Ultrathin Carbon Nitride Research Articles

Single-atom Ru modified flake g-C3N4 enhances photogenerated electron transport for rapid degradation of tetracycline antibiotics: Non-radical mechanism and ecotoxicity studies

Design of green and low-cost single-atom catalysts (SACs) with high-performance is key to moving photocatalytic degradation of antibiotics toward applications. In order to achieve SACs for large-scale manufacturing, we prepared ultrathin flake carbon nitride (FCN) by low-energy-consuming physical knockout means, and also applied an in situ growth strategy with stable and easy-operating effect to anchor the Ru element on FCN in the form of single atom. Notably, in the PMS/Vis/0.5Ru-FCN system, the degradation rate of tetracycline achieved 100 % in just five minutes, with an apparent rate constant of 0.236 min−1. Ru-FCN exhibits selective and stable determination due to narrow bandgap, unique photoresponsivity and low photogenerated carrier complexation rate. Mechanism investigation reveal that Ru-N4 sites accelerated the electron transfer between Ru-FCN and PMS, while the low oxidation state of Ru elements reduced the risk for metal corrosion. DFT calculations predict the attack sites of reactive oxygen species. This work provides a rational explanation for the charge transfer and resistance to external disturbance by Ru single atom, and it also provides a new direction to enhance the efficiency of water treatment.

Construction of a In2O3/ultrathin g-C3N4 S-scheme heterojunction for sensitive photoelectrochemical aptasensing of diazinon

A single semiconductor-based photoelectrochemical (PEC) aptasensor usually faces a challenge of low sensitivity due to poor solar energy utilization and a high photogenerated carrier recombination rate. Herein, an ultra-thin carbon nitride nanosheet-coated In2O3 (In2O3/CNS) S-type heterojunction-based PEC aptasensor has been established to achieve highly sensitive detection of diazinon (DZN) pesticide in water environment. Construction of S-type heterojunction induces a band shift and an electric field effect, enhancing light utilization and accelerating directional transmission of carriers, leading to outstanding PEC performance. The creation of internal electric field at interface ensures stable carrier transport. Additionally, ultrathin CNS structure can effectively shorten the transport path of carriers. The close coating of In2O3 and CNS promotes the transfer of charge. The synergistic effects amplify the sensor’s response, ultimately enabling the effective detection of DZN residue over a wide detection range (0.98 ∼ 980.0 pg mL−1), a low detection limit (0.33 pg mL−1, S/N = 3) and excellent accuracy in practical application (RSD < 5 %). This work provides a reference for the construction of a new S-type heterojunction-based PEC sensor.

In situ growth of large-scale and ultrathin carbon nitride films shield common metal substrates from corrosion and oxidation

A centimeter-size carbon nitride (CN) film, with nanoscale thickness, is in situ deposited on various metals through the thermal condensation of melamine, achieving broad and uniform coverage, without any pre- and post-treatments. As the temperature rises, the nitrogen content in the film increases, leading to the part of CN to transform into g-C3N4. Benefit from higher Gibbs adsorption free energies of g-C3N4 with Cl- and O2 in aqueous environment, a 30 nm CN film deposited at 475 ℃ with large g-C3N4 network, minimal segregation and low internal stress enables pure metals and alloys to achieve over 90 % protection efficiency.

Boosting lactic acid photocatalytic synthesis from biomass sugars: The synergistic effect of N-doped carbon dots on ultrathin carbon nitride

The green and sustainable production of lactic acid via photocatalytic conversion of biomass-derived sugars is highly significant owing to its enhanced efficiency and reduced energy requirements. Consequently, the investigation has engineered a metal-free photocatalyst (NCDs/CCN), consisting of N-doped carbon dots (NCDs) and ultrathin carbon nitride (CCN). This catalyst has an enhanced light absorption range, facilitating a marked acceleration in the separation rate of photogenerated carriers. It has demonstrated the capability to achieve a lactic acid yield of up to 87.6 % in just 90 min with a mere 20 mg catalyst concentration in a xylose-alkali system. Electron Paramagnetic Resonance (EPR) and quenching experiments indicate that superoxide radicals (·O2−) are the primary oxidizing active species in the photocatalytic system, followed by h+, ·OH, and 1O2. DFT analysis suggests nitrogen doping enhances interaction with xylose, lowering adsorption energy and accelerating lactic acid generation, thus improving economic feasibility and sustainability.

