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Article

Accelerated Photodegradation of Organic Pollutants over BiOBr/Protonated g-C3N4

1
College of Materials & Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310036, China
2
Key Lab of Applied Chemistry of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
*
Authors to whom correspondence should be addressed.
Catalysts 2022, 12(10), 1109; https://doi.org/10.3390/catal12101109
Submission received: 30 August 2022 / Revised: 20 September 2022 / Accepted: 21 September 2022 / Published: 25 September 2022
(This article belongs to the Special Issue Feature Papers in Catalysis in Organic and Polymer Chemistry)

Abstract

:
Interfacial engineering has emerged as an effective strategy to optimize the photocatalytic activity of heterojunctions. Herein, the interface between graphitic carbon nitride (g-C3N4) and BiOBr was readily regulated by a protonation treatment. The synthesized BiOBr/g-C3N4 heterojunctions were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The results show that pretreating g-C3N4 in diluted HCl solution led to a partial protonation of g-C3N4, which ensured intimate contact and high dispersion of supported BiOBr without changing the surface area, bulk g-C3N4 structure, or visible light absorption. The abundant BiOBr/g-C3N4 interfaces remarkably improved the separation and transfer of photogenerated carriers, which produced more h+ and O2●− to accelerate the photocatalytic degradation of organic pollutants. The photocatalytic activities of the BiOBr/g-C3N4 heterojunctions were evaluated by the degradation of RhB under visible-light irradiation (λ ≥ 420 nm). The apparent reaction (pseudo-first-order) rate constant of BiOBr supported on partially protonated g-C3N4 (Bpg-C3N4-0.75) is ca. 3-fold higher than that of BiOBr supported on pristine g-C3N4 (Bg-C3N4), verifying interfacial engineering as an effective strategy to optimize the catalytic activity of heterojunctions.

1. Introduction

With organic pollutant-induced water contamination becoming a serious global issue, the development of efficient and green technologies to degrade organic pollutants has become increasingly important. As a kind of advanced oxidation process, semiconductor-based photocatalysis has been frequently used to degrade organics in wastewater. [1] However, the high recombination rates of photogenerated electron–hole pairs in a single photocatalyst limit the reaction efficiency. Heterojunction has emerged as a potential solution to address this problem. [2,3,4,5,6] Successful fabrication of heterojunctions relies on not only the selection of suitable lattice and energy-level-matched semiconductors but also on the engineering of a heterojunction interface. [7,8,9] For a given heterojunction, the intimate and large-area contact interface facilitates the separation and transfer of photogenerated carriers, [10] which motivates researchers to engineer interfacial heterojunctions. For example, in our previous study [7], we reported that the abundant BiOI/ZnO interfaces resulting from the high dispersion of BiOI on ZnO can promote the separation and transfer of photogenerated carriers. Peng et al. [11] fabricated a face-to-face heterojunction of BiOCl/Bi2WO6 by in situ topotactic transformation, which exhibited improved photocatalytic activity for tetracycline degradation under visible light. Yang et al. [12] prepared BiOBr/pg-C3N4 by an electrostatically driven in situ growth method and reported the critical role of intimate interfaces in photocatalytic degradation of rhodamine B (RhB).
Graphite carbon nitride (g-C3N4) is a novel non-metallic semiconductor and has been frequently used to fabricate heterojunctions. [13,14,15,16,17] The heterointerface in g-C3N4-based heterojunctions can be readily regulated by the dispersion of supported semiconductors [18,19,20]. However, the typical methods for enhancing dispersion are usually associated with the modification of the bulk structure and the surface area of g-C3N4, which adds new variables that affect the catalytic efficiency of heterojunctions. To reveal the intrinsic influence of heterointerfaces in g-C3N4-based heterojunctions, it is desired yet challenging to develop a method that can achieve high dispersion of supported semiconductors without changing the bulk g-C3N4 structure, surface area, and light absorption properties.
Herein, we report a partial protonation of g-C3N4 that can achieve high dispersion of supported BiOBr without changing the surface area, bulk g-C3N4 structure, and visible light absorption of BiOBr/g-C3N4 heterojunctions. g-C3N4 were prepared by the calcination of melamine. A subsequential pretreatment in diluted HCl solution (X mL HCl in 10 mL H2O, X = 0, 0.25, 0.5, 0.75 and 1.0) led to a partial protonation of g-C3N4, denoted as pg-C3N4-X. Dispersing pg-C3N4-X in Bi(NO3)3 solution, followed by the addition of KBr, produced BiOBr/pg-C3N4-X heterojunctions. The intrinsic structure–property relationship of the heterointerface in BiOBr/g-C3N4 heterojunctions is discussed herein on the basis of the comparison between BiOBr supported on protonated (Bpg-C3N4-X) and pristine g-C3N4 (Bg-C3N4).

