Sugarcane Bagasse Hydrolysis by Metal Ions Mediated Synthesis of

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Sugarcane bagasse hydrolysis by metal ions mediated synthesis of perovskite LaCoO3 and the photocatalytic performance for hydrogen from formaldehyde solution under visible light Minghui Wu, Mingping Luo, Minxue Guo, and Lishan Jia ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.7b02884 • Publication Date (Web): 08 Oct 2017 Downloaded from http://pubs.acs.org on October 8, 2017

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ACS Sustainable Chemistry & Engineering

Sugarcane bagasse hydrolysis by metal ions mediated synthesis of perovskite LaCoO3 and the photocatalytic performance for hydrogen from formaldehyde solution under visible light Minghui Wua, Mingping Luoa, Minxue Guoa, Lishan Jiaa* a

Department of Chemical and Biochemical Engineering, College of Chemistry and

Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China * Corresponding author. Tel.: +86 0592 2188283; Fax: +86 0592 2184822. E-mail address: [email protected] ABSTRACT: Perovskite LaCoO3 was successfully synthesized using natural sugarcane bagasse with tunable oxygen vacancy. The preparation process was studied to elucidate the interaction between sugarcane bagasse and metal ions. And the prepared catalysts were characterized by XRD, SEM, XPS, DRS and PL. The results indicated that bagasse was partly hydrolysed by metal nitrate solution, and the gel was formed by adsorption and complexation between rich organic groups and metal ions, differing from citric acid complexation with metal ions. The bagasse fragments mediation in the process could modulate the amount of oxygen vacancy. An appropriate oxygen vacancy may act as defect energy level above the valence band of LaCoO3 to adjust band gap and accelerate charge transfer, resulting in high photocatalytic performance. Photocatalytic tests in formaldehyde aqueous solution under visible light demonstrated that LaCoO3 prepared by sugarcane bagasse exhibited higher hydrogen production than that prepared by conventional citric acid method. 1

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KEYWORDS: Sugarcane bagasse; Hydrolysis; Perovskite; Oxygen vacancy; Photocatalysis INTRODUCTION The development of clean hydrogen fuels is one of the concerns of current research, which can effectively resolve the unsustainable fossil fuels resulting in environmental pollution problems.1, 2 In many processes, photocatalytic water splitting to hydrogen has always been a promising clean and green technology.3, 4 For commercial applications, further enhancement of the visible light absorption and water splitting hydrogen release performance of photocatalysts has been a concern.5 In recent decades, most photocatalytic studies are focused on the development of novel catalyst such as non metal (C, S, N) doped metal oxide,6-8 heterojunction structure composite,9, 10 and noble metal surface modified semiconductor11-13 with high photocatalytic performance. In general, the photocatalyst, especially containing lattice defects and oxygen vacancies exhibits good photocatalytic properties,14-16 which can be attributed to the formation of moderate impurity levels to promote the narrowing of the band gap and to suppress the photogenerated electron-hole recombination.17 Among many preparation methods for obtaining such structure photocatalysts, the formation of sol-gel by metal ion and complex organic reagent is an effective method for various defect materials, because the precursors can be mixed on the molecular level to guarantee a good chemical homogeneity of the system.18 However, it is limited in practical applications due to the complexity of the process and the high cost of reagents.19

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Many studies have used soluble biomass as complexing agent to synthesize composite catalysts by sol-gel method.20, 21 Natural biomass not only could replace the conventional chemical reagents because of the advantages of being green, environmental and low cost, but also provide abundant functional groups to interact with the metal ions leading to change the surface properties, and even form a unique structure of the synthesized photocatalysts, which could bring lattice defects and tune the amount of oxygen vacancy.22 In our previous studies, biomass extracts as complexing agents were formed by sol-gel with metal ions, and the perovskite containing defects and oxygen vacancies was obtained for photocatalytic hydrogen production with high performance.23,

