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Kinetics, Catalysis, and Reaction Engineering

In Situ Fabrication of Foamed Titania Carbon Nitride Nanocomposite and its Synergetic Visible Light Photocatalytic Performance Muhammad Shakeel, Baoshan Li, Ghulam Yasin, Muhammad Arif, Wajid Rehman, and Hashmat Daud Khan Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b01090 • Publication Date (Web): 29 May 2018 Downloaded from http://pubs.acs.org on May 29, 2018

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Industrial & Engineering Chemistry Research

In Situ Fabrication of Foamed Titania Carbon Nitride Nanocomposite and its Synergetic Visible Light Photocatalytic Performance Muhammad Shakeela, Baoshan Lia*, Ghulam Yasina, Muhammad Arifa, Wajid Rehmanb, Hashmat Daud Khana a. State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, P.R China. b. Department of Chemistry HAZARA University Mansehra, 21120, KPK, Pakistan.

Corresponding author. E-mail address: [email protected] (B. Li).

1 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ABSTRACT Efficient visible light driven materials is a key for environmental remediation. The foamed titania-carbon nitride nanocomposite (FTCN) was synthesized, by in situ microemulsification followed by calcination using bulk g-C3N4 and TBOT. During calcination the bulk g-C3N4 transformed into ultrathin nano sheets. The nano composite is

characterize by state of the art physicochemical techniques, the structure look like foam with mesoporous cavities. The carbon nitride nano sheets uniformly distributed and mostly embedded inside the bulk of titania with close interfacial connection. The FTCN3 nanocomposite has superior degradation performance for MB and RhB with rate constant 0.096 and 0.061 k(min-1) respectively. This upmost photocatalytic activity could be

ascribed to large SBET (339 m2g-1) and foamed structure. These are considered significant factors for efficient visible light absorption and slow recombination of charges during photocatalysis. This is consider an inventive strategy to enhance the potential of TiO2 in diverse fields.


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Key Words: TiO2 nano-spheres, g-C3N4 nanosheets, foamed titania-carbon nitride nanocomposite, visible light photocatalyst, degradation of dyes.



1. INTRODUCTION Photocatalysis based on semiconductors has been approved an efficient green strategy for environmental pollution remediation and energy conversions.1-3 TiO2 based materials have been studied broadly and demonstrated as most promising catalysts to eliminate organic pollutants by utilizing solar energy. This is due to its easiness for availability, cheap, superb stability and non toxicity.4-5 Unfortunately TiO2 has few shortcomings, such as unable to exploit the visible light, large excitation band gap (3.2 eV), limits also included rapid recombination of photo-generated charge careers that hamper its practicability.6 Therefore, great efforts has been dedicated to expend its energy spectrum from ultra violet to visible spectral region, and decreased the recombination rate of photo generated charges.7-8 A significant development has been achieved in this field by metal/non-metal doped TiO2,9 dye-sensitizing,10 surface alteration and combination of semiconductors.11 The semiconductor coupling to assembled hetero-junction has been approved an efficient technique to get the desired goals.

12-14

Recently, g-C3N4 (2.7 eV)

considered as potential visible light responsive material for various catalytic reactions due to its photo stability and superior charge transferring capability.15-17 The combination of TiO2 and g-C3N4 considered an appropriate progress towards maximum visible light absorption, deals with the transfer and recombination of photo generated charges due to their suitable band-edge positions.18 Numerous studies have been reported about the catalytic activity of modified TiO2 with g-C3N4. Chang et al. synthesized a chain of TiO2/g-C3N4 nanohybrids and explored its photocatalytic performance for the degradation RhB dye.19 The Tong et al. structured TiO2/g-C3N4 nanocomposite by a biomimetic method and concluded that the hetero-junction enhanced the electron-hole


