Fe2O3 Z-Scheme Heterostructured Photocatalyst

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A ternary rGO/InVO4/Fe2O3 Z-scheme heterostructured photocatalyst for CO2 reduction under visible light irradiation Anurag Kumar, Pankaj Kumar Prajapati, Ujjwal Pal, and Suman Lata Jain ACS Sustainable Chem. Eng., Just Accepted Manuscript • Publication Date (Web): 19 May 2018 Downloaded from http://pubs.acs.org on May 19, 2018

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ACS Sustainable Chemistry & Engineering

A ternary rGO/InVO4/Fe2O3 Z-scheme heterostructured photocatalyst for CO2 reduction under visible light irradiation Anurag Kumar,1,2 Pankaj Kumar Prajapati,1,2 Ujjwal Pal3 and Suman L. Jain,1* 1

Chemical Sciences Division, CSIR-Indian Institute of Petroleum, Haridwar road, Mohkampur Dehradun-248005, India 2 3

Academy of Scientific and Industrial Research (AcSIR), New Delhi, India

Nanomaterials Unit, Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad-500007, India *Email: [email protected]

ABSTRACT The present paper describes an excellent improvement in photoreduction of CO2 to methanol using newly developed rGO/InVO4/Fe2O3 Z-scheme heterostructured photocatalyst, which was readily synthesized from chitosan functionalized reduced graphene oxide and InVO4/Fe2O3 via a facile deposition-precipitation method. The maximum yield of methanol was reached 16.9 mmol g1

cat over Z-scheme photocatalyst by using TEA as a sacrificial electron donor. The obtained

yield of methanol was very much higher in comparison to the rGO, InVO4 and InVO4/Fe2O3 semiconductors i.e. 2.3 mmol g-1cat, 1.1 mmol g-1cat and 9.8 mmol g-1cat, respectively under identical experimental conditions. The synergistic effect of all components in ternary rGO/InVO4/Fe2O3 Z-scheme heterostructure resulted to the efficient charge carrier separation and charge mobility on catalyst surface which led to the highly efficient CO2 reduction and excellent improvement in methanol yield.

KEYWORDS: CO2 photoreduction; nanocomposite; methanol; photocatalysis; Z-scheme; visible light

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Introduction Carbon dioxide (CO2), which is recognized as the leading contributor to global warming as a greenhouse gas and its rapid accumulation in atmosphere has become a major concern in recent decades.1,2 Furthermore, the rapid depletion of fossil resources is leading to the urgent need of for the alternative energy sources.3 The utilization of carbon dioxide to value-added chemicals using visible light irradiation offers a potential approach to deal with both issues simultaneously, i.e CO2 mitigation and alternative energy.4-6 Since the pioneering work of Inoue and coworkers,7 photocatalytic reduction of CO2 has extensively studied and a number of photocatalysts have developed so far. Besides this enormous progress, the photo-catalytic reduction of CO2 is a tremendous challenge in recent decades, mainly due to the poor conversions and selectivity of the products. The process of photocatalysis arises from the production of charge carriers like holes and electrons of the semiconductor photocatalyst by light, which participates in the reduction of CO2 and oxidation reaction, respectively.8,9 For an efficient photocatalytic reaction to be occurred, the efficient separation of holes and electrons is essential. A single semiconductor shows low photocatalytic activity by cause of rapid electron-hole pair recombination.10 In the recent years, heterogeneous semiconductor composite photocatalysts, mainly Z-scheme systems where two semiconductors behave like p-n heterojunction, have shown a huge potential to be established as efficient alternatives of most commonly known semiconductor photocatalysts for CO2 reduction.11,12 The Z-scheme photocatalysts mainly work on a two-step photo-excitation process, in which one semiconductor has positive valence band and generates electron-hole pairs after absorption of visible light. Oxidation of water occurs in holes while the electrons are shifted to the valence band of the second semiconductor unit that has the negative value conduction band.13,14 Then the transfer of electrons occurs from valence band to the


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conduction band after absorption of visible light and can be used for the reduction CO2. In this context, a number of visible light assisted Z-scheme heterostructured photocatalysts, such as SC/[MCE],15 r-STO/InP/[RuCP],16 and Ag/TaON-RuBLRu,17 have emerged for CO2 reduction in recent years. However, the poor conversions and limited stability of the photocatalysts still leave a scope for the development of new highly active and robust Z-scheme photocatalyst.18 Indium vanadate (InVO4), as an important mixed metal oxide semiconductor, has been widely studied for its use in air purification,19 gas sensors,20 and lithium-ion batteries.21 Indium vanadate (InVO4) have precise band gap energy of 2.0 eV (λ ≤ 500) and show activity in visible light. It shows high absorption in the solar spectrum region, stability across photo-corrosion and can be synthesized using various facile methods.22 On the other hand, the band gap of Fe2O3 is 2.2 eV, can absorb visible light; however, the faster recombination of light induced electron-hole pairs limits its activity. Hence, for the improvement of photocatalytic activity of semiconductors, combining of more than one semiconductor is a promising approach.23 Jia et al24 reported heterogeneous semiconductor InVO4/Fe2O3 for CO2 reduction to methanol with the maximum yield reached upto 191.45 ppm after 8 h of visible illumination. Meng et al.25 studied the Zscheme InVO4/CdS composite for the photocatalytic RhB degradation. Hu et al.26 reported gC3N4/nano-InVO4 nanocomposites with the enhanced photocatalytic activity for hydrogen production under visible light. Li et al.27 described the synergistic mechanism of the Cu2O/Fe2O3 composite for the photoreduction of CO2 to methanol under visible light irradiation. In continuation to our perpetual research on photoreduction of CO2, here we report a novel ternary heterostructured rGO/InVO4/Fe2O3 Z-scheme photocatalyst for the reduction of CO2 into methanol by using visible light irradiation in the presence of TEA as the sacrificial electron donor under visible light irradiation (Scheme 1).


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Scheme 1. Carbon dioxide photoreduction to methanol using rGO/InVO4/Fe2O4.

Results and discussion Synthesis and characterization of photocatalyst The designed rGO/InVO4/Fe2O4 was synthesized by grafting of InVO4/Fe2O3 onto the chitosan functionalized rGO surface via a facile deposition-precipitation method.28 A representative schematics of the synthesis of Z-scheme heterostructured photocatalyst is shown in Scheme 2.

Scheme 2. Synthesis of rGO/InVO4/Fe2O3 nanocomposite photocatalyst.