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However, this has been rarely reported to

directly utilize insoluble natural biomass for the synthesis of composite oxides, because natural polymer molecules are difficult to make metal ions to form uniformly dispersed sol-gel. Recently, there are many reports that metal ions hydrolyze cellulose and other insoluble biomass macromolecules to make them into soluble biomass small molecules to further synthesize silver nanoparticles.25,

26

It’s known that sugarcane bagasse is

mainly composed of hemicellulose, cellulose and lignin, which can be hydrolyzed, breaking the macromolecule into small molecular units.27-29 The rich functional groups such as carboxyl, hydroxyl could provide binding sites and play a dominant role in complexing and interaction with metal ions, which is beneficial to the synthesis of composite catalysts.30, 31 Perovskite oxide LaCoO3 as a typical photocatalyst has been

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extensively investigated because of its interesting physicochemical properties.32, 33 As reported, the structure and property of this material is closely correlative to the synthesis of precursor and/or dopant,34-36 which could bring lattice defects and tune the amount of oxygen vacancy. A certain number of oxygen vacancy acts as defect level could narrow the band gap and retard the recombination of photogenerated electrons and holes effectively on the surface of the photocatalyst so as to affect the material properties.37-39 Therefore, how to efficiently synthesize LaCoO3 with promising performance through constructing oxygen vacancy is taken into consideration. Hence, our work tends to directly use various quantity of natural sugarcane bagasse because of the forementioned specific characteristics to interact with metal ions and synthesize perovskite LaCoO3. The bagasse is characterized to elucidate the interaction with metal ions and its role in preparation process. Besides, the relationship between the amount of oxygen vacancy on the perovskite induced by biomass and the performance of photocatalytic hydrogen production is investigated. EXPERIMENTAL SECTION Materials The sugarcane bagasse was harvested from Fujian Province in China. It was put into a drying oven until water removal was completed. The dried bagasse was ground into fragments and sieved to particles of sizes below 200 µm. La(NO3)3‧6H2O, Co(NO3)2‧6H2O, and citric acid (C6H8O7‧3H2O) were of analytical reagent grade, purchased from Sinopharm Chemical Reagent Co. Ltd. Sample preparation La(NO3)3‧6H2O and Co(NO3)2‧6H2O with a La/Co molar ratio of

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1/1 were dissolved in deionized water under manual stirring to obtain a 100 mL 0.4 mol ‧L-1 metal nitrate solution. And sugarcane bagasse (1.0 g dry weigh) was added and stirred, then put the mixture into drying oven at 80℃. To investigate the interaction between bagasse and metal ions, the mixture was impregnated in the metal nitrate solution for 1 h, 6 h, 8 h, then filtrated and dried to get sugarcane bagasse residue, marked as SB-1, SB-6 and SB-8, respectively. The original sugarcane bagasse without impregnation in metal nitrate solution was denoted as SB. The above mixture dried in oven for more than 12 h could obtain a gel-like product, noted as SB-gel. The gel prepared by citric acid was signed as CA-gel for comparison. The gel-like product, after roasting by heating mantle and grinding with an agate mortar, was calcined at 700℃ for 2 h to form perovskite phase, defined as LaCoO3-SB1.0. The added amount of sugarcane bagasse was surveyed. For the dosage 0.3 g, 0.5 g and 1.5 g of sugarcane bagasse, the resultants were labeled LaCoO3-SB0.3, LaCoO3-SB0.5, and LaCoO3-SB1.5, respectively. Conventional LaCoO3 photocatalyst prepared by citric acid40 (the molar ratio of metal cations/citric acid, 2:0.6) was named as LaCoO3-CA. And the one added no complexing reagent was named after LaCo. All the catalysts were prepared by the same process except complexing reagent. Characterization X-ray diffraction (XRD) patterns were gained on a Panalytical X-pert spathic powder diffractometer with Cu Kɑ radiation source. Scanning electron microscopy (SEM) analysis was obtained using a LEO 1530 scanning electron microscope, with which Energy dispersive spectrometer (EDS) analysis was taken.

