Graphitic Carbon Nitride with Carbon Vacancies for Photocatalytic

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Graphitic Carbon Nitride with Carbon Vacancies for Photocatalytic Degradation of Bisphenol A Xiaofei Liang, Guanlong Wang, Xiaoli Dong, Guowen Wang, Hongchao Ma, and Xiufang Zhang ACS Appl. Nano Mater., Just Accepted Manuscript • DOI: 10.1021/acsanm.8b02089 • Publication Date (Web): 28 Dec 2018 Downloaded from http://pubs.acs.org on January 2, 2019

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ACS Applied Nano Materials

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Graphitic Carbon Nitride with Carbon Vacancies for

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Photocatalytic Degradation of Bisphenol A

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Xiaofei Liang, Guanlong Wang, Xiaoli Dong, Guowen Wang, Hongchao Ma, Xiufang Zhang*

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School of Light Industry and Chemical Engineering, Dalian Polytechnic University, Dalian 116034, China

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* Corresponding author: Xiufang Zhang; E-mail: [email protected]

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ACS Paragon Plus Environment

ACS Applied Nano Materials 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

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ABSTRACT

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Photocatalysis is intensely employed to remove refractory organic pollutants in water, but

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suffers from low efficiency due to rapid recombination of photogenerated electrons and holes. Here,

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carbon vacancies modified g-C3N4 (VC-C3N4) is prepared via a handy two-step calcination method

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and firstly applied in the photocatalytic removal of bisphenol A (BPA). Compared to pristine

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g-C3N4, the photocatalytic degradation activity of VC-C3N4 for BPA is largely enhanced, whose

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kinetic constant (k) of BPA degradation is 1.65 times as that of pristine g-C3N4. The enhanced

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photocatalytic performance of VC-C3N4 is ascribed to critical role of carbon vacancies: On the one

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hand, carbon vacancies serve as the reservoir of photogenerated electrons to inhibit the

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recombination of photogenerated holes and electrons. On the other hand, carbon vacancies as

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conversion centers transfer trapped photogenerated electrons to absorbed O2 for generation of

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abundant superoxide radical (•O2-), which takes a dominant effect in the photocatalytic degradation

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process.

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KEYWORDS: carbon vacancies, g-C3N4, bisphenol A, •O2- species, photocatalytic degradation.

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1 INTRODUCTION

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Recently, water pollution due to the unrestrained misuse of emerging organic materials (such

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as antibiotics, endocrine disrupters, and etc) has become one of important factors threating human

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health. Specially, bisphenol A (BPA) is one of the most widely used industrial organic materials in

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the world and long-time exposure to BPA could trigger abnormal release of human hormones and

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harm of liver and kidney function [1-4]. Due to the high toxicity, great stability and difficult

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degradation of these pollutants in aqueous system [5], people have been devoted to finding an

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efficient, fast, universally applicable method with no secondary pollution to eliminate or reduce

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these toxic and organic substances. Semiconductor photocatalytic technology has long been

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considered as a high-efficiency, low cost and green method to remove stubborn pollutants in the

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water or split water for hydrogen generation [6-13]. Oxidative active species produced by

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semiconductor, for instance, hydroxyl radicals (•OH), superoxide radicals (•O2-) and photogenerated

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holes (h+), can oxidize organic pollutants. Among kinds of semiconductor photocatalysts, graphitic

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carbon nitride (g-C3N4) is deemed as a potential catalyst for pollutant degradation under visible

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light [14-16] due to its low cost synthesis, high yield, appropriate band gap energy (Eg) (about 2.7

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eV ) and great chemical stability [17-22]. However, the performance of g-C3N4 is still restrained

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because of its rapid recombination of photogenerated electrons and holes [23]. Consequently,

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researchers have been trying to effectively inhibit the recombination of photogenerated holes and

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electrons of g-C3N4 by modifying their chemical structure via doping mental/non-mental elements

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(such as Fe, Ka, Ag, Be, N) [24-28], controlling morphology [29, 30], constructing heterojunction

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[31] or introducing vacancies [32]. Some excellent works addressed BPA degradation with

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modified g-C3N4. Oh et al. [33] fabricated Ag/S-doped g-C3N4 photocatalyst and its improved

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photocatalytic performance for BPA oxidation was determined. In his work, they also illustrated the

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oxidation pathways of BPA in the photocatalytic process. Qiu et al. [34] reported that the