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The microstructure and morphology of the synthesized material was checked using HR-TEM measurement (Fig. 1). HR-TEM images of reduced graphene oxide (rGO) at 100 nm scale clearly revealing wrinkled nanosheets like morphology (Fig. 1a).29 In rGO/InVO4/Fe2O3 nanocomposite at 20 nm scale, the InVO4 crystals are of customary spherical shape with an average diameter of several micrometers (Fig. 1b, c). The occurrence of some dark spots on the sheet surface suggests the presence of Fe2O3 in the nanocomposite material. HR-TEM image in high resolution mode (5 nm), clearly displayed the lattice plane with 0.36 nm interplanar distance correspond to (012) plane of Fe2O3.30 In addition, the lattice fringes with interplanar distance about 0.33 and 0.38 nm correlated to the (220) and (111) plane of orthorhombic InVO4, respectively (Fig. 1d). Selected area electron diffraction pattern of rGO/InVO4/Fe2O3 nanocomposite shows diffraction spots corresponding to (111), (200) and (202) planes of InVO4 (JCPDS card No. 48-0898) and (113) plane of Fe2O3 (JCPDS card no. 33-0664). The successful synthesis was additionally substantiated by elemental mapping of rGO/InVO4/Fe2O3 nanocomposite. The existence of all the desired elements C, Fe, V, In and O was further verified by EDX analysis.


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Fig. 1 HR-TEM images: a) rGO; b,c) rGO/InVO4/Fe2O3 at 20 nm and 10 nm showing fringes; d) at 5 nm scale bar showing interplanar d-spacing; SAED pattern and EDX Pattern of rGO/InVO4/Fe2O3. The FTIR spectrum of pure-InVO4 revealed peaks at 690, 780 and 850 cm-1 are assigned to V-OIn bridging and V-O stretching respectively (Fig. 2a).31 In the case of rGO, peaks at 1561, 1205 cm-1 are due to the vibrations of C=C and C-OH stretching vibrations, respectively (Fig. 2b).32 In rGO/chitosan composite, the peak at 2925 cm-1 corresponded to the C–H vibration of -CH3 and at 1084 cm-1 was arisen due to the stretching vibration for -C-O-C of the glucosamine ring of chitosan (Fig. 2c).33 In Fe2O3 an intense absorption peak at 1630 cm-1 showed the presence of N– H bending vibration of SLS used in the synthesis of Fe2O3. The absorption peaks at 1140 cm-1 and 554 cm-1 are related to the iron oxide nanoparticles in which absorption peak at 554 cm-1 is due to the vibration of the Fe-O.34 Finally, the absorption peaks at 3430 cm-1 represented the presence of -OH groups on the surface (Fig. 2d). In the absorption spectrum of rGO/InVO4/Fe2O3 the peaks at 1636 cm-1, 1420 cm-1, 1070 cm-1, and 850 cm-1 are related to the typical stretching modes of different groups present in the InVO4 and Fe2O3. The absorption band at 1080 cm-1 corresponds to the stretching of -C-O-C bond of chitosan, confirmed the presence of chitosan in the rGO/InVO4/Fe2O3 nanocomposite.35 In addition, the presence of characteristic peaks of all components proved the prosperous synthesis of the rGO/InVO4/Fe2O3 nanocomposite (Fig. 2e).


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Fig. 2 FTIR Spectra of: a) InVO4, b) rGO, c) rGO/chitosan composite d) Fe2O3 and e) rGO/InVO4/Fe2O3.

The XRD diffraction patterns of the synthesized materials are shown in Fig.3. In InVO4, sharp characteristic peaks as per the JCPDS card No. 48-0898 revealed its crystalline nature (Fig 3a).36 XRD pattern of the rGO showed a weak and broad diffraction peak at 24.2o, indicating a reduced interlayer spacing of 0.367 nm, that might be due to the removal of some oxygen-containing functional groups (Fig 3b).37 X-ray diffraction pattern of Fe2O3 showed some narrow and sharp peaks due to its crystalline nature.34 Peaks at 2θ value 24.1o (012), 33.1o (104), 35.6o (110), 40.8o (113), 43.5o (024), 54.0o (116), 57.4o (122), 62.4o (214), 63.9o (300) and 71.9o (1010) attributed to the rhombohedral phase of Fe2O3 with JCPDS card no. 33-0664 (Fig 3c). In


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rGO/InVO4/Fe2O3, peaks at 2θ value 23.0o (111), 33.0o (112), 51.0o (042) and 62.4o (214) clearly indicated the presence of InVO4 and Fe2O3 in the composite (Fig 3d). The decreased intensity of the characteristic peaks of InVO4 and Fe2O3 in nanocomposite can be attributed to the higher loading of rGO in the nanocomposite.

Fig. 3 XRD Pattern of: a) InVO4, b) rGO, c) Fe2O3, d) rGO/InVO4/Fe2O3.

The X-ray photoelectron spectroscopy (XPS) of rGO/InVO4/Fe2O3 nanocomposite explained the surface chemical properties as shown in Fig. 4. Wide survey spectrum showed the binding energy peaks at 285.3, 399.5, 443.3, 517.3, 531.6 and 711.6 eV attributed to the C1s, N1s, In3d, V2p, O1s and Fe2p, respectively (Fig. 4a). The presence of rGO in the composite was confirmed by comparing the XPS spectra of GO and rGO (Fig. 4b, c). In case of GO (Fig. 4b), C1s region clearly shows a considerable degree of oxidation with four components that confirmed the carbon atoms in different functional groups like C-C, C-O, C=O and O-C=O at 284.3, 285.6,


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286.6 and 289.2 eV correspondingly. The values match well with the previous previously reported literature.38 Whereas, in rGO, the much stronger peaks related to graphitic sp2 carbon at 284.1 and diminished peaks at binding energy 285.3, 287.4 and 288.2 corresponded to C-O, C=O and O-C=O consequently, suggests considerable deoxygenation of GO that leads to the formation of rGO in the nanocomposite (Fig. 4c).39 XPS spectra for the N1s revealed three kinds of nitrogen species at binding energy 389.6, 400.3 and 401.2 eV corresponding to the -NH2, NHC=O and -NH3+ respectively (Fig. 4d).40 For Fe2p spectrum, two peaks of Fe2p3/2 and Fe2p1/2 at 710.6 and 724.1 eV, consequently confirmed the presence of Fe2O3 in the composite (Fig. 4e).41 The peaks of In3d5/2 and In3d3/2 at 444.1 and 452 eV respectively indicated the existence of In+3 (Fig. 4f); whereas peaks of V2p3/2 and V2p1/2 at 516.1 and 524.5 eV (Fig. 4g) confirmed the presence of V+5 species in the composite.31 Similarly, O1s region also deconvoluted into three peaks (Fig. 4h), in which lattice oxygen of InVO4 and Fe2O3 appeared at 530.2 eV and surface adsorbed oxygen at 531.8 eV. The small shoulder peak at 532.2-532.8 eV was due to the chemisorbed water or other (Fig. 4h).42


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Fig 4. HR-XPS spectra of rGO/InVO4/Fe2O3 nanocomposite: a) survey scan; b) C1s(GO); c) C1s; d) N1s; e) Fe2p; f) In3d; g) V2p; h) O1s region.

