Carbon Nitride Photocatalyst Research Articles

Sustainable Photocatalytic Mitigation of 2-Mercaptobenzothiazole by Expired Medicine Derived Metal-Free Graphitic Carbon Nitride Photocatalyst

Sustainable Photocatalytic Mitigation of 2-Mercaptobenzothiazole by Expired Medicine Derived Metal-Free Graphitic Carbon Nitride Photocatalyst

Visible-Light-Induced Rapid Elimination of Antibiotic Resistance Contaminations Using Graphitic Carbon Nitride Tailored with Carrier Confinement Domains.

Solar water disinfection facilitated by photocatalyst has been considered a viable point-of-use (POU) method for mitigating antibiotic resistance contaminations at the household or community levels. Here, density functional theory calculations are used to guide the fabrication of a carrier confinement domains (CCD)-decorated graphitic carbon nitride (CN) photocatalyst. The CCD integration effectively disrupts the electron distribution symmetry of CN, amplifies its local electron density, and facilitates the formation of long-range ordered structure, thereby enhancing charge separation efficiency. Importantly, the CCD directs the migration of photogenerated carriers to specific regions upon light illumination, effectively minimizing their spatial proximity. As a result, the overall reactive oxygen species level of the photocatalytic system is markedly elevated, with a twelvefold increase in H2O2 concentration, alongside a nearly two-order-of-magnitude rise in •O2 - and •OH steady-state concentrations. Remarkably, a record-high disinfection efficiency is attained, successfully inactivating 7 log of antibiotic-resistant bacteria within 30min. Additionally, the photocatalyst can be integrated into a continuous-flow fixed-bed reactor, facilitating clean water production for up to 60h at a rate of 121Lm-2day-1, highlighting its significant potential for POU applications.

Metal Single Atom-Hydroxyl Incorporation in Poly(heptazine imide) to Create Active Sites for Photocatalytic Water Oxidation.

Poly(heptazine imide) (PHI) salts are extensively researched crystalline carbon nitride photocatalysts, but their photocatalytic water oxidation (PWO) performance is scarcely researched because of the difficulty in creating efficient active sites. Interference of metal ion (e.g., Na+ and K+) loss from the PHI salts in their PWO research has hardly been considered. Herein, metal single atom─OH (e.g., Co─OH) groups are incorporated into PHI to create efficient PWO active sites, via simple ion metathesis, hydrolysis, and deprotonation. The Co─OH modified PHI exhibits 9.3-fold higher PWO (oxygen evolution) activity than PHI, with an external quantum yield reaching 0.44% even at 600 nm. Excluding interference of the metal ion loss, the function of the Co─OH incorporation is evidenced mainly to facilitate the oxygen evolution reaction, as well as to promote photogenerated charge separation and raise visible light absorption, with the role of the OH especially revealed. Moreover, it is discovered that Na+ loss from sodium PHI will decrease its PWO activity, protonation of PHI has a detrimental effect on its PWO performance, and some other metal single atom─OH incorporation in PHI can also enhance its PWO activity. Overall, this work provides a general way to create PWO active sites in PHI.

Optimized Carbon Coupling for Enhanced Ethylene Production via a Unique Single-Atom-Substrate Synergy Mechanism within Photocatalytic Processes.

The utilization of solar-driven technologies for the direct conversion of methanol (CH3OH) into two or multi-carbon compounds through controlled carbon-carbon (C-C) coupling is an appealing yet challenging objective. In this study, we successfully demonstrate the photocatalytic CH3OH coupling to ethylene (C2H4), a valuable chemical raw material, by employing a carbon nitride-based catalyst. Specifically, we modify the layered polymer carbon nitride (PCN) photocatalyst through the incorporation of Au single atoms (Au1/PCN) using a chemical-scissors method. The synergistic effect between the PCN substrate and the Au single atoms reduces the potential barrier associated with C-C coupling, thereby enhancing the efficiency of CH3OH reforming to C2H4. This investigation not only reveals a novel pathway for C2H4 production via CH3OH reforming but also provides fresh insights into the possibilities of C-C coupling.

