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1.
ZnIn2S4 microspheres (ZIS MSs) were for the first time decorated with carbon quantum dots (CQDs) and platinum nanoparticles (NPs) as dual co‐catalysts of for photocatalytic H2 production. The ZIS MSs co‐loaded with CQDs and Pt exhibited a high photocatalytic H2 production rate of 1032.2 μmol h?1 g?1 with an apparent quantum efficiency of 2.2 % (420 nm) in triethanolamine aqueous solution under visible‐light irradiation, which was much higher than the respective photocatalytic rates of pure ZIS, Pt loaded ZIS, and CQDs‐decorated ZIS. Such a great enhancement was attributed to the integrative effect of good crystallization, enhanced light absorption, high electrical conductivity of CQDs, and the vectorial electron transfer from ZIS to CQDs and Pt NPs (ZIS→CQDs→Pt).  相似文献   

2.
In this study, the photocatalytic activity of graphitic carbon nitride (g‐C3N4) synthesized via different precursors (urea, thiourea, and dicyandiamide) is investigated in the degradation process of tetracycline. Owing to the efficient charge separation and transfer, prolonged radiative lifetime of charge, large surface area, and nanosheet morphology, the urea‐derived g‐C3N4 exhibits superior photocatalytic activity for tetracycline degradation under visible‐light irradiation. This performance can compare with that of most reported g‐C3N4‐based composite photocatalysts. Through the time‐circle degradation experiment, the urea‐derived g‐C3N4 is found to have an excellent photocatalytic stability. The presence of NO3?, CH3COO?, Cl? and SO42? ions with the concentration of 10 mm inhibits the photocatalytic activity of urea‐derived g‐C3N4, where this inhibitory effect is more obvious for Cl? and SO42? ions. For the coexisting Cu2+, Ca2+, and Zn2+ ions, the Cu2+ ion exhibits a significantly higher inhibitory effect than Ca2+ and Zn2+ ions for tetracycline degradation. However, both the inhibitory and facilitating effects are observed in the presence of Fe3+ ion with different concentration. The h+, .OH and .O2? radicals are confirmed as major oxidation species and a possible photocatalytic mechanism is proposed in a urea‐derived g‐C3N4 reaction system. This study is of important significance to promote the large‐scale application of g‐C3N4 photocatalysts in antibiotic wastewater purification.  相似文献   

3.
Herein, a novel broken case‐like carbon‐doped g‐C3N4 photocatalyst was obtained via a facile one‐pot pyrolysis and cost‐effective method using glyoxal‐modified melamine as a precursor. The obtained carbon/g‐C3N4 photocatalyst showed remarkable enhanced photocatalytic activity in the degradation of gaseous benzene compared with that of pristine g‐C3N4 under visible light. The pseudo‐first‐order rate constant for gaseous benzene degradation on carbon/g‐C3N4 was 0.186 hr?1, 5.81 times as large as that of pristine g‐C3N4. Furthermore, a possible photocatalytic mechanism for the improved photocatalytic performance over carbon/g‐C3N4 nanocomposites was proposed.  相似文献   

4.
The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low‐cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g‐C3N4) from a low‐cost precursor, urea, is reported. The g‐C3N4 exhibits an extraordinary hydrogen‐evolution rate (ca. 20 000 μmol h?1 g?1 under full arc), which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5 % under visible light, which is nearly an order of magnitude higher than that observed for any other existing g‐C3N4 photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen‐evolution rate is significantly enhanced.  相似文献   

5.
In this work, alcian blue 8GX (AB), a copper(II) phthalocyanine derivative, was employed to functionalize graphitic carbon nitride (g‐C3N4) for the preparation of a highly efficient photocatalyst. The approach relies on a facile AB‐assisted ethanol/water mixed‐solvent exfoliation of bulk g‐C3N4. The as‐prepared g‐C3N4/AB hybrid possesses significantly enhanced solution dispersibility and photoelectrochemical performance resulting from the synergistic effect between g‐C3N4 and AB, which involves the optimization of intimate interfacial contact, extension of light absorption range, and enhancement of charge‐transfer efficiency. This synergy contributes enormously to the photocatalytic degradation of rhodamine 6G (R6G) under light irradiation.  相似文献   

