Significantly Enhanced Photocatalytic Activities and Charge Separation Mechanism of Pd-Decorated ZnO–Graphene Oxide Nanocomposites

Abstract

Electron-hole recombination is one of the major factors limiting the efficiency of ZnO-based photocatalysts. In this work, a 2-fold enhancement strategy was employed to suppress electron-hole recombination and boost photocatalytic efficiency. First, significantly enhanced photocatalytic activity of ZnO by introducing graphene oxide (GO) was systematically investigated. Hybrid photocatalysts with different weight ratios of ZnO to GO (from 0.95:0.05 to 0.70:0.30) were synthesized and characterized. The results indicated that when the proportion ratio of ZnO to GO reached 0.85:0.15, the as-synthesized ZnO-GO nanocomposite exhibited the maximum photocatalytic efficiency on methylene blue with an apparent rate constant κapp almost 10 times faster than that of pure ZnO under UV illumination. GO was suggested to enhance the photocatalytic activity of ZnO because of its great capability in dye adsorption and charge separation. Second, Pd nanoparticles were introduced to decorate ZnO-GO to produce generally better photocatalyst ZnO-GO-Pd nanocomposites. The junction between Pd and ZnO was believed to also effectively separate the photogenerated charges due to the metal-semiconductor diode effect. These two systems of ZnO-GO and ZnO-GO-Pd nanocomposites are expected to have a broad range of applications in environmental conservation.

Synthesis, characterization and photocatalytic activity of visible-light-driven reduced graphene oxide–CeO2 nanocomposite

“…However, emission intensity of CeO 2 is significantly quenched when it is anchored on RGO sheets or CNTs surface. As reported by other groups, such emission quenching represents interfacial charge-transfer processes [49][50][51][52]. In the present case, PL quenching is ascribed to electron transfer from conduction band of to RGO or CNTs.…”

Effect of Ag doping on structural, optical, and photocatalytic properties of ZnO nanoparticles

“…The decrease in UV intensity was due to the interactions between the excited ZnO nanoparticles and Ag particles in the grain boundaries. These kinds of interactions via the Schottky contact, metal-semiconductor diode effect, decrease the recombination of electrons and holes generated from UV light irradiation 23,47 and improved the photocatalytic activities 48 . On the other hand, reduction in the intensity of UV radiation was due to the interstitial Ag atoms at ZnO lattice and created a large amount of defects, as confirmed by Zeferino et al 49 .…”

Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

“…TiO 2 is also attractive for this application because of its opto-electronic properties, which can be tuned by changing lattice defects or oxygen stoichiometry, its superior chemical stability and photocorrosion resistance, and its low cost [4][5][6][7][8]. These unique properties have enabled TiO 2 to be utilized in a wide range of applications including solar energy conversion, antimicrobial and self-cleaning surfaces, paint whiteners, ceramics, textiles, personal care products, and environmental catalysis [9][10][11][12][13][14][15][16][17][18][19].…”