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separation and decreased the rate of recombination. 20 Wang et al. customized TiO2 nano rod arrays by g-C3N4 under vapor deposition method.21 Regardless of recent development, the realistic applications of the g-C3N4/TiO2 nanocomposites for photocatalytic reaction is still unacceptable, either due to limited visible light effectiveness or very long time photo-degradation reaction. Therefore it is challenge for the researchers to introduce the visible light effective photocatalyst having excellent morphology with high-flying active sites for the environmental remediation. To achieve this goals, great efforts has been taken to exploit the hierarchically nano structured photocatalysts with multi dimensional pore structure. These are usually fabricated by the congregation of nano sized structural units such as nano-tubes, nanorods and nano-sheets. Considerably the hierarchical structured acquired unified porous network with large surface area that benefitted the visible light absorption, provides adequate space for the adsorption of dyes and transportation of photo active charges.22-23 Consequently, the controlled morphology of g-C3N4/TiO2 is predicted to be efficient for photocatalysis. Herein, we reported a novel foamed titania-carbon nitride (FTCN) nanocomposite synthesized via in situ micro-emulsification followed by calcination. This foamy structure improved the visible light absorption and reduced the recombination of electron-hole pairs. The as-prepared sample was investigated as outstanding visible light photocatalyst to degrade two stable organic dyes MB and RhB in very short time intervals, as compare to pure g-C3N4 and foamed titania (FT). Hence provided new insights to the fabrication of foamy materials and extending its industrial applications. 2. EXPERIMENTAL SECTION



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2.1. Materials Absolute

C2H5OH

and

NH3

(25

wt%),

n-octane,

CTAB,

TBOT

and

dicyandiamide(DCDA) were purchased from different local industries of china. All the chemicals used in the reactions was of analytical grade. 2.2. Fabrication of bulk g-C3N4 The bulk g-C3N4 was fabricated by annealing the DCDA. Usually known quantity of dicyandiamide calcined at 550 °C for 4h@3°Cmin-1 to get yellow solid material, that was grinded into very fine till light yellow powder of bulk g-C3N4. 2.3. Fabrication of foamed titania-carbon nitride (FTCN) nano composite The foamed titania-carbon nitride was synthesized using bulk g-C3N4 and TBOT by in situ micro-emulsification followed by calcination (see scheme 1). Typically titania-carbon nitride (TCN) was synthesized by dropping 2.2 g of TBOT into 2 mL acetyl-acetone and 3 mL of n-octane with constant stirring for 30 min at 25° C. Then the homogenized dispersion of bulk g-C3N4 in n-octane was dropped into the above mixture with vigorous string of 30 min. During the reaction positive end of titania attracted towards the nitrogen of carbon nitride to form TCN. Afterward for foaming followed the procedure reported in our previous studies.24 Consequently it was hydrothermally treated at 100 °C for 24 h. Then the pallets was collected, washed several times with water and ethanol to washed out all the impurities, then dried over night. Finally calcined at 500° C for 3h@3°min-1, during calcination the bulk carbon nitride transformed into thin nano sheets on the surface of titania and designated as foamed titania-carbon nitride FTCN-x%. Where x% was the percent loading of the bulk g-C3N4, so the resulting product was labeled as FTCN-1 (3%), FTCN-2 (6%), FTCN-3 (9%),


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FTCN-4 (12%) and FTCN-5 (15%). The pure foamed titania (FT) was also prepared for comparative studies under the same experimental conditions without g-C3N4.

Scheme 1. Schematic elaboration of the fabrication of foamed titania-carbon nitride nanocomposite via in situ micro-emulsification followed by calcination.