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Fourier transform infrared spectroscopy (FTIR) was conducted using Nicolet Avatar 330 Fourier transform spectrometer with KBr as dispersant. X-ray photoelectron spectroscopy (XPS) was carried on a PHI Quantum 2000 Scanning ESCA microprobe with a monochromatized microfocused Al X-ray source. Ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS) was measured with a Varian Cary 5000 UV-vis spectrophotometer. Photoluminescence spectrum (PL) was recorded at room temperature with a Hitachi F-7000 spectrophotometer using Xe lamp as the excitation source. The process of gelation for utilizing sugarcane bagasse to synthesize perovskite LaCoO3 was investigated by XRD, EDS and FTIR to integratedly clarify the interaction between bagasse and metal ions. Thereinto, the crystallinity index (CI) was obtained from the ratio between the intensity of the 002 peak (I002) and the minimum dip (Iam) between the 002 and the 101 peaks according to Equation 1,27, 28 CI = (I002-Iam) / I002 × 100

(1)

where I002 is the intensity of plane 002 at around 22° and Iam is related to the amorphous structure at around 18°. And the prepared catalysts were characterized by XRD, XPS, DRS and PL. Photocatalytic reaction Photocatalytic production reaction of H2 was estimated in a self-made quartz inner reaction vessel. The photocatalyst (0.2 g) was suspended with a magnetic stirrer in aqueous formaldehyde solution (1.5 M) for a total solution volume of 160 mL. And a jacket between the lamp and reaction chamber to keep the reactor

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temperature constant at 50℃ was filled with 2 mol‧L-1 NaNO2 solution, served as an internal circulation cooling medium to eliminate UV-light (cut-off < 400 nm). Before irradiation, the solution was sostenuto bubbled with N2 at a rate of 60 mL‧min-1 for 30 min. Then the gas content was checked by GC to confirm that no oxygen was present. A 125 W xenon lamp was used as light source. And the evolution gas was gathered and analyzed by GC (TCD, molecular sieve 5 Å column and Ar carrier). RESULTS AND DISCUSSION XRD characterization Fig. 1 shows XRD patterns of sugarcane bagasse samples and the prepared catalysts. As can be seen in Fig. 1A, SB, SB-1 and SB-6 display typical cellulose diffraction peaks, where the highest peak at around 22°corresponds to the (002) crystallographic planes. Obviously, the peaks of sugarcane bagasse impregnated with metal nitrate solution are weaker compared to SB. The crystallinity index of sugarcane bagasse samples is calculated according to Equation 1 and summarized in Table 1. SB, SB-1 and SB-6 show 42%, 25% and 22% of crystallinity, respectively. The result indicates that the cellulose chain of bagasse may be partially destroyed, due to the hydrolysis by metal ions. It may improve the exposure of active groups such as hydroxyl, and enhance interaction between bagasse and metal ions contributing to adsorption and complexation with metal ions. With the increase of time, the crystalline structure of bagasse is extremely destroyed in SB-8. In Fig. 1B, the diffractogram shows no cellulose diffraction peaks but well matched with the characteristic diffraction peaks of La2Co3(NO3)12‧24H2O (JCPDS 29-0746). The result implies that the mixture of

