High-performance In2O3@PANI core@shell architectures with

ultralong charge carriers lifetime for photocatalytic degradation of

gaseous 1,2-dichlorobenzene

Fei Zhanga,b, Xinyong Lia,*, Qidong Zhaoa, Guohua Chenb,*, Qianzhe Zhanga,c

a State Key Laboratory of Fine Chemicals, Key Laboratory of Industrial Ecology and

Environmental Engineering (MOE), School of Environmental Science and

Technology, Dalian University of Technology, Dalian 116024, Chinab Department of Mechanical Engineering, The Hong Kong Polytechnic University,

Hung Hom, Kowloon, Hong Kong SAR, Chinac Institut de Ciència de Material de Barcelona ICMAB, Consejo Superior de

Investigaciones Científicas CSIC, Campus UAB 08193 Bellaterra, Catalonia, Spain

*Corresponding authors:

E-mail: xyli@dlut.edu.cn (X.Y. Li); guohua.chen@polyu.edu.hk (G.H. Chen)

Summary: This file contains 11 pages, 8 figures, and 1 table.

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Materials and reagents

Indium (III) chloride hydrate (InCl3·xH2O, 99.99% metals basis), polyaniline

(PANI), trisodium citrate dehydrate (Na3cit, C6H5Na3O7·2H2O, 99.0%), urea

(CO(NH2)2, 99.0%), absolute ethanol (EtOH, 99.7%) and N-methyl-2-pyrrolodone

(NMP, 99.5%) were supplied by Alfa Aesar, Thermo Fisher Scientific. 5,5-dimethyl-

1-pyrroline-N-oxide (DMPO, 99.0%) as the spin-trap reagent and 1,2-

dichlorobenzene (HPLC grade, 99.0%) as model pollutant were both purchased from

Sigma-Aldrich Chemical Co., Milwaukee, USA. All the chemicals were of analytical

grade (AR) and used without any further purifications. Deionized water (18.2 MΩ cm,

Millipore) was used throughout the experiments.

Characterization methods

The crystallographic and component information of the resulting samples were

acquired by X-ray diffraction (PANalytical B.V. Empyrean, Netherlands) with Cu Kα

radiation (1.5406 Å) in the angular range of 10–70o. The micro-morphologies of

In2O3@PANI core@shell composites were observed by scanning electron microscope

(SEM, JEOL JSM-6700F, Japan). Elemental mapping images were achieved by

combining the scanning module of the microscopy to energy dispersive X-ray

spectrometer (EDS) detector. Transmission electron microscopy (TEM) and high-

resolution TEM (HRTEM) images were visualized using a FEI Tecnai G2 F20

operating at 300 kV. The electronic states of elements in the resulting samples were

investigated using X-ray photoelectron spectroscopy (XPS, Thermo Scientific

ESCALAB 250Xi, USA) equipped with an monochromatized Al Kα source (photo

energy = 1486.6 eV) and charge neutralizer. The curve-fitting was achieved by XPS

PEAK 4.1 software, using a Shirley background substraction. The Raman

spectroscopy was carried out with a Thermo scientific DXR confocal Raman

microscope utilizing argon ion laser as the exciting source (λ = 532 nm), and the laser

power at the sample position was typically 1.0 mW. The UV–vis diffuse reflectance

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spectra (DRS) of the photocatalysts were recorded on a UV-550 UV–vis

spectrophotometer equipped with an integrating sphere and converted from reflection

to absorbance based on the standard Kubelka–Munk theory. The steady-state

photoluminescence (PL) emission spectra were collected on a fluorescence

spectrophotometer (Hitachi F–7000) with a scanning speed of 240 nm min–1 at

ambient temperature. The surface photovoltage spectroscopy (SPV) was scanned on a

self-made apparatus, which consisted of a source of monochromatic light, a lock-in

amplifier (model SR 830-DSP) with a light chopper (model SR 540), a sample

chamber, and a photovoltaic cell. The monochromatic light was provided by passing

light from a 500 W xenon lamp through a grating monochromator (model Omni-λ

3005), which chopped with a low frequency of ~20 Hz. The time-resolved

photoluminescence (TRPL) spectra were collected on FL sp920 (Edinburgh

Analytical Instrument, UK) at room temperature. The reactive oxygen-containing

species, e.g., •OH and •O2–, were detected by using electron spin resonance (ESR)

technology via Bruker EC106 X-band spectrometer. The as-synthesized

photocatalysts dispersed in 30 mL DMPO solution with phosphate buffer (pH = 7.0)

were used for detecting DMPO–•OH adducts, while dispersed in anhydrous methanol

solution for DMPO–•O2– adducts. The ESR detection was performed immediately

after 5 min of visible-light illumination. Herein, the irradiation source was supplied by

a xenon lamp (XQ-500W, Shanghai Lansheng Electronics Co., Ltd.) equipped with an

UV cutoff filter (λ > 400 nm). The incident visible light intensity was 40.5 mW cm2.

