Preparation And Application Of Bamboo-like Ag/CuO/TiO₂ Nanotube Arrays Photocatalyst

For the past few years, the serious environmental pollution problem has received enormous attention from the scientists. Photocatalytic technology as a low cost and feasible treatment way is an effective route to environmental conservation, and in which TiO2 is the most representative semiconductor photocatalyst. TiO2 shows great potential for practical environmental purification due to its exceptional ability to photocatalytically decompose organic pollutants, low cost, nontoxicity and chemical and mechanical stability. Unfortunately, several disadvantages retard the practical applications of TiO2. The wide bandgap energy of 3.2 eV and fast recombination of photoinduced electron-hole pairs limit its photocatalytic efficiency. Hence, we make efforts to construct the CuO nanosheets and Ag nanoparticles co-decorate TiO2 nanotubes arrays (Ag/CuO/TiO2) composite. The optimized geometrical configuration of multiple active materials into hierarchical nanoarchitecture is essential for the creation of photocatalytic degradation system that can mimic natural photosynthesis. Being inspired by natural bamboo morphology where the leaves can be fully exposed to the sun, we presented here a bamboo-like Ag/CuO/TiO2 architecture. The p-n heteroj unction and the surface plasma resonance (SPR) effect of Ag nanoparticles can enhance the photocatalytic activity of composite. Consequently, we combine the electrochemical deposition technique in our work, the details are listed as follows:(1) Fabrication and characterization of the bamboo-like ternary Ag/CuO/TiO2 nanotube array:A bamboo-like architecture, CuO nanosheets and Ag nanoparticles co-decorated TiO2 nanotube arrays (Ag/CuO/TiO2), was fabricated by using simple solution-immersion and electrodeposition process. The surface morphologies, crystal phases, elements and photoelectrochemical properties of the as-prepared samples were characterized by SEM, TEM, and XRD etc. The experiment results show that CuO nanosheets and Ag nanoparticles are well-dispersed on TiO2 nanotubes arrays. The ternary Ag/CuO/TiO2 nanotube array shows lower charge recombination rate than bare TiO2 nanotubes arrays and binary composite (Ag/TiO2 and CuO/TiO2). The ternary Ag/CuO/TiO2 nanotube array exhibits enhanced absorption in the visible-light region.(2) Photocatalytic activity of the bamboo-like ternary Ag/CuO/TiO2 nanotube array:Photocatalytic degradation of 2,4-DNP in aqueous solution with Ag/CuO/TiO2 under simulated solar light irradiation has been investigated. The experiment results clearly reveal that the ternary Ag/CuO/TiO2 nanotube array shows higher photocatalytic activity than bare TiO2 nanotubes arrays and binary composite (Ag/TiO2 and CuO/TiO2). The results show that ternary Ag/CuO/TiO2 nanotube array possess large absorption capacity towards 2,4-DNP and the decomposition efficiency of 2,4-DNP achieves almost 100% in 80 min under simulated solar light irradiation. The removal efficiency analyzed by TOC for 2,4-DNP over Ag/CuO/TiO2 is as high as 80%, which further verifies the excellent photocatalytic activity of the composite. In addition, the photocatalytic mechanism of the Ag/CuO/TiCh are also investigated, which indicates ·OH and ·O2- are the main active species. The results show that the photocatalytic removal efficiency of 2,4-DNP over Ag/CuO/TiO2 maintains 97.4% in the fifth cycle. At the same time, Ag/CuO/TiO2 could also effectively photocatalytically degrade pentachlorophenol (PCP),2,4-dichlorophenoxyacetic (2,4-D) and Rhodamine B (RhB).