Cu2O Nanoparticle Hyper-Cross-Linked Polymer Composites for the

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Cu2O Nanoparticle Hypercrosslinked Polymer Composites for the Visible-Light Photocatalytic Degradation of Methyl Orange Qiang Zhao, Kewei Wang, Junli Wang, Yong Guo, Akihiro Yoshida, Abuliti Abudula, and Guoqing Guan ACS Appl. Nano Mater., Just Accepted Manuscript • DOI: 10.1021/acsanm.9b00210 • Publication Date (Web): 10 Apr 2019 Downloaded from http://pubs.acs.org on April 10, 2019

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ACS Applied Nano Materials

Cu2O Nanoparticle Hypercrosslinked Polymer Composites for the Visible-Light Photocatalytic Degradation of Methyl Orange Qiang Zhao†,‡,§, Kewei Wang‡, Junli Wang‡, Yong Guo‡, Akihiro Yoshida†,§, Abuliti Abudula†, Guoqing Guan*,†,§ †Graduate

School of Science and Technology, Hirosaki University, 1-Bunkyocho, Hirosaki

036-8560, Japan. ‡School

of Chemistry and Environmental Engineering, Shanxi Datong University, Datong

037009, China. §Energy

Conversion Engineering Laboratory, Institute of Regional Innovation (IRI), Hirosaki

University, 2-1-3, Matsubara, Aomori 030-0813, Japan.

ACS Paragon Plus Environment

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ABSTRACT

To improve the activity and stability of Cu2O photocatalyst under visible light, a kind of hypercross-linked polymer, named as KAPs-B (Knitting Aromatic compound Polymers-Benzene) with high surface area and special benzene rings structure, was loaded on Cu2O to form a composite of KAPs-B/Cu2O by using the precipitation method for the first time. The activities of various KAPsB/Cu2O composite photocatalysts with different loading amounts of KAPs-B were tested by methyl orange (MO) degradation. Comparing with the bare Cu2O, significantly enhanced photocatalytic performances were found for the degradation of MO over KAPs-B/Cu2O under visible light. In particular, the 7% KAPs-B/Cu2O showed the highest photocatalytic performance, by which approximately 92% of MO was decomposed within 60 min. Also, it showed an excellent reusability. It is found that the loading of KAPs-B on Cu2O can not only effectively enhance the adsorption of organic matter on the catalyst ascribed to its high surface area and meanwhile stabilize the Cu2O in oxidizing environments, but also enhance the separation rate of the photoinduced electron-hole pairs, leading to the photocatalytic activity and stability enhancement. These results indicate that it is a feasible method to improve the visible light photocatalytic performance of Cu2O by compositing with the hypercrosslinked polymer. KEYWORDS: photocatalysis; methyl orange (MO); visible light; Cu2O; KAPs-B


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INTRODUCTION

In recent years, photocatalytic degradation of organic pollutants under visible light is regarded a promising way to solve the global energy crisis by using the inexhaustible solar energy. Among the numerous visible-light-driven photocatalysts, Cu2O is a p-type semiconductor with narrow band gap energy ranging from 2.0-2.2 eV,1,2 which could effectively utilize the large amount of visible light in the sunlight. Thusly, the Cu2O based photocatalysts have been widely applied for the organic-pollutant decontamination nowadays. 3-5 However, there are still many constraints on its application, such as the instability in oxidizing conditions, the rapid recombination of photogenerated holes and electrons and the transformation of crystalline structure during the reaction. Therefore, further improvement of the Cu2O photocatalytic characteristics is still required. Generally, this can be realized by compositing of it either with other materials, which include semiconductors such as TiO2,6,7 ZnO,8 Fe3O4,9 C3N4,10 CdS,11 AgBr,12 and BiVO4,13 or conductive materials like the graphene oxide (GO),14 reduced graphene oxide (RGO),15 exfoliated graphite (EG),16 carbon quantum dots (CQDs),17 multi-walled carbon nanotube (MWCNTs),18 carbon sphere (CS),19 and polypyrrole (PPy).20 However, photocatalytic efficiency and stability are still necessary to be further improved. Hyper-cross-linked polymers (HCPs), a series of permanent microporous polymer materials with high surface areas, have been intensively used as solid absorbents for the treatment of wastewater, adsorption of organic vapors and so on.21 Especially, HCPs have abundant narrow micropores, which can let the adsorbate molecules transferred from the surface to the inner micropores so that the adsorption capacity and adsorption rate are greatly enhanced. In addition, HCPs have strong affinity towards organic molecules due to their hydrophobic skeleton.22


