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Improving the Visible-Light Photocatalytic Activity of Graphitic Carbon Nitride by Carbon Black Doping
摘要： Hydrogen production by water splitting and the removal of aqueous dyes by using a catalyst and solar energy are an ideal future energy source and useful for environmental protection. Graphitic carbon nitride can be used as the photocatalyst with visible light irradiation. However, it typically suffers from the high recombination of carriers and low electrical conductivity. Here, we have developed a facile mix-thermal strategy to prepare carbon black-modified graphitic carbon nitrides, which possess high electrical conductivity, a wide adsorption range of visible light, and a low recombination rate of carriers. With the help of carbon black, highly crystallized graphitic carbon nitrides with built-in triazine and heptazine heterojunctions are obtained. Improved photocatalytic activities have been achieved in carbon black-modified graphitic carbon nitride. The dye removal rate can be three times faster than that of pristine graphitic carbon nitride and the photocatalytic H2 generation is 234 μmol h?1 g?1 under visible light irradiation.
关键词： aqueous dyes removal,hydrogen production,carbon black doping,graphitic carbon nitride,visible-light photocatalytic activity
更新于2025-09-23 15:21:21
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An Investigation into the Stability of Graphitic C <sub/>3</sub> N <sub/>4</sub> as a Photocatalyst for CO <sub/>2</sub> Reduction
摘要： The increasing CO2 concentration in the atmosphere exerts a significant influence on global warming and climate change. The capture and utilization of CO2 by conversion to useful products is an area of active research. In this work, the photo-driven reduction of CO2 was investigated using graphitic carbon nitride (g-C3N4) as a potential photocatalyst. The photocatalytic reduction of CO2 was investigated with g-C3N4 powder immobilized on a glass support in a batch gas phase photoreactor. The experiments were carried out under UV-Vis irradiation at 70°C and an initial pressure of 2.5 bar. The only gas phase product detected during the irradiation of the g-C3N4 in the presence of CO2 was CO, and the rate of production was observed to decrease over time. Oxygen doped g-C3N4 was also tested for CO2 reduction but had lower efficiency that the parent g-C3N4. Repeated cycles of photocatalytic CO2 reduction showed a decline in the activity of the g-C3N4. In the absence of CO2 some CO generation was also observed. Characterization of used and unused materials, using FTIR and XPS, showed an increase in the oxygen functional groups following UV-Vis irradiation or thermal treatment. While others report the use of g-C3N4 as a photocatalyst, this work highlights the important need for replicates and control testing to determine material stability.
关键词： CO2 reduction,photocatalysis,oxygen doping,graphitic carbon nitride,material stability,g-C3N4
更新于2025-09-23 15:21:21
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Sulfur-doped porous graphitic carbon nitride heterojunction hybrids for enhanced photocatalytic H2 evolution
摘要： Graphitic carbon nitride (g-C3N4) is considered as an attractive, efficient and newly generated photocatalyst material owing to its distinct properties such as metal free, suitable band gap and high physicochemical stability. Nevertheless, the photocatalytic activity of pure g-C3N4 was limited by the fast recombination rate of photoinduced electron–hole pairs and relatively low specific surface area. In this study, we provide a new prospect to overcome the problem by using another suitable precursor urea-assisted copolymerization with thiourea which is expected to optimize the process of thermal condensation, inhibit agglomeration and improve the specific surface area; meanwhile, the formed isotype heterogeneous junction effectively inhibits charge carrier recombination. The formed g-C3N4 isotype heterojunction photocatalyst manifested significant improvement photocatalytic hydrogen production than the single and pure g-C3N4 sample. This significant enhanced photocatalytic performance is mainly ascribed to inhibited recombination, enriched active site and enlarged specific surface area.
关键词： porous graphitic carbon nitride,heterojunction hybrids,photocatalytic H2 evolution,Sulfur-doped
更新于2025-09-23 15:21:21
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Transient photoinduced phenomena in graphitic carbon nitride as measured at nanoseconds resolution by step-scan FTIR
摘要： Transient FTIR measurements were performed on graphitic carbon nitride using a step-scan method, facilitating temporal resolution of a few nanoseconds. Variations in the location and the intensity of specific peaks and emerging of new peaks were observed during the first 170 nanoseconds after excitation. A comparison was made between graphitic carbon nitride prepared at two temperatures: 510 °C and 650 °C. The material prepared at 650 °C revealed very strong non-specific absorption beginning 35 nanoseconds after excitation and lasting for 20 nanoseconds. This phenomenon, termed “IR-blackening” was observed neither in g-C3N4 prepared at 510 °C nor in g-C3N4 prepared at 650 °C that was exposed to hole scavengers (ethanol and benzyl alcohol). In contrast, exposure of material prepared at 650 °C to an electron scavenger (methyl viologen) hardly alter the “IR-blackening” phenomenon. The results were explained by a mechanism, predicting higher reductive activity for materials having imperfect heptazine polymerization, as indeed was found in the photocatalytic degradation of 4-nitrophenol.
