Preparation and Visible Light Photocatalytic Activity of a Graphite-Like Carbonaceous Surface Modified TiO2 Photocatalyst

By using water-soluble linear phenolic resin (PF) as C-source, a graphite-like carbonaceous surface modified TiO2 photocatalyst (PF/TiO2) was successfully synthesized through a hydrothermal process. The as-formed PF/TiO2 exhibited significantly higher photocatalytic activity than bare TiO2 toward the degradation of methyl orange (MO) under visible irradiation, while a tetrahydrofuran (THF) postrinsing operation can further enhance the photocatalytic activity of PF/TiO2. To exploit the mystery of surface carbonaceous covering, a series of characterizations such as XPS, TG, TEM, and FTIR, as well as H-1 NMR were employed. It is proposed that PF experienced a cross-linking and a carbonization process that are catalyzed by TiO2 at the surface of TiO2. The as-formed organics covering on the PF/TiO2 seems composed of four portions from the surface of TiO2 to the outside as oxidized graphite-like carbon (OGC), graphite-like carbon (GC), cross-linked PP (cl-PF), and PF. OGC and GC substances endow the catalysts visible absorption and photocatalytic activity, which are insoluble in the THF; meanwhile, PF and cl-PF are adverse to the visible light photocatalysis and can be rinsed out with THF. The visible light photocatalytic activity unrinsed PF/TiO2 reaches its optimal condition at a PF dosage of 0.7 g (for 5.0 g titanium sulfate) while the THF rinsed PF/TiO2 presents the highest photocatalytic activity with the maximum PP dosage in this work and gives a MO degradation rate of 100% in 4 h.