Photocatalytic Oxidation of Aqueous Ammonia over Microwave-Induced Titanate Nanotubes

摘要

Characterizations of microwave-induced titanate nanotubes (Na_xH_(2-x)Ti_3O_7, TNTs) were conducted by the determinations of specific surface area (S_(BET)), X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS), ionic coupled plasma-atomic emission spectrometry(ICP-AES), scanning electron microscopy/ energy dispersive X-ray (SEM/EDX), and high-resolution transmission electron microscopy (HR-TEM). The applied level of microwave irradiation during the fabrication process is responsible for both the intercalation intensity of Na atoms into TNTs and the type of crystallization phase within TNTs, which dominate the efficiency of photocatalytic NH_3/NH_4~-. A pure TNT phase presents no powerful ability toward photocatalytic NH_3/ NH_4~+, while the photocatalytic efficiency can be enhanced with the presence of a rutile phase within TNTs. In addition, the mixture of anatase and rutile phase within P25 TiO_2 prefers forming NO_3~-, whereas TNTs yield higher NO_2~- amount. Regarding the effect of acid-washing treatment on TNTs, the acid-treated TNTs with enhanced ion exchangeability considerably improve the NH_3/NH_4~+ degradation and NO_2~-/NO_3~- yields. This result is likely ascribed to the easy intercalation of NH_3/ NH_4~+ into the structure of acid-washing TNTs so that the photocatalytic oxidation of intercalated NH_3/NH_4~+ is not limited to the shielding effect resulting from the overload of TNTs.