The detailed parameters for ESR detection were as follows: temperature, 298 K;

microwave power, 19.5 mW; microwave frequency, 10 GHz; sweep width, 5200 G;

center field, 3400 G; scan times, 8.

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Fig. S1. A schematic illustrating of the in situ FTIR reactor for photodegradation of

gaseous 1,2-dichlorobenzene.

Rubber hose is used for injecting liquid 1,2-dichlorobenzene and sampling gaseous

intermediate products.

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A series of in situ FTIR spectra of gaseous 1,2-dichlorobenzene were recorded in

the dark in order to investigate the establishment of adsorption-desorption process. As

shown in Fig. S2, two bands located at 1037 and 1130 cm−1 could be assigned to the

C−Cl stretching vibration mode [1]. While two bands centered at 1435 and 1460 cm−1

are ascribed to the C=C degenerated stretching vibrations in the aromatic ring [2]. As

the adsorption time goes on, the intensities of these peaks increase gradually within 1

h. However, the intensities maintain stable and obvious increase could not be

observed from 80 min to 120 min. It indicates that liquid 1,2-dichlorobenzene can

completely volatilize, and adsorption-desorption equilibrium is achieved at the

interface of 1,2-dichlorobenzene molecular and catalysts after 120 min.

Fig. S2. In situ FTIR spectra for the adsorption of gaseous 1,2-dichlorobenzene over

In2O3@8%PANI core@shell composite.

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Fig. S3. XPS survey spectrum of In2O3@10%PANI core@shell composite.

Fig. S4. Digital images of pure In2O3 nanospheres (a), In2O3@3%PANI (b),

In2O3@5%PANI (c), In2O3@8%PANI (d), and In2O3@10%PANI core@shell

composites (e).

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Table S1. Comparison of transient PL emission decay parameters from this study with

previously reports on some In2O3-based composites and other transition-metal oxide-

based composites for visible-light photocatalysis.

Material Short lifetime τ1 (ns)

Long lifetime τ2 (ns)

Reference

In2O3@PANI core@shell

composites2109.0 8142.1 This work

In2S3/In2O3 heterostructures 0.41 1.94 [3]

ZnFe2O4/In2O3 nanoheterostructures 0.6 3.3 [4]

In2O3/g-C3N4 composites 0.71 3 [5]

Ag:Zn-In-S quantum dots 12.58 316.91 [6]

ZnIn2S4–In2O3 tubular composites 1.01 5.98 [7]

In2O3-TiO2-Pt heterojunction 1.4 0.17 [8]

TiO2-Ni3V2O8 heterostructures 0.1 16.67 [9]

CdS-MoS2 nanocrystal 3.6 28.5 [10]

SnS2/g-C3N4 nanosheets 1.27 4.30 [11]

Honeycomb-like C3N4 22.3 165.4 [12]

g-PAN/g-C3N4 composites 1.26 4.45 [13]

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Fig. S5. Pseudo-first-order constants for the photodegradation of gaseous 1,2-

dichlorobenzene over various photocatalysts.

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Fig. S6 shows the reusability performance of In2O3@8%PANI core@shell

composite for the degradation of gaseous 1,2-dichlorobenzene. After irradiated for 24

h (3 consecutive cycles without regeneration after each cycle), the photocatalytic

reactivity decreased from initial 82.6% to 69.2%, which might be caused by the

adsorption of degradation products or intermediates. After the 3rd run, the catalyst

wafer was illuminated under UV light to eliminate the surface absorbed products and

thus regenerated the catalytic activity. Interestingly, the degradation rate resumed to a

higher value of 78.7%, which is very close to that in the 1st cycle. Meanwhile, the

XRD pattern of In2O3@8%PANI composite after four cycles of photocatalytic

degradation of gaseous 1,2-dichlorobenzene (Fig. S7a) reveals similar feature in

crystal structure after stability test. Besides, TEM image of the In2O3@8%PANI

composite after four cycles (Fig. S7b) indicates that the PANI film was attached

intimately around the In2O3 nanospheres.

Fig. S6. Consecutive runs to probe the stability performance of In2O3@8%PANI core@shell composite toward the decomposition of gaseous 1,2-dichlorobenzene for four cycles. The reaction conditions are similar with the previous degradation experiments for various samples.

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Fig. S7. (a) XRD patterns of the In2O3@8%PANI core@shell composite before and after four cycles of photocatalytic degradation of gaseous 1,2-dichlorobenzene. (b) TEM image of the In2O3@8%PANI core@shell composite after four cycles of photocatalytic degradation of gaseous 1,2-dichlorobenzene.

Fig. S8. UV–vis absorption spectrum (a), bandgap energy (b), and XPS-VB spectrum

(c) of PANI.

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