2. Results and Discussion

Figure 1a shows the X-ray diffraction (XRD) patterns of Bg-C3N4 and Bpg-C3N4-X (X = 0.25, 0.50, 0.75, 1.00) samples. Interestingly, all the samples exhibit similar peaks at 13.1° and 27.4°, corresponding to (001) and (002) planes of g-C3N4 (JCPDS card No. 87-1526) [21]. No obvious changes in peak shape and location are observed, suggesting that the protonation treatment exerts little influence on the bulk structure of C3N4, likely because the protonation of g-C3N4 occurs in diluted HCl solution, which modifies the surface charge but does not change the bulk structure of g-C3N4. The similar surface areas (ca. 10 m2 ·g−1) of g-C3N4, pg-C3N4-X, Bg-C3N4, and Bpg-C3N4-X further exclude the exfoliation of bulk g-C3N4. Other peaks located at 10.9°, 25.2°, 31.7°, 32.2°, 46.3°, and 57.2° can be readily indexed to (001), (101), (102), (110), (200), and (212) planes of tetragonal phase BiOBr (JCPDS card No. 85-0862), respectively [8]. However, the shape of these diffraction patterns varies. In particular, the samples exhibit very different diffraction intensity ratios of (110)/(102) planes. In the literature [22,23], the I110/I102 ratio has been frequently investigated to illustrate the preferential orientation of BiOBr because (110) and (102) planes correspond to the major peaks of the XRD profile and are the lateral surfaces for BiOBr with [010] orientation. Changes in the I110/I102 ratio indicate the differential growth behavior of BiOBr. In the standard card of BiOBr (JCPDS: 85-0862), the I110/I102 ratio is lower than 1.0. As shown in Figure 1b, the I110/I102 ratio increases from 1.19 for Bg-C3N4 and 1.98 for Bpg-C3N4-0.50 to 2.35 for Bpg-C3N4-0.75 and then decreases to 1.94 for Bpg-C3N4-1.0. The significantly higher I110/I102 ratio relative to the standard ratio (<1.0) indicates that BiOBr preferably grows along (110) orientations on pg-C3N4. The variation in the I110/I102 ratio with the X in Bpg-C3N4-X, on the other hand, suggests that the preferential orientation of BiOBr is influenced by the protonation treatment of g-C3N4 support. [24] The highest I110/I102 ratio is achieved by Bpg-C3N4-0.75, indicating that median protonation is beneficial. Considering that all the samples have similar surface area and bulk structures of g-C3N4, the preferential orientation of BiOBr is most likely influenced by the different surface charge of protonated g-C3N4, as it can influence the dispersion of Bi3+ on the surface to affect the nucleation and growth of BiOBr. A detailed explanation will be provided below.
The growth behavior not only changes the preferential orientation of BiOBr but also leads to varying microstructures of Bg-C3N4 and Bpg-C3N4-0.75. As demonstrated in Figure 2a, Bg-C3N4 is composed of two separated components. The nanoflowers assembled by many nanoflakes are BiOBr, whereas the micrometer lamellar materials are g-C3N4. The phase separation of these two components is further confirmed by the inhomogeneous elemental distribution. As shown in Figure 2b–f, Bi and Br elements are observed only in the region marked with a white circle, suggesting the agglomeration of BiOBr on the surface of g-C3N4. However, when BiOBr is supported on pg-C3N4-0.75, the situation changes. As shown in Figure 3a, BiOBr nanoflakes with a diameter of ca. 10 nm are highly dispersed on the surface of pg-C3N4-0.75. The homogeneous distribution of Bi, Br, C, and N elements throughout Bg-C3N4-0.75 (Figure 3b–f) confirms the intimate contact between g-C3N4-0.75 and BiOBr. Semi-quantitative XPS analysis also suggests that Bpg-C3N4-0.75 exhibits higher surface Bi/N and Br/N ratios than Bg-C3N4. Taking the above results together, we conclude that the protonation of g-C3N4 significantly promotes the dispersion of supported BiOBr. Similar results were previously reported in an AgBr/g-C3N4 system. [25]