The structural and electronic properties of rGO/InVO4/Fe2O3 nanocomposite were explained with the help of Raman spectroscopy. In case of InVO4 the bands appeared at 207, 312.8, 377.2 and 928 cm-1 ascribed to the typical vibrations of the orthorhombic phase of InVO4 (Fig. 5a).43 rGO showed two bands, i.e. D band and G band at 1329 and 1587 cm-1 respectively (Fig. 5b).44 The intensity ratio of D to G defines the degree of distortion in the graphitic sheets. For Fe2O3, three broad bands were observed at 468, 924, 1237 cm-1 (Fig. 5c).45 The presence of corresponding bands of all components at 312, 468, 924, 1329 and 1587 cm-1 confirmed the presence of rGO, InVO4 and Fe2O3 in the composite material (Fig. 5d).


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Fig. 5 Raman spectra of: a) InVO4, b) rGO, c) Fe2O3, d) rGO/InVO4/Fe2O3.

The optical properties of the synthesized materials were determined by UV-visible spectroscopy. In rGO, the absorbance in the 250-280 nm region due to π-π* transitions of aromatic C-C bonds indicated the restoration of the extensive conjugated framework of sp2 carbons.46 The synthesized Fe2O3 nanoparticles revealed a poor absorbance in UV region and a broad band spanning between 380-600 nm in the visible region, due to the d-orbital transitions.47 In pure InVO4 a broad absorption range from ultraviolet to the visible light region with an absorption edge at approximately 300 nm was observed.48 Combination of all components in rGO/InVO4/Fe2O3 nanocomposite led to an increased absorption in the visible region (Fig. 6).


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Fig. 6 UV/Vis absorption spectra of InVO4, rGO, Fe2O3 and rGO/InVO4/Fe2O3. Further, the band gap of prepared samples was investigated with the help of a Tauc plot with linear extrapolation (Fig. 7). The band gap of InVO4, rGO and Fe2O3 was found to be 2.0 eV, 1.3 eV and 2.2 eV respectively, which suggested that all the components can absorb light under visible illumination.


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Fig. 7 Tauc plot for band gap determination of a) InVO4, b) rGO, c) Fe2O3. Further, to determine the electron flow in Z-scheme photocatalyst (Scheme 3), the band position of the conduction band (ECB) and valence band (EVB) of InVO4 and Fe2O3 semiconductors was calculated by using the following equations. ECB = X – Ee – 0.5Eg

(1)

EVB = ECB + Eg

(2)

Where ECB and EVB are the CB and VB band edge potential, X is the electronegativity of the semiconducting material, which is the geometric mean of the electronegativity of the constituent atoms, Ee is the energy of free electrons on the hydrogen scale (4.5 eV), and Eg is the band gap energy of the semiconductor. By using the eq. 1-2, the CB and VB edge potentials of pure InVO4


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were found to be -0.50 eV and 1.50 eV, respectively. However, the values for Fe2O3 were found to be 0.30 eV and 2.50 eV, respectively. These values suggested the transfer of photogenerated electrons from the CB of Fe2O3 to VB of InVO4 and then to the CB of InVO4 through Z-scheme for photocatalytic reduction of CO2 as depicted in Scheme 3. Photoluminescence spectra (PL) is a well-known technique to analyze the efficiency of trapping, migration and recombination rate of charge carriers in the semiconductor materials (Fig. 8).49 The PL intensity is correlated with the photocatalytic performance of the material, for example low PL intensity shows inferior recombination nature of charge carriers, which facilitates higher photocatalytic performance.50 In the current study, PL of InVO4 and Fe2O3 showed a sharp peak at 390 and 464 nm with high intensity respectively (Fig. 8a,b). However, in case of composite rGO/InVO4/Fe2O3, a lower PL intensity indicates less charge recombination and therefore higher photocatalytic activity than InVO4 and Fe2O3.

Fig. 8 PL spectra of a) InVO4, b) Fe2O3, c) rGO/InVO4/Fe2O3.


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The thermo-gravimetric analysis is an important tool to analyze the thermal stability and degradation pattern of the synthesized materials (Fig. 9). Under the nitrogen flow, the thermogram of rGO/InVO4/Fe2O3 nanocomposite showed a weight loss in between 100-200 °C due to the dehydration of adsorbed water molecules and degradation of remaining oxygencontaining groups on rGO sheets.51 Another major weight loss (app 48.2%) between 220-280 °C indicated the degradation of chitosan linker species present in the composite material.52 A very slight weight loss (~7%) at around 430 ᵒC was detected due to the breakdown of graphitic sheets.

Fig. 9: TG-DTA of rGO/InVO4/Fe2O3.

The surface properties of synthesized materials were determined with the help of adsorption and desorption of the nitrogen gas on the surface of material by using BET theory of multilayer adsorption and desorption. N2 Adsorption desorption isotherm of all samples was of type-(IV)53 which explained the mesoporous nature of the materials (Fig. 10). The BET surface area (SBET), total pore volume (Vp) and mean pore diameter (rp) of InVO4 were found to be 37.38 m2 g−1, 0.26 cm3 g−1, and 29.86 nm, respectively (Fig. 10a). The SBET and pore volume for rGO were found to be 110.2 m2g-1 and 1.50 cm3g−1 respectively, which also confirmed the higher absorption capacity of rGO (Fig. 10b). For Fe2O3, the value of BET surface area, total pore volume (Vp) and


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mean pore diameter (rp) were found to be 27.98 m2 g–1, 48.27 nm and 0.18 cm3 g–1, respectively (Fig. 10c). For hybrid rGO/InVO4/Fe2O3 nanocomposite, the surface area increased up to 180.94 m2 g-1, which gave a clear evidence of enfolding of rGO nanosheets on InVO4 and Fe2O3 semiconducting materials, respectively (Fig. 10d).

