Abstract
In this study, electrodes of titanium dioxide nanotube arrays (TNAs) were successfully synthesized by applying the anodic oxidation etching method, as well as the use of green synthetic technology to add reducing agents of tea or coffee to reduce metal palladium from palladium chloride. Synthesis of palladium modified TNAs (Pd/TNAs) was conducted by the microwave hydrothermal method after the metal palladium was reduced. In order to identify the surface structure, light absorption and elemental composition, TNAs and Pd/TNAs were characterized by X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Furthermore, to test the photocurrent density, electron resistance, and hydroxyl radicals by I-t plot, electrochemistry impedance spectroscopy (EIS), and electron paramagnetic resonance (EPR) were investigated. The photocurrent (4.0 mA/cm2) of Pd/TNAs-C (using coffee as the reducing agent) at +1.0 V (vs. Ag/AgCl) was higher than that of the pure TNAs (1.5 mA/cm2), illustrating that Pd/TNAs-C can effectively separate photogenerated electrons and holes. Pd/TNAs is a favorable material as a photoanode for the photoelectrochemical (PEC) removal of organic pollutants in wastewater.
Highlights
Chemical oxidation methods such as Fenton, ozone, hydrogen peroxide and chlorine oxidation are common used for the degradation of organic pollutants [1,2,3]
The results indicated that Cu2 O/titanium dioxide nanotube arrays (TNAs) can PEC oxidize Ibuprofen effectively
Findings, that depositing Pd on TNAs can enhance the photo-response of TNAs, leading to the generationCatalysts of a photocurrent
Summary
Chemical oxidation methods such as Fenton, ozone, hydrogen peroxide and chlorine oxidation are common used for the degradation of organic pollutants [1,2,3]. To completely degrade persistent organic compounds, huge amounts of oxidation chemical are needed. The Fenton method applies Fe2+ as a catalyst to react with H2 O2 to form hydroxyl radicals (·OH) and oxidize organic compounds, but it is accompanied with sludge, which leads to another environmental problem. The PEC system has demonstrated the ability to reduce the recombination of photo-generated holes and electrons, and, to enhance the oxidation ability of TNAs [1,13]. Studies have attempted to solve the limitation of the light response of TNAs. Metals, non-metals, and metal oxides have been employed to modify TNAs. Peng et al (2017) applied carbon and nitrogen to modify TNAs and found that this approach is useful to degrade perfluorooctanoic acid (PFOA). The above studies show good examples of using TNAs for modification These methods are either energy consuming or require chemicals that may cause other environmental problems. Methyl orange was selected as a target compound for the PEC oxidation experiment
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