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photocatalytic capacity of mesoporous g-C3N4 was improved under visible-light irradiation after the

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modification of Co3O4. What’s more, they also testified that both ·OH and ·O2- radical species take

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crucial effect on BPA photodegradation capacity. Ag2O/g-C3N4 composites were also employed for

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the photocatalytic degradation of phenolic compounds under UV-/visible light. Ren et al. found that



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the highly dispersed Ag2O particles can promoted the photocatalytic performance of Ag2O/g-C3N4

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heterojunction photocatalyst, because it facilitates visible-light absorption of catalyst and efficient

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separation of photoinduced electron-holes [35]. It was investigated by Zhao and co-authors that

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adding persulfate (PS) in g-C3N4 can strengthen the photocatalytic ability of BPA under visible light

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[36]. Instead of SO4•-, •O2- and •OH were the major active radicals in the photocatalytic degradation

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process of BPA.

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Vacancy, which is a usual defect in catalysts, can play a crucial part in modifying electronic

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structure of photocatalytic material and thereby improve the photocatalytic degradation ability of

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the catalysts. Lately, there are a few studies about carbon vacancies defects in g-C3N4. For instance,

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Dong et al. prepared carbon vacancy regulated ultrathin VC-C3N4 nanosheets in photoreduction of

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NO to N2 [37], it was found that carbon vacancy of VC-C3N4 could accelerate the separation of

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photogenerated electron-holes. Li et al. proposed that carbon vacancy modulated g-C3N4 exhibited

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efficient hydrogen peroxide generation under visible light [38]. Carbon vacancies present unpaired

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electrons after the loss of carbon atoms, thereby it is easy for them to attract electrons from external

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substances, such as photogenerated electrons, organic pollutants with electron-rich aromatic

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structure or O2. The capture of photogenerated electrons by carbon defects could validly restrain the

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recombination of photoinduced electron-holes and the enhanced absorption towards organic

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pollutants is favorable for the photocatalytic degradation process. Moreover, carbon vacancies are

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likely to facilitate the reaction between photogenerated electrons and dissolved O2 for the

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generation of •O2- species, which may take significant effect in the photocatalytic degradation

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process. Inspired by it, it is assumed that maybe g-C3N4 with carbon vacancies modification could

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realize the enhanced the photocatalytic degradation of BPA. Nevertheless, there is no investigation

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about constructing carbon vacancies mediated g-C3N4 (VC-C3N4) for photocatalytic removal of

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organic pollutants such as BPA. Moreover, the intrinsic role of carbon vacancies in VC-C3N4 for

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photocatalytic removal of organic contaminants remains unknown.

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In our work, g-C3N4 catalyst with carbon vacancies was prepared via a handy two-step

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calcination method. The photocatalytic performance of VC-C3N4 for BPA removal was enhanced.

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The relevant mechanism of the photocatalytic oxidation of BPA, and especially the contribution of


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carbon vacancies to the enhanced photocatalytic ability were discussed in detail.

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2 EXPERIMENTAL SECTION

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2.1 Reagents

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All of the reagents were purchased from Tianjin Guangfu co., Itd and used without purification.

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The cellulose acetate membranes were purchased from Tianjin Jinteng co., Itd. Ar (≥99.999%) gas

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was purchased from Dalian Special Gases co., Itd.

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2.2 Samples Preparation

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The VC-C3N4 was prepared as follows: 10 g melamine was added into a semi-closed crucible

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(50 mL), and was heated at 550 ℃ for 2 h in muffle furnace. When it reached 25 ℃, the resulting

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yellow product was grinded to powder. Then, the as-prepared g-C3N4 sample was calcined again in

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tube furnace at 520 ℃ for another 2 h under pure Ar gas flow (120mL·min-1). The resulting bright

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yellow powder was denoted as VC-C3N4. Scheme 1 was the structural illustration of carbon

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vacancies modified g-C3N4 formation.

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Pristine g-C3N4 sample was prepared by the same method without Ar gas.

Scheme 1. Structural illustration of carbon vacancies modified g-C3N4 formation.