2.4. Characterization The phase structure was investigated by XRD technique on a Rigaku-D/Max-2500VBZ+/PC-diffractometer. The SEM with EDS spectra and HRTEM images was taken by (SEM Hitachi S-4700) and (HRTEM JEM-3010). The BET and BJH measurements was carried out on Micromeritics ASAP2020M instrument. The optical properties was recorded on UV-Vis./NIR Spectrophotometer UV-3600 (Shimadzu). The surface analysis and binding energy was determined on x-ray photoelectron spectrometer ESCALAB-250. Reactive Oxygen Species (ROS) was detected by recording the EPR spectra on a Bruker E-500 spectrometer. 2.5. Photocatalytic performance The visible light induced catalytic activity of the as-fabricated nanocomposite was investigated by the degree of decomposition of MB and RhB as stable organic pollutants. 7 ACS Paragon Plus Environment


Generally 0.1 g of the catalyst was put in a 200 mL mixed solution of MB and RhB with initial concentration of 50 mgL-1of each dye, then added in pyrex reactor equipped with a 50 W Hg lamp. An adsorption-desorption equilibrium must be developed in dark prior to irradiations. Latter on the reactor was exposed to the visible light source with steady stirring of the system. After irradiation for specific intervals, the appropriate amount pipette out and centrifuged it at 3000 rpm and examined the photo degradation of dyes by Shimadzu UV-3600 spectrophotometer. The change in the dye concentration was measured by standard curve method. Finally the degraded amount was measured by plotting Ct/Co vs time. 2.6. Electrochemical measurements To determined the separation and recombination of charges during photocatalysis the EIS and photo-current responses was carried out in 1M KOH solution on a three electrode electrochemical work station (CHI760E CH. Instrument Co. USA). 3. RESULTS AND DISCUSSION 3.1. Characterization of material The XRD measurements was carried out to elucidate the structure as depicted in Figure 1. The peaks at 27.56° and 12.7° corresponds to interlayer stacking (002) and planer diffractions (100) of g-C3N4. The peak at 17° (101) and 22° (100) generally ascribed to a disordered melon structure of polymeric carbon nitrides. The peak at 44° (200) assigned to the triazine based structure.25-26 The existence of such peaks inveterate the successful formation of g-C3N4 after thermal treatment. No obvious peaks of g-C3N4 nano sheets found in the FTCN nano composites, which may be probably due to deprived crystallization, low content or could be due to very fine g-C3N4 nano sheets, that


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immersed deeply and overlapped into the bulk phase of mesoporous titania due to foaming characteristics.27 However the existence of g-C3N4 is confirmed by X-rays photo electron spectroscopy with very weak peak intensity. Whereas, the prominent peaks at 25.2°, 37.9°, 48.0°, 53.9°, 55.0°, 62.4° and 68.8° corresponds to (101), (004), (200), (105), (211), (204), and (220) (JCPDS 21-1272) was observed for TiO2 respectively. Notably, there was no variations in position and widths of the characteristic diffraction peaks of FTCN nano composite by doping with g-C3N4 indicated no alteration in the crystal planes of TiO2. While there is gradual decrease in the relative peak intensities of FTCN composite by increasing mass of g-C3N4 nanosheets which completely overlapped and covered the whole surface of TiO2, indicated strong interactions between g-C3N4 nanosheets and TiO2 nanospheres.28

Figure 1. XRD pattern of (a) g-C3N4 nano sheets (b-f) FTCN-1, FTCN-2, FTCN-3, FTCN-4, FTCN-5 foamed titania-carbon nitride nanocomposite with different mass loading of g-C3N4 respectively (g) Degussa P25.

The morphology and micro structure was explored by SEM and HRTEM measurements. The SEM images of pure titania and titania-carbon nitride nano composite showed foam 9 ACS Paragon Plus Environment


like structure with jointed spherical nano spheres about 75-135 nm. In case of pure foamed titania the shells of large spheres consist of smooth surfaces small spheres. While in foamed titania-carbon nitride nano composite all the spheres are rough and encompass close contact with each other due to dispersion of thin g-C3N4 nano sheets as shown in Figure 2. These nanosheets homogeneously covered the surface of titania nano spheres result in minimizing the surface energy.29 Significantly, the g-C3N4 nano sheets grow onto the TiO2 nano spheres without destroying its intrinsic structure. Moreover, the porosity in the structure of (FTCN) is caused by the disintegration of bulk g-C3N4 into some gaseous products during calcination, which is more and beneficial for adsorption process.29

Figure 2. SEM images of the (a) pure foamed titania nano spheres (b) foamed titania-carbon nitride nano composite with optimal g-C3N4 loading.