In order to understand the support protonation effect on the growth behavior of BiOBr, we analyzed the zeta potential of pg-C3N4-X (Figure 4). In conventional studies [26], the protonation of g-C3N4 is usually conducted in strong acids with high concentration. The acid–base interaction between abundant –C–NH–/–C–NH2 motifs in the g-C3N4 framework and H+ usually changes the surface charge from negative to positive. [27] In this study, because the protonation of g-C3N4 was conducted in diluted HCl, only partial –C–NH–/–C–NH2 motifs were protonated. As a result, g-C3N4-X samples are still negatively charged. With increased HCl concentration (i.e., the value of X), more –C–NH–/–C–NH2 motifs are protonated, and the zeta potential increases accordingly. It is important to note that unprotonated –C–NH–/–C–NH2 motifs can also serve as anchoring sites toward metal ions. In the deposition of BiOBr onto pg-C3N4, Bi3+, ions are anchored by unprotonated –C–NH–/–C–NH2 motifs before in situ reaction with Br to produce BiOBr. A high dispersion of Bi3+ on the surface of g-C3N4 enables a bounded nucleation and growth of BiOBr, which eventually leads to a high dispersion and preferential orientation of BiOBr perpendicular to the plane of the supports [7]. Notably, partial protonation of g-C3N4 is beneficial to the dispersion of Bi3+ because it can isolate the unprotonated –C–NH–/–C–NH2 motifs. Excessively protonated –C–NH–/–C–NH2 motifs, on the other hand, significantly decrease the anchoring sites of Bi3+. The free Bi3+ may react with Br in solution to form aggregated BiOBr particles. To this end, median protonation is beneficial. In this study, the optimal HCl addition was determined to be 0.75 mL, as evidenced by the highest I110/I102 ratio (Figure 1b) and the high dispersion of BiOBr revealed by SEM (Figure 3).
The high dispersion of BiOBr on pg-C3N4-0.75 produces abundant BiOBr/pg-C3N4-0.75 interfaces, which may promote the transfer and separation of photogenerated hole−electron pairs to improve the catalytic performance [5,7]. To verify this hypothesis, we investigated the photocurrent responses of Bg-C3N4 and Bpg-C3N4-0.75. As shown in Figure 5, both Bg-C3N4 and Bpg-C3N4-0.75 exhibit stable photocurrent response in the light on–off cycles. The photocurrent density of Bpg-C3N4-0.75 (0.11μA·cm−2) is twice that of Bg-C3N4 (0.05 μA·cm−2), confirming its superior separation and transfer of the photogenerated carriers. Notably, Bpg-C3N4-0.75 and Bg-C3N4 display similar Bi 4f XPS spectra (Figure 6a). The peaks located at 159.2 and 164.5 eV can be readily ascribed to Bi 4f5/2 and Bi 4f7/2 of BiOBr [12,28], suggesting that the protonated supports exert little influence on the valence states of the supported BiOBr. In addition, Bpg-C3N4-0.75 and Bg-C3N4 heterojunctions exhibit similar absorption responses in the visible region (Figure 6b), suggesting that the protonated supports have no impact on the light responses. Taking all above results together, the efficient separation of the photogenerated carriers of Bpg-C3N4-0.75 can be attributed to the abundant BiOBr/pg-C3N4-0.75 interfaces. The intimate contact between BiOBr and pg-C3N4-0.75 shortens the diffusion length of the photogenerated carriers, which enables a timely charge transfer between BiOBr and pg-C3N4-0.75 and inhibits the recombination of photogenerated carriers [29]. Similar results were reported in BiOI/ZnO systems in our previous publication [7].
The photocatalytic activities of the BiOBr/g-C3N4 heterojunctions were evaluated by the degradation of RhB under visible-light irradiation. As indicated in Figure 7a, both pure g-C3N4 and pg-C3N4-0.75 exhibit poor photocatalytic activity toward RhB degradation (less than 10% within 60 min). However, once BiOBr is loaded, the photocatalytic activity is considerably promoted. Bg-C3N4 degrades 50% of RhB within 60 min, which is significantly higher than that of g-C3N4. This improved activity originates from the formation of BiOBr/g-C3N4 heterojunctions, which facilitate the separation and transfer of photogenerated carriers. For the catalysts with BiOBr/g-C3N4 heterojunctions, the catalytic performance is determined by the different structure of g-C3N4. As shown in Figure 7a, the catalytic performance of BiOBr/g-C3N4 follows the trend