Synthesis of Visible-Light-Responsive Cu and N-Codoped AC/TiO(2) Photocatalyst Through Microwave Irradiation

N–Cu-activated carbon (AC)/TiO(2) nanoparticles were prepared by the sol-gel technique through microwave irradiation to modify the visible-light response of TiO(2). 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/TiO(2) and monodoped AC/TiO(2). X-ray photoelectron spectroscopy of N–Cu-AC/TiO(2) showed that Cu atoms replaced Ti atom sites, whereas N atoms occupied the O atom sites and interstitial sites in the TiO(2) lattice, which changed the electric and band-gap structures of the photocatalyst. N or Cu monodoping of AC/TiO(2) reduced the energy band gap of TiO(2) from 2.86 eV to 2.81 or 2.61 eV, respectively. In (N, Cu)-codoped AC/TiO(2), N and Cu were incorporated into the TiO(2) framework and narrowed the band gap of TiO(2) 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/TiO(2) 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/TiO(2) activity by modifying the nonmetallic and metallic species.