6.
An interconnected framework of mesoporous graphitic‐C3N4 nanofibers merged with in situ incorporated nitrogen‐rich carbon has been prepared. The unique composition and structure of the nanofibers as well as strong coupling between the components endow them with efficient light‐harvesting properties, improved charged separation, and a multidimensional electron transport path that enhance the performance of hydrogen production. The as‐obtained catalyst exhibits an extremely high hydrogen‐evolution rate of 16885 μmol h?1 g?1, and a remarkable apparent quantum efficiency of 14.3 % at 420 nm without any cocatalysts, which is much higher than most reported g‐C3N4‐based photocatalysts even in the presence of Pt‐based cocatalysts.  相似文献   

7.
Bandgap narrowing and a more positive valence band (VB) potential are generally considered to be effective methods for improving visible‐light‐driven photocatalysts because of the significant enhancement of visible‐light absorption and oxidation ability. Herein, an approach is reported for the synthesis of a novel visible‐light‐driven high performance polymer photocatalyst based on band structure control and nonmetal and metal ion codoping, that is, C and Fe‐codoped as a model, by a simple thermal conversion method. The results indicate that compared to pristine graphitic carbon nitride (g‐C3N4), C+Fe‐codoped g‐C3N4 shows a narrower bandgap and remarkable positively shifted VB; as a result the light‐absorption range was expanded and the oxidation capability was increased. Experimental results show that the catalytic efficiency of C+Fe‐codoped g‐C3N4 for photodegradation of rhodamine B (RhB) increased 14 times, compared with pristine g‐C3N4 under visible‐light absorption at λ>420 nm. The synergistic enhancement in C+Fe‐codoped g‐C3N4 photocatalyst could be attributed to the following features: 1) C+Fe‐codoping of g‐C3N4 tuned the bandgap and improved visible‐light absorption; 2) the porous lamellar structure and decreased particle size could provide a high surface area and greatly improve photogenerated charge separation and electron transfer; and 3) both increased electrical conductivity and a more positive VB ensured the superior electron‐transport property and high oxidation capability. The results imply that a high‐performance photocatalyst can be obtained by combining bandgap control and doping modification; this may provide a basic concept for the rational design of high performance polymer photocatalysts with reasonable electronic structures for unique photochemical reaction.  相似文献   

8.
Inspired by the crucial roles of phosphates in natural photosynthesis, we explored an environmental “phosphorylation” strategy for boosting photocatalytic H2 production over g‐C3N4 nanosheets under visible light. As expected, a substantial improvement was observed in the rate of H2 evolution to 947 μmol h?1, and the apparent quantum yield was as high as 26.1 % at 420 nm. The synergy of enhanced proton reduction and improved hole oxidation is proposed to account for the markedly increased activity. Our findings may provide a promising and facile approach to highly efficient photocatalysis for solar‐energy conversion.  相似文献   

9.
《化学:亚洲杂志》2017,12(3):361-365
In this work, graphitic C3N4 decorated with a CoP co‐catalyst (g‐C3N4/CoP) is reported for photocatalytic H2 evolution reaction based on two‐step hydrothermal and phosphidation method. The structure of g‐C3N4/CoP is well confirmed by XRD, FTIR, TEM, XPS, and UV/Vis diffuse reflection spectra techniques. When the weight percentage of CoP loading is 3.4 wt % (g‐C3N4/CoP‐3.4 %), the highest H2 evolution amount of 8.4×102 μmol g−1 is obtained, which is 1.1×103 times than that over pure g‐C3N4. This value also is comparable with that of g‐C3N4 loaded by the same amount of Pt. In cycling experiments, g‐C3N4/CoP‐3.4 % shows a stable photocatalytic activity. In addition, g‐C3N4/CoP‐3.4 % is an efficient photocatalyst for H2 evolution under irradiation with natural solar light. Based on comparative photoluminescence emission spectra, photoelectrochemical I –t curves, EIS Nyquist plots, and polarization curves between g‐C3N4/CoP‐3.4 % and pure g‐C3N4, it is concluded that the presence of the CoP co‐catalyst accelerates the separation and transfer of photogenerated electrons of g‐C3N4, thus resulting in improved photocatalytic activity in the H2 evolution reaction.  相似文献   

10.
The photocatalytic activity of graphite‐like carbon nitride (g‐C3N4) could be enhanced by heterojunction strategies through increasing the charge‐separation efficiency. As a surface‐based process, the heterogeneous photocatalytic process would become more efficient if a larger contact region existed in the heterojunction interface. In this work, ultrathin g‐C3N4 nanosheets (g‐C3N4‐NS) with much larger specific surface areas are employed instead of bulk g‐C3N4 (g‐C3N4‐B) to prepare AgIO3/g‐C3N4‐NS nanocomposite photocatalysts. By taking advantage of this feature, the as‐prepared composites exhibit remarkable performances for photocatalytic wastewater treatment under visible‐light irradiation. Notably, the optimum photocatalytic activity of AgIO3/g‐C3N4‐NS composites is almost 80.59 and 55.09 times higher than that of pure g‐C3N4‐B towards the degradation of rhodamine B and methyl orange pollutants, respectively. Finally, the stability and possible photocatalytic mechanism of the AgIO3/g‐C3N4‐NS system are also investigated.  相似文献   