The HRTEM images provided profound justifications about the structure and morphology of nano composite, corresponding results displayed in Figure 3. The FTCN nano composite exhibited lattice planes with spacing (d = 0.318 nm) indexed as (002) inter plane of g-C3N4 and (d = 0.35 nm) correspond to (101) planer reflections of anatase TiO2. These findings revealed to be stable interfaces relation of TiO2 nano spheres and g-


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C3N4 nanosheets. Moreover the g-C3N4 nano sheets deeply embedded inside the TiO2 nano spheres that allowed the transportation of charges between two interfaces. 30

Figure 3. (a,b) HRTEM images of foamed titania-carbon nitride with optimal mass loading of g-C3N4. (c) lattice interfacial correlation of TiO2 and g-C3N4 nano sheets (d) magnified state of image “c” that showing the obvious interfacial connection.

The elemental composition of FTCN-1, FTCN-3 and FTCN-5 with diverse mass loading of g-C3N4 was studied by EDS. The Figure 4 illustrated the validate persistence of the corresponding elements such as Ti, O, C and N in the nano composites. Moreover elemental mapping is also attached with EDS spectra.



Figure 4. EDS spectra of (a) FTCN-1(3%), (b) FTCN-3(9%) and (c) FTCN-5(15%) with corresponding elemental mapping.

The chemical composition and elemental binding energies of the FTCN nanocomposite was further confirmed by XPS spectroscopy. Figure 5a displayed the survey spectra corresponding to the elemental composition that authenticate the subsistence of C, O, N and Ti. The C1s exhibited peaks at 284.75 eV, 285.90 eV and 288.35 eV consequent to cyclic structured sp2 hybridized (N-C=N), sp3 hybridized carbon (C-(N)3) and CN with polymeric graphitic structure shown in Figure 5b.31-32 The Ti2p spectrum consist of two main peaks Ti2p3/2 and Ti2p1/2 shown in Figure 5c. The peak fitting of Ti2p3/2 (457.90 eV) and Ti2p1/2 at (463.40 eV) further corroborate the inclusion of N atom with the configuration of the Ti-N phase.33 The XPS results together with the HRTEM and EDS obviously revealed the formation of foamed titania carbon nitride nano structure with chemically bound interfaces.


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Figure 5. The XPS spectra (a) elemental survey (b) C1s and (c) Ti2p of foamed titania-carbon nitride with optimal loading of g-C3N4.

The surface area and pore sizes of pure FT and FTCN nanocomposite was determined by BET and BJH measurements as shown in Figure 6. It can be concluded from BET results that FTCN exhibited type IV isotherm as distinctive mesoporous features. There are two hysteresis loops in FTCN nano composite indicating the enhanced adsorption at relative pressure 0.4 < P/P0 < 0.9. This could be considered the N2 gas filling and monolayer adsorption in the hollow voids due to regular mesopores and large SBET. While pure FT doesn’t have regular micro pores and mesopores, while the rapid increase at P/P0 > 0.9 could be due to irregular mesopores. Similarly BJH curve of FTCN nanocomposite exhibited that most of the mesopores are regularly distributed between 5-20 nm. Conversely, FT shows mesopores centered at 5~6 nm, however the size is widely distributed. The wide pore diameter of the FTCN is due to the progressive incorporation of g-C3N4 nano sheets into the cavities of TiO2.34 The SBET of FTCN nanocomposite and pure FT was measured by the BET equation, found to be 339 m²g-1 and 346 m²g-1 respectively. Generally g-C3N4 loading increases the pore diameter (Dp), because the gC3N4 contents expend the cavities result in widening the pore diameter. Meanwhile the surface area of the sample decreases. 35-36 The textural features summarized in Table 1. 13 ACS Paragon Plus Environment


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Figure 6. BET isotherms for surface area and inset BJH curve for pore size distribution (a) pure foamed titania (b) foamed titania-carbon nitride nano composite with optimal carbon nitride mass loading.