Self-Assembly Synthesis of Oxygen and Sulfur Co-Doped Porous Graphitic Carbon Nitride Nanosheets for Boosting CO2 Photoreduction.

Graphitic carbon nitride (CN) has garnered considerable attention in the field of visible-light CO2 photoreduction, but its efficiency remains limited by the intrinsic π-conjugated skeleton. Here, O and S were co-doped CN (O, S/CN) by a facile "hydrolysis + calcination" approach to modulate the physicochemical and electronic structure. Distinctive from S doped CN (SCN), O, S/CN owned porous layer structure with several nanosheets and less SO4 2- groups on the surface. The amount of heteroatom-doping was achieved by changing the hydrothermal temperature. The optimum O, S/CN-80 achieved moderate CO production rate of 1.29 μmol g-1 h-1, which was 3.79 times as much as SCN (0.34 μmol g-1 h-1). The O and most S atoms were substitutionally doped and the effect of S doped state on the improved efficiency of CO generation in O, S/CN was also explored based on the theoretical calculations. This work provides an inspiration to develop efficient dual-doped CN photocatalysts for photocatalytic CO2 reduction.

Heterostructure of perovskite coupled graphitic carbon nitride for enhanced photodegradation under visible light

This study aimed to prepare and characterize LaFeO3 nanoparticles loaded graphitic carbon nitride (LFO/g-C3N4) photocatalyst and investigate the degradation of organic pollutants under UV and natural sunlight exposure. It is observed that LFO nanoparticles of an average size of about 67 nm were distributed on g-C3N4 sheets through chemical bonding owing to the formation of a composite. Compared to LFO and g-C3N4, composite has a good absorption ability to harvest more UV and visible light due to its large surface area and pore size. The photocatalytic studies revealed that the g-C3N4/LFO composite exhibits higher catalytic efficiency and stability for methylene blue (MB) degradation under UV and visible light. Under UV irradiation, the degradation efficiency of LFO, g-C3N4, and g-C3N4/LFO composite in synthetic wastewater was found to be around 50, 80 and 93 % with corresponding rate constants 0.05, 0.02, and 0.1 min−1 in 30 min, respectively. Under natural sunlight, the composite degraded 97 % of MB in 180 min with a rate constant of 0.016 min1. The higher photocatalytic activity of the composite was attributed to the interfacial charge transfer between LaFeO3 and g-C3N4, which are responsible for effective charge separation in the composite. Further, it has been investigated that singlet oxygen species (1O2) and hydroxyl radicals (•OH) are the main reactive species that contributed considerably to the complete degradation of MB. The nanocomposite was also demonstrated to be a stable catalyst and can be reused without any further modification.

Novel carbon nitride for efficient degradation of organic pollutants and value-added recycled plastics: synergistic effects of nitrogen vacancies and Fe

The introduction of nitrogen vacancies (VN) and iron (Fe) single atoms sites significantly enhances the visible light absorption and charge transfer ability of carbon nitride (CN) catalysts. This paper presents the successful synthesis of a VN-rich, Fe single atoms incorporated CN, a catalyst that demonstrates exceptional degradation performance and cycling stability. The 2-mercaptobenzothiazole (MBT) removal rate by 20Fe-CN reached 99.51% within just 11min under visible light, and the catalyst maintained superior photocatalytic performance upon repeated use. Additionally, the 20Fe-CN/Photo/High-temperature system effectively converted polystyrene (PS) to benzoic acid (BA), achieving a BA yield of 19.73% after 48hours. Under visible light irradiation, the VN sites captured electrons and facilitated their rapid transfer to neighboring Fe sites, enhancing the photocatalytic redox processes. This study also identified ·O2- as the primary active species in the photocatalytic process. This research supports the development of diverse single-atom modified carbon nitride photocatalysts, holding significant potential for wastewater treatment and plastic resource recycling, and providing valuable insights for future photocatalysts in environmental remediation.

