-performance 2D photocatalyst with an extended spectral response is achieved by incorporating a novel phenol-like structure into the conjugated framework of ultrathin g-C3N4 nanosheet. This novel strategy features targeted pyrimidine doping to create a conjugated carbon zone in heptazine structure, offering a thermodynamically favorable pathway for hydroxyl functionalization during the annealing exfoliation process. Consequently, the π-π* transition energy in the material is significantly decreased, and the active lone pair electrons in phenol-like structure induces a new n-π* transition with notably enhanced absorption from 500 to 650nm. The optimized material shows a dramatic enhancement in photocatalytic activity, achieving ≈72 times than the activity of bulk g-C3N4, and demonstrating a measurable H2 production rate of 6.57µmol g-1 h-1 under 650nm light. This study represents a significant step forward in the strategic design of 2D photocatalysts, with tailored electronic structures that significantly boost light absorption and photocatalytic efficiency.

Revitalizing CO2 photoreduction: Fine-tuning electronic synergy in ultrathin g-C3N4 with amorphous (CoFeNiMnCu)S2 high-entropy sulfide nanoparticles for enhanced sustainability

Sustainability is a key issue in developing stable and efficient catalysts for solar-catalyzed CO2 conversion. The concept of structural stabilization by quenching the Gibbs free energy, which is achieved by increasing the configurational entropy level of the system, introduced high-entropy materials. However, because alloying immiscible multimetallic atoms into a unit system is still an arduous process, the potential of high-entropy materials has not yet been fully exploited. Surprisingly, although metal sulfide photocatalysts have an enviable reputation for CO2 photoreduction (CO2-PR) owing to their optical/electronic merits and more negative redox potential than other materials, the capability of high-entropy metal sulfides has been completely disregarded. Herein, an adaptable, self-templating metal alkoxide appropriately addresses the immiscibility of metallic constituents by the well-blended metal ions with polyalcohol in the metal glycerate. Consequently, (CoFeNiMnCu)S2 high-entropy metal sulfide nanoparticles (HEMS-Nps) were grown in situ on crossed ultrathin g-C3N4 (UCN) monolayers during the sulfidation of the metal glycerate. The as-synthesized HEMS-Np has a crystalline–amorphous structure, which is conducive to the acceleration of charge transfer to/from reaction sites, and a convincing orientation for CO2 adsorption. These features are combined with synergistic electronic multimetallic interactions, facilitating a heterogeneous valence electron distribution and atomic disorder. The CO2-PR power of the (CoFeNiMnCu)S2@UCN nanostructure was noticeable in realizing added-value products in both the liquid–solid (1063 µmol/g h of syngas and 250 µmol/g h of methane) and gas–solid phases (1883 µmol/cm2 h of syngas and 321 µmol/cm2 h of methane). To prove its utility, long-term and corresponding time-equivalent cycling experiments were conducted, demonstrating a highly stable system that endured for a long time. Overall, this approach simultaneously exploits the advantages of sulfide-based materials and high-entropy materials in stable structures to generate sustainable CO2-PR materials.

Fabrication and improved photocatalytic performance of 2D/0D structured g-C3N4/WO3 composite materials

In this work, WO3 quantum dots grow in situ on the synthesized ultra-thin g-C3N4 nanosheets, ultimately forming a type of tightly bound 2D/0D Z-type heterojunctions. It was found that WO3 quantum dots were closely combined with g-C3N4 nanosheets through SEM and TEM measurements. XRD, IR, and XPS characterization proved a g-C3N4/WO3 heterojunction material was formed. The construction of g-C3N4/WO3 heterojunctions enhanced visible light absorption, improved carrier separation efficiency, and reduced charge transfer resistance. Photocatalytic hydrogen production tests showed that the hydrogen production rate of 20% g-C3N4/WO3 composite materials was 2.8 times that of the original g-C3N4, and the hydrogen production amount within 3 h was 3.7 times that of the original g-C3N4. Photocatalytic degradation of Rhodamine B and 4-chlorophenol under visible light irradiation showed that compared with g-C3N4, the photocatalytic degradation efficiency of 20% g-C3N4/WO3 composite materials was enhanced. The results reveal that the special structured g-C3N4/WO3 composite materials have excellent photocatalytic activity, which can not only efficiently produce hydrogen but also efficiently degrade organic pollutants, providing an important reference for solving energy crises and environmental problems.