11.
As a metal‐free nitrogen reduction reaction (NRR) photocatalyst, g‐C3N4 is available from a scalable synthesis at low cost. Importantly, it can be readily functionalized to enhance photocatalytic activities. However, the use of g‐C3N4‐based photocatalysts for the NRR has been questioned because of the elusive mechanism and the involvement of N defects. This work reports the synthesis of a g‐C3N4 photocatalyst modified with cyano groups and intercalated K+ (mCNN), possessing extended visible‐light harvesting capacity and superior photocatalytic NRR activity (NH3 yield: 3.42 mmol g?1 h?1). Experimental and theoretical studies suggest that the ‐C≡N in mCNN can be regenerated through a pathway analogous to Mars van Krevelen process with the aid of the intercalated K+. The results confirm that the regeneration of the cyano group not only enhances photocatalytic activity and sustains the catalytic cycle, but also stabilizes the photocatalyst.  相似文献   

12.
Graphitic carbon nitride (g‐C3N4)‐based photocatalysts have received considerable attention in the field of photocatalysis, especially for photocatalytic H2 evolution. However, the intrinsic disadvantages of g‐C3N4 seriously limit its practical application. Herein, CdS nanospheres with an average diameter of 135 nm prepared using a solvothermal method were used as co‐catalysts to form CdS/g‐C3N4 composites (CSCN) to enhance the photocatalytic activity. Various techniques were employed to characterize the structure, composition and optical properties of the as‐prepared samples. It was found that the CdS nanospheres were relatively uniformly dispersed on the surface of g‐C3N4. Moreover, the photocatalytic H2 generation activity of the samples was evaluated using lactic acid as sacrificial reagent in water under visible light irradiation. When the amount of CdS nanospheres loaded in the hybridized composites was 5 wt%, the optimal H2 evolution rate reached 924 μmol g?1 h?1, which was approximately 1.4 times higher than that (680 μmol g?1 h?1) of Pt/g‐C3N4 (3 wt%). Based on the results of analysis, a possible mechanism for the photocatalytic activity of CSCN is proposed tentatively.  相似文献   

13.
Facile and direct synthesis of porous nanorod‐type graphitic carbon nitride/CuO composite ( CuO‐g‐C3N4 ) has been achieved by using a Cu–melamine supramolecular framework as a precursor. The CuO‐g‐C3N4 nanocomposite demonstrated improved visible‐light‐driven photocatalytic activities. The results indicate that metal–melamine supramolecular frameworks can be promising precursors for the preparation of efficient g ‐C3N4 nanocomposite photocatalysts.  相似文献   

14.
Access to high‐quality, easily dispersible carbon quantum dots (CQDs) is essential in order to fully exploit their desirable properties. Copolymers based on N‐acryloyl‐D ‐glucosamine and acrylic acid prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization are self‐assembled into micelle‐like nanoreactors. After a facile graphitization process (170 °C, atmospheric pressure), each micellar template is transformed into a CQD through a 1:1 copy process. These high‐quality CQDs (quantum yield=22 %) with tunable sizes (2–5 nm) are decorated by carboxylic acid moieties and can be spontaneously redispersed in water and polar organic solvents. This preparation method renders the mass production of multifunctional CQDs possible. To demonstrate the versatility of this approach, CQDs hybridized TiO2 nanoparticles with enhanced photocatalytic activity under visible‐light have been prepared.  相似文献   

15.
A rapid and highly efficient strategy for introducing C into g‐C3N4 involves copolymerizing π‐electron‐rich barbituric acid with melamine via a facile microwave‐assisted heating, thereby eliminating the issues in conventional electric furnace heating, such as the severe volatilization, owing to the mismatch of the sublimation temperatures of barbituric acid and melamine. The g‐C3N4 catalyst after optimizing the C‐doping content actively generates increased amounts of H2 under visible light exposure with the highest H2 generation rate of 25.0 μmol h?1, which is nearly 20 times above that using g‐C3N4 produced by conventional electric furnace heating of two identical monomers (1.3 μmol h?1). As such, the microwave‐assisted heating strategy may stand out as an extremely simple route to incorporating π‐electrons into g‐C3N4 with markedly improved photocatalytic performance.  相似文献   

