Porous Graphitic Carbon Nitride Research Articles

Enhanced performance of a Na3.5Co4[Bi2Co2W19.75O70(H2O)6]/porous graphitic carbon nitride heterojunction based photocatalyst realized by the addition of copper sulfide nanoparticles.

Photocatalytic hydrogen (H2) evolution can effectively solve the global energy problem, in which the key factor is the synthesis of efficient photocatalytic materials. In this study, we successfully synthesized a novel photocatalyst, BiWCo/CuS/PGCN, by functionalizing porous graphitic carbon nitride (PGCN) with sandwich-type polyoxometalate Na3.5Co4[Bi2Co2W19.75O70(H2O)6]·39.5H2O (BiWCo) and introducing copper sulfide (CuS) nanoparticles as a cocatalyst. This approach was aimed at enhancing the built inner electric field between interfaces, resulting in a significant improvement in photocatalytic H2 evolution performance. This research adopts a step-by-step method to synthesize BiWCo/CuS/PGCN composites with p-n heterojunctions, which has high visible light absorption and a synergistic effect of multiple elements. PGCN with a high specific surface area contributes to the uniform distribution of active sites. In addition, the nano-CuS cocatalyst provides abundant active sites and more electron transfer pathways for photocatalysis. Therefore, the H2 production efficiency of BiWCo/CuS/PGCN is 6.3 times that of PGCN, 4.5 times that of BiWCo and 2.5 times that of BiWCo/PGCN under visible light. The H2 production rate of BiWCo/CuS/PGCN reaches 3477.58 μmol g-1 h-1. At the same time, the ternary photocatalyst shows high stability after 30 hours and 5 cycles. This work demonstrates that BiWCo/CuS/PGCN has good application prospects in H2 evolution, and provides a new strategy for the design of efficient ternary photocatalytic materials.

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.

Defect-Rich porous graphitic phase carbon nitride layer grafted MXene as desolvation promoter for efficient sulfur conversion in extremely harsh conditions

Lithium-sulfur (Li-S) batteries exhibit superior theoretical capacity and energy density but are still hindered by the sluggish redox conversion kinetic of lithium polysulfides arising from the significant desolvation barrier, especially under high current density or low-temperature environments. Herein, a two-dimensional (2D) porous graphitic phase carbon nitride/MXene (CN-MX) heterostructure with intrinsic defects was designed via electrostatic adherence and in-situ thermal polycondensation. In the design, the defect-rich CN with abundant catalytic activity and porous structure could efficiently facilitate the lithium polysulfides capture, the dissociation of solvated lithium-ion (Li+), and fast Li+ diffusion. Concurrently, 2D MXene nanosheets with high electronic conductivity could act as charge transport channels and provide electrochemical active sites for sulfur redox reactions. The Li-S cells with CN-MX heterostructure modified separator demonstrated uncommon rate performance (945 mAh/g at 4.0C) and satisfactory areal capacity (5.5 mAh cm−2 at 0.2C). Most remarkably, even at 0 °C, the assembled Li-S batteries performed favorable cycle stability (91.6 % capacity retention after 100cycles at 0.5C) and outstanding rate performance (695 mAh/g at 2.0C), and superior high loading performance (5.1 mAh cm−2 at 0.1C). This work offers exciting new insights to enable Li-S batteries to operate in extreme environments.

Preparation of nanosheet g-C3N4 coupled with Polycalix [4] resorcinarene: Survey characterization and photocatalytic activity for the degradation of 4-Nitrophenol