Construction of g-C3N4/Ti3CN MXene Schottky heterojunctions for boosting photocatalytic hydrogen production

Converting solar energy into clean hydrogen (H2) fuel via photocatalytic hydrogen production technology is a promising strategy for sustainable social development. Graphitic carbon nitride (g-C3N4) has attracted much attention due to its unique visible light activity and excellent tunable atomic structure. However, bulk g-C3N4 suffers from challenges such as sluggish charge carrier dynamics and limited active catalytic sites, resulting in lower solar-to-hydrogen conversion efficiency. Herein, we prepare defective ultrathin g-C3N4 nanosheets and subsequently construct 2D g-C3N4/2D Ti3CN MXene heterojunction via electrostatic-driven assembly. The optimized composite CM-2 exhibits the highest hydrogen evolution rate of 7630.5 µmol g−1 h−1. The increase in the hydrogen production rate is attributed to the effective coupling of two materials to form Schottky heterojunctions, which may inhibit the recombination of electron-hole pairs. Additionally, this work explores the pathway of electron transfer in Schottky photocatalyst, and further unveils the synergy of defects and built-in electric field in accelerating photo-induced charge transport as well as enhancing the hydrogen-evolving activity, thereby providing valuable insights for the rational design of highly efficient photocatalytic materials.

Manipulating the morphology and charge accumulation driven- Schottky functionalized type II-scheme heterojunction for photocatalytic hydrogen evolution and SERS detection

Inspired by energy conversion and sensing strategies, the construction of a type-II heterojunction proves advantageous in enhancing interfacial charge transfer, redox capabilities, and sensitive detection. Herein, we have developed as-prepared a hierarchical heteronanostructure composed of 2D ultrathin g-C3N4 (g-CN) nanosheets, 3D SrTiO3 (STO) nanocubes, and Ag plasmonic nanoparticles (NPs) with a well-controlled configuration and intimate contact for improved practical applications. This multifunctional heterojunction not only exhibits outstanding hydrogen evolution reaction (HER) performance but also shows excellent SERS detection. The creation of hybrid morphologies and type II schemes contributes to expanding visible light absorption and shortening the path of charge carrier transition. The ternary sample also exhibits an efficient photocatalytic HER rate of 9378 μmol g−1 h−1, which is 13.3 and 26.3 times higher than that of STO (703 μmol g−1 h−1) and g-CN (356 μmol g−1 h−1), respectively. Photoluminescence spectroscopy and linear sweep voltammetry (LSV) measurements suggest that the synergistic effect among g-CN nanosheets, STO nanocubes and Ag contributes to enhanced charge separation, as indicated by the applied potential of −0.9 V vs. saturated Ag/AgCl to obtain a photocurrent density of −15 mA cm−2 for the HER. The obtained STO/g-CN/Ag sample exhibits significant capability in enriching small molecules, facilitating the determination of organic pollutants even at ultralow concentrations. Additionally, it exhibits impressive SERS sensitivity and photocatalytic performance. Crystal Violet (CV) at low concentrations can be distinguished and undergoes almost complete degradation under visible-light illumination. The detection platform exhibits ultralow detection capability down to 10−10 M for CV. The outstanding SERS detection may be assigned to the combined enrichment abilities of g-CN, STO and the localized surface plasmon resonance (LSPR) of Ag NPs. Furthermore, the type-II heterojunction of the ternary photocatalyst and the mechanisms governing charge carrier flow and transfer on the conductive Ag co-catalyst were also investigated. This work provides novel insights and techniques for effectively engineering 3D STO-like semiconductors, facilitating both green energy production and the detection of trace molecules.

Construction of carbon and nitride double vacancy defects on ultrathin porous g-C3N4 nanosheets assisted by freeze-drying for enhanced photocatalysis

Graphitic carbon nitride based photocatalysts have been found extensive application in the degradation of antibiotics and organic pollutants. However, the insufficient of surface active sites and the low efficiency of photogenerated charge carriers separation hinder the development. Herein, ultrathin porous polymer carbon nitride nanosheets (PCNS-F) with carbon and nitride double vacancy defects were successfully fabricated. The facile freeze-drying step, following solvent-thermal treatment and preceding the thermal etching process, stands as a critical step for triggering vacancy generation and adjusting the carbon/nitride ratio. The optimized PCNS-F photocatalyst exhibits an ultrathin structure featuring a substantial abundance of defects in a porous state, resulting in exceptional structural characteristics (183.3 m² g-1, 0.84 cm³ g-1). Surface defect sites increase, and the efficient separation and transfer of photo-generated charge carriers are promoted with the introduction of a suitable vacancy density. PCNS-F demonstrated outstanding photocatalytic degradation performances for tetracycline (81.7 %) and methylene blue (97.7 %) under visible light irradiation for 2 h, which are 10 and 7.2 times higher than those of bulk g-C3N4. The active species of ∙O2- was confirmed to play a major role in the photodegradation process. This work provides a mild approach for engineering carbon and nitride double vacancy defects on g-C3N4 nanosheets, accompanied by tuning carbon/nitride ratio, to effectively eliminate pollutants and cleanse the environment.’

