Lead-free organic-inorganic hybrid perovskite heterojunction composites for photocatalytic applications

Heterojunction structured MASnI(3)/TiO2 photocatalysts (MA represents CH3NH3+) are prepared via a facile wet-chemical method and characterized by various techniques. The characterization demonstrates the formation of a heterojunction structure and the good crystallinity of MASnI(3)/TiO2 (1 : 9) (mass ratio of MASnI(3) and TiO2 is 1 : 9). Moreover, the results also display the improved visible light absorption of MASnI(3)/TiO2 (1 : 9) and low recombination of photoinduced carriers. As a result, MASnI(3)/TiO2 (1 : 9) could completely degrade rhodamine B (97%) in 40 min, which has higher photocatalytic ability than pure MASnI(3) and pure TiO2. The improved photocatalytic activity could be ascribed to the improved light harvesting ability and easy transfer of photogenerated carriers of the materials generated by the formation of a heterojunction structure and the suitable energy band position between MASnI(3) and TiO2. In particular, coupling of MASnI(3) and TiO2 could also avoid oxidation and hydrolysis of MASnI(3) so that the long-term stability of the composite could be efficiently maintained. It is the first report on MASnI(3) and TiO2 composites being used as photocatalysts for dye degradation. A possible mechanism for the enhancement of photocatalytic activity under light irradiation is also proposed.