Fig. 10 BET adsorption-desorption isotherm of a) InVO4, b) rGO, c) Fe2O3, d) rGO/InVO4/Fe2O3. The photo-catalytic activity The photocatalytic activity of nanocomposite rGO/InVO4/Fe2O3 and its components like rGO, InVO4, Fe2O3 and InVO4/Fe2O3 was tested for CO2 reduction in solvent system dimethylformamide/water/triethylamine (3:1:1) saturated with CO2 using a 20 W white cold LED as a visible light source. The progress of the reaction was monitored by collecting samples after every 2h interval. Due to the heterogeneous nature, the photocatalyst was seperated with the


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help of a syringe filter (2 nm PTFE, 13 mm diameter). For the analysis, 1 µl of sample was withdrawn and injected in a GC/FID using an autosampler for accuracy measurement purpose. Peak area of methanol was matched with the standard solution of methanol. The product was calibrated with a standard calibration curve for quantitative determination of methanol. For gaseous product analysis, samples were tested with the help of GC-RGA (TCD-FID), no possible products such as CH4, CO etc. were observed. The MeOH formation (mmol g-1 cat) as a function of reaction time was calculated and plotted in Fig. 10. After 24 h of visible light irradiation, the methanol yield for rGO/InVO4/Fe2O3 nanocomposite was found to be 16.9 mmol/g cat with quantum yield 1.6 by using triethylamine (TEA) as a sacrificial agent. The yield of methanol for other components like rGO, InVO4 and InVO4/Fe2O3 (1:1) was found to be 2.3, 11.1 and 9.8 mmol/g cat, respectively (Table 1). The corresponding quantum yield (ϕ) for methanol production was found to be 0.2, 1.1 and 0.9 consequently. The higher photocatalytic activity of Z-scheme nanocomposite was attributed to the better charge separation and charge mobility on the extended conjugated structure of reduced graphene oxide sheets. The quantum yield of methanol was calculated by the following formula: ϕproduct = [P] x n/[γ] Where, ϕproduct is quantum yield, [P] is moles of desired product, n is number of electrons needed for reduction and [γ] is moles of incident photons.


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Table 1. Photocatalytic reduction of CO2 into methanol using different photocatalysts.a

a

Entry

Photocat.

React.

Visible light

Methanol Yield (mmol/ g cat)

Quantum Yield(mole einstien 1 )

1

-

CO2

Yes

-

-

2

rGO

CO2

Yes

2.3

0.2

3

InVO4

CO2

Yes

11.1

1.1

4

Fe2O3

CO2

Yes

-

-

5

InVO4/Fe2O3 (1:1)

CO2

Yes

9.8

0.9

6

rGO/InVO4/Fe2O3

N2 CO2 CO2

Yes No[b] Yes

16.9

1.6

Reaction condition: photocatalyst, 100 mg, solvent: DMF/H2O/Et3N (30/10/10), 20 Watt LED

(λ>400 nm) as light source, time: 24 h; bwithout light (dark condition).

In order to confirm that the produced methanol was resulted from the reduction of CO2 and not from the degradation of photocatalyst or other organic components present in the system, following blank experiments were perfromed: i) visible light irradiation but no photocatalyst, ii) presence of photocatalyst but no light (in dark), iii) using N2 in place of the CO2. No photoreduction product was obtained in all three cases, clearly indicated that visible light and photocatalyst were essentially required and the produced methanol was originated from photoreduction of CO2 (Fig. 11).


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Fig. 11 Conversion of CO2 to methanol over time using (a) Blank Reaction, b) InVO4, c) rGO, d) Fe2O3, e) InVO4/Fe2O3 (1:1), f) rGO/InVO4/Fe2O3.

Furthermore, the recycling ability of the nanocomposite rGO/InVO4/Fe2O3 photocatalyst was studied by performing the recycling experiments under described reaction conditions. After the completion of reaction, photocatalyst was effectively recovered by filtration through the syringe filter, dried and reused for consecutive run. The recovered photocatalyst was tested for five consecutive runs (Fig. 12). The approximate similar yield of methanol in all cases clearly indicated the higher stability (robustness) and efficient recycling of the photocatalyst. Importantly, the metal content i.e. V, Fe and In in the fresh photocatalyst and recovered after 5th recycling run was determined by ICP-AES analysis (Table 2). Almost similar values of the V, Fe and In in both cases further confirmed that the synthesized photocatalyst was robust in nature and no significant leaching had occurred during the photoreduction experiments.


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Fig. 12 Recyclability experiments of rGO/InVO4/Fe2O3photocatalyst. Table 2. ICP-AES analysis of rGO/InVO4/Fe2O3 nanocomposite photocatalyst. Element

V (wt%)

Fe (wt%)

In (wt%)

Fresh photocatalyst

2.16

11.26

4.12

After Vth recycling

1.98

10.52

3.93

The comparison of the developed photocatalyst with reported rGO wrapped semiconductor composites for photoreduction of CO2 is shown in Table 3. As shown, the synthesized ternary Zscheme photocatalyst provided much improved yield (16994 µmol/ g cat) of methanol from CO2 photoreduction than the existing ones.


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Table 3: Comparison of the developed Z-scheme photocatalyst with reported rGO wrapped nanocomposite photocatalysts.

Entr y 1

Solvent

Methano l Yield (µmol/ g cat)

Reference

24

DMF/water

2656

[12]

24

DMF/water

1282

[54]

Photocatalyst

Time (h)

rGO@CuZnO@Fe3O4 rGO-CuO124

2 3

Ni@NiO/InTaO4-N

2

Water

320

[55]

4

rGO/InVO4/ Fe2O3

24

DMF/water

16994

This work

The exact mechanism of the reaction is not known at this stage; however, predicated on the anterior reports, a plausible mechanism is depicted in the Scheme 3. For the efficient reduction of CO2 to CH3OH the position of conduction band of semiconductor have to be more negative than reduction potential of CO2/CH3OH (-0.38 V vs NHE at pH 7) and the position of valence band need to be more positive than oxidation potential of H2O/O2 (+1.23 V vs NHE at pH 7).56 Due to lower band gap energy, the light absorption led to the charge separation and the photoelectrons from the Fe2O3 valence band excited to its conduction band.57 In the subsequent step, the transfer of electrons occurred from the conduction band of Fe2O3 to valence band of InVO4 and then excited to the conduction band (Z-Scheme). The electrons from the conduction band of InVO4 got higher mobility on the rGO sheets and used for the CO2 reduction on the rGO surface as depicted in the Scheme 3. The holes generated in the valence band were used for water splitting and oxidation of triethylamine to provide essential electrons and protons for the CO2 reduction to methanol. After the oxidation, triethylamine converted to its degradation products such as imines and other reported products.