2.3 Characterizations

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The crystalline properties of g-C3N4 and VC-C3N4 were tested by an X-ray diffractometer

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(XRD, Shimadzu LabX-6100) with Cu-Kα radiation (λ=1.5418 Å). The surface groups were

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determined by an IRAffinity-1 Fourier transform infrared (FT-IR). The micro-morphologies and

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element compositions were obtained with the field emission scanning electron microscope (SEM)

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(JSM‐7800F, JEOL). The UV-2450 UV-vis spectrophotometer (Shimadzu) was used to record the



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diffuse reflectance spectra (DRS) of catalysts. As for the photoluminescence spectra (PL) of

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catalysts, fluorescence spectrometer (LS-55) was used in this work. The electrochemical experiment

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and photoelectrochemical experiment were all performed by using a CHI-660D electrochemical

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workstation (Chenhua, China). X-ray photoelectron spectroscopies (XPS) were measured by the

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ESCALAB250. Electron Spin Resonance (ESR) spectra were recorded on a Brüker A200

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spectrometer (JES FA200) at 77K. Specific surface areas were calculated via the

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Brunauer-Emmett-Teller (BET) model. The concentrations of BPA were analyzed by Agilent 1260

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HPLC (G7115A) with a Discovery C18 (25 ℃). The operating conditions were as follows: C18

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reverse phase column, alcohol: water = 7:3, λmax = 278 nm, flow-rate = 0.8 mL·min-1. Cr (VI)

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concentration was obtained by the conventional diphenylcarbazide colorimetric method [30].

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2.4 Photocatalytic experiments

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All the photocatalytic experiments were conducted in a Pyrex photocatalytic reactor. A 350W

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Xenon lamp was used as the light source (equipped with a λ ＞ 420 nm optical filter). 0.03 g

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photocatalyst was dispersed in 100 mL prepared BPA (10.0 mg·L-1) or Cr (VI) (15 mg·L-1 ) solution.

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The pH of Cr (VI) solution was adjusted to 3.0 by using diluted HCl. Before the irradiation, the

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mixture was mildly stirred in dark for 60 min to reach the adsorption-desorption equilibrium. At

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certain time intervals, 5 mL of samples was withdrawn and filtrated by 0.22 μm cellose acetate

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membrane filters.

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For the detection of active species in the photocatalytic process, disodium ethylenediamine

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tetra acetic acid (EDTA-Na2), benzoquinone (BQ) and tertiary butanol (TBA) solutions were added

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into BPA solution to trap holes (h+), hydroxyl radicals (•OH) and superoxide radicals (•O2-),

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respectively. The concentration of these radical scavengers was all 0.3 mmol·L-1.

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2.5 Photoelectrochemical Experiments

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The Mott-Schottky experiment and transient photocurrent experiment were all recorded in an

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electrochemical workstation with conventional three-electrode cell, in which a Pt wire serves as

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counter electrode, a saturated calomel electrode (SCE) as reference electrode, and a carbon rod as

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working electrode with 0.28 cm2 exposed area. In details, 5 mg of photocatalyst was added in 1.5


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mL of mixture which contained 0.5 mL ultrapure water and 1.0 mL alcohol. Then the obtained

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solution was ultrasonically dispersed for 30 min to get homogeneous dispersion. Finally, 5.0 μL

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above homogeneous solution was dropped on the top of carbon rod, which was then naturally dried.

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During the test process, three electrodes were all immersed in 0.1 M NaSO4 solution.

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3 RESULTS AND DISCUSSION

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3.1 Crystal Analysis

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Fig. 1 XRD patterns of g-C3N4 and VC-C3N4.

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The crystalline structure of Vc-C3N4 and g-C3N4 was measured by XRD. The spiky peak at

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2θ=27.3° corresponds to (002) (d=0.324 nm) diffraction plane, which represents the interlayer stack

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of graphene-like structure (Fig. 1). The other peak at 2θ=13.1° corresponds to (001) (d=0.682 nm)

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diffraction plane caused by the in-plane cellular structure [15]. The crystalline structure of VC-C3N4

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is alike to that of g-C3N4, explaining that calcination process under Ar atmosphere did not change

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its holistic crystal structure.

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3.2 Analysis of Carbon Vacancy Formation



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Fig. 2 FT-IR spectra of VC-C3N4 and g-C3N4.

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The surface groups on samples were determined by FT-IR spectra. The sharp peak of VC-C3N4

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at 808 cm-1, corresponding to the C-N stretching vibration of the characteristic 1-3-s-triazine cycles,

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is slightly weaker than that of g-C3N4 (Fig. 2). This could be ascribed to the appearance of carbon

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vacancies, which destroy the structural integrity of 1-3-s-triazine cycles. A series of small peaks at

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1200-1700 cm-1 are in concerned with the stretching of aromatic C-N. The broad peak at around

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3200 cm-1 in the spectra of g-C3N4 corresponds to the N-H stretching vibration modes. Clearly,

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there is no evident structure change of VC-C3N4 after high-temperature process compared with

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pristine g-C3N4.