Green Protocol For Synthesis of Cu2O@g‐C3N4 Photocatalysts For 1, 4 Radical Oxidative Addition of Trans Crotonaldehyde Under Visible Light Condition

AbstractUsing visible light conditions, we have developed a green protocol to prepare copper oxide‐doped graphitic carbon nitride (Cu2O@g‐C3N4) photocatalysts with varied ratios of g‐C3N4 nanosheets to copper oxide‐dopant (0.1 %, 0.5 %, 0.7 %, and 5 % respectively) and characterized through various physicochemical techniques. These photo‐responsive catalysts were used for the 1,4 radical oxidative addition of trans crotonaldehyde into β‐hydroxybutyric acid (BA) as a major product, utilizing 30 % hydrogen peroxide as an oxidant and a white LED (Light Emitting Diode) source. Under the innoculous eco‐friendly stipulations, Cu2O@g‐C3N4 (5 %) exclusively promoted the aforementioned reaction leading to 99.85 % trans crotonaldehyde conversion with 66.57 %, 24.1 %, and 9.1 % selectivity for β‐hydroxybutyric acid, crotonic acid and subsequent radical synthesis, respectively.

Sustainable photodegradation of tetracycline by surface-functionalized carbon nitride: Mechanism insight and toxicity assessment

Here, we report the facile preparation of amino- and vacancies-abundant carbon nitride photocatalyst using acetone as a low-boiling-point solvent and describe its successful performance of environmental purification. As a demonstration of the notion, tetracycline (TC) antibiotic as an emerging aqueous contaminant has been used as a model substrate for assessing the photoactivity of the modified carbon nitride and clarifying its intrinsic mechanism. 96 % of TC can be photocatalytically removed within 30 min, accompanied by a discernible mitigation in ecotoxicological impact. Reactive species, including •OH, •O2-, and photogenerated holes, are considered the critical oxidants. Meanwhile, the possible intermediates and transformation pathways of TC degradation were investigated utilizing the LC-MS technique, the Fukui function, and the T.E.S.T. software. The comprehensive approach furnishes valuable insights for assessing the evolutionary dynamics of tetracycline in an advanced oxidation process (AOP). This study offers a sustainable, cost-effective, and eco-friendly approach to preparing carbon nitride material, which is believed to open an avenue for the facile design of heterogeneous environmental photocatalysts and to provide insights into the various environmental applications.

Enhanced CO2 Reduction via S-Scheme Heterojunction of Amorphous/Crystalline Metal-free Carbon Nitride Photocatalysts

Metal-free carbon nitride nanosheets (CNs) are promising photocatalysts, but face challenges with severe charge recombination and limited visible light absorption. To overcome these challenges, we have developed a 2D/2D amorphous/crystalline carbon nitride (CNs/CCN) S-scheme heterojunction photocatalyst through electrostatic self-assembly. The built-in electric field in the CNs/CCN heterojunction facilitates an S-scheme transfer of photogenerated electrons from CCN to CNs, effectively enhancing electron-hole separation. Our optimized CNs/CCN-1/3 heterojunction exhibits substantially higher production rates of CO and CH4 compared to its individual components. Notably, CNs/CCN-1/3 maintains excellent CO2 reduction efficiency even under irradiation at wavelengths exceeding 700 nm. This study introduces an innovative strategy for the development of CNs-based photocatalysts with improved charge separation and enhanced visible-light absorption.