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Scheme 3: Z-scheme mechanism of CO2 photoreduction using rGO/InVO4/Fe2O3.

Conclusions

The present paper demonstrated a ternary Z-scheme nanocomposite comprising of rGO, InVO4 and Fe2O3 for the reduction of CO2 to methanol under visible light in the presence of TEA as sacrificial donor. The synthesized ternary nanocomposite showed excellent enhancement in the methanol yield as compared to its other components such as rGO, InVO4, InVO4/Fe2O3. The maximum methanol yield after 24 h of visible irradiation was obtained as 16.9 mmol/g cat, which is significantly higher than the literature reported methanol yield using InVO4/Fe2O3 composite. The synthesized composite acts like a Z-scheme semiconductor and provides efficient efficiency as a result of higher charge separation and mobility on the rGO sheets. We believe that the designing of such composites comprising different semiconductors grafted on rGO sheets


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will open new possibilities to construct high performance photocatalytic materials for artificial photosynthesis of CO2 to give higher value chemicals.

Experimental Materials Iron(III) chloride hexahydrate (98%), sodium dodecyl sulfate (99%), Indium chloride (98%), urea (99.5%), ammonium molybdate (98%), chitosan and hydrazine hydrate (98%) were purchased from Sigma-Aldrich and used without further purification. Ammonia solution (35%) was purchased from Fisher chemical. Solvents such as dimethylformamide (DMF), triethylamine and water were of HPLC grade. All other chemicals were used without further purification. Reduced graphene oxide was prepared from GO as per the literature procedure.58 Techniques used The morphology of the prepared samples was determined with the help of High Resolution Transmission Electron Microscopy (HR-TEM) using JEOL 2100 LaB6 working at 200 KV equipped with a STEM module and an Oxford SDD 80 mm2 EDX detector. For the preparation of HR-TEM sample, a very dilute aqueous dispersion of the photocatalyst was deposited on a lacey carbon-coated copper grid. The images were taken with a GATAN Orius 200 D for medium resolution and a GATAN Ultra Scan 1000 for high resolution. FT-IR spectra of the samples (as pellets in KBr) were recorded using Fourier transform infrared spectroscopy (Perkin–Elmer spectrum RX-1 IR spectrophotometer) in the range of 4000-400 cm-1. The crystal structures of the samples were determined by X-ray diffraction (XRD) spectroscopy using a Bruker D8 Advanced X-ray diffractometer at 40 KV with Cu Kα radiation (λ= 0.15418 nm) as the X-ray source. The UV-Visible absorption spectra were measured in the range of 200-800 nm


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on a Perkin Elmer lambda-19 UV-Vis-NIR spectrophotometer using 10 mm quartz cell, and BaSO4 as a reference. Photoluminescence (PL) emission spectra were measured on fluorescence spectrophotometer with 320 nm excitation wavelength at room temperature. The laser beam changed into focused with a 100 mm focal length lens to engender a 30-micron diameter spot on the sample. The incident power on the sample was 10 mW. The Brunauer-Emmett-Teller (BET) explained surface properties like BET surface area (SBET), mean pore diameter, BJH porosity etc. were examined by N2 adsorption-desorption isotherm at 77 K by using VP; Micromeritics ASAP2010. TGA of samples was performed by using a thermal analyzer TA-SDT Q-600. Analysis was achieved in the temperature range of 40 to 800 °C under N2 flow with heating rate 10 °C/min. LED light (Model: HP-FL-20W-F, Hope LED Opto-Electric Co., Ltd) with wavelength λ > 400 nm (maximum at 515 nm) was used for visible light radiance. The conversions and selectivity of the liquid and gaseous products have been determined by using high-resolution GC-FID (Varian CP-3800) and GC-RGA, respectively. Synthesis of orthorhombic InVO459 In a typical synthesis, indium chloride (2.21 g) and ammonium metavanadate (1.16 g) were dissolved in two separate beakers and then liquids were mixed together with constant stirring. The pH of the solution was adjusted to about 7 by adding ammonia solution. After that the solution was placed in Teflon coated stainless steel autoclave at 150 oC for 4 h. Thus, obtained white precipitate was separated by centrifugation, washed with DI dihydrogen monoxide for 2-3 times to abstract the remained Cl- and NH4+ ions and eventually dried in vacuum oven at 60 oC for 12h. Synthesis of Fe2O3 nanoparticles 34


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The synthesis of Fe2O3 nanoparticles was obtained by dissolving of FeCl3.6H2O (4.06 g) and sodium dodecyl sulfate (1 g) in DI water (100 mL) under sonicating water bath at 85 oC until a relatively steady solution system was composed. After centrifugation and washing, the solid was dried in vacuum oven at 60 oC and calcined at 300 oC for 4 h respectively. Synthesis of hybrid rGO/InVO4/Fe2O4 nanocomposite28 The composite InVO4/Fe2O4 was combined with reduced graphene oxide support by using chitosan as a linker. At first, the rGO-chitosan composite was synthesized by dispersing rGO (30 mg) in a chitosan solution (0.5 wt%, 40 ml) using ultra-sonication and the pH of the suspension was adjusted to 4.5 using 0.1 M HCl. Subsequently, InVO4/Fe2O3 (10 mg, 10 mL) was mixed in the solution of rGO-chitosan under ultrasonication, which resulted in the chemical adsorption of the nanocomposite InVO4/Fe2O3 onto the rGO-chitosan surface. The resulting product rGO/InVO4/Fe2O3 was accumulated by centrifugation and dried under vacuum at 70 oC for 5-6 h.

Acknowledgment We are thankful to Director, IIP for granting permission to publish these results. AK and PKP are thankful to Council of Scientific and Industrial Research (CSIR) New Delhi for providing research fellowships. DST, New Delhi is kindly acknowledged for providing financial assistance under the project GAP-3125. The analytical department of the Institute is acknowledged for providing analysis of the samples.


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REFERENCES [1]

Cox, P. M.; Betts, R. A.; Jones, C. D.; Spall, S. A.; Totterdell, I. J., Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model, Nature, 2000, 408, 184-187, DOI 10.1038/35041539.

[2]

Dale, V. H.; Houghton, R. A.; Hall, C. A. S., Estimating the effects of land-use change on global atmospheric CO2 concentrations, Can. J. For. Res., 1991, 21, 84-90, DOI 10.1139/x91-013.