Table 1. Surface properties of pure foamed titania and foamed titania-carbon nitride nanocomposite with optimal mass loading of g-C3N4.

Photocatalyst FTCN FT

SBET (m2g-1) 339

Dp (nm) 12.5

Vp (cm3g-1)

346

5.5

0.068

1.096

The optical properties of FT, g-C3N4 and FTCN nanocomposites were investigated by UV-Vis spectrophotometer. The Figure 7a indicated that the FT has a meaningful absorption in ultra violet region and to some extant in 400 nm to 800 nm. The g-C3N4 has perceptible absorption of visible light with absorption edge of 470 nm. While it can be advently seen that the FTCN nano composites has strong absorption under 400 nm to 800 nm ascribed to the synergetic contact of g-C3N4 and anatase titania.26 Band gap energy could be measured by a plot of (αhν)2 vs (hν) using the Eq. 37 (αhν)2 = A(hν − Eg )


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Where α is absorption coefficient, h is Planck’s constant, ν is light frequency, A is constant and Eg is band gap energy. The Eg of the as-prepared g-C3N4, FT and FTCN was found to be 2.68, 3.04 and 2.37 eV respectively (Figure 7b). It was logical that the physically bonded nano composites contain similar (Eg) as pure samples while FTCN exhibits a mixed and assorted absorption of g-C3N4 and FT. This is consistent with the strong interaction of TiO2 and g-C3N4, also due to exceptional morphology that could provided wide porous pathway for efficient absorption within whole visible light region.38 The above findings justified that the introduction of proper amount of g-C3N4 function as photo sensitizer that broaden the TiO2 absorption spectrum to visible region. The superior light absorption leads to the generation of superfluous photo charge careers, consequently results an enhanced degradation performance.

Figure 7. (a) Optical properties of foamed titania (FT), g-C3N4 (CN) and foamed titania-carbon nitride (FTCN) nano composite with optimal mass loading (b) Plots of (αhν)2 vs photon energy (hν) for band gap energy.

3.2. Photocatalytic performance The MB and RhB have been considered chief motive of the industrial water pollution, put diverse toxic influence on the human health are indispensable to eliminate from effluents. In present investigation photocatalytic behavior of as synthesized nanocomposite and



reference samples was investigated for the degradation of desired aqueous solution of pollutants. An adsorption-desorption equilibrium must be assured prior to irradiations and decrease in the concentration of dyes was noted. The foamy structure of the nanocomposite provided sufficient space for the adsorption. A parallel reaction was also conducted without catalyst to observe the effect of light on the degradation of dyes. The outcomes indicated that both the catalyst and light played a key role for the photodegradation. The Figure 8 displayed that the FT and P25 exhibited very weak visible light induced photocatalytic activity, because

of their absorption mostly in UV region.

Conversely the FTCN nanocomposite showed superior catalytic activity because of its influential visible light absorption capability.39 Remarkably, all the FTCN photocatalysts exhibited better catalytic activity than pure FT and P25. The photocatalytic activity of FTCN nanocomposites increases by successive g-C3N4 loading while decreases with the surface saturation. This is because the FTCN with low g-C3N4, absorbed insufficient visible light that required for charge transfer in the space. While the over loading of gC3N4 on the TiO2 could destruct the surface active sites, consequently decrease the photocatalytic performance.40-41 Hence the FTCN with optimal mass loading (9%) exhibited the superior photocatalytic activity and degraded ≈ 95.50% MB and ≈ 93.12% RhB in short time than the corresponding reference samples (Table 2). The photocatalytic degradation activities of the reported g-C3N4/TiO2 materials [32, 43, 46, 47] provided for comparative studies (Table 4). The foamed titania-carbon nitride nanocomposite reveal better photo degradation performance due to its excellent surface morphology, large surface area and close interfaces.40, 42-43 Table 2. (%) photocatalytic degradation of MB and RhB over FTCN and other reference samples. Initial concentration of each dye was 200 mL (50 mgL-1). 16 ACS Paragon Plus Environment