Here, we have synthesized Polycalix[4]resorcinarene (PC4RA) covalently coupled with carbon-modified porous graphitic carbon nitride (g-C3N4). The nanocomposites were characterized by (FTIR), (XRD), (SEM), Transmission (TEM), and DRS–UV–Vis spectroscopic methods. Photocatalytic activities of the PC4RA/g-C3N4 nanocomposites with different ratios of g-C3N4 were evaluated for degradation of 4-Nitrophenol under visible light irradiation under light irradiation of λ ≥ 320 nm. Three parameters were applied including the initial concentration of 4-nitrophenol, the amount of photocatalyst, and irradiation time. and the results of the photocatalytic performance suggest that the catalytic activity is strongly influenced by the presence of the g-C3N4 content. Especially the nanocomposite’s photocatalytic efficiency was the highest (98.32 % after 120 min) when the ratio of g-C3N4 was (1/2). However, an increase of the photocatalytic activities was related to the interfacial transfer of photogenerated electrons and holes, leading to the effective charge separation. The durability and stability of the nanocomposites have been examined and can endure the experimental conditions even after eight successive cycles. This approach opens up an avenue for the fabrication of graphitic carbon nitrite-based metal-free heterogeneous nanocomposites with high catalytic performance.

Enhanced hydrogen evolution and tetracycline degradation by a Z-scheme g-C3N4 nanosheets loaded CeO2 photocatalyst under visible light irradiation

In the quest to enhance photocatalytic performance, structural regulation and interface engineering stand out as effective strategies for amplifying active sites and fostering the separation of photogenerated electron-hole pairs. In this study, a pioneering approach was employed, utilizing a straightforward two-step calcination method to prepare a novel photocatalyst: porous graphite carbon nitride (g-C3N4, CN) nanosheets (NS) loaded with mesoporous cerium oxide (CeO2/CNNS). The distinctive architecture of CeO2/CNNS not only elevates the specific surface area and catalytic active sites but also facilitates efficient mass transfer. Experimental results and density functional theory (DFT) calculations corroborate the existence of an internal electric field (IEF) within the Z-scheme heterojunction formed by uniformly dispersed CeO2 and CNNS. This IEF proves pivotal in promoting charge separation and migration, thereby maintaining robust redox capabilities. Under visible light irradiation, CeO2/CNNS demonstrates an impressive 4.2-fold increase in the hydrogen production rate compared to bulk g-C3N4 (BCN), coupled with a 48.5% boost in the photocatalytic degradation rate constant (k) of tetracycline (TC). This study not only unveils the innovative design of CeO2/CNNS but also paves the way for a fresh perspective on the design and preparation of multifunctional photocatalysts.

Facile synthesis of porous graphitic carbon nitride modulated by up-conversion carbon quantum dots for visible light-triggered photocatalysis towards bacteria inactivation

In this work, novel porous g-C3N4 nanosheets modulated by up-conversion carbon quantum dots (CQDs/CNS) were successfully fabricated. Using the photocatalytic inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as the model reaction, the visible light-triggered antibacterial activity was evaluated. It was found that the photocatalytic performance towards bacterial inactivation is significantly improved, with the minimum inhibitory concentration (MIC) in CQDs/CNS against E. coli and S. aureus only being 12.5 and 40 ppm, respectively. The enhancement in antibacterial behavior can be attributed to the introduction of up-conversion CQDs. On the one hand, it extends absorption region to the visible light which promotes the generation of e- - h+ pairs. On the other hand, it narrows the energy band gap which accelerates the separation of carriers and transferance of charges at the interface. This study provides a new insight for developing a CQDs-based g-C3N4 system for effective bacterial disinfection.

Sugars induced exfoliation of porous graphitic carbon nitride for efficient hydrogen evolution in photocatalytic water-splitting reaction

Photocatalytic hydrogen evolution holds great promise for addressing critical energy and environmental challenges, making it an important area in scientific research. One of the most popular photocatalysts is graphitic carbon nitride (gCN), which has emerged as a noteworthy candidate for hydrogen generation through water splitting. However, ongoing research aims to enhance its properties for practical applications. Herein, we introduce a green approach for the fabrication of porous few-layered gCN with surface modifications (such as oxygen doping, carbon deposition, nitrogen defects) with promoted performance in the hydrogen evolution reaction. The fabrication process involves a one-step solvothermal treatment of bulk graphitic carbon nitride (bulk-gCN) in the presence of different sugars (glucose, sucrose, and fructose). Interestingly, the conducted time-dependent process revealed that porous gCN exfoliated in the presence of fructose at 180 °C for 6 h (fructose_6h) exhibits a remarkable 13-fold promotion of photocatalytic hydrogen evolution compared to bulk-gCN. The studied materials were extensively characterized by microscopic and spectroscopic techniques, allowing us to propose a reaction mechanism for hydrogen evolution during water-splitting over fructose_6h. Furthermore, the study highlights the potential of employing a facile and environmentally friendly fructose-assisted solvothermal process to improve the efficiency and stability of catalysts based on graphitic carbon nitride.

