Study on the Visible-Light Photocatalytic Performance and Degradation Mechanism of Diclofenac Sodium under the System of Hetero-Structural CuBi2O4/Ag3PO4 with H2O2

Abstract

Two kinds of CuBi2O4/Ag3PO4 with different heterojunction structures were prepared based on the combination of hydrothermal and in-situ precipitation methods with surfactant additives (sodium citrate and sodium stearate), and their characteristics were systematically resolved by X-ray Diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscope (SEM)/ High-resolution Transmission Electron Microscopy (HRTEM), UV-vis Diffuse Reflectance Spectra (DRS) and Photoluminescence (PL). Meanwhile, the photocatalytic properties of the catalysts were determined for diclofenac sodium (DS) degradation and the photocatalytic mechanism was also explored. The results indicate that both of the two kinds of CuBi2O4/Ag3PO4 exhibit higher photocatalytic efficiency, mineralization rate, and stability than that of pure CuBi2O4 or Ag3PO4. Moreover, the catalytic activity of CuBi2O4/Ag3PO4 can be further enhanced by adding H2O2. The free radical capture experiments show that in the pure CuBi2O4/Ag3PO4 photocatalytic system, the OH• and O2•− are the main species participating in DS degradation; however, in the CuBi2O4/Ag3PO4 photocatalytic system with H2O2, all OH•, h+, and O2•− take part in the DS degradation, and the contribution order is OH• > h+ > O2•−. Accordingly, the photocatalytic mechanism of CuBi2O4/Ag3PO4 could be explained by the Z-Scheme theory, while the catalysis of CuBi2O4/Ag3PO4 with H2O2 follows the heterojunction energy band theory.

Improved Visible Light Photoactivity of CuBi2O4/CuO Heterojunctions for Photodegradation of Methylene Blue and Metronidazole

“…Especially, photocatalyst materials able to degrade or mineralize persistent pollutants such as dyes, pharmaceuticals, pesticides, and other organic compounds which are not naturally degraded in the environment has been intensively investigated. − Nowadays, it is a consensus that the most explored semiconductor material for photocatalytic reactions was TiO 2 ; − however, its photocatalytic activity stands only in the UV region of the solar spectrum (wavelength < 390 nm), limiting severely their practical applications due to the operating costs . As visible light corresponds to almost 45% of the solar radiation, new photocatalyst able to convert solar light to reactive species that may efficiently promote oxidation and/or reduction of pollutant molecules has been the object of research in the last years. − …”

“…The copper bismuth oxide (CuBi 2 O 4 ), on the other hand, is a ternary metal oxide with p-type semiconductor characteristics which presents interesting and attractive photocatalytic properties, including an absorption window throughout the entire visible spectrum (<800 nm) due to its band gap of ∼1.8 eV . The photocatalytic activity of CuBi 2 O 4 has been enhanced by exploring the material morphology; heterojunction formation with other semiconducting materials, e.g., CuBi 2 O 4 /Ag 3 PO 4 , CuBi 2 O 4 /MWCNT, CuBi 2 O 4 /Bi 2 O 3 , CuBi 2 O 4 /Bi 2 WO 6 , , CuBi 2 O 4 /SnO 2 , CuBi 2 O 4 /CeO 2 , CuBi 2 O 4 /WO 3 ; , as well as by co-catalyst deposition or structure doping. ,, The CuO nanoparticles-decorated nanodendrite-structured CuBi 2 O 4 electrocatalysts have been recently reported for electrochemical detection of glucose . The CuBi 2 O 4 /CuO heterojunction films showed a synergistic catalytic enhancement, rendering superior electrocatalytic activity for oxidation of glucose compared to pristine CuO or CuBi 2 O 4 .…”

Surface Potential/Wettability and Interface Charge Transfer Engineering of Copper-Oxide (Cu–MOx, M = W, Ti, and Ce) Hybrids for Efficient Wastewater Treatment through Adsorption–Photocatalysis Synergy

“…The strong intensity of PL spectra indicated rapid recombination. 59,60 As displayed in Figure 9b, the pure WO 3 and the Cu−WO 3 -0.12 composites showed different emission intensities. The emission intensity of the Cu−WO 3 -0.12 sample was weaker than the WO 3 cube, which suggests that introducing Cu particles into WO 3 nanocubes could effectively inhibit the rapid recombination of photogenerated carriers.…”

Mechanistic insights into enhanced photocatalytic H2O2 production induced by a Z-scheme heterojunction of copper bismuth oxide and molybdenum sulfide

“…28 However, photoactivity of pristine CBO is marred due to its high charge recombination and unfavorable band edge line-up with the water oxidation reaction. 29 Hence, a heterostructure that combines CBO with another photocatalyst having an appropriate band edge line-up for water oxidation can alleviate the above problems.…”