A facile route to prepare TiO2/g-C3N4 nanocomposite photocatalysts by atomic layer deposition

Abstract

A simple method to prepare TiO2/g-C3N4 nanocomposite photocatalysts by atomic layer deposition (ALD) has been developed. A uniform ultra-thin TiO2 coating was coated conformally on g-C3N4 powders via ALD. After 500 °C annealing process, amorphous TiO2 turns into anatase nanocrystals and forms heterojunctions between TiO2 and g-C3N4, which greatly improves the separation efficiency of photo-generated carriers of g-C3N4. Moreover, an exfoliation phenomenon of g-C3N4 based on ALD is also observed with dramatically increased specific surface areas from 10.4 m2/g (g-C3N4) to 31.2 m2/g (annealed TiO2/g-C3N4), providing a new way for the exfoliation of layered materials. As a result, annealed 50TiO2/g-C3N4 nanocomposite exhibits the best photocatalytic activity with the methyl orange degradation efficiency of 98.2% in 90 min under visible light irradiation, much better than pure g-C3N4 with only 45% degradation efficiency. The first-order reaction rate constant of annealed TiO2/g-C3N4 nanocomposite is 0.0406 min−1 with the half-life period of only 17 min, which is 5.8 times higher than that of the pure g-C3N4 powders. The enhanced photocatalytic performance of annealed TiO2/g-C3N4 nanocomposites can be ascribed to the synergetic effect of heterojunctions between crystalline TiO2 and g-C3N4 and the increased specific surface areas. Above all, ALD may be a kind of promising and feasible method to fabricate g–C3N4–based nanocomposite powders for photocatalytic applications.