Feb 19, 2018 - This would affect the micromixing performance in the plugs. The Villermauxâ. Dushman method on the basis of a parallel competing reaction.
Article pubs.acs.org/IECR
Cite This: Ind. Eng. Chem. Res. 2018, 57, 3263−3273
Continuous Synthesis of Ag/AgCl/ZnO Composites Using Flow Chemistry and Photocatalytic Application Sha Tao,†,‡ Mei Yang,*,† Huihui Chen,†,‡ Shuainan Zhao,†,‡ and Guangwen Chen*,† †
Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China ‡ University of Chinese Academy of Sciences, Beijing 100049, China S Supporting Information *
ABSTRACT: Ag/AgCl/ZnO composites were successfully synthesized in a continuous microfluidic system under visible light irradiation, which was employed in situ to reduce a portion of AgCl to metallic Ag. The formation of Ag/AgCl/ZnO composites was confined in small aqueous plugs, which were dispersed by octane as the continuous phase. In this way, enhanced mixing, low risk of channel clogging, and uniform light distribution were achieved. The characterization results revealed that the as-prepared Ag/AgCl/ZnO composites were composed of flowerlike ZnO with Ag/AgCl nanospheres anchored to them. It was found that the synthesis parameters such as water/oil volume flow ratio, total volume flow rate, temperature, and the molar ratio of Zn2+ to Ag+ had effects on the synthesis of Ag/AgCl/ZnO composites. Furthermore, the as-prepared Ag/AgCl/ZnO composites outperformed Ag/ZnO composites and AgCl/ZnO composites in the visible-light-driven degradation of methyl orange. active.23−25 Actually, Ag/AgX itself is an efficient plasmonic photocatalyst.22,26,27 Anchoring Ag/AgX to ZnO to fabricate a ternary composite catalyst brings several advantages: (1) The LSPR-induced electrons on Ag can transfer to the conduction band of ZnO. This further prevents the electrons and holes from recombination. (2) The amount of Ag and corresponding catalyst cost can be reduced remarkably because of the high dispersion of Ag/AgX.28−31 According to the published literature studies regarding Ag/ AgX/ZnO, this ternary composite catalyst is mainly synthesized by the deposition of AgX over ZnO via a deposition− precipitation method, followed by a portion of reduction of AgX/ZnO to Ag/AgX/ZnO with proper reducing agents or visible light. Reducing AgX/ZnO with visible light is an energyefficient and environmentally benign process and is widely used for the synthesis of Ag/AgX/ZnO. Li et al. presented a two-step synthesis method to fabricate Ag/AgCl/ZnO NPs.23 Different amounts of AgCl were deposited on the as-prepared ZnO NPs and then converted to metallic Ag under visible light irradiation in the presence of methanol. Shi et al. reported a deposition− precipitation method followed by reducing AgBr/ZnO to Ag/ AgBr/ZnO composites, which exhibited extraordinary photocatalytic activity with good stability after utilization in 10 cycles.24 On the basis of the synthesis strategy mentioned
1. INTRODUCTION The past decades have witnessed an explosive growth in the development of semiconductor-based photocatalysts for the photodegradation of organic contaminations because of the growing concern about energy and environmental problems. Among the various semiconductor-based photocatalysts, ZnO with a direct wide band gap (3.3 eV) has attracted increasing attention because of its high activity, low cost, abundance, nontoxicity, etc.1−4 Unfortunately, the photon-induced electron−hole pairs on the surface of ZnO are liable to recombine quickly, resulting in a decrease in the photocatalytic activity. In addition, the efficiency of sunlight utilization over ZnO is poor because it can be merely excited by ultraviolet (UV) light (λ