关键词： Photocatalysis,IR- blackening,Step-scan,graphitic carbon nitride,Transient FTIR
更新于2025-09-23 15:21:21
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Fabrication of hierarchical sheet-on-sheet WO3/g-C3N4 composites with enhanced photocatalytic activity
摘要： Novel hierarchical sheet-on-sheet WO3/g-C3N4 (WOCN) composites were successfully fabricated by simple calcination method using acid-treated SrWO4/g-C3N4 as precursors. The morphological observation showed that WO3 nanosheets were closely anchored on the surface of g-C3N4 nanosheets to construct a hierarchical nanostructure. The as-synthesized WOCN composites exhibited a significantly higher photocatalytic activity towards the photocatalytic degradation of rhodamine B (RhB) compared to pristine g-C3N4 and WO3 under simulated sunlight irradiation. The optimum photocatalytic activity of the WOCN at a WO3 mass content of 34.6% was 6.5 and 3.0 times higher than that of pristine WO3 and g-C3N4, respectively. The enhanced photocatalytic activities of WOCN composites were attributed to the formation of hierarchical heterostructure, which provided larger specific surface area, better visible-light absorption capability, reduced the recombination of photogenerated electron-hole pairs and enhanced separation efficiency of charge carriers. A Z-scheme photocatalytic mechanism was proposed according to active species trapping experiments.
关键词： Graphitic carbon nitride,Photocatalytic degradation,Tungsten oxide,Hierarchical heterostructure,Strontium tungstate
更新于2025-09-23 15:21:21
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Simultaneously engineering K-doping and exfoliation into graphitic carbon nitride (g-C3N4) for enhanced photocatalytic hydrogen production
摘要： Doping and exfoliation are effective strategies to improve the photocatalytic activity of bulk graphitic carbon nitride (g-C3N4). Therefore, it can be inferred that engineering element-doping and exfoliation into g-C3N4 would further enhance the photocatalytic performance. Herein, we demonstrated a KOH-assisted hydrothermal-reformed melamine strategy for achieving the simultaneous K-doping and exfoliation of g-C3N4. The as-synthesized K-doped g-C3N4 ultrathin nanosheets displayed much enhanced photocatalytic hydrogen evolution rate (HER) of about 13.1 times higher than that of the bulk g-C3N4 under visible-light irradiation, achieving an apparent quantum efficiency of 6.98% at 420 nm. The improved photocatalytic HER can be attributed to the high surface area offering numerous photocatalytic active sites, enlarged conductive band edge optimizing photoreduction potential, and K-doping promoting charge generation and separation as well as the long life-time of photogenerated carriers. This work would provide a promising way to integrate co-doping and exfoliation into new g-C3N4-based materials.
关键词： Graphitic carbon nitride,Exfoliation,Photocatalytic hydrogen evolution,Nanosheet,K-doping
更新于2025-09-23 15:21:21
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Modified Nanopillar Arrays for Highly Stable and Efficient Photoelectrochemical Water Splitting
摘要： Atomically modified graphitic carbon nitride quantum dots (QDs), characterized by strongly increased reactivity and stability, are developed. These are deposited on arrays of TiO2 nanopillars used as a photoanode for the photoelectrochemical water splitting. This photoanode shows excellent stability, with 111 h of continuous work without any performance loss, which outperforms the best-reported results by a factor of 10. Remarkably, our photoanode produces hydrogen even at zero bias. The excellent performance is attributed to the enhancement of photoabsorption, as well as to the promotion of charge separation between TiO2 nanopillars and the QDs.