[3]

Chynoweth, D. P.; Owens, J. M.; Legrand, R., Renewable methane from anaerobic digestion of biomass, Renewable Energy, 2001, 22, 1-8, DOI 10.1016/S09601481(00)00019-7.

[4]

Kumar, A.; Kumar, P.; Borkar, R.; Bansiwal, A.; Labhsetwar, N.; Jain, S. L., Metalorganic hybrid: Photoreduction of CO2 using graphitic carbon nitride supported heteroleptic iridium complex under visible light irradiation, Carbon, 2017, 123, 371–379, DOI 10.1016/j.carbon.2017.07.080.

[5]

Low, J.; Yu, J.; Ho, W., Graphene-Based Photocatalysts for CO2 reduction to solar fuel, J. Phys. Chem. Lett., 2015, 21, 4244-4251, DOI 10.1021/acs.jpclett.5b01610.

[6]

Kumar, P.; Joshi, C.; Labhsetwar, N.; Boukherroub, R.; Jain, S. L., A novel Ru/TiO2 hybrid nanocomposite catalyzed photoreduction of CO2 to methanol under visible light, Nanoscale, 2015, 7, 15258-15267, DOI 10.1039/C5NR03712C.

[7]

Takeda, H.; Koike, K.; Inoue, H.; Ishitani, O., Development of an efficient photocatalytic system for CO2 reduction using rhenium(I) complexes based on mechanistic studies, J. Am. Chem. Soc., 2008, 130, 2023-2031, DOI 10.1021/ja077752e.


26

Page 27 of 35 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


[8]

Linsebigler, A. L.; Lu, G.; Yates, J. T., Photocatalysis on TiO2 surfaces: Principles, mechanisms

and

selected

results,

Chem.

rev.,

1995,

95,

735-758,

DOI

10.1021/cr00035a013. [9]

Habisreutinger, S. N.; Mende, L. S.; Stolarczyk, J. K., Photocatalytic reduction of CO2 on TiO2

and

other

semiconductors,

Angew.

Chem.,

2013, 52,

1-39,

DOI

0.1002/anie.201207199. [10] Ni, M.; Leung, M. K. H.; Leung, D. Y. C.; Sumathy, K., A review and recent developments in photocatalytic water-splitting using TiO2 for hydrogen production, Renewable

and

Sustainable

Energy

Rev.,

2007, 11,

401-425,

DOI

10.1016/j.rser.2005.01.009. [11] Wang, J. C.; Yao, H. C.; Fan, Z. Y.; Zhang, L.; Wang, J. S.; Zang, S. Q.; Li, Z. J., Indirect Z-scheme BiOI/g-C3N4 photocatalysts with enhanced photoreduction CO2 activity under visible light irradiation, ACS Appl. Mater. Interfaces., 2016, 8, 3765-3775, DOI 10.1021/acsami.5b09901. [12] Kumar, P.; Joshi, C.; Barras, A.; Sieber, B.; Addad, A.; Boussekey, L.; Szunerits, S.; Boukherroub, R.; Jain, S. L., Core-shell structured reduced graphene oxide wrapped magenatically separable rGO@CuZnO@Fe3O4 microspheres as superior photocatalyst for CO2 reduction under visible light, Appl. Cat B, 2017, 205, 654-665, DOI 10.1016/j.apcatb.2016.11.060. [13]

Maeda, K., Z-scheme water splitting using two different semiconductor photocatalysts, ACS Catal., 2013, 3, 1486-1503, DOI 10.1021/cs4002089.

[14] Maeda, K.; Higashi, M.; Lu, D.; Abe, R.; Domen, K., Efficient nonsacrificial water splitting through two step photoexcitation by visible light using a modified oxynitride as a


27


Page 28 of 35

hydrogen evolution photocatalyst, J. Am. Chem. Soc., 2010, 132, 5858-5868, DOI 10.1021/ja1009025. [15] Sato, S.; Arai, T.; Morikawa, T.; Uemura, K.; Suzuki, T. M.; Tanaka, H.; Kajino, T., Selective CO2 conversion to formate conjugated with H2O oxidation utilizing semiconductor/complex hybrid photocatalysts, J. Am. Chem. Soc., 2011, 133, 1524015243, DOI 10.1021/ja204881d. [16] Arai, T.; Sato, S.; Kajino, T.; Morikawa, T., Solar CO2 reduction using H2O by a semiconductor/metal-complex

hybrid

photocatalyst:

enhanced

efficiency

and

demonstration of a wireless system using SrTiO3 photoanodes, Energy Environ. Sci., 2013, 6, 1274-1282, DOI 10.1039/C3EE24317F. [17] Sekizawa, K.; Maeda, K.; Domen, K.; Koike, K.; Ishitani, O., Artifiucial Z-scheme constructed with a supramolecular metal complex and semiconductor for the photocatalytic reduction of CO2, J. Am. Chem. Soc., 2013, 135, 4596-4599, DOI 10.1021/ja311541a. [18] Wang, Y.; Wang, X.; Antonietti, M., Polymeric graphitic cxarbon nitride as a heterogeneous photocatalyst: from photochemistry to multipurpose catalysis to sustainable chemistry, Angew. Chem., 2012, 51, 68-89, DOI 10.1002/anie.201101182. [19] Ai, Z.; Zhang, L.; Lee, S. C., Efficient visible light photocatalytic oxidation of NO on aerosol flow-synthesized nanocrystalline InVO4 hollow microsphere, J. Phys. Chem. C, 2010, 114, 18594-18600, DOI 10.1021/jp106906s. [20] Qin, Y.; Fan, G.; Liu, K.; Hu, M., Vanadium pentoxide hierarchical structure natworks for high performance ethanol gas sensor with dual working temperature cheracteristic, Sens. Actuator B, 2014, 190, 141-148, DOI 10.1016/j.snb.2013.08.061.


