Abstract
A series of TiO2, TiO2/Pd, and TiO2/PdO hollow sphere photocatalysts was successfully prepared via a combination of hydrothermal, sol-immobilization, and calcination methods. The structure and optical properties of the as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Telleranalysis, Barrett-Joyner-Halenda measurement, and UV-Vis diffuse reflectance spectroscopy. The photocatalysis efficiencies of all samples were evaluated through the photocatalytic degradation of rhodamine B under visible light irradiation. Results indicated that TiO2/PdO demonstrated a higher photocatalytic activity (the photocatalytic degradation efficiency could reach up to 100% within 40 min) than the other samples and could maintain a stable photocatalytic degradation efficiency for at least four cycles. Finally, after using different scavengers, superoxide and hydroxyl radicals were identified as the primary active species for the effectiveness of the TiO2/PdO photocatalyst.
Highlights
Semiconductor materials have been received and extensively applied as photocatalysts in photocatalytic water splitting and photodegradation of organic pollutants
For each photocatalytic activity measurement, 30 mg of photocatalyst was added to 50 mL of rhodamine B (Rh B) aqueous solution with the concentration of 30 mg/L
The photocatalysis efficiencies of all asprepared samples were evaluated through the photocatalytic degradation of Rh B under visible light irradiation
Summary
Semiconductor materials have been received and extensively applied as photocatalysts in photocatalytic water splitting and photodegradation of organic pollutants. TiO2 is an important semiconductor in wide applications, such as in photocatalysts [1, 2], solar cells [3], electrorheology [4, 5], and antibacterial agents [6] It has been exhaustively explored for its merits of environment friendliness, chemical inertness, high stability, nontoxicity, and low cost when utilized as a photocatalyst for environment remediation and photodegradation of organic pollutants [7,8,9]. Sarkar and Chattopadhyay [12] synthesized a large-scale mesoporous TiO2 microsphere for photocatalysis degradation These TiO2 photocatalysts exhibit high photocatalytic activity only under UV irradiation. This finding can be ascribed to the intrinsic properties of TiO2: a wide band gap (3.2 eV), which limits its use in the UV region of the solar spectrum, which accounts for a very small fraction of solar energy [13]. The photocatalytic reaction mechanism was discussed on the basis of trapping experiments of active species
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