of Bg-C3N4 < Bpg-C3N4-0.25 < Bpg-C3N4-0.50 < Bpg-C3N4-0.75 > Bpg-C3N4-1.00, which is consistent with the trend of the I110/I102 ratio. In particular, the optimal Bpg-C3N4-0.75 catalyst degrades 96% of RhB within 60 min, which is significantly higher than that of Bg-C3N4. The photodegradation behavior of RhB over these samples can be fitted as the pseudo-first-order kinetics model (Figure 7b). Interestingly, the calculated rate constant (k) also follows the trend of Bg-C3N4 < Bpg-C3N4-0.25 < Bpg-C3N4-0.50 < Bpg-C3N4-0.75 > Bpg-C3N4-1.00 (Figure 7c), suggesting that the partial protonation of the support is beneficial to the photocatalytic performance. The highest k value observed on Bpg-C3N4-0.75 (0.045 min−1) is ca. threefold higher than that on Bg-C3N4 (0.011 min−1), demonstrating its superior photocatalytic performance. The degradation efficiency within 70 min of visible light irradiation remains higher than 95% in four consecutive runs (Figure 7d), indicating its excellent catalytic stability, which is consistent with the stable photocurrent response shown in Figure 5. Considering that Bpg-C3N4-0.75 and Bg-C3N4 have similar bulk structure of g-C3N4 (Figure 1a), surface area, valence state of BiOBr (Figure 6a), and visible-light absorption (Figure 6b), the superior photocatalytic activity of Bpg-C3N4-0.75 most likely originates from the high dispersion of BiOBr (Figure 3), which produces abundant BiOBr/g-C3N4 interfaces to promote the separation and transfer of photogenerated carriers (Figure 5). Regulating the amount of HCl added into the protonation of g-C3N4 modifies the surface charge of pg-C3N4, which eventually regulates the dispersion and the preferential orientation of supported BiOBr. The median protonation achieves the best BiOBr dispersion and the most BiOBr/g-C3N4 interfaces, which effectively separate and transfer the photogenerated carriers for efficient photocatalytic degradation of RhB.
Radical-trapping experiments were further carried out to identify the active species involved in the photodegradation of RhB over Bpg-C3N4-0.75. As shown in Figure 8a, the addition of tert-butanol as a scavenger for OH radicals barely changes the degradation rate, excluding OH radicals as the main reactive oxygen species (ROS) involved in the reaction. In stark contrast, adding disodium ethylenediaminetetraacetate (Na2-EDTA) and p-benzoquinone (BQ) as scavengers for h+ and O2●− remarkably decreases the degradation efficiency, indicating that h+ and O2●− are the key ROS involved in the photocatalytic degradation of RhB over Bpg-C3N4-0.75. According to the literature [30,31,32], the conduction band (CB) potential of BiOBr (0.22 eV vs NHE) is more positive than E0(O2/O2●− = −0.046 eV vs NHE), so the photogenerated electrons of BiOBr barely react with O2 to produce O2●−. The reactive O2●− should therefore be produced by the reaction between O2 and the photogenerated electrons of g-C3N4, of which the CB potential (−1.12 eV vs NHE) is more positive than E0(O2/O2●−). On the other hand, the valence band (VB) potential of BiOBr is more positive than the VB potential of g-C3N4 and is thus more reactive toward the oxidation of RhB. Taken together, the BiOBr/g-C3N4 heterojunctions would prefer an S-scheme pathway (Figure 8b). [32] Specifically, when the junction is irradiated by visible light, electrons in the VB of both g-C3N4 and BiOBr are excited to their CB. Owing to the band bending, the built-in electric field, and Coulomb interactions, the photogenerated electrons in the CB of BiOBr will combine with the photogenerated holes in the VB of g-C3N4. The reserved electrons in the CB of g-C3N4 can react with O2 to produce reactive O2●− for RhB degradation, whereas the reserved holes in the VB of BiOBr can oxidize RhB directly. Increasing BiOBr/g-C3N4 interfaces facilitates the combination of photogenerated electrons in the CB of BiOBr with the photogenerated holes in the VB of g-C3N4. As a result, more electrons in the CB of g-C3N4 and the holes in the VB of BiOBr can be used to produce ROS for RhB degradation.