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metal (La, Co) nitrate ions may react with biological fragments and form a complex net-like structure and further produce a gel. As shown in Fig. 1C for the catalysts, with the increasing amount of sugarcane bagasse, the X-ray diffraction peaks tend to form perovskite LaCoO3. The characteristic diffraction peaks confirm that LaCoO3-CA, LaCoO3-SB1.5, LaCoO3-SB1.0 and LaCoO3-SB0.5 form a perovskite structure corresponding to the standard diffraction pattern given in XRD data card (JCPDS 84-0848). Conversely, LaCoO3-SB0.3 and LaCo are identified as LaCoO3 (JCPDS 84-0848), La(OH)3 (JCPDS 83-2034) and Co3O4 (JCPDS 80-1532), suggesting moderate sugarcane bagasse benefits the formation of perovskite structure. Fig. 1D presents the main peaks of LaCoO3-CA, LaCoO3-SB1.5, LaCoO3-SB1.0 and LaCoO3- SB0.5 in the 32.0-34.5° 2θ range. A shift toward higher 2θ angles is observed in LaCoO3 prepared by sugarcane bagasse, suggesting distortion of the crystal lattice of LaCoO3, which is possibly caused by the interaction between bagasse and metal ions in the process of forming perovskite. EDS characterization EDS analysis (Table 2) confirms the interaction of metal ions and sugarcane bagasse. In original sugarcane bagasse (SB), C and O are determined to be the main elements. After being treated with metal nitrate solution, La and Co elements appear, and the amount of which grows with the increasing of the impregnation time. There are N elements appearing and the highest percent of oxygen in SB-8 among all the samples. It’s ascribed to the adsorption of nitrate ions, in agreement with the XRD analysis, which demonstrates the formation of La2Co3(NO3)12‧24H2O,

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involved into the biological fragments and create a gel. FTIR characterization FTIR spectra of different sugarcane bagasse samples and gels are shown in Fig. 2A. As can be seen, SB, SB-1 and SB-6 show the similar spectrum curves, corresponding to the characteristic vibration of sugarcane bagasse.27, 28 And the bands of SB-8 resemble those of SB-gel and CA-gel, which suggests that in SB-8 sample, abundant metal ions have been involved into sugarcane bagasse and formed xerogel after drying. To investigate the interaction between sugarcane bagasse and metal ions, the enlargement spectrogram of SB, SB-1 and SB-6 is carefully examined, shown in Fig. 2B. On the infrared spectra of original sugarcane bagasse (SB), the absorption bands at 1733 cm-1, 1604 cm-1, 1513 cm-1 and 1250 cm-1 are features of the functional groups in lignin. To be specific, the bands at 1733 cm-1 and 1604 cm-1 are ascribed to C=O and C-Ph, respectively. The 1513 cm-1 can be identified as benzene ring vibration mode, and peak at 1250 cm-1 is due to C-O stretching of phenols.28, 41, 42 The band at 1328 cm-1 corresponds to C-H stretching mode in cellulose.41 Then band at 1048 cm-1 is due to the C-O stretching vibration in hemicellulose and cellulose.43 These peaks of close position can also be observed on curves for SB-1 and SB-6, indicating that sugarcane bagasse treated with metal nitrate solution keeps the main organic functional groups, benefiting to complexing with metal ions. Meanwhile, it deserves to notice that the bands mentioned above are distinctly reduced with some slight redshift in spectra of SB-1 and SB-6, due to the binging of metal ions.44 Bands at 1162 cm-1 and 1108 cm-1 are assigned

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to glycosidic C-O-C bonds,27,

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and the intensity decrease after treated with metal

nitrate solution, illustrating the degradation of cellulose chains. It’s also verified by the XRD results (Fig. 1). And peak at 1376 cm-1 attributed to O-H vibration of phenolic group28 shifts to 1384 cm-1 with intensity increased, revealing the existence of N-O adsorption.38 It can be concluded that the disruption of sugarcane bagasse may due to the interaction and hydrolysis of metal nitrate solution. Confirmed by the similar FTIR spectra of SB-gel and CA-gel in Fig. 2A, it’s considered both sugarcane bagasse and citric acid can be used as complexing agents in preparing LaCoO3 perovskite. For comparison, Fig. 2C presents the infrared spectrogram of SB-8, SB-gel and CA-gel with wavenumbers range from 1250 cm-1 to 500 cm-1. The bands at 1159 cm-1 and 1105 cm-1 from SB-8, SB-gel attract attention. These two bands are both attributed to C-O-C stretching of glycosidic bonds (original sugarcane bagasse (SB) at 1162 cm-1, 1108 cm-1). Hence it can be inferred that metal ions are involved into bagasse fragments to form a special gel, different from that produced by conventional chemical complexing reagents. The existence of varisized biomass fragments mediates the formation of perovskite, which may affect the structure and surface properties of catalysts. XPS characterization Fig. 3A presents the O1s XPS spectra of LaCoO3-CA, LaCoO3-SB1.5, LaCoO3-SB1.0 and LaCoO3-SB0.5. The binding energies around 528.6 eV and 531.3 eV are attributed to surface lattice oxygen and absorbed oxygen species, respectively.46 And the ratio of adsorbed oxygen to surface lattice oxygen is shown in