Ultrathin‐N2C‐Deficient Carbon Nitride for Stabilized Enhancement of Electrochemiluminescence

AbstractIn the realm of electrochemiluminescence (ECL), the issue of weak signal intensity and instability linked with pure graphitic carbon nitride (CN) is widely recognized. This study suggests a method to produce nitrogen‐deficient (N2C) porous ultrathin CN (UACN) using ammonium acetate and ultrasonication. The ultrathin porous nature of UACN provides numerous N2C defects as catalytic sites, aiding in the decomposition of K2S2O8, a conclusion supported by density functional theory (DFT). Importantly, N2C defects serve as electron traps, assisting in electron localization and enhancing the recombination of electron‐hole pairs, thereby achieving stable and intensified luminescence from UACN. In practical use, UACN, acting as an ECL emitter, is utilized in detecting the tumor marker carcinoembryonic antigen (CEA), effectively establishing a highly sensitive immunosensing platform. This study elucidates the correlation between UACN structure and ECL performance, offering crucial insights for comprehending ECL mechanisms and designing high‐performance ECL materials.

Ultrathin Porous Carbon Nitride Anchored with Pt Nanoclusters for Synergistic Enhancement of Hydrogen Production in Alkaline Photocatalytic Polyester Reforming.

Photocatalytic reforming (PR) of polyester waste, fueled by renewable sources like solar energy, offers a sustainable method for producing clean H2 and valuable by-products under mild conditions. The design of high-performance photocatalyst plays a pivotal role in determining the efficacy of an alkaline polyester PR system, influencing H2 generation activity and selectivity. Here, ultrathin porous carbon nitride nanosheets (UP-CN) loaded with Pt nanoclusters (Pt NCs, average diameter of 1.7nm) with uniform Pt NCs distribution are introduced. The resulting Pt NCs/UP-CN catalyst can accelerate charge and mass transfer while providing additional active sites, achieving superior H2 generation rates of 11.69mmol gcat -1 h-1 and 2923mmol gPt -1 h-1 under AM 1.5 light, which nine times higher than that of Pt nanoparticles-bulk graphitic carbon nitride composite (1.29mmol gcat -1 h-1 and 258mmol gPt -1 h-1) as counterpart. This performance also surpasses that of previously reported carbon nitride-based and TiO2-based photocatalysts. Moreover, the density functional theory calculations reveal a significant reduction in the energy barrier for the water dissociation step (H2O + * → *H + OH) at the interface between UP-CN and anchored Pt NCs, showcasing the synergistic effect between Pt NCs and UP-CN. This catalytic system also exhibits universality across various polyester plastics.

Modulation of π-Electron Density in Ultrathin 2D Layers of Graphite Carbon Nitride for Efficient Photocatalytic Hydrogen Production.

The rational design and synthesis of novel semiconductor nano-/quantum materials have been ambitiously pursued in the field of photocatalysis as the technology is promising and critical for attaining future energy and environmental sustainability. Herein, the integrity of aromatic carbon into graphitic carbon nitride (CN) at the same molecular plane with a few 2D layers is achieved by using modulated precursors of CN, forming carbon regulated ultrathin CN (CUCN) with improved charge transfer kinetics and photocatalytic hydrogen production. The grafted graphite rings adjacent to carbon nitride frameworks induce a significant rearrangement and relocalization of the overall framework, and form conjugated sp2 hybridized interfaces and internal electric fields that drive the separation and directional transfer of photogenerated electrons from CN sheets towards intralayer graphite regions, where the photocatalytic hydrogen evolution reaction occurs extensively, yielding largely increased HER rate of 2231.8 µmol g-1 h-1 by 8.2 times relative to CN, as well as a remarkable apparent quantum yield of 2.93% under monochromatic light at 420 nm. The high physicochemical stability and low synthesis cost of CUCN make it a potential benchmark photocatalyst that can be readily modified via element doping, heterojunction introduction, defect engineering, and so on, to further enhance its HER performance.

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.

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.

