Microwave-Assisted Synthesis of Carbon-Based (N, Fe)-Codoped TiO(2) for the Photocatalytic Degradation of Formaldehyde

A microwave-assisted sol–gel method was used to synthesize (N, Fe)-codoped activated carbon (AC)/TiO(2) photocatalyst for enhanced optical absorption in the visible light region. The prepared samples were characterized via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, ultraviolet–visible light spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy. The results showed no significant difference in the surface area of AC/TiO(2) (approximately 500 m(2)/g) after doping. TiO(2) was uniformly distributed on the surface of AC, which exhibited coexisting anatase and rutile structures with a mean crystallite diameter of approximately 20 nm. N and Fe monodoping on AC/TiO(2) reduced the energy band gap of TiO(2) to 2.81 and 2.79 eV, respectively, which mainly attributed to the impurity energy formed in the energy gap of TiO(2). In (N, Fe)-codoped AC/TiO(2), N and Fe are incorporated into the TiO(2) framework and narrow the band gap of TiO(2) to 2.58 eV, thereby causing a large redshift. Codoping of N and Fe enhanced the production of hydroxyl radicals (⋅OH) and improved the photocatalytic activity of the resultant AC/TiO(2) compared with those of undoped and N- or Fe-monodoped AC/TiO(2). N-Fe-AC/TiO(2) degraded 93 % of the formaldehyde under Xe-lamp irradiation. Moreover, the photocatalyst was easily recyclable. In summary, a novel and efficient method to mineralize low concentrations of HCHO in wastewater was discovered.