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Recently, a series of reasonably priced HCPs-based catalysts were reported for the organic transformations.23-25 However, no studies have been reported yet on combining them with photocatalysts for the organic pollutants degradation by using visible light. In this work, KAPs-B (Knitting Aromatic compound Polymers-Benzene), which is a kind of HCPs, was loaded on Cu2O with various amounts by a one-step precipitation method.26 The photocatalytic ability of the as-obtained catalyst was tested by degradation of methyl orange (MO) as the pollutant under visible light. Since KAPs-B is a hydrophobic, chemically robust and porous polymer with a structure that benzene rings are connected with methylene linkers (Figure 1), it is expected that the excellent adsorption ability of KAPs-B could enhance the catalytic performance of Cu2O and meanwhile stabilize the Cu2O in oxidizing environments.

EXPERIMENTAL

Chemicals and Materials All chemicals (A. R. grade) were used without further treatment. Copper(II) chloride (CuCl2) was provided by Tianjin Hongyan Chemical Corp. Sodium hydroxide, Hydroxylamine hydrochloride (NH2OH·HCl) and ethanol (EtOH) were provided by Tianjin Chemical Reagent Supply and Marketing Company. Catalysts Preparation KAPs-B was prepared by the method as reported in the reference27. The schematic diagram for the synthesis of KAPs-B/Cu2O catalyst is shown in Figure 1. CuCl2 was applied as the Cu2O precursor. In a typical synthesis of KAPs-B loaded Cu2O (KAPs-B/Cu2O), KAPs-B (0.007 g), deionized water (83.4 mL), EtOH (20 mL) and CuCl2 solution (0.5 M, 5 mL) were successively


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added to a beaker (500 mL) with stirring and then ultrasound treated at 25

for 30 min.

Thereafter, 9 mL of sodium hydroxide solution (1.0 M) and 30 mL of ethanol were added into the obtained suspension, and then 9.8 mL of NH2OH·HCl solution (0.1 M) was rapidly introduced into it in a short time (5 s). After stirring for 10 minutes, the mixture was maintained for 3 hours with a constant temperature of 40

to enhance the growth of Cu2O crystal. After that, the mixture

was centrifuged for 10 minutes with the speed of 5000 rpm and the obtained solid was washed with mixed solution (V

2

:

3

2

= 1:1). The operations of centrifugation and washing were

conducted alternatively several times until the remaining reagents were completely removed. Finally, the solid was purified with 5 mL ethanol and dried at 35

under vacuum state. As such,

7 wt% of KAPs-B loaded Cu2O (7% KAPs-B/Cu2O) composite was obtained. Similarly, 1% KAPs-B/Cu2O, 3% KAPs-B/Cu2O, 5% KAPs-B/Cu2O, 10% KAPs-B/Cu2O composites were also synthesized by the same procedure. In addition, the pure Cu2O without the loading of KAPs-B was synthesized using the same procedure.

Figure 1. The schematic diagram for the synthesis process of KAPs-B/Cu2O catalyst Catalyst Characterizations


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The crystal structure of the catalyst was measured by a Bruker D8 diffractometer in the L range of 10-80° using Cu

Cu2O Nanoparticle Hyper-Cross-Linked Polymer Composites for the

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