Anchoring Pt single atoms on specific nitrogen vacancies of carbon nitride to accelerate photogenerated carrier transfer

The anchoring sites of metal single atoms are closely related to photogenerated carrier dynamics and surface reactions. Achieving smooth photogenerated charge transfer through precise design of single-atom anchoring sites is an effective strategy to enhance the activity of photocatalytic hydrogen evolution. In this study, Pt single atoms were loaded onto ultra-thin carbon nitride with two-coordination nitrogen vacancies (VN2c-UCN-Pt) and ultra-thin carbon nitride with three-coordination nitrogen vacancies (VN3c-UCN-Pt). This paper investigated the photocatalytic hydrogen evolution performance and photogenerated carrier behavior of Pt single atoms at different anchoring sites. Surface photovoltage measurements indicated that VN2c-UCN-Pt exhibits a superior carrier separation efficiency compared to VN3c-UCN-Pt. More importantly, the surface photovoltage signal under the presence of H2O molecules revealed a significant decrease. Theoretical calculations suggest that VN2c-UCN-Pt exhibits superior capabilities in adsorbing and activating H2O molecules. Consequently, the photocatalytic hydrogen evolution efficiency of VN2c-UCN-Pt reaches 1774 µmol g−1h−1, which is 1.8 times that of VN3c-UCN-Pt with the same Pt loading. This work emphasized the structure–activity relationship between single-atom anchoring sites and photocatalytic activity, providing a new perspective for designing precisely dispersed single-atom sites to achieve efficient photocatalytic hydrogen evolution.

Enhanced Electron Delocalization Induced by Ferromagnetic Sulfur doped C3N4 Triggers Selective H2O2 Production.

For the 2D metal-free carbon catalysts, the atomic coplanar architecture enables a large number of pz orbitals to overlap laterally, thus forming π-electron delocalization, and the delocalization degree of the central atom dominates the catalytic activity. Herein, designing sulfur-doped defect-rich graphitic carbon nitride (S-Nv-C3N4) materials as a model, we propose a strategy to promote localized electron polarization by enhancing the ferromagnetism of ultra-thin 2D carbon nitride nanosheets. The introduction of sulfur (S) further promotes localized ferromagnetic coupling, thereby inducing long-range ferromagnetic ordering and accelerating the electron interface transport. Meanwhile, the hybridization of sulfur atoms breaks the symmetry and integrity of the unit structure, promotes electron enrichment and stimulating electron delocalization at the active site. This optimization enhances the *OOH desorption, providing a favorable kinetic pathway for the production of hydrogen peroxide (H2O2). Consequently, S-Nv-C3N4 exhibits high selectivity (>95 %) and achieves a superb H2O2 production rate, approaching 4374.8 ppm during continuous electrolysis over 300 hour. According to theoretical calculation and in situ spectroscopy, the ortho-S configuration can provide ferromagnetic perturbation in carbon active centers, leading to the electron delocalization, which optimizes the OOH* adsorption during the catalytic process.

Fabrication of Z-scheme heterojunction of UCN/BWO for selective photocatalytic benzylamine oxidation

Nanosheet materials have larger specific surface area and more active sites than bulk materials. In this paper, ultrathin graphite carbon nitride (UCN) nanosheets were first prepared by a multi-step calcination method, and then Bi2WO6 nanoflowers were grown in-situ on the surface of UCN by a simple hydrothermal method to synthesize ultrathin graphite carbon nitride and bismuth tungstate composite (UCN/BWO). The synthesized catalyst was applied to the photocatalytic oxidative coupling of benzylamine (BA). After reacted 5 h under light in air atmosphere, BA was almost completely converted into N-benzylidenebenzylamine, which was 3.8 times higher than that of bulk graphite carbon nitride (BCN). The enhanced photocatalytic activity was not only attributed to the thin nanosheet structure of UCN which shortened the migration distance of photogenerated electrons, but also because the construction of Z-scheme heterojunction that inhibited the recombination of photogenerated carriers and improved the oxidation ability of the catalyst. Based on density functional theory (DFT) calculation and photoelectric performance test, the existence of Z-scheme heterojunction was proved. Combined with the active species capture experiments, the pathway of electron transfer in the reaction process and the possible reaction mechanism were proposed.