关键词： hydrogen evolution,quantum dots,graphitic carbon nitride,photoelectrochemistry,TiO2 nanopillars
更新于2025-09-23 15:21:21
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Carbon quantum dots-decorated TiO2/g-C3N4 film electrode as a photoanode with improved photoelectrocatalytic performance for 1,4-dioxane degradation
摘要： In this study, carbon quantum dots (CQDs) were used to decorate a TiO2/g-C3N4 (TCN) film electrode. The morphological, optical, and electrochemical properties of the TiO2/g-C3N4/CQDs nanorod arrays (TCNC NRAs) film were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and electro-impedance spectroscopy (EIS). The improved optical properties, photoelectrochemical chemical properties and photoelectrocatalytic (PEC) performance of photoanode can be observed by doping CQDs onto the TCN NRAs film. Compared with TiO2 NRAs and TCN NRAs, the narrower band gap of 2.47 eV and longer lifetime of photoinduced electron-hole pairs were observed in the TCNC NRAs. Under visible light irradiation and a bias voltage of 1.2 V, the photocurrent density and 1,4-dioxane (1,4-D) removal rate of PEC process with TCNC NRAs electrode reached 0.16 mA/cm2 and 77.9%, respectively, which was 2.5 times and 1.5 times of that with TCN NRAs electrode. TCNC NRAs electrode could keep >75% of the 1,4-D removal rate during five cycles tests. High PEC performance with TCNC NRAs electrode could be attributed to the enhanced charge separation and the change of electron transfer mechanism from typical heterojunction to Z-scheme, which may increase the active species production and change the dominant reactive species from O2?- to ?OH. Our experimental results should be useful for studying the degradation of 1,4-D and developing efficient PEC materials.
关键词： Graphite carbon nitride,TiO2 nanorods,1,4-Dioxane,Carbon quantum dots,Photoelectrocatalysis
更新于2025-09-23 15:21:01
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Photocatalytic degradation of phenol wastewater over Z-scheme g-C3N4/CNT/BiVO4 heterostructure photocatalyst under solar light irradiation
摘要： A series of carbon nanotubes (CNT) modified g-C3N4/BiVO4 photocatalysts were synthesized via wet-impregnation method and evaluated via degradation of phenol under solar light irradiation. The physicochemical properties of the as-developed photocatalyst were characterized using FTIR, XRD, FESEM, XPS, SAP and DR-UV Vis. The formation of g-C3N4/CNT/BiVO4 photocatalysts resulted in remarkable enhancement in the performance in which almost six times higher degradation rate in comparison to the pristine g-C3N4 and obeyed the pseudo-first-order kinetics and Temkin adsorption model. Congruously, the synergistic interaction between 2 wt. % of CNT and 5 vol. % of H2O2 as an oxidizing agent was capable of removing 80.6 % of phenol within 120 minutes. The profound photodegradation performance monitored was attributed to the better crystallinity structure obtained as shown in XRD and XPS analysis. Furthermore, the intimate contact between the CNT, g-C3N4 and BiVO4 in the heterostructure sample as shown in FESEM micrograph images does help in allowing a smooth electron-hole pair separation and migration, resulting in more available ?OH and ?O2ˉ radicals for photocatalytic degradation activities. The possible Z-scheme reaction mechanism has been proposed and active species trapping experiments have been carried out to find the role of active radical species responsible for the phenol degradation. Additionally, the g-C3N4/CNT/BiVO4 photocatalysts retained excellent stability even after several cycles. Congruently, a mathematical representation for understanding the interaction between CNT loading and H2O2 for photodegradation of phenol using response surface methodology (RSM) was successfully generated.
关键词： phenol degradation,bismuth vanadate,carbon nanotube,wastewater,graphitic carbon nitride,photocatalyst
更新于2025-09-23 15:21:01
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Carbon Vacancies in a Melon Polymeric Matrix Promote Photocatalytic Carbon Dioxide Conversion
摘要： Photosynthetic conversion CO2 into fuel and chemicals is a promising but challenging technology. The bottleneck of this reaction lies in the activation of CO2, owing to the chemical inertness of linear CO2. Herein, we present a defect engineering methodology to construct CO2 activation sites by implanting carbon vacancies (CVs) on the melon polymer (MP) matrix. Positron annihilation spectroscopy confirms the location and density of the CVs in the MP skeleton. transform spectroscopy and density functional theory (DFT) study reveals that the CVs can function as active sites for CO2 activation, while stabilizing COOH* intermediates, thereby boosting the reaction kinetics. As a result, the modified MP-TAP-CVs display a 45-fold improvement in CO2-to-CO activity over the pristine MP. The apparent quantum efficiency of the MP-TAP-CVs achieves 4.8 % at 420 nm, which exceeds most of the heterogeneous reduction of CO2 under visible light. This study will shed new light on the design of high-efficiency polymer semiconductors for CO2 conversion.
关键词： Carbon nitride,Photocatalysis,CO2 reduction,Carbon vacancy
更新于2025-09-23 15:21:01