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Fig. 3 SEM images and corresponding EDX results of (a-d) g-C3N4 and (e-h) Vc-C3N4.

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The SEM images and EDX analytic results of pristine g-C3N4 and VC-C3N4 are shown in the

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Fig. 3. Three random regions (A-C) are chosen to measure surface element composition of g-C3N4

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and Vc-C3N4. It is clear that three C/N radios of VC-C3N4 are all less than g-C3N4, and the average

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C/N value of VC-C3N4 and g-C3N4 is 0.43 and 0.55, respectively. This result verifies that the carbon

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vacancies of VC-C3N4 form owing to the loss of carbon atoms

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Fig. 4 ESR spectra of VC-C3N4 and g-C3N4.

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In addition to FT-IR and EDX analysis, ESR is also used to further confirm the generation of

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carbon vacancy. In Fig. 4, a characteristic ESR signal at g=2.00, which is caused by the unpaired

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electrons of aromatic rings [23], is in both g-C3N4 and VC-C3N4 samples. As shown in scheme 1, the

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loss of carbon atoms in g-C3N4 gives rise to the N atoms carrying unpaired electrons. Compared

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with the pristine g-C3N4 which only contains the C atoms with unpaired electrons at the edge, the

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carbon vacancy-modified g-C3N4 contains more atoms (unsaturated N atoms) carrying unpaired

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atoms. Distinctly, the VC-C3N4 possesses an exceedingly high ESR signal compared with g-C3N4,

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demonstrating the evident increase of unpaired electrons in VC-C3N4 (Fig. 4). The analysis of ESR

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spectra forcefully validates the existence of carbon vacancies in VC-C3N4, which is in accordance

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with previous FT-IR and EDX analysis.

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To sum up, the carbon vacancies are successfully introduced into g-C3N4. At high temperature,

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the carbon atoms maybe obtain energy from flowing Ar gas which carried enormous energy, which

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then flee from 1-3-s-triazine cycles and thus result in the electron-deficient carbon vacancies [39].

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3.3 Photocatalytic Capability


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Fig. 5(a) The degradation of BPA and (b) kinetic constants (k) with g-C3N4 and VC-C3N4 under visible light.

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The photocatalytic degradation ability of g-C3N4 and VC-C3N4 under visible light (λ > 420 nm)

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was assessed using BPA as a target pollutant (Fig. 5(a)). It was found that BPA degradation

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followed the pseudo-first-order kinetics ln(C0/Ct) = −kt (t is time and k is kinetic constant), and Fig.

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5(b) shows the corresponding kinetic constants (k) of BPA degradation by g-C3N4 and VC-C3N4. In

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the direct photolysis, the concentration of BPA was nearly unchanged under the visible light

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illumination, meaning that BPA cannot be degraded by direct photolysis (Fig. 5(a)). The BPA

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removal rate was only 10.3 % when came to adsorption-desorption equilibrium within 40 min. But

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the photocatalytic removal of BPA over VC-C3N4 reached 90.0% in 420 min illumination. The

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result is attributed to the great photocatalytic degradation ability of VC-C3N4. In comparison, the

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photocatalytic degradation efficiency of g-C3N4 was only 77.7% in the same duration, indicating

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that carbon vacancies facilitated the enhancement of the photocatalytic activity of VC-C3N4.

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Moreover, the k of VC-C3N4 (0.0056 min-1) was 1.65 times as that of g-C3N4 (0.0034 min-1).



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Fig. 6 Cycling runs of BPA degradation efficiency by VC-C3N4.

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The stability of catalysts is another vital property of the photocatalysts in the aspect of

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practical application, thereby, it is essential to evaluate the reusability of the VC-C3N4. The stability

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of the VC-C3N4 was measured by evaluating its photocatalytic performance in repeated use. After

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five cyclic experiments (Fig. 6), the photocatalytic ability of VC-C3N4 was almost unchanged,

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indicating good stability of VC-C3N4 in photocatalytic process.

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3.4 Proposed Mechanism Analysis

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Fig. 7(a) PL and (b) transient photocurrent respond of g-C3N4 andVC-C3N4.