28

Page 29 of 35 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


[21] Wang, Y.; Cao, G. Z., Synthesis and electrochemical properties of InVO4 nanotube arrays, J. Mater. Chem., 2007, 17, 894-899, DOI 10.1039/B607268B. [22] Shi, W.; Guo, F.; Chen, J.; Che, G.; Lin, X., Hydrothermal synthesis of InVO4/graphitic carbon

nitride

heterojunctions

and

excellent

visible-light-driven

photocatalytic

performance for rhodamine B, J. Alloy and Compounds, 2014, 612, 143-148, DOI 10.1016/j.jallcom.2014.05.207. [23] Duret, A.; Gratzel, M., Visible light-induced water oxidation on mesoscopic α-Fe2O3 films made by ultrsonic spray pyrolysis, J. Phys. Chem. B, 2005, 109, 17184-17191, DOI 10.1021/jp044127c. [24] Jia, Z.; Wang, F.; Bai, Y.; Liu, N., Photocatalytic reduction of CO2 to methanol using the InVO4-based photocatalysts, Adv. Mater. Res. 2012, 396-398, 2033-2037, DOI 10.4028/www.scientific.net/AMR.396-398.2033. [25] Meng, Y.; Hong, Y.; Huang, C.; Shi, W., Fabrication of of novel Z-scheme InVO4/CdS heterojunctions

with

efficiently

enhanced

visible

light

photocatalytic

activity,

CrystEngComm, 2017, 19, 982-993, DOI 10.1039/C6CE02465C. [26] Hu, B.; Cai, F.; Chen, T.; Fan, M.; Song, C.; Yan, X.; Shi, W., Hydrothermal synthesis gC3N4/Nano-InVO4 nanocomposites and enhanced photocatalytic activity for hydrogen production under visible light irradiation, ACS Appl. Mater. Interfaces, 2015, 7, 1824718256, DOI 10.1021/acsami.5b05715. [27] Wang, J. C.; Zhang, L.; Fang, W. X.; Ren, J.; Li, Y. Y.; Yao, H. C.; Wang, J. S.; Li, Z. J., Enhanced photoreduction CO2 activity over direct Z-scheme α-Fe2O3/Cu2O heterostructures under visible light irradiation, ACS Appl. Mater. Interfaces, 2015, 7, 8631-8639, DOI 10.1021/acsami.5b00822.


29


Page 30 of 35

[28] Lin, X.; Wang, Y.; Zheng, J.; Liu, C.; Yang, Y.; Che, G., Graphene quantum dot sensitized leaf-like InVO4/BiVO4 nanostructure: a novel ternary heterostructured QDRGO/InVO4/BiVO4 composite with enhanced visible-light photocatalytic activity, Dalton Trans., 2015, 44, 19185-19193, DOI 10.1039/C5DT03251B. [29] Hou, C.; Quan, H.; Duan, Y.; Zhang, Q.; Wang, H.; Li, Y., Facile synthesis of waterdispersible Cu2O nanocrystal-reduced graphene oxide hybrid as a promising cancer therapeutic agent, Nanoscale, 2013, 5, 1227-1232, DOI 10.1039/C2NR32938G. [30] Lv, B.; Liu, Z.; Tian, H.; Xu, Y.; Wu, D.; Sun, Y., Single-crystalline dodecahedral and octadecahedral α-Fe2O3 particles synthesized by a fluoride anion-assisted hydrothermal method, Adv. Funct. Mater., 2010, 20, 3987-3996, DOI 10.1002/adfm.201001021. [31] Cimino, N.; Artuso, F.; Decker, F.; Orel, B.; Vuk, A. S.; Zanoni, R., XPS and IR studies of transparent InVO4 films upon Li charge-discharge reactions, Solid State Ionics, 2003, 165, 89-96, DOI 10.1016/j.ssi.2003.08.020. [32] Gong, Y.; Li, D.; Fu, Q.; Pan, C., Influence of graphene microstructures on electrochemical performance for supercapacitors, Progress in Natural Science Materials International, 2015, 25, 379-385, DOI 10.1016/j.pnsc.2015.10.004. [33] Kumari, S.; Rath, P.; Kumar, A. S. R; Tiwari, T. N., Extraction and characterization of chitin and chitosan from fishery waste by chemical method, Environmental technology & Innovation, 2015, 3, 77-85, DOI 10.1016/j.eti.2015.01.002. [34] Hao, C.; Feng, F.; Wang, X.; Zhou, M.; Zhao, Y.; Ge, C.; Wang, K., The preparation of Fe2O3 nanoparticles by liquid phase-based ultrasonic-assisted method and its application as enzyme-free sensor for the detection of H2O2, RSC Adv., 2015, 5, 21161-21169, DOI 10.1039/C4RA17226D.


30

Page 31 of 35 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


[35] Rashid, S.; Shen, C.; Chen, X.; Li, S.; Chen, Y.; Wen, Y.; Liu, J., Enhanced catalytic activity of chitosan-Cu-Fe bimetal complex for the removal of dyes in aqueous solution, RSC Adv., 2015, 5, 90731-90741, DOI 10.1039/C5RA14711E. [36] Lin, X.; Xu, D.; Lin, Z.; Jiang, S.; Chang, L., Construction of heterostructureed TiO2/InVO4/RGO microspheres with dual-channels for photo-generated charge separation, RSC Adv., 2015, 5, 84372-84382, DOI 10.1039/C5RA17676J. [37] Shen, J.; Yan, B.; Shi, M.; Ma, H.; Li, N.; Ye, M., One step hydrothewrmal synthesis of TiO2-reduced graphene oxide sheets, J. Mater. Chem., 2011, 21, 3415-3421, DOI 10.1039/C0JM03542D. [38] Stankovich, S.; Dikin, D. A.; Piner, R. D.; Kohlhaas, K. A.; Kleinhammes, A.; Jia, Y.; Wu, Y.; Nguyen, S. T.; Ruoff, R. S., Synthesis of graphene based nanosheets via chemical reduction of exfoliated graphite oxide, Carbon, 2007, 45, 1558–1565, DOI 10.1016/j.carbon.2007.02.034. [39] Paredes, J. I.; Rodil, S. V.; Alonso, A. M.; Tascon, J. M. D., Graphene oxide dispersions in organic solvents, Langmuir, 2008, 24, 10560-10564, DOI 10.1021/la801744a. [40] Zheng, L.; Wang, C.; Shu, Y.; Yan, X.; Li, L., Utilization of Diatomite/chitosan-Fe (III) Composite for the Removal of Anionic Azo Dyes from Waste water: Equilibrium, Kinetics and Thermodynamics, Colloids and Surfaces A: Physicochem. Eng. Aspects, 2015, 468, 129-139, DOI 10.1016/j.colsurfa.2014.12.015. [41] Kumar, A.; Kumar, P.; Joshi, C.; Ponnada, S.;. Pathak, A.; Ali, A.; Sreedhar, B.; Jain, S. L., A [Fe(bpy)3]2+ grafted graphitic carbon nitride hybrid for visible light assisted oxidative coupling of benzylamines under mild reaction conditions, Green Chem., 2016, 18, 2514-2521, DOI 10.1039/C5GC02090E.