Synthesis of Fluoroalkylated Indolines Using Molten-Salt Carbon Nitride Photocatalysts

Synthesis of Fluoroalkylated Indolines Using Molten-Salt Carbon Nitride Photocatalysts

Performance and mechanism insights into S-doped superhydrophilic carbon nitride for photocatalytic hydrogen evolution and degradation

Carbon nitride (CN) photocatalyst possesses great potential in alleviating energy and environmental crisis, while the insufficient active sites exposure, limited light harvest and poor charge behavior, as well as inferior dispersibility in water limit its photocatalytic activity. In this research, a loose porous crimp S doped CN photocatalyst with superhydrophilicity was tailored via facile one-pot thermal-melting followed thermal induce copolymerization of urea with 2-mercaptonicotinic acid. The dope of 2-mercaptonicotinic acid leads to the significant enhancement of specific surface area, range/intensity of visible-light harvest and charge behavior, as well as hydrophilicity of CN. The photocatalytic hydrogen evolution rate achieves a remarkable improvement of 7.61 times compared to CN alone, reaching 88.14 μmol h−1. Additionally, the photodegradation of tetracycline is enhanced by approximately 3.96 times compared to pristine CN, resulting in a degradation efficiency of 90.5 %. Via active species capture tests, ESR, LC-MS, toxicity prediction and DFT calculations, the main active species, degradation pathway, intermediates toxicity and promoted mechanism of photocatalytic performance are explored. This study presents a straightforward and cost-effective approach to enhance the intrinsic activity of CN-based photocatalysts by simultaneously regulating their active sites exposure, light absorption and charge behavior for addressing environmental and energy concerns.

Ternary ZnS/ZnO/Graphitic Carbon Nitride Heterojunction for Photocatalytic Hydrogen Production.

Ternary ZnS/ZnO/graphitic carbon nitride (gCN) photocatalysts were prepared by coupling gCN sheets with ZnO nanorods under solvothermal conditions followed by sulfurization using Na2S. SEM and TEM analyses show that small-sized ZnS particles (ca. 7.2 nm) deposit homogeneously on the surface of ZnO/gCN nanohybrids. Photoluminescence and electrochemical impedance spectroscopy show that ZnS allows for an enhanced charge separation efficiency as well as prolonged lifetime of photogenerated charge carriers, leading to improved hydrogen photoproduction under UV light irradiation compared to ZnO/gCN. Moreover, the deposition of ZnS nanoparticles improves the photostability of the ZnS/ZnO/gCN catalyst for hydrogen production. A double Z-scheme mechanism is proposed for hydrogen photoproduction using the ZnS/ZnO/gCN heterojunction.

Enhanced Gas-Phase pollutant removal using Pt nanoparticle-modified exfoliated carbon nitride photocatalysts under UV and visible light

Platinum nanoparticles (Pt NPs) have been prepared by the organometallic approach on the surface of exfoliated graphitic carbon nitride (exf-g-CN) with different metal loadings. Multi-technique characterisation shows a good dispersion of Pt NPs on the surface of exf-g-CN with a narrow size distribution between 1.7–2.2 nm and a BET area of about 120 m2/g. The Pt NPs are mainly composed of platinum metal with a minor contribution of oxidic surface species. The effect of UV-A and Vis light of different wavelengths on the photocatalytic performance is investigated. The as-prepared hybrid materials show excellent photocatalytic activity for the decontamination of air from volatile organic compounds (VOCs, in particular trichloroethylene, C2HCl3) under low power visible light irradiation. The conversion value reaches a maximum close to 85% at 405 nm Vis light for 0.5 wt% Pt loading. At this level of Pt content, electron and hole recombination rates are suppressed according to photoluminescence analysis. Photonic efficiencies of around 0.3% were achieved under Vis light. The optimised material shows high stability from 2,500 min of operation. XPS analysis suggests the crucial role of Pt/Pt2+ and chlorine species detected on used samples in the reaction rate and stability of the material.