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Catalyst

Photocatalytic degradation of (MB)

Photocatalytic degradation of (RhB)

FTCN-3

95

93

FTCN-1

82

80

FTCN-5

73

73

FT

27

24

P25

15

14

The degradation rate of MB and RhB was measured by rate equation (−ln(Ct/Co) = kt), where k is rate constant. The photocatalytic degradation followed pseudo-first order reaction while maximum degradation rate found for FTCN-3 (Table 3). This enhancement in the photo-degradation activity could be attributed due following obvious reasons: 1. Interfacial connection between g-C3N4 nano sheets and TiO2 nano spheres.42-44 2. The large specific surface area (339 m2g-1) and foamy structure that provide sufficient contact with dyes. 3. The better light absorption efficiency played a vital role in photodegradation.39, 45 The light-transfers path way are produced by the cavities that induced the incident photons to the inner surfaces of the catalyst, that allowed light irradiations to go through deep inside the catalyst and excite the electron more efficiently. Moreover the internal cavities could act as light dispersion centers which made it more efficient to absorb light.45 Table 3. Kinetic studies for the photocatalytic degradation of MB and RhB over FTCN and other reference samples. Catalyst

Kinetic rate constant, k(min-1) of MB

Kinetic rate constant, k(min-1)of RhB

FTCN-3

0.096

0.061

FTCN-1

0.057

0.033



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FTCN-5

0.038

0.026

FT

0.0079

0.0034

P25

0.0035

0.0014

Figure 8. (a & c) Visible light photocatalytic degradation of FTCN nanocomposite and reference samples (b & d) kinetic plots for the rate of reaction as a function of time.

On the basis of above findings and related studies the expected mechanism of the photocatalytic reaction provided in Supporting Information (Figure S2). In case of gC3N4 and FT the majority of photo-generated charges under visible light irradiations


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quickly recombine, while a tiny proportion have taken part in the catalytic reaction ensuring its inferior activity.20, 27 While in case of FTCN nanocomposite the electrons from (CB) of g-C3N4 shifted to the interface between g-C3N4 and TiO2 (band gap matching), that could effectively decreased their recombination. Meanwhile these trapped electrons react with dissolved oxygen to produced the O2•− radicals. The (HO2•) and •OH radicals was further produced from O2•− radicals. The holes in the (VB) are captured by hydroxyl or H2O molecules yielded •OH radicals that decomposed the dyes by breaking their organic chain.46-47 The recombination of photo generated charges could be suppressed by passing through the long electron transport process, results in elevated photocatalytic activity. 48-49 Superior photocatalytic activity of FTCN attributed to higher conductivity, which is related with the generation and recombination behavior of photo generated charges.50 Therefore to test the conductivity EIS was carried out as shown in Figure 9(a). The semicircles in the Nyquist diagrams correlated with charge transfer resistance. A smaller diameter semicircle can be observed for FTCN than FT indicated its smaller Rct and high conductivity, accountable for its superior electron-transfer execution during the photocatalytic reaction.51-52 The further justification of transfer and recombination of charges the transient photocurrent responses was tested under the chopped light. The as synthesized samples exhibited switched action with light pulsation shown in Figure 9(b). The photo-current of FTCN is 1.18 times higher than pure FT. The higher photo-current responses and high conductivity could be due to synergistic coupling and foamy structure that increase the interfacial charge separation between TiO2 and g-C3N4 leading to improve photocatalytic activity.18, 53-54



Figure 9. (a) The EIS measurements (b) Photo-current density under the illumination of chopped light for FT and FTCN nanocomposite.