Low dose, high function: Visible light photocatalytic performance of in-situ sensitized Ti3+/Ov self-doped rutile TiO2-x nanorods with a small amount of ultrathin g-C3N4 nanosheets

Harnessing solar energy for photocatalytic sewage purification represents a significant strategy for addressing water pollution. This study focused on synthesizing ultrathin g-C3N4 nanosheets through ultrasonic refluxing g-C3N4 aggregates in a mixture of water and triethylamine. Subsequently, Ti3+/oxygen vacancy (Ov) self-doped rutile TiO2 (TiO2-x) nanorods were synthesized via an in-situ mixed solvothermal reaction. By sensitizing a minimal quantity of these ultrathin g-C3N4 nanosheets, a Z-scheme heterojunction with reduced rutile TiO2-x nanorods was achieved. Various analytical techniques were employed, including X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), and transient photocurrent analysis. These methods determined the phase, structure, morphology, and photoelectrochemical properties of the fabricated materials. The visible light photocatalytic performance was tested using rhodamine B, methyl orange, and Cr2O72- solutions as simulated pollutants and three distinct types of actual wastewater from a pharmaceutical factory as photocatalytic degradation object. The findings revealed that Ti3+/Ov self-doping significantly enhances the visible light responsiveness of rutile TiO2. The integration of minimal amounts of ultrathin g-C3N4 nanosheets with rutile TiO2-x nanorods, formed via an in-situ mixed solvothermal reaction, effectively promoted the separation of photogenerated electrons and holes, thereby increasing the photocatalytic efficiency. Interestingly, increasing the g-C3N4 content in the mixture led to an increase in the number of defects within TiO2-x and a reduction in crystallinity. Wastewater treatments yielded varied results: wastewater containing solely phenols underwent effective photocatalytic degradation, while samples with high salt content or complex compositions proved more challenging. This study demonstrated that the heterojunction formed by sensitizing rutile TiO2-x nanorods with a small amount of ultrathin g-C3N4 nanosheets retained remarkable photocatalytic activity. These findings offer valuable insights for the design of effective photocatalysts and their application in sewage treatment.

P-doped ultrathin g-C3N4/In2S3 S-scheme heterojunction enhances photocatalytic hydrogen production and degradation of ofloxacin

In this work, ultrathin lamellar g-C3N4/In2S3 S-scheme heterojunctions doped with P were synthesized by urea recrystallization and investigated to see which ratio was more favorable for photocatalysis. The P doping formed a new Fermi energy level and reduced the forbidden bandwidth. The ultrathin lamellar structure facilitated rapid charge transfer, and the formation of S-scheme heterojunction, the presence of the interfacial electric field, and band bending effectively separated strong redox-capable electron-hole pairs, thus significantly improving the photocatalytic performance. Among the prepared materials, the 50UP-C3N4/In2S3 photocatalyst with 50 % UP-C3N4 mass fraction showed optimal photocatalytic H2 production performance, with a hydrogen production rate of 12,387 μmol h−1 g−1. Moreover, it showed good performance in photocatalytic degradation, with a degradation efficiency of up to 90.2 % of ofloxacin after 120 min of light exposure. This article provided a new perspective on the synthesis of other photocatalysts with carbazide-based S-scheme heterojunction structures.

Electrochemically assisted preparation of graphitic carbon nitride nanosheet membranes for efficient water purification

The development of a highly effective nanofiltration membrane for water purification is crucial for wastewater recovery. The graphitic carbon nitride (g-C3N4) membrane can be an ideal candidate for advanced water treatment due to its intrinsic porous structure and superior physicochemical stability. However, the developments of the g-C3N4 membranes are limited by their traditional preparation methods involving complicated processes, long reaction time and high-temperature conditions. A simple electrochemical-assisted strategy for the rapid preparation of the g-C3N4 nanosheet membranes at room temperature has been developed in this study. The ultra-thin g-C3N4 membrane with a uniform structure can be synthesized within 40 min, which is at least 7 times quicker compared to the traditional methods. The as-prepared g-C3N4 membrane shows a high water flux rate of ∼ 90 L m−2 h−1 bar−1. Simultaneously, an excellent rejection rate of 99.1% toward Evans blue is achieved based on the synergistic effect of size sieving and electrostatic repulsion. The breakthrough in the preparation method of g-C3N4 nanosheet membranes in this work is of great significance to the development of g-C3N4 membranes in the field of water purification.