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Table 3. As can be seen, the ratio value of LaCoO3 prepared by sugarcane bagasse decreases with the increasing amount of bagasse, but is still above 1.29 for LaCoO3-CA. The results manifest that sugarcane bagasse could play a part in adjusting the amount of oxygen vacancy. An appropriate of oxygen vacancy, which may become defect level and then reduce band gap and enhance charge transfer to improve photocatalytic activity.37, 40, 47 Fig. 3B shows the Co 2p core level spectra. There are two characteristic peaks located at around 780 eV and 796 eV, corresponding to 2p3/2 and 2p1/2 spin–orbit doublet peaks, respectively.32 It’s noticed that peaks of LaCoO3-SB0.5 apparently shift to lower binding energies, consistent with the O1s XPS analysis, in which LaCoO3-SB0.5 presents the highest ratio (3.16) of adsorbed oxygen to surface lattice oxygen. The binding energy of a component is usually affected by its surrounding chemical environment.48 Coupling with XRD measurements, the different proportion of sugarcane bagasse hydrolyzate and metal (La, Co) nitrate ions can produce different structural complex precursor, which may lead to form corresponding oxygen vacancies and surface defects on the perovskite surface after the heat treatment process. It can be concluded that sugarcane bagasse interacts with metal ions to change the structure and surface properties of catalysts. UV-vis DRS characterization As can be seen in Fig. 4A, all photocatalysts have similar diffuse reflection curves. And it’s apparent that at the wavelength range from 200 nm to 800 nm, LaCoO3 prepared by sugarcane bagasse presents higher absorbance than LaCoO3-CA, especially in visible light region. From the spectra in the UV-vis

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region, the positions of the absorption edges are determined by the interception of the straight line fitted through the low-energy side of the curve [F(R)‧hv]2 versus hv, where F(R) is the Kubelka-Munk function and hv is the energy of the incident photon.49 The corresponding transformed diffuse reflectance spectra are shown in Fig. 4B, and the band gap energy is evaluated by the extrapolation method50 summarized in Table 4. The optical absorption thresholds of LaCoO3-CA is calculated to be 468 nm, corresponding to the band gap energy of 2.65 eV, whereas LaCoO3-SB1.0 shows a red shift of the absorption edge, which is 534 nm, corresponding to the narrowest band gap energy of 2.32 eV. A narrow band gap energy is benefit in the light harvesting process,40 which may well cause by the existence of defect level for oxygen vacancy. PL characterization Photoluminescence (PL) emission spectra of as-prepared photocatalysts are shown in Fig. 5. From the spectra of LaCoO3-SB1.5, LaCoO3-SB1.0 and LaCoO3-SB0.5, PL intensity changes with the added amount of sugarcane bagasse, and LaCoO3-SB1.0 exhibits the lowest PL signal, whereas LaCoO3-CA presents highest PL intensity. PL emission is the result of the recombination of excited electrons and holes. As reported, the lower PL intensity of the samples demonstrates a lower recombination rate.51 It is reasonable to assume that sugarcane bagasse could interact with metal ions to affect the surface structure of LaCoO3, and the formation of appropriate oxygen vacancy can trap electrons to retard the recombination of photogenerated electron-holes, benefiting to promoting the photocatalytic activity. Conceivable formation mechanism Through the above analysis of sugarcane bagasse