Enhanced uranium capture by xanthan gum-polyacrylic acid bound porous g-C3N4 electrode via electrosorption, coordination and electrocatalytic reduction

Electrosorption holds extraordinary promise for uranium (U(VI)) capture but is still limited by the finite accessible active sites of electrode materials, poor surface wettability and its intrinsic co-ion repulsion effect. Here we originally designed KOH-etched porous graphitic carbon nitride (g-C3N4) as active material, and multi-functional crosslinked xanthan gum-polyacrylic acid (XG-PAA) as binder to fabricate g-C3N4-X electrode for U(VI) capture. The abundant in-plane nanopores on 2D g-C3N4 lamellar, rich O- and N-containing active sites, and 3D tough interconnected conductive architecture, endowed g-C3N4-X electrode with fast electron/ion transport channels, alleviated co-ions exclusion, superior electrochemical properties, and hydrophilicity. These unique structure characteristics enabled U(VI) ions to form micro electric-field attraction with negatively charged COO- groups in advance to alleviate co-ion repulsion, then to electro-migrate towards and coordinate with active sites, and eventually to be electrocatalytic reduced into U(IV) deposits. Consequently, the g-C3N4-X electrode exhibited a 1.87 times faster adsorption kinetics, a much higher removal ratio of 98.1% within 70 min than traditional PVDF-bound electrode. Meanwhile, the cumulative adsorption capacity of g-C3N4-X electrode after six cycles was up to 1459.1 mg g−1. This efficient, scalable, and cost-effective g-C3N4-X electrode represents a significant step forward toward the practical applications of U(VI) electrosorption.

Structural engineering and nitrogen doping of graphitic carbon nitride for photocatalytic degradation of organic pollutants under visible light

The ultrathin and porous graphitic carbon nitride (g-C3N4) nanosheets with structural design and abundant nitrogen dopants were synthesized via a one-step calcination procedure. The exfoliated and doped g-C3N4 (NT-CN) displayed enhanced photocatalytic activity for degradation of hydrochloride tetracycline and rhodamine B degradation in the complex water matrixes with different pH values or even in the presence of various anions (Cl−, CO2–3, NO- 3, and SO2–4). N-doped porous structure provided an extremely high surface area and enhanced basicity, enabling NT-CN catalyst to adsorb the abundant active species and pollutants. Moreover, NT-CN exhibited a wide band gap with a strong negative CB minimum of −1.07 eV that facilitated the formation of more photoexcited electrons. During the reaction process, the generated electrons reacted with dissolved O2 to produce the ·O2− species, and then transformed into highly reactive and stable 1O2 species, which play a predominant role in eliminating pollutants.

Exploring the Remarkably High Photocatalytic Efficiency of Ultra-Thin Porous Graphitic Carbon Nitride Nanosheets.

Graphitic carbon nitride (g-C3N4) is a metal-free photocatalyst used for visible-driven hydrogen production, CO2 reduction, and organic pollutant degradation. In addition to the most attractive feature of visible photoactivity, its other benefits include thermal and photochemical stability, cost-effectiveness, and simple and easy-scale-up synthesis. However, its performance is still limited due to its low absorption at longer wavelengths in the visible range, and high charge recombination. In addition, the exfoliated nanosheets easily aggregate, causing the reduction in specific surface area, and thus its photoactivity. Herein, we propose the use of ultra-thin porous g-C3N4 nanosheets to overcome these limitations and improve its photocatalytic performance. Through the optimization of a novel multi-step synthetic protocol, based on an initial thermal treatment, the use of nitric acid (HNO3), and an ultrasonication step, we were able to obtain very thin and well-tuned material that yielded exceptional photodegradation performance of methyl orange (MO) under visible light irradiation, without the need for any co-catalyst. About 96% of MO was degraded in as short as 30 min, achieving a normalized apparent reaction rate constant (k) of 1.1 × 10-2 min-1mg-1. This represents the highest k value ever reported using C3N4-based photocatalysts for MO degradation, based on our thorough literature search. Ultrasonication in acid not only prevents agglomeration of g-C3N4 nanosheets but also tunes pore size distribution and plays a key role in this achievement. We also studied their performance in a photocatalytic hydrogen evolution reaction (HER), achieving a production of 1842 µmol h-1 g-1. Through a profound analysis of all the samples' structure, morphology, and optical properties, we provide physical insight into the improved performance of our optimized porous g-C3N4 sample for both photocatalytic reactions. This research may serve as a guide for improving the photocatalytic activity of porous two-dimensional (2D) semiconductors under visible light irradiation.