Enhanced visible light photocatalytic activity of Pt cluster modified carbon nitrides for U(VI) removal

Photocatalysis has been regarded as one of the effective methods of removing U(VI) from radioactive wastewater in recent years, due to the benefits of being environmentally friendly and efficient. In this work, a Pt cluster modified carbon nitride photocatalyst (Pt-CN) was synthesized in zinc chloride molten salt. The photocatalysts were characterized by XRD, IR, XPS, UV–vis, PL and EIS. The result demonstrated that the doping of Pt makes Pt-CN show higher electronic conductivity and better charge separation and migration, leading to an enhanced photocatalytic activity and faster kinetics compared with bulk graphitic carbon nitride (g-C3N4). Moreover, for uranium contained solution photocatalytic treatment, Pt-CN reached 94.6 % removal efficiency after 300 min of illumination with Xe light, and the kinetics improved by a factor of three compared to that of g-C3N4. Furthermore, the good reusability and photostability of the Pt-CN was confirmed as the removal efficiency remained at 83.7 % even after being recycled and reused five times. The photocatalytic reaction product was characterized as (UO2)O2·2 H2O, and the mechanism was deduced as uranium species reacting with H2O2 generated by light illumination in an open system. This molten salt one-step synthesis and Pt doping method and the performance of U(VI) extraction in air showed a promising potential for the application of Pt-CN for U(VI) extraction and removal from water.

Construction of sulfur-chloride co-doped triazine/heptazine homojunction carbon nitride photocatalyst for simultaneous production of H2O2 and lignin C-C bond cleavage

Photocatalytic H2O2 production and cleavage of lignin C-C bonds is a typical strategy that follows sustainable development. Unfortunately, the photocatalytic efficiency of these two reactions still faces significant challenges. Herein, a carbon nitride photocatalyst (tri/hep-CN) with sulfur-chloride co-doped triazine and heptazine structures was synthesized. It was simultaneously used for photocatalytic H2O2 production and lignin C-C bond cleavage. In the air atmosphere, the yield of H2O2 reached 1171.9 μmol•g−1•h−1 after the addition of β-1 lignin model 1,2-diphenylethanol (Dpol) to the solvent. The yield of H2O2 increased by 20 times compared with no addition of Dpol. The lignin C-C bond in Dpol is also efficiently broken, producing benzaldehyde and benzyl alcohol. tri/hep-CN has excellent photogenerated carrier separation efficiency and positive valence potential, which improves the photocatalytic H2O2 production and lignin C-C bond cleavage performance. Notably, coupling photocatalytic H2O2 production with lignin C-C bond cleavage to fully use photogenerated electrons and holes is also very important to obtain outstanding photocatalytic performance. Mechanistic studies have shown that photocatalytic H2O2 production follows an indirect reaction mechanism. Meanwhile, the cleavage of lignin C-C bond follows the Cβ radical mechanism and the single electron transfer mechanism. This work is very instructive for simultaneous photocatalytic H2O2 production and lignin C-C bond cleavage studies.

Efficient selective cleavage of C−C bonds in lignin under visible light enabled by the Fe-doped mesoporous graphitic carbon nitride photocatalyst

To obtain high-valued aromatic products, it is paramount to cleave the Cα−Cβ bonds in lignin under mild conditions selectively. Nevertheless, this task remains daunting due to the formidable dissociation energies and steric hindrance associated with these bonds. Herein, a facile, efficient and cost-effective strategy for selectively breaking the Cα−Cβ bond in lignin with visible-light irradiation and room temperature is proposed, facilitated by the utilization of the ferric-doped mesoporous graphitic carbon nitride (Fe/mpg-CN) photocatalyst. Collective contributed by the reduced band gap and photoluminescence, combined with intensified visible-light absorption and enhanced photocurrent, the effectiveness in photocatalytic activity of Fe/mpg-CN is offered. Specifically, a high conversion rate (98 %) of the lignin model compound (2-phenoxy-1-phenylethanol), coupled with an excellent selectivity of 98 % in cleaving the Cα−Cβ bonds is achieved by Fe/mpg-CN. Photogenerated holes are indicated as the main active species through comprehensive mechanistic investigations. Additionally, the successful photocatalytic depolymerization of the complex dimer model compound (conversion rate ∼ 96 %) and pine kraft lignin further corroborate the satisfying photocatalytic activity and selectivity of Fe/mpg-CN. This study introduces a promising and viable strategy for the selective breaking of lignin through photocatalysis, offering significant implications for the sustainable production of valuable aromatic compounds.

