Abstract
N–Cu-activated carbon (AC)/TiO2 nanoparticles were prepared by the sol-gel technique through microwave irradiation to modify the visible-light response of TiO2. Their structure, surface chemical composition, and optical absorption properties were characterized. The results showed that the codoped particles had a higher surface area and smaller particle size than pure AC/TiO2 and monodoped AC/TiO2. X-ray photoelectron spectroscopy of N–Cu-AC/TiO2 showed that Cu atoms replaced Ti atom sites, whereas N atoms occupied the O atom sites and interstitial sites in the TiO2 lattice, which changed the electric and band-gap structures of the photocatalyst. N or Cu monodoping of AC/TiO2 reduced the energy band gap of TiO2 from 2.86 eV to 2.81 or 2.61 eV, respectively. In (N, Cu)-codoped AC/TiO2, N and Cu were incorporated into the TiO2 framework and narrowed the band gap of TiO2 to 2.47 eV, causing a large red shift and enhancing visible-light utilization efficiency. Photocatalytic activities were further examined by formaldehyde degradation under visible-light irradiation. N–Cu-AC/TiO2 was found to have the highest activity (ca. 94.4 % formaldehyde degradation efficiency) and to be easily recyclable. These results show an important and innovative method of improving AC/TiO2 activity by modifying the nonmetallic and metallic species.
Highlights
Experimental Methods Catalyst Preparation activated carbon (AC) was prepared by the means described in a previous study [30]
Given that activated carbon (AC) has a large specific surface area, the reaction rate constant of AC/TiO2 is high for the photocatalytic degradation of organic pollutants [6]
It can be seen that the TiO2 crystals obtained via the microwave radiation method with only 15 min, which is conducive to stabilize the AC structure and makes for a more energy-efficient process compared with the traditional heating method [7]
Summary
Nanocrystalline TiO2 has potential for application to photocatalytic degradation of harmful pollutants dispersed in the environment because of its relatively low cost, nontoxicity, favorable optoelectronic properties, and excellent chemical stability [1, 2]. The photocatalytic activity and utilization efficiency of visible light are limited because of the small specific surface area and large band gap (3.2 eV) of pure TiO2 [3,4,5]. Wang et al [13] reported that a Cu-doped TiO2 thin film exhibited much improved photocatalytic activity compared with pure TiO2 thin film in the degradation of a 10 mg/L methylene blue solution under simulated solar-driven irradiation. Codoping Cu and N to TiO2 to reduce its band gap and load it onto the AC through a microwave-assisted method has rarely been reported. An important and innovative method has been attempted to enhance the photodegradation activity of AC/TiO2 with visible-light response via modification with Cu and N through microwave irradiation. The concept used in this research can be further applied to modify other materials for improved photocatalytic performance
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