From Porphyrin-Like Rings to High-Density Single-Atom Catalytic Sites: Unveiling the Superiority of p-C2N for Bifunctional Oxygen Electrocatalysis.

With effective utilization of the catalytic site, single-atom catalysts (SACs) supported by nitrogen atoms surrounding built-in pores of two-dimensional (2D) materials, such as porphyrin/phthalocyanine-based covalent organic frameworks, have been highly promising electrocatalysts in the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) processes for the air electrode of the metal-air battery. However, the number of stable single-atom anchoring sites, i.e., accessible single-atom metal sites, has been concerning as a result of the appearance of heterogeneous or large and even supersized pores in substrate materials. 2D porous graphitic carbon nitride (PGCN) with a stronger stability and smaller component is regarded as a more potential alternative owing to similar controllability and designability. In this work, inspired by the robust coordinated TM-N4 environment of porphyrin/phthalocyanine molecules, novel p-C2N with a high density of porphyrin-like organic units is rationally designed. In well-designed p-C2N, a higher homogeneity and uniformity of coordination sites can enhance the electrocatalytic activity in the whole catalytic material and better prevent SACs from sintering and agglomerating into thermodynamically stable nanoclusters. Utilizing density functional theory (DFT), the stability of the p-C2N monolayer, TM@p-C2N, and OER/ORR catalytic activities of TM@p-C2N (TM including Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au) are systematically evaluated. Among them, Ir@p-C2N (0.31 V of the OER and 0.36 V of the ORR), Co@p-C2N (0.47 and 0.22 V), and Rh@p-C2N (0.55 and 0.27 V) are screened as promising SACs for the bifunctional ORR and OER. The proposal of p-C2N guides a new direction for the development of TM-N-C-based SAC bifunctional electrocatalysts.

Supermolecule Polymer Derived Porous Carbon Nitride Microspheres with Controllable Energy Band Structure for Photocatalytic Hydrogen Evolution Reaction.

Porous graphitic carbon nitride microsphere with large specific surface area and controllable energy band structure is synthesized via a simple method with the supermolecule polymer of melamine-cyanuric acid (MCA) as the intermediates. The energy band structure and morphology of carbon nitride are closely correlative to the calcination time. And the CN-20 catalyst fabricated by calcination for 20h exhibit superior photocatalytic activity of hydrogen evolution reaction (HER) under visible-light (λ ≥420nm) irradiation. The photocatalytic and photoelectrochemical test results indicate that Pt is the optimum cocatalyst candidate compared with Pd, Ru, and Ag. Meanwhile, the time-dependent process of the intermediate pyrolysis to carbon nitride and the internal mechanism of photogenerated charge transfer between semiconductors and cocatalyst is investigated and supplemented by theoretical calculations. This work provides a novel and energy band structure controllable manufacture strategy for porous carbon nitride semiconductor with satisfying visible-light photocatalytic reduction performance.