3. Materials and Methods

3.1. Preparation of Protonated g-C3N4 (pg-C3N4)

First, 3.0 g of melamine in a covered crucible was heated at 550 °C for 2 h to obtain g-C3N4. Subsequently, 0.3 g of the as-synthesized g-C3N4 was dispersed in 10 mL of water under stirring for 20 min at room temperature. Afterwards, certain amount of HCl (ca. 37 wt%, X mL, X = 0.25, 0.50, 0.75, 1.00) was added to the above suspension drop by drop. The mixture was stirred for 2 h for protonation. The solid products were collected and calcined in a covered crucible at 300 °C for 2 h to obtain the final products, which were designated as protonated g-C3N4-X (pg-C3N4-X, X = 0.25, 0.50, 0.75, 1.00).

3.2. Preparation of BiOBr-pg-C3N4-X (Bpg-C3N4-X) Heterojunctions

A volume of 10 mL of ethylene glycol dissolving 0.053 g of Bi(NO3)3·5H2O was mixed with 8 mL of water containing 0.3 g of as-synthesized pg-C3N4-X. After vigorous stirring for 30 min, 2 mL of water containing 0.065 g of KBr was slowly added into the above mixture. After reaction for 1 h at room temperature, the solids were collected, washed, and dried. The product was labelled as Bpg-C3N4-X. BiOBr-g-C3N4 (Bg-C3N4) was synthesized using unprotonated g-C3N4 under the same conditions of Bpg-C3N4-0.75.

3.3. Characterizations

The crystal structure was studied on a Rigaku Ultimate IV diffractometer (Rigaku, Tokyo, Japan) using Cu Kα radiation. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometric (EDX) microanalyses were performed on a Hitachi SU8100 (Hitachi, Tokyo, Japan). The specific surface area was measured by a nitrogen sorption analyzer (Micromeritics ASAP 2020, Norcross, GA, USA). The surface chemical states were verified by X-ray photoelectron spectroscopy (XPS, Thermo Scientific Escalab 250, Waltham, MA, USA). The Zeta potential of the samples was assessed using a Zetasizer Nano ZS (Malvern Instruments Ltd, Malvern, UK). UV-Vis diffuse reflectance spectra were measured using a Shimadzu UV-2450 (Shimadzu, Kyoto, Japan) spectrophotometer. The zero-biased photocurrent was measured using a CHI 660E electrochemical workstation (CHI instruments, Shanghai, China) with 0.1 M Na2SO4 solution as electrolyte. A 300 W Hg lamp with cutoff filters (λ ≥ 420 nm) was utilized as a visible light source.

3.4. Photocatalytic Degradation of RhB

The visible-light photodegradation of RhB (15 mg·L−1) at 25 °C was selected as the probe reaction to test the catalytic performances of as-synthesized heterojunctions. A high-pressure Hg lamp (300 W) with an optical filter (λ ≥ 420 nm) was utilized as the light source. Briefly, 15 mg of catalyst and 50 mL of RhB solution were vigorously stirred in the dark for 60 min to achieve adsorption–desorption equilibrium. Afterwards, an appropriate amount of the suspension was extracted at given time intervals of light irradiation and centrifuged to remove the solids. The concentration of RhB in the solution was detected by recording the absorbance at the characteristic band of 553 nm using a Shimadzu UV-2450 spectrophotometer.

3.5. Radical-Trapping Experiments

Radicals-trapping experiments were carried out in a similar manner as photocatalytic degradation. Disodium ethylenediaminetetraacetate (Na2-EDTA), tert-butanol, and p-benzoquinone were used as scavengers to trap h+, OH, and O2●− radicals, respectively [5,7,24]. Prior to the photocatalytic test, 200 µL of scavengers (10 mM) was dripped into the reaction mixture once the mixture reached equilibrium. The suspension extracted at given time intervals under light irradiation was centrifuged and analyzed to obtain the concentration of pollutant.

4. Conclusions

In summary, a facile engineering of BiOBr/g-C3N4 heterojunction interface and its influence on the catalytic performances were reported herein. Protonating g-C3N4 in dilute HCl resulted in modification of surface charge without changing its bulk structure. When used as supports to load BiOBr, protonated g-C3N4 enabled high BiOBr dispersion and abundant BiOBr/g-C3N4 interfaces, which remarkably improved the separation and transfer of photogenerated carriers. The optimal catalyst, Bpg-C3N4-0.75, exhibited similar surface area, bulk g-C3N4 structure, and visible light absorption as Bg-C3N4, but its pseudo-first-order catalytic rate constant was ca. threefold higher than that of Bg-C3N4. These results verify interfacial engineering as an effective strategy to optimize the photocatalytic activity of heterojunctions.