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in preparation process and the characterization of prepared catalysts, we put forward a probable formation mechanism of LaCoO3 prepared by sugarcane bagasse, and try illuminating the synthesis process and the role of sugarcane bagasse. As a reference, Fig. 6 shows the schematic diagram of preparation process for LaCoO3-SB1.0. Firstly, sugarcane bagasse is hydrolyzed with the interaction of metal ions, and then disintegrated into small fragments as interaction enhances. Those bagasse fragments provide special structure and abundant organic functional groups to adsorb and chelate with metal ions to form a network-like gel, which is different from the conventional citric acid complexation with metal ions. For roasting and calcination proceeding, perovskite phase forms with nitrates and sugarcane bagasse pyrolysis. Sugarcane bagasse mediation in preparation process helps produce special gel to form perovskite structure and adjust the number of oxygen vacancy to improve photocatalytic activity simultaneously. Photocatalytic activity Fig. 7 shows the photocatalytic activity of prepared photocatalysts in hydrogen production from formaldehyde solution under visible light irradiation for 120 min. In the figure, LaCo prepared with no complexing agent, has no photocatalytic activity. The hydrogen evolution rate improves with the increasing amount of the sugarcane bagasse, which facilitates the formation of perovskite structure. LaCoO3-SB1.0 presents optimum photocatalytic performance, of which the hydrogen evolution rate eaches 106 µmol‧h-1‧g-1, much higher than that of LaCoO3-CA (62 µmol ‧h-1‧g-1). Moreover, all samples prepared by sugarcane bagasse reveal advantage in

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harvesting visible light than that produced by citric acid. The photocatalytic activity changes with the oxygen vacancy content. These results demonstrate that photocatalytic activity is closely related to the perovskite structure of LaCoO3. An appropriate oxygen vacancy as a defect level can narrow band gap and favor the transfer of charge carriers to efficiently affect photocatalytic activity. The comparison of H2 evolution rate of related literature-reported photocatalysts is shown in Table 5. The result shows that LaCoO3-SB1.0 has a relatively high activity among composite metal oxide photocatalysts.

This indicates that the preparation of perovskite by biomass hydrolysis is not only a green process but also a unique method for perovskite structure of LaCoO3, which contributes to the photocatalytic hydrogen production system. CONCLUSION Hydrolysis of bagasse by metal ions mediated the synthesis of perovskite. With the interaction of metal nitrate solution, the sugarcane bagasse was transformed into small biomass fragments with rich organic functional groups. The adsorption and complexation of metal ions with organic groups such as hydroxyl and carboxyl groups on the biomass fragments formed the gel, further helping develop the structure and crystal of perovskite. Simultaneously, the interaction between biomass fragments and metal ions could produce appropriate oxygen vacancy on the perovskite. The prepared perovskite had excellent photocatalytic performance in hydrogen production from formaldehyde solution under visible light irradiation. This work presents a simple, cheap and green method to prepare perovskite oxides with higher photocatalytic

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activity. ACKNOWLEDGMENTS This work is supported by general program of the National Natural Science Foundation of China (Grant No. 21176203). And we thank Analysis and Testing Center of Xiamen University for the analysis and equipment support in this study. REFERENCE [1] Salvi, B. L.; Subramanian, K. A. Sustainable development of road transportation sector using hydrogen

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Fig. 1 X-ray diffractograms of sugarcane bagasse samples and prepared catalysts. (A)SB, SB-1 and SB-6. (B) SB-8. (C) (a) LaCoO3-CA, (b) LaCoO3-SB1.5, (c) LaCoO3-SB1.0, (d) LaCoO3-SB0.5, (e) LaCoO3-SB0.3 and (f) LaCo. (D) The corresponding XRD patterns in the 32.0-34.5° 2θ range of (a-d). (♢) LaCoO3, (♦)La(OH)3, and (♣)Co3O4. 24


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Fig. 2 (A) The infrared spectra (FTIR) of sugarcane bagasse samples and gels. The corresponding FTIR spectra of (B) SB, SB-1 and SB-6 from 2000-800 cm-1 and (C) SB-8, SB-gel and CA-gel from 1250-500 cm-1 (SB: original sugarcane bagasse; SB-1, SB-6, SB-8: sugarcane bagasse impregnated with 0.1 mol‧L-1 metal nitrate solution for 1 h, 6 h, 8 h; SB-gel: gel prepared by sugarcane bagasse; CA-gel: gel prepared by citric acid).