Efficient photocatalytic degradation of tetracycline using Z-scheme GCN/Bi12O17Br2 composites under visible light: Process and mechanism

In this paper, GCN/Bi12O17Br2 photocatalysts with Z-scheme heterojunction was prepared by in-situ growth of Bi12O17Br2 nanosheets on porous cross-layer graphitic carbon nitride (GCN), which were used for efficient and stable tetracycline (TC) degradation. The construction of Z-scheme heterojunction effectively improved the separation efficiency of photogenerated carriers and promote the formation of ·O2− and·OH. In addition, ultra-thin porous GCN showed a better morphology and structure, which was conductive to exposing more active sites. The results of experiments showed that TC degradation efficiency of 20-GCN/Bi12O17Br2 photocatalysts with good stability could reach 97% under 80 min illumination. Besides, the mechanism of electron transfer was inferred by XPS, valence band and work function, and degradation products and pathways were deduced based on LC-MS. This work provides an effective method for constructing Z-scheme heterojunction between g-C3N4 and bismuth halide to improve photocatalytic degradation performance.

Synergy of defect engineering and curvature effect for porous graphite carbon nitride nanotubes promoted photocatalytic hydrogen evolution

AbstractGraphite carbon nitride (g‐C3N4) nanotubes have received extensive attention due to its unique morphology and electronic migration. Herein, the defective porous g‐C3N4 nanotube (DTCN) is prepared through a simple thermal reduction process. The construction of N vacancy and tubular structure can synergistically promote the separation of photogenerated charge carriers. As a result, DTCN demonstrates a higher photocatalytic hydrogen evolution rate (1440 μmol·g−1·h−1), which is 5 times higher than that of the initial g‐C3N4 nanotube (TCN). Importantly, combined with density functional theory calculations and experimental results, it is the first time to prove that the synergy of curvature effect and N vacancy of nanotubes can enhance the adsorption energy of hydrogen and decrease the work function, resulting in more superior photocatalytic performance than the layered structure. This work provides more in‐depth comprehension for the photocatalytic mechanism of nanotube materials, which has inspirational significance for the design of the g‐C3N4 photocatalyst with high performance.

2D/2D combination effects of pBN/gC3N4/TiO2 nanocomposites for photocatalytic CO2 conversion with alternative cationic scavengers

In this study, a series of pBN/gCN and pBN/gCN/TiO2 ternary nanocomposites was successfully fabricated by integrating 2D porous boron nitride and 2D graphitic carbon nitride with TiO2 using different amounts of gCN. First-principles DFT calculations were used for the first time to explore the electronic structure and electron flow in the ternary nanocomposites. The successful junctions of pBN/gCN/TiO2 were determined by analytical techniques, and all the results agreed that pBN, gCN, and TiO2 had interfacial connections with the efficient separation of photogenerated electrons and holes, thereby supplying plentiful photoinduced electrons to CO2R. In the photocatalytic CO2 reduction test, the light source was the principal component of the reactor; thus, we used visible light of different intensities (15 W, 75 W, and 100 W). In NaHCO3 solvent with a TEA electron donor, the CH3OH rates over TBCN2 were 13.79, 15.59, and 14.02 %, respectively. The enhanced efficiency of photocatalytic CO2 reduction is not only explained by the excellent capture of CO2 and the activation performance of TBCN2 with 2D/2D junctions, but also by the rapid charge separation and transfer of photogenerated charge carriers. Hence, this work demonstrates the use of 2D pBN and gCN with TiO2 ternary nanocomposites as novel and efficient catalysts for CO2R.

A Novel Synthetic 3D Interconnected Porous Carbon-Rich Graphitic Carbon Nitride for Boosting Visible Light Photocatalytic Hydrogen Production and Dye Contaminant Degradation

The use of photocatalysis to address environmental pollution and energy shortage is an attractive choice. Herein, we successfully synthesized a novel 3D interconnected porous carbon-rich g-C3N4 catalyst via facile thermal polymerization to enhance photocatalytic hydrogen production and photodegradation of dye contaminants. Enhanced hydrogen evolution (1956.23 μmol g−1 h−1) and photocatalytic RhB degradation (96.74%) efficiency were achieved with the as-obtained catalysts. Based on the photocatalytic experimental data and characterization analyses, an enhancement mechanism was proposed. The 3D interconnected porous structure endowed the g-C3N4 with numerous active sites and a large specific surface area, and the carbon modification facilitated the separation and transfer of the photoinduced charge carriers. Nanoshape engineering and the carbon-rich structure showed a synergetic effect in increasing photocatalytic performance. This study offers an applicable methodology for the exploitation of an economical catalyst to alleviate environmental pollution and energy shortages.