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Based on the above study, it is speculated that the elevated photocatalytic capacity of VC-C3N4

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is owing to the high-efficiency separation of photoinduced electron-holes induced by carbon

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vacancies. To verify this hypothesis, we tested separation and migration efficiency of photoinduced


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charge carriers in semiconductors by PL and transient photocurrent. The PL peak of VC-C3N4 is

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weaker than pristine g-C3N4 (Fig. 7(a)), meaning that the recombination of photogenerated electrons

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and holes of VC-C3N4 is effectively limited. This phenomenon could be ascribed to valid capture of

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photogenerated electrons by carbon vacancies. Unexpectedly, the position of PL peak of VC-C3N4

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presents red shift from 450 nm to 468 nm. This phenomenon implies that the band gap of VC-C3N4

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may be changed. Moreover, the high-efficiency separation of photogenerated electron-holes can be

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further evidenced by transient photocurrent measurement. According to Fig. 7(b), the VC-C3N4

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exhibits a significantly larger photocurrent response than g-C3N4. The photocurrent density of

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VC-C3N4 reaches about 6 μA·cm-2, almost 3 times as that of g-C3N4 (about 2 μA·cm-2), doubtlessly

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confirming the high-efficiency separation of photogenerated electron-holes in VC-C3N4.

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Fig. 8(a) DRS, (b) the plot of (αhv)2 versus photo energy (hv), (c) Mott-Schottky plots and (d) the band position schematic of g-C3N4 and VC-C3N4.

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Optical absorption property is also an important factor in reflecting the photocatalytic ability of

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photocatalysts. Fig. 8(a) exhibits that the adsorption edge of VC-C3N4 exhibits an evident red shift

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(extended from 450 nm to 462 nm) compared to g-C3N4, the movement of adsorption edge is in

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good agreement with above PL results. Fig. 8(b) shows the corresponding Eg of two samples, which



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is calculated from the DRS spectra by the equation (1): (hν·α) =A(hν-Eg)n

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(1)

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where α is the absorption coefficient, hν is light frequency, and A is Planck’s constant.

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Moreover, n is 1/2 for direct band gap material. The Eg of VC-C3N4 is narrowed from 2.76 eV to

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2.65 eV, indicating that the introduction of carbon vacancies alters band gap. Narrow band gap

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gives rise to better visible-light response and then enhances photocatalytic degradation ability.

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Whether the conduction band (CB) position of VC-C3N4 is still high enough to reduce O2 (the

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potential of O2/superoxide radical (•O2-)) after the band gap was narrowed. The CB position of

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VC-C3N4 was determined by the Mott-Schottky measurement. The flat-band potentials (Vfb) of

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g-C3N4 and Vc-C3N4 are -1.10 V and -0.95 V (vs. SCE), respectively, corresponding to -0.86 V and

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-0.71 V (vs. NHE), respectively (Fig. 8c). As is well-known, the Vfb of n-type semiconductor is

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more positive by 0.2 V than its CB position [40]. Hence, the CB position of g-C3N4 and Vc-C3N4

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are -1.06 V and -0.91 V (vs. NHE), respectively, and the CB position of Vc-C3N4 is still higher than

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the position of O2/•O2- (-0.044 eV vs. NHE) [41]. Consequently, VC-C3N4 can theoretically generate

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•O2- in photocatalytic process. The EVB of g-C3N4 and Vc-C3N4 were calculated by the equation of

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Eg=EVB-ECB, therefore the EVB of g-C3N4 is 1.70 eV, and the EVB of Vc -C3N4 is 1.74 eV (vs. NHE)

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(Fig. 8d).

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The BET surface area is another vital factor, which can influence the photocatalytic

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performance of catalyst. By determination, the BET surface areas of g-C3N4 and VC-C3N4 were 30.1

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and 14.7 m2·g-1, respectively, indicating the calcination under Ar atmosphere decreased the specific

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surface area. This change would not contribute to the enhanced photocatalytic performance.


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Fig. 9(a) The degradation of BPA with different scavengers; (b) N2 and O2 blowing experiment; (c) The C/C0 for Cr (VI) photocatalytic degradation with g-C3N4 and VC-C3N4 and (d) the action mechanism of carbon vacancies under visible light irradiation.

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Obviously, BPA can be significantly photodegraded by VC-C3N4, and the oxidative species (h+,

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•O2- and •OH) generated in the photodegradation process are deduced to be possible oxidants.