Graphene with suitable-size nitrogen-doped cavity being an excellent photocatalyst for proton-coupled electron transfer in water splitting

Aiming to attain porous carbon nitride photocatalysts with high specific surface area, abundant active sites, broad absorption range and effective electron-hole separation, we remove carbon rings from graphene and replace all the edge carbon atoms of the cavity with nitrogen atoms. The accurate electronic structures and exciton properties of the proposed materials are revealed by the ab initio many-body Green's function theory. Computational results show that the absorption of the designed materials can cover both the visible and the near-infrared light region. The exciton binding energies of the materials are one order of magnitude lower than those of the typical two-dimensional photocatalyst graphitic carbon nitride. Due to the formation of hydrogen bonds between pyridinic nitrogen atoms and water molecules during water splitting, the key excited-state proton-coupled electron transfer reactions are barrierless. These findings could serve as guidelines for the realization of high-performance metal-free two-dimensional photocatalysts.

The coexistence of highly dispersed Pt2+ and Pt0 co-catalysts on chemically oxidized g–C3N4 via metal-support interaction: The effect of reduction time on Pt species and hydrogen evolution of Pt/g-C3N4 photocatalysts

Platinum (Pt) cocatalyst greatly enhances the photoactivity of the graphitic carbon nitride (g-C3N4) photocatalyst for photocatalytic H2 evolution where the Pt properties are critical to determine the photocatalytic activity. In this study, highly dispersed Pt was successfully loaded onto chemically oxidized g–C3N4 (OCN) via a hydrogen reduction process over different reduction time. OCN photocatalysts containing highly dispersed Pt2+/Pt0 exhibited outstanding charge separation efficiency and photocatalytic performance. Symmetrical –CO groups on the OCN surface specifically interacted with atomic Pt2+, and the Pt2+ atoms were stably reduced to Pt0 atoms along with the generation of –OH groups over time. The coexistence of Pt0 and Pt2+ promoted superior photocatalytic performance because the photoinduced charge transfer was facilitated by the Pt0 atoms, which was evidenced by the DFT calculation and the EIS, PL, and photocurrent response results. Consequently, after the 24 h reduction, the highly stable and active Pt2+/Pt0 atoms were effectively distributed over OCN, resulting in the highest HER activity at 4091.3 µmol g−1 h−1.

Multilayered photo-bioanode for simultaneous conversion of CO2 and industrial refractory organics into bioelectricity in a microbial fuel cell system

CO2 and toxic wastewater were converted into bioelectricity through photo-bioanode in a microbial fuel cell (MFCs). Photo-bioanode provided multifunctional regions due to four distinct layers: the first layer integrates a Fe-doped graphitic carbon nitride photocatalyst. In contrast, the second layer contains refractory organics (RO) degrading microbes. Sequentially, the third layer consists of CO2-consuming bacteria and the fourth layer accommodates exoelectrogens. The first layer not only generated plentiful electrons upon illumination but also quenched electrons from the inner layers, facilitating the degradation of RO. The second layer transformed RO into ions (NH4, NO3/NO2) and C6H12O6, sequentially transported into the third and fourth layers. Within the third layer, CO2-consuming bacteria utilized CO2 leaked from the exoelectrogenic layer, effectively curbing its accumulation in the fourth layer. Here, exoelectrogens employed ions and C6H12O6 as their energy source, producing an electricity output 1.4 times greater than the benchmark. This synergistic performance yielded a voltage of 2.5 V, a current of 2.8A, and a power yield of 1.98 W/organic loading rate (OLR). Thus, the unique layered structure of the photo-bioanode facilitated the self-development of distinct microbial communities, thereby formulating a multifunctional and highly dynamic system with zero-liquid discharge.