Extended light absorption and accelerated charge migration in ultrathin twisted carbon nitride nanoplates for efficient solar hydrogen production

Extended light absorption and accelerated charge migration in ultrathin twisted carbon nitride nanoplates for efficient solar hydrogen production

Abundant Edge Active Sites-Modified High-Crystalline g-C3N5 for Hydrogen Peroxide Production from Pure-Water via a Quasi-Homogeneous Photocatalytic Process.

Ultrathin carbon nitride pioneered a paradigm that facilitates effective charge separation and acceleration of rapid charge migration. Nevertheless, the dissociation process confronts a disruption owing to the proclivity of carbon nitride to reaggregate, thereby impeding the optimal utilization of active sites. In response to this exigency, the adoption of a synthesis methodology featuring alkaline potassium salt-assisted molten salt synthesis is advocated in this work, aiming to craft a nitrogenated graphitic carbon nitride (g-C3N5) photocatalyst characterized by thin layer and hydrophilicity, which not only amplifies the degree of crystallization of g-C3N5 but also introduces a plethora of abundant edge active sites, engendering a quasi-homogeneous photocatalytic system. Under visible light irradiation, the ultra-high H2O2 production rate of this modified high-crystalline g-C3N5 in pure water attains 151.14µmh-1. This groundbreaking study offers a novel perspective for the innovative design of highly efficient photocatalysts with a quasi-homogeneous photocatalytic system.

Schottky Junction Enhanced Photosynthesis of Hydrogen Peroxide by Ultrathin Porous Carbon Nitride Supported Ni Nanoparticles.

Artificial photosynthesis for high-value hydrogen peroxide (H2O2) through a two-electron reduction reaction is a green and sustainable strategy. However, the development of highly active H2O2 photocatalysts is impeded by severe carrier recombination, ineffective active sites, and low surface reaction efficiency. We developed a dual optimization strategy to load dense Ni nanoparticles onto ultrathin porous graphitic carbon nitride (Ni-UPGCN). In the absence and presence of sacrificial agents, Ni-UPGCN achieved H2O2 production rates of 169 and 4116 μmol g-1 h-1 with AQY (apparent quantum efficiency) at 420 nm of 3.14% and 17.71%. Forming a Schottky junction, the surface-modified Ni nanoparticles broaden the light absorption boundary and facilitate charge separation, which act as active sites, promoting O2 adsorption and reducing the formation energy of *OOH (reaction intermediate). This results in a substantial improvement in both H2O2 generation activity and selectivity. The Schottky junction of dual modulation strategy provides novel insights into the advancement of highly effective photocatalytic agents for the photosynthesis of H2O2.

Directional charge transfer modulation in ultrathin polyporous carbon nitride nanotubes for enhanced peroxymonosulfate activation

Achieving enhanced degradation efficiency of the legacy pesticidal persistent organic pollutants in a photocatalysis coupling peroxymonosulfate activation (PC-PMS) system by boosting photogenerated carrier separation, remains considerable challenges. Herein, we delved into the directional charge transfer modulation of built-in electric field (BEF) within polyporous ultrathin carbon nitride nanotubes for strengthened PC-PMS mediated pesticide degradation. The ultrathin polyporous tubular nanostructure, are critical in shortening the diffusion pathways for the transport of photogenerated electron-hole pairs to the reaction interface, while simultaneously ensuring the abundant contact sites for the reaction medium. Additionally, the heptazine units containing amino groups served as oxidation centers under visible light, targeting the generation of reactive oxygen species of h+, O2•−, 1O2. While the heptazine units containing cyano groups and boron dopants acted as reduction centers, activating PMS and O2 to produce SO4•−, •OH and O2•−. The efficient generation of the radical species contributed to the ultrafast imidacloprid degradation in PC-PMS system. This study demonstrates that the combination of morphology and BEF engineering is a promising strategy for enhanced degradation efficiency of pesticide pollutants in the PC-PMS system.

