The work aims to overcome the disadvantages of TiO2 powders which are used as photocatalysts such as difficult recovery, easy conglomeration, and limited catalytic activity, while improving the visible-light-driven photocatalytic activity. Firstly, the reduced graphene oxide (rGO) was added to the MAO electrolyte to fabricate an rGO/TiO2 composite coating on the surface of the TC4 alloy by micro-arc oxidation (MAO) technology. Subsequently, Cu nano-particles were deposited on the surface of rGO/TiO2 composite coating by electroless plating and the Cu@rGO/TiO2 composite coatings as the precursor were obtained at different electroless temperatures of 30 ℃, 35 ℃, 40 ℃, 45 ℃ and 50 ℃ respectively. At last, hydrothermal treatment was applied to the precursor composite coatings to make CuO nanosheets in situ grow on the rGO/TiO2 composite MAO coating and then CuO@rGO/TiO2 composite photocatalysts were successfully fabricated. The microstructure, phase composition and surface elemental states of the rGO/TiO2 composite MAO coating and the CuO@rGO/TiO2 composite coating were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FT-IR). Methylene blue (MB) solution was used as the degradation target, then the experimental materials were put into and the photocatalytic performance of the experimental materials was evaluated by measuring the absorbance changes of the MB solution after 2 hours of visible-light irradiation with UV-Vis spectrophotometer. The TiO2 coating made by MAO technology on the surface of TC4 alloy exhibits a typical porous "volcano-like" morphology and its phase is composed of Anatase TiO2 and Rutile TiO2. The porosity of the MAO coating increases with the addition of reduced graphene oxide (rGO) but the micro-pore size of the coating decreases. The surface of the MAO coating becomes more even. Through electroless plating and hydrothermal treatment, nano-CuO in-situ grows on the surface of rGO/TiO2 composite coating. The in-situ growth nano-CuO sheet vertically grows on the surface of the rGO/TiO2 composite MAO coating at the plating temperature of 40 ℃. The phase composition of CuO@rGO/TiO2 composite photocatalytic coating is Anatase TiO2, Autile TiO2, rGO, CuO and Cu. As for MAO coating and rGO/TiO2 coating, the MB degradation efficiency is 62.26% and 70.7% respectively, because the addition of rGO enhances the MB degradation efficiency to some extent. When the rGO/ TiO2 coating is modified by in-situ growth of CuO Nano-sheet, the degradation rate of the MB degradation efficiency for CuO@rGO/TiO2 composite photocatalytic coating initially increases and then decreases with the rising plating temperature. The highest degradation rate (83.45%) is achieved at the plating temperature of 40 ℃. The porous structure of the coating modified with the CuO nanosheet provides additional active sites for photocatalytic reactions, enhancing light absorption, and facilitating charge separation and transport. The synergistic catalytic effect is attributed to a synergistic catalytic effect which is generated by the multiphase coexistence of CuO, reduced graphene oxide (rGO) and TiO2. Furthermore, the photocatalytic materials prepared via micro-arc oxidation and electroless plating employ a metal substrate as carrier, which significantly simplifies the recovery process and reduces the cost of TiO2 photocatalysts. This innovative approach demonstrates promising potential for practical applications in wastewater degradation treatment.
Key words
electroless plating temperature /
CuO@rGO/TiO2 composite photocatalytic coating /
micro-arc oxidation /
electroless plating /
photocatalytic performance
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Funding
Fundamental Research Funds for Province Universities of Heilongjiang Province (2021-KYYWF-1457, 2022- KYYWF-0535)
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