3.3. Measurement of reactive species To recognize the function of various reactive species in the degradation of dyes, the scavengers trapping experiments was carried out during the photocatalytic studies (Figure 10a). The Isopropyl alcohol, benzoquinone and Na2EDTA was applied as a hydroxyl radicals, superoxide radicals and holes scavengers respectively. The (0.1 mmol) of the scavengers dropped in aqueous solution of the dyes when the catalysts reached at equilibrium. It was observed that an insignificant activity of the catalyst was observed with isopropyl alcohol and benzoquinone, while no obvious decrease in activity was found with the Na2EDTA, which persuasively verified that the •OH and O2•− was the active species for photo-degradation of dyes as compared to the holes. Moreover the reactive oxygen species was further detected by EPR technique. The DMPO was commonly applied in aqueous and methanolic dispersions as trapping reagent for the (•OH) and (O2•−) as shown in Figure 10b,c. These findings along with scavenger trapping experiments demonstrated that (•OH) and (O2•−) was the foremost oxidants in the photo degradation of dyes.


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The stability of the any material is very imperative matter for extensive recurring use and practical applications. The recycling experiment was conducted to evaluate the long term durability of the catalyst under same experimental condition and found that the degradation of MB and RhB was still supercilious after five consecutive degradation cycles which ensuring its good stability (Figure 10d). The XRD pattern of the recycled catalyst has been provided in Supporting Information, Figure S1 exhibited the same peaks position as in fresh sample, which assume that the photocatalyst maintain its crystalline phase and prevented any components being lost, which verified its outstanding structural stability after five degradation cycles.

Figure 10. (a) Reactive oxygen species scavenging experiments (b) DMPO-•OH EPR spectra in aqueous dispersion (c) DMPO-O2•− EPR spectra in methanolic dispersion, signals were recorded after 20 s of visible light irradiation (d) Photo stability test of FTCN nanocomposite.

Table 4. Comparative studies of the photocatalytic activity of FTCN with reported g-C3N4/TiO2 photocatalysts under visible light irradiations. 21 ACS Paragon Plus Environment


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Catalyst

(%) Dye Decomposition

Irradiation Time (min)

Initial concentration of catalyst and dye

g-C3N4/TiO2

RhB (99%)

140 min

1.0 gL-1 10 mgL-1

55

g-C3N4/TiO2

RhB (99%)

80 min

1.30 gL-1 10 mgL-1

56

g-C3N4/TiO2

RhB (98%)

50 min

4.80 gL-1 10 mgL-1

42

g-C3N4/TiO2

RhB (98%)

60 min

0.50 gL-1 10 mgL-1

49

g-C3N4/TiO2

MB (88%)

180 min

1.0 gL-1 20 mgL-1

57

g-C3N4/TiO2

MB (90%)

120 min

1.0 gL-1 20 mgL-1

30

FTCN

MB (95%)

30 min

0.10 gL-1 50 mgL-1

This Work

FTCN

RhB (93%)

50 min

0.10 gL-1 50 mgL-1

This Work


References

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4. CONCLUSION An incredible improvement in visible light induced photocatalytic degradation activity has achieved by designing a novel foamed titania-carbon nitride nanocomposite via in situ micro-emulsification proceeded by calcination. The bulk phase of g-C3N4 was transformed into thin nano sheets during calcination. The results of various characterization justified the foamy features of the nano composite with large surface area and porous structure. The FTCN nanocomposites has batter photocatalytic degradation performance than pure TiO2 and g-C3N4 and the optimal contents of g-C3N4 for superior activity was found to be 9%. This improvement in the photocatalytic degradation activity was primarily ascribed to the adequate visible light absorption, slow recombination of photo generated charges and direct contact of dyes with the interfacial photocatalyst. The FTCN nanocomposite has efficient potential for dyes degradation, hence provides a way to design active materials for waste water treatment. ASSOCIATED CONTENT Supporting information The adsorption tests in aqueous solution, Measurements of reactive species, XRD spectra of recycled sample and schematic illustration of the fabrication and photocatalytic degradation mechanism. ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (No. 21271017) and the National Science and Technology Supporting Plan of the twelthfive-year (No. 2014BAE12B0101). REFERENCES



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