31


Page 32 of 35

[42] Yang, W.; Tan, G.; Huang, J.; Ren, H.; Xia, A.; Zhao, C., Enhanced magnetic property and photocatalytic activity of UV-light responsive N-doped Fe2O3/FeVO4 heterojunction, Ceramics International, 2015, 41, 1495-1503, DOI 10.1016/j.ceramint.2014.09.084. [43] Kong, Z.; Yuan, Y. J.; Chen, D.; Fang, G.; Yang, Y.; Yang, S.; Cao, D., Noble-metal-free MoS2 nanosheet modified- InVO4 heterostructures for visible-light-driven photocatalytic H2 production, Dalton Trans., 2017, 46, 2072-2076, DOI 10.1039/C7DT00019G. [44] Su, C. Y.; Xu, Y.; Zhang, W.; Zhao, J.; Tang, X.; Tsai, C. H.; Li, L. J., Electrical and spectroscopic characterizations of ultr-long reduced graphene oxide monolayers, Chem. Matter., 2009, 21, 5674-5680, DOI 10.1021/cm902182y. [45] Sanchez, J. L.; Serrano, A.; Campo, A. D.; Abuin, M.; Fuente, O. R. I., Sol-Gel syntresis and Micro-Raman characterization of ε-Fe2O3 micro and nanoparticles, Chem. Mater., 2016, 28, 511-518, DOI 10.1021/acs.chemmater.5b03566. [46] Chen, M.; Zhang, Z.; Li, L.; Liu, Y.; Wang, W.; Gao, J., fast synthesis of Ag-Pd@reduced graphene oxide bimetallic nanoparticles and their applications as carbon-carbon coupling catalysts, RSC Adv., 2014, 4, 30914-30922, DOI 10.1039/C4RA05186F. [47] Li, X.; Wang, Z.; Zhang, Z.; Chen, L.; Cheng, J.; Ni, W.; Wang, B.; Xie, E., Light illuminated α-Fe2O3/Pt nanoparticles as water activation agent for photoelectrochemical water splitting, Sci Rep., 2015, 5, 9130, DOI 10.1038/srep09130. [48] Hu, B.; Cai, F.; Chen, T.; Fan, M.; Song, C.; Yan, X.; Shi, W., Hydrothermal synthesis gC3N4/Nano-InVO4 nanocomposites and enhanced photocatalytic activity for hydrogen production under visible light irradiation, ACS Appl. Mater. Interfaces, 2015, 7,1824718256, DOI 10.1021/acsami.5b05715.


32

Page 33 of 35 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


[49] Guo, M.; Wang, Y.; He, Q.; Wang, W.; Wang, W.; Fu, Z.; Wang, H., Enhanced photocatalytic activity of S-doped BiVO4 photocatalysts, RSC Adv., 2015, 5, 5863358639, DOI 10.1039/C5RA07603J. [50] Zhang, Y. Q.; Li, S.; Zhang, B. P., Controllable synthesis of Bi2S3/CuS heterostructures by an in situ ion-exchange solvothermal process and their enhanced photocatalytic performance, RSC Adv., 2016, 6, 103215-103223, DOI 10.1039/C6RA19365J. [51] Jana, M.; Saha, S.; Khanra, P.; Murmu, N. C.; Srivastava, S. K.; Kuila, T.; Lee, J. H., Bioreduction of graphene oxide using drained water from soaked mung beans (Phaseolus aureus L.) and its application as energy storage electrode material, Mater. Sci. Eng. B, 2014, 186, 33-40, DOI 10.1016/j.mseb.2014.03.004. [52] Cardenas, G.; Miranda, S. P., FTIR and TGA studies of chitosan composite films, J. Chil. Chem. Soc., 2004, 49, 291-295, DOI 10.4067/S0717-97072004000400005. [53] Rouquerol, J.; Avnir, D.; Fairbridge, C. W.; Everett, D. H.; Haynes, J. M.; Pernicone, N.; Ramsay, J. D. F.; Sing, K. S. W.; Unger, K. K., Recommendations for the characterization of

porous

solids,

Pure.

Appl.

Chem.,

1994,

66,

1739-1758,

DOI

10.1351/pac199466081739. [54] Gusain, R.; Kumar, P.; Sharma, O. P.; Jain, S. L.; Khatri, O. P, Reduced graphene oxideCuO nanocomposites for photocatalytic conversion of CO2 into methanol under visible light irradiation, App. Cat. B, 2016, 181, 352-362, DOI 10.1016/j.apcatb.2015.08.012. [55] Tsai, C. W.; Chen, H. M; Liu, R. S.; Asakura, K.; Chan, T. S., Ni@NiO Core-shell structure-modified nitrogen-doped InTaO4 for solar driven highly efficient CO2 reduction to methanol, J. Phys. Chem. C, 2011, 115, 10180-10186, DOI 10.1021/jp2020534.


33


Page 34 of 35

[56] Ye, C.; Wang, X. Z.; Li, J. X.; Li, Z. J.; Li, X. B.; Zhang, L. P.; Chen, B.; Tung, C. H.; Wu, L. Z., Protonated graphitic carbon nitride with surface attached molecule as hole relay for efficient photocatalytic O2 evolution, ACS Catal., 2016, 6, 8336–8341, DOI 10.1021/acscatal.6b02664. [57] Wu, W.; Jiang, C.; Roy, V. A. L., Recent progress in magnetic iron oxide-semiconductor composite nanomaterials as promising photocatalysts, Nanoscale, 2015, 7, 38-58, DOI 10.1039/C4NR04244A. [58] Park, S.; An, J.; Potts, J. R.; Velamakanni, A.; Murali, S.; Ruoff, R. S., Hydrazinereduction of graphite and graphene oxide, Carbon, 2011, 49, 3019-3023, DOI 10.1016/j.carbon.2011.02.071. [59] Ge, L.; Xu, M.; Fang, H., Synthesis of novel photocatalytic InVO4-TiO2 thin films with visible

light

photoactivity,

Materials

Letters,

2007,

61,

63-66,

DOI

10.1016/j.matlet.2006.04.006.


34

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For Table of Content Use Only A novel, efficient and reusable reduced graphene oxide supported Z-scheme photocatalyst for CO2 reduction under visible light provided significantly improved methanol yield than reported ones has been described.


35

Fe2O3 Z-Scheme Heterostructured Photocatalyst

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