16.
A stable and selective electrocatalyst for CO2 reduction was fabricated by covalently attaching graphitic carbon nitride onto multiwall carbon nanotubes (g‐C3N4/MWCNTs). The as‐prepared composite is able to reduce CO2 exclusively to CO with a maximum Faraday efficiency of 60 %, and no decay in the catalytic activity was observed even after 50 h of reaction. The enhanced catalytic activity towards CO2 reduction is attributed to the formation of active carbon–nitrogen bonds, high specific surface area, and improved material conductivity of the g‐C3N4/MWCNT composite.  相似文献   

17.
Carbon quantum dots (CQDs) were synthesized by heating various carbon sources in HNO3 solution at reflux, and the effects of HNO3 concentration on the size of the CQDs were investigated. Furthermore, the oxygen‐containing surface groups of as‐prepared CQDs were selectively reduced by NaBH4, leading to new surface states. The experimental results show that the sizes of CQDs can be tuned by HNO3 concentration and then influence their photoluminescent behaviors; the photoluminescent properties are related to both the size and surface state of the CQDs, but the photocatalytic activities are determined by surface states alone. The different oxygen‐containing groups on the surface of the CQDs can induce different degrees of the band bending upward, which determine the separation and combination of the electron–hole pairs. The high upward band bending, which is induced by C?O and COOH groups, facilitates separation of the electron–hole pairs and then enhances high photocatalytic activity. In contrast, the low upward band bending induced by C? OH groups hardly prevents the electron–hole pairs from surface recombination and then exhibits strong photoluminescence. Therefore, both the photocatalytic activities and optical properties of CQDs can be tuned by their surface states.  相似文献   

18.
Graphitic carbon nitride (g‐C3N4) has been widely used in fields related to energy and materials science. However, nanostructured g‐C3N4 photocatalysts synthesized by traditional thermal polycondensation methods have the disadvantage of small specific surface areas and wide band gaps; these limit the catalytic activity and application range of g‐C3N4. Based on the unique nanostructure of g‐C3N4, it is a feasible method to modify g‐C3N4 with metals to design novel metal–semiconductor composites. Metals alter the photochemical properties of g‐C3N4, in particular, narrow the band gap and expand photoabsorption into the visible range, which improves the photocatalytic performance. This review covers recent progress in metal/g‐C3N4 nanocomposites for photocatalysts, organic systems, biosensors, and so on. The aim is to summarize the synthetic methods, nanostructures, and applications of metal/g‐C3N4 nanocomposite materials, as well as discuss future research directions in these areas.  相似文献   

19.
Halide perovskite quantum dots (QDs) have great potential in photocatalytic applications if their low charge transportation efficiency and chemical instability can be overcome. To circumvent these obstacles, we anchored CsPbBr3 QDs (CPB) on NHx‐rich porous g‐C3N4 nanosheets (PCN) to construct the composite photocatalysts via N?Br chemical bonding. The 20 CPB‐PCN (20 wt % of QDs) photocatalyst exhibits good stability and an outstanding yield of 149 μmol h?1 g?1 in acetonitrile/water for photocatalytic reduction of CO2 to CO under visible light irradiation, which is around 15 times higher than that of CsPbBr3 QDs. This study opens up new possibilities of using halide perovskite QDs for photocatalytic application.  相似文献   

20.
Heterojunctions of g‐C3N4/Al2O3 (g‐C3N4=graphitic carbon nitride) are constructed by an in situ one‐pot hydrothermal route based on the development of photoactive γ‐Al2O3 semiconductor with a mesoporous structure and a high surface area (188 m2g?1) acting as electron acceptor. A structure modification function of g‐C3N4 for Al2O3 in the hydrothermal process is found, which can be attributed to the coordination between unoccupied orbitals of the Al ions and lone‐pair electrons of the N atoms. The as‐synthesized heterojunctions exhibit much higher photocatalytic activity than pure g‐C3N4. The hydrogen generation rate and the reaction rate constant for the degradation of methyl orange over 50 % g‐C3N4/Al2O3 under visible‐light irradiation (λ>420 nm) are 2.5 and 7.3 times, respectively, higher than those over pristine g‐C3N4. The enhanced activity of the heterojunctions is attributed to their large specific surface areas, their close contact, and the high interfacial areas between the components as well as their excellent adsorption performance, and efficient charge transfer ability.  相似文献   

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