25



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Fig. 3 (A) O1s and (B) Co2p XPS spectra of (a) LaCoO3-CA, (b) LaCoO3-SB1.5, (c) LaCoO3-SB1.0 and (d) LaCoO3-SB0.5.

Fig. 4 (A) UV–vis DRS patterns and (B) the plots of [F(R)‧hν]2 versus hν of LaCoO3-CA, LaCoO3-SB1.5, LaCoO3-SB1.0 and LaCoO3-SB0.5. 26


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Fig. 5 PL spectra of LaCoO3-CA, LaCoO3-SB1.5, LaCoO3-SB1.0 and LaCoO3-SB0.5. (excitation wavelength at 295 nm)

Fig. 6 (a) Proposed formation mechanism of LaCoO3-SB1.0, (b) Photo of sugarcane bagasse and metal nitrate solution mixture, (c) Photo of SB-gel, (d) SEM micrographs of LaCoO3-SB1.0, (e) Structural representation of LaCoO3-SB1.0. 27



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Fig. 7 Photocatalytic activity of different photocatalysts from formaldehyde aqueous solution under xenon-lamp irradiation. (catalyst concentration = 1.25 g‧L-1; HCHO concentration = 1.5 M; reaction time = 120 min; reaction temperature = 50 ℃)

Table 1 Crystallinity of sugarcane bagasse samples. Sample

Crystallinity index (%)

SB

42

SB-1

25

SB-6

22

28


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Table 2 EDS analysis results of sugarcane bagasse samples. Atomic ratio (%)

C

O

N

La

Co

SB

62.25

37.76

/

/

/

SB-1

61.43

38.30

/

0.15

0.12

SB-6

59.36

39.95

/

0.38

0.31

SB-8

33.06

50.16

14.61

1.20

0.97

Table 3 The ratio of adsorbed oxygen to surface lattice oxygen for photocatalysts. Binding energy (eV)

The ratio of adsorbed oxygen to

Catalyst Adsorbed oxygen

surface lattice oxygen

surface lattice oxygen

LaCoO3-CA

531.4

528.8

1.29

LaCoO3-SB1.5

531.1

528.7

1.44

LaCoO3-SB1.0

531.0

528.8

1.50

LaCoO3-SB0.5

531.1

528.6

3.16

Table 4 The band gap energy of photocatalysts. Photocatalysts

Value (eV)

Photocatalysts

Value (eV)

LaCoO3-CA

2.65

LaCoO3-SB1.5

2.49

LaCoO3-SB1.0

2.32

LaCoO3-SB0.5

2.43

29



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Table 5 H2 evolution rate of photocatalysts based on oxide and noble metal doped oxide. Photocatalyst

Light source

The highest H2 production

refs

(µmol g-1cat h-1) Nb-Fe-codoped La2Ti2O7

500W xenon lamp

66

[52]

Fe3O4@SiO2@Bi2WO6@g-C3N4

350W xenon lamp

125

[53]

Bi2O3/ZrO2

125W mercury lamp

5.56

[54]

LaCoO3-SB1.0

125W xenon lamp

106

This work

30


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Perovskite LaCoO3 was successfully synthesized using natural sugarcane bagasse without chemical complexing agents and exhibited good photocatalytic performance for H2 evolution. 84x47mm (300 x 300 DPI)


Sugarcane Bagasse Hydrolysis by Metal Ions Mediated Synthesis of

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