Cyclic performance of carbon-coated TiO2 for photocatalytic activity of methylene blue decomposition.

Carbon-coated TiO2 powders were prepared from the mixtures of anatase (ST-01) and carbon precursor poly(vinyl alcohol) in different ratios by carbonization at 900 degrees C in a flow of either Ar or N2. Carbon-coated TiQ2 thus prepared was either fixed on an adhesive tape or formed into a film by using the organic binder poly(tetrafluoroethylene) and used for photodecomposition of methylene blue in water repeatedly. On the samples fixed on adhesive tapes, the rate constant was reproduced with about 10-20% scattering during repeated uses in a fresh methylene blue solution up to 7 times. On the samples formed into films by using the organic binder, the rate constant was reproduced after the 3rd or 4th cycle. The mutual relations in rate constant were almost the same among three different conditions for the determination, suspending the sample particles, fixed on an adhesive tape and formed into a film. The rate constant for the photodecomposition was found to give a maximum on the sample containing about 9 mass% carbon.