An S-scheme heterojunction of single Ni sites decorated ultrathin carbon nitride and Bi2WO6 for highly efficient photothermal CO2 conversion to syngas

Solar-driven conversion of CO2 and H2O to value-added chemicals or fuels is an ideal strategy to tackle the energy crisis and environmental issues. However, construction of highly efficient photosynthesis systems remains a challenge. This work reports a heterojunction catalyst consisting of ultrathin carbon nitride with single Ni sites and Bi2WO6 for photothermal conversion of CO2 and H2O to syngas. The catalyst exhibits exceptional activity at medium temperature of 250 °C, with CO and H2 production rates of 4493 and 9191 μmol g−1 h−1, respectively. Experimental results and DFT calculations reveal that the construction of S-scheme heterojunction and the introduction of single Ni sites greatly improve the separation of photogenerated carriers as well as the adsorption and activation of CO2. Meanwhile, it is proved that light drives the generation of H+ and activates the CO2 molecules, while heat accelerates the generation and diffusion of H+. The photothermal synergistic effect promotes the catalyst activity by two orders of magnitude.

Ultra-thin carbon nitride activated periodate for efficient tetracycline degradation with the assistance of visible light

This study developed a novel activated periodate (PI, IO4−) system mediated by ultra-thin carbon nitride (UCN) and visible light (Vis), and investigated its efficiency and kinetics of tetracycline hydrochloride (TC) degradation in water. UCN/PI/Vis system could remove 96% TC within 16 min through the mixed radical/non-radical pathway dominated by IO3•, 2.3 times higher than that of polymerized carbon nitride (PCN)/PI/Vis system. This gap was attributed to UCN having a greater specific surface area, more active sites, and a shorter charge transfer path. The UCN/PI/Vis system has outstanding recyclability, attractive pH adaptability, and remarkable tolerance to co-existing substances and natural water bodies. The fascinating degradation efficiency was ascribed to the synergistic effect among UCN that produced photoelectrons, TC as an electron donor, and PI as an electron acceptor. The quantum confinement effect of the ultra-thin structure improved the band gap and enhanced the redox capacity of photogenerated carriers, which greatly improved the photocatalytic activation of PI by UCN.

(Invited) Polymeric Carbon Nitride for Photocatalytic Overall Water Splitting

Photocatalytic overall water splitting can be achieved using Z-scheme systems that mimic natural photosynthesis by combining dissimilar semiconductors in series. However, coupling well-suited H2- and O2-evolving components remains challenging. Here, we fabricate a Z-scheme system for photocatalytic overall water splitting based on boron-doped, nitrogen-deficient carbon nitride two-dimensional (2D) nanosheets. We prepare ultrathin carbon nitride nanosheets with varying levels of boron dopants and nitrogen defects, which leads to nanosheets that can act as either H2- or O2-evolving photocatalysts. Using an electrostatic self-assembly strategy, the nanosheets are coupled to obtain a 2D/2D polymeric heterostructure. Owing to their ultrathin nanostructures, strong interfacial interaction and staggered band alignment, a Z-scheme route for efficient charge-carrier separation and transfer is realized. The obtained heterostructure achieves stoichiometric H2 and O2 evolution in the presence of Pt and Co(OH)2 co-catalysts, and the solar-to-hydrogen efficiency reaches 1.16% under one-sun illumination.

Platinum single atoms anchored on ultra-thin carbon nitride nanosheets for photoreforming of glucose

Photoreforming of biomass is a fascinating process that harnesses renewable sunlight and biomass to produce hydrogen under ambient conditions, holding a significant promise for future energy sustainability. However, the main challenge lies in developing highly active and stable photocatalysts with high light harvesting efficiency. In this study, we adopted a simple yet effective approach that combines thermal exfoliation and photodeposition to anchor Pt single atoms onto ultra-thin g-C3N4 nanosheets (MCNN). The incorporation of Pt single atoms induced a distinct red-shift in the visible light region, augmenting the solar energy absorption capacity, while the enlarged surface area of g-C3N4 nanosheets improved the mass transfer. Moreover, the enhanced photoelectric properties further contributed to the superior performance of Pt-MCNN-3.0 % in the photoreforming of glucose for hydrogen evolution. Remarkably, Pt-MCNN-3.0 % demonstrated an impressive hydrogen generation rate, approximately 59 times higher than that of MCNN, after a 3 h visible-light irradiation, maintaining a satisfied photo-stability. This work addresses the critical need for design of efficient photocatalysts, bringing us one step closer to realizing the potential of biomass photoreforming as a sustainable and clean energy conversion technology.