Porous Defect-Modified Graphitic Carbon Nitride as an Effective Adsorbent for the Removal of Hg From Surface Water

Porous Defect-Modified Graphitic Carbon Nitride as an Effective Adsorbent for the Removal of Hg From Surface Water

Constructing CoP[sbnd]C/g-C3N4 nanocomposites with P[sbnd]C bond bridged interface and van der Waals heterojunctions for enhanced photocatalytic H2 evolution

Enhancing the charge transmission rate at the interface of transition metal phosphide cocatalysts is an efficient technique to reinforce the photocatalytic activity action of semiconductors, but achieving a faster interface charge transfer rate remains a challenge. This paper reported the coupling of a two-dimensional carbon layer supported CoP (CoPC) as a non-noble metal heterostructure catalyst and a two-dimensional porous graphite carbon nitride (CN) photocatalyst to enhance the transmission rate of photogenerated carriers at the interface. Detailed characterizations and mechanism research have confirmed that the PC bond and Van der Waals heterojunction at the interface function as a novel charge transmission channel, which facilitates the effective transfer of photogenerated carriers from CN to CoP. Furthermore, the large contact area exhibited by the 2D/2D Van der Waals heterojunction offers an increased number of active sites for hydrogen evolution reactions. Consequently, the composite material (CoPC/CN) formed by the coupling of CoPC and CN has an enhanced H2 production rate of 1503 μmol∙g−1∙h−1 (AQY: 3.03 % at 400 nm) and favorable H2 production stability under visible light irradiation. This investigation not only provides a new idea for the regulation of interface charge transfer pathway but also offers new inspiration for the photocatalytic system's design with the synergistic impacts of 2D/2D VDW heterojunction and chemical bonds.

Synergistic sulfur doping and nitrogen vacancies in porous graphite carbon nitride for enhanced photocatalytic H2O2 production

The oxygen adsorption ability of the photocatalyst is essential for photocatalytic production of H2O2, whereas the investigation of influence of oxygen adsorption ability on the photocatalytic H2O2 production seems to be overlooked in most studies. Herein a facile ammonium persulfate assisted hydrothermal method is developed to synthesize porous and fluffy graphite carbon nitride (CN) with sulfur doping and nitrogen vacancies. The introduction of sulfur doping and nitrogen vacancies in combination of high surface area is found to be beneficial to improve the oxygen adsorption ability, which results in the increased H2O2 yield of 293.2 μM within 4 h compared to the pristine CN (123.2 μM). The developed strategy provides new insight for the design of highly efficient photocatalysts in a facile way.

A novel method to synthesis of oxygen doped graphitic carbon nitride with outstanding photocatalytic efficiency for the degradation organic pollutants

Contamination of water sources with organic pollutants seriously threatens the environment and living organisms, so it is necessary to remove them from these sources with a proper method. Photocatalytic degradation of such pollutants can be an effective, low-cost and eco-friendly method. In this study, a new method, porous oxygen-doped Graphitic carbon nitride (POCN) photocatalyst was synthesized by pre-exfoliation of bulk graphitic carbon nitride in hydrogen peroxide followed by calcination of the resulting exfoliated and oxygenated sample at 550 °C. In fact, in this method, a combination of three strategies, nanostructure preparation, band gap engineering and defect introduction into the g-C3N4 were used to improve the efficiency of photocatalyst. The synthesized sample was characterized using XRD, FESEM, TEM, FTIR, DRS, PL, EDX, XPS, and BET-EJH. The efficiency of the prepared photocatalyst was evaluated with its ability to degrade Congo Red (CR) in aqueous solution under visible light using two light sources, LED lamp and daylight. POCN removed the CR in a short time. The degradation rate was higher under sunlight. The free radical trapping tests showed that superoxide radical anions (O2−) are the active species and are mainly responsible for color degradation.