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Hence, the quenching experiment was conducted to identify which oxidation species contribute in

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photodegradation process of VC-C3N4 (Fig. 9(a)). EDTA-Na2, BQ, and TBA were used to quench h+,

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•O -, 2

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BPA was not obviously affected when EDTA-Na2 was added, meaning that h+ specie generated tiny

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effect in BPA photocatalytic process. After the addition of TBA and BQ, the photocatalytic

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degradation efficiency of BPA obviously decreased from 92.0% to 48.0% and 21.3 %, respectively,

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which indicated that •O2- was the leading active radical and •OH was secondary important active

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radical in the photodegradation process. For further testify the role of •O2-, N2 and O2 blowing

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experiment were carried. Blowing N2 was to eliminate the dissolved O2 which was the source of

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•O2- species in solution, and blowing O2 was to increase the concentration of dissolved O2. From the

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Fig. 9(b), the photocatalytic removal of BPA was tremendously decreased after N2 blowing, but it

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was raised after O2 blowing. The two results consistently certify that •O2- species were the dominant

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oxidation species during photocatalytic process and were generated from the dissolved O2. To

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further explore the role of carbon vacancies, Cr (VI) was selected to reveal the photoreduction

and •OH active species, respectively. Obviously, the photocatalytic degradation efficiency of



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capacity of VC-C3N4 under visible light irradiation. Interestingly, the photoreduction ability of

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VC-C3N4 for Cr (VI) was inferior to g-C3N4 (Fig. 9(c)). This phenomenon signifies that compared

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with g-C3N4, less photogenerated electrons of VC-C3N4 are used in reduction of Cr (VI). Generally,

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photogenerated electrons of semiconductor have two main depletion ways: some photogenerated

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electrons directly participate in the reduction reaction with pollutants; some others react with O2 for

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the generation of •O2-. Since less photogenerated electrons of VC-C3N4 were consumed in reduction

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process, it is more likely that the photogenerated electrons react with O2 produce •O2-, which is

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different from that of g-C3N4. Consequently, carbon vacancies serve as the conversion center

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beneficial to transfer photogenerated electrons to O2 and produce abundant •O2-, leading to the

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improved photocatalytic ability of VC-C3N4.

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Based on the previous characterization and discussion results, a possible mechanism for the

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enhanced photocatalytic ability of VC-C3N4 was presented and demonstrated in Fig. 9(d). After the

296

escape of carbon atoms from g-C3N4, the unpaired electron around the carbon vacancies makes

297

them exceedingly electrophilic. Hence, the negatively charged molecules such as the BPA with

298

electron-rich aromatic structure and the dissolved O2 are prior to adsorb on these carbon vacancies.

299

Once illuminated by visible light, VC-C3N4 is immediately excited, and then many photogenerated

300

holes and electrons are generated. Electron-deficient carbon vacancies of VC-C3N4 can promptly

301

capture these electrons, and thus restrain its recombination with photogenerated holes. Then these

302

photogenerated carriers migrate to the surface of VC-C3N4 and participate in the reaction. Therefore,

303

the improved photocatalytic degradation ability of VC-C3N4 is partly ascribed to efficient separation

304

of photogenerated electron-holes. More importantly, the carbon vacancies, serving as the

305

conversion center, transfer the most of captured photogenerated electrons to the absorbed O2 for the

306

formation of •O2-, which is the dominant oxidative specie for degradation of BPA.

307

CONCLUSION

308

To sum up, the carbon vacancies modified g-C3N4 with enhanced photocatalytic capacity was

309

fabricated via a handy calcination method. The kinetic constant of BPA degradation with VC-C3N4

310

is nearly 1.65 times as that of g-C3N4. After the carbon vacancies introduction, the recombination


Page 17 of 22 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


311

rate of photogenerated electron-holes is largely decreased. Moreover, carbon vacancies, serving as

312

conversion centers, transfer most trapped photoinduced electrons to absorbed O2 for the generation

313

of •O2-. This work provides an attractive avenue for designing and constructing novel photocatalyst

314

towards efficient removal of refractory organic pollutants.

315

AUTHOR INFORMATION

316

Corresponding author

317

E-mail: [email protected]；

318

Notes

319 320 321

There is no competing financial interest.

Acknowledgments We thank the financial supported from the Natural Science Foundation of China (21577008,

322

21878031), and Fundamental Research Funds for Central Universities (2016J004).

323

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Graphitic Carbon Nitride with Carbon Vacancies for Photocatalytic

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