Author Contributions

Conceptualization, J.L. and S.Z.; methodology, J.L.; validation, J.L., H.G. and Q.N.; investigation, J.L., H.G. and H.Y.; writing—original draft preparation, J.L.; writing—review and editing, S.Z.; visualization, J.L.; supervision, J.L. and S.Z.; project administration, J.L. and S.Z.; funding acquisition, J.L. and S.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work was financially supported by the National Natural Science Foundation of China (21703050, 21802122) and the Zhejiang Province Natural Science Foundation (LY22B030010).

Data Availability Statement

The data presented in this study are available upon request from the corresponding author.

Acknowledgments

The authors acknowledge Fang Chen for kind help in the scanning electron microscopy characterization.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. (a) XRD patterns and (b) the diffraction intensity ratio of (110)/(102) planes of Bg-C3N4 and Bpg-C3N4-X samples (X is the amount (in mL) of HCl added in the protonation treatment of g-C3N4; X = 0.25, 0.50, 0.75, 1.00).
Figure 1. (a) XRD patterns and (b) the diffraction intensity ratio of (110)/(102) planes of Bg-C3N4 and Bpg-C3N4-X samples (X is the amount (in mL) of HCl added in the protonation treatment of g-C3N4; X = 0.25, 0.50, 0.75, 1.00).
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Figure 2. (a,b) SEM images and (cf) element mapping of Bg-C3N4. The aggregated BiOBr nanoflowers are marked with white circle.
Figure 2. (a,b) SEM images and (cf) element mapping of Bg-C3N4. The aggregated BiOBr nanoflowers are marked with white circle.
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Figure 3. (a) SEM image (high-resolution image inset) and (bf) element mapping of Bpg-C3N4-0.75.
Figure 3. (a) SEM image (high-resolution image inset) and (bf) element mapping of Bpg-C3N4-0.75.
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Figure 4. Zeta potential of g-C3N4-X samples.
Figure 4. Zeta potential of g-C3N4-X samples.
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Figure 5. Photocurrent responses of Bg-C3N4 and Bpg-C3N4-0.75.
Figure 5. Photocurrent responses of Bg-C3N4 and Bpg-C3N4-0.75.
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Figure 6. (a) Bi 4f spectra and (b) UV-Vis spectra of Bg-C3N4 and Bpg-C3N4-0.75.
Figure 6. (a) Bi 4f spectra and (b) UV-Vis spectra of Bg-C3N4 and Bpg-C3N4-0.75.
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Figure 7. (a) Photodegradation of RhB (15 mg·L−1) under visible-light irradiation (λ ≥ 420 nm); (b) pseudo-first-order kinetic linear simulation lines; (c) the corresponding pseudo-first-order kinetic constants (k); (d) RhB degradation efficiency within 70 min of visible-light irradiation for four consecutive runs.
Figure 7. (a) Photodegradation of RhB (15 mg·L−1) under visible-light irradiation (λ ≥ 420 nm); (b) pseudo-first-order kinetic linear simulation lines; (c) the corresponding pseudo-first-order kinetic constants (k); (d) RhB degradation efficiency within 70 min of visible-light irradiation for four consecutive runs.
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Figure 8. (a) The photodegradation of Bpg-C3N4-0.75 with different scavengers; (b) schematic illustration of the photodegradation of RhB over BiOBr/g-C3N4.
Figure 8. (a) The photodegradation of Bpg-C3N4-0.75 with different scavengers; (b) schematic illustration of the photodegradation of RhB over BiOBr/g-C3N4.
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Liu, J.; Guo, H.; Yin, H.; Nie, Q.; Zou, S. Accelerated Photodegradation of Organic Pollutants over BiOBr/Protonated g-C3N4. Catalysts 2022, 12, 1109. https://doi.org/10.3390/catal12101109

AMA Style

Liu J, Guo H, Yin H, Nie Q, Zou S. Accelerated Photodegradation of Organic Pollutants over BiOBr/Protonated g-C3N4. Catalysts. 2022; 12(10):1109. https://doi.org/10.3390/catal12101109

Chicago/Turabian Style

Liu, Juanjuan, Heng Guo, Haoyong Yin, Qiulin Nie, and Shihui Zou. 2022. "Accelerated Photodegradation of Organic Pollutants over BiOBr/Protonated g-C3N4" Catalysts 12, no. 10: 1109. https://doi.org/10.3390/catal12101109

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