Zinc hydroxide/oxide and zinc hydroxy stannate photocatalysts as potential scaffolds for environmental remediation

Abstract

This work describes the facile aqueous solution based syntheses and detailed characterization of zinc based hydroxide/oxide and zinc hydroxy stannate materials and their efficient utilization as catalyst for the photodegradation of harmful organic dye, i.e. Rhodamine B. The detailed studies revealed that the reaction time and temperature are important parameters by which the crystal phases and morphology of prepared materials can be controlled. Therefore, it was observed that with increasing the reaction time and temperature, a mixed phase of Zn(OH)₂ and ZnO and pure ZnO can be prepared. The detailed characterizations showed that zinc hydroxy stannate cubes grow in high density and possess cube shaped morphologies. The detailed photocatalytic experiments revealed that as-synthesized ZnSn(OH)₆ cubes possess higher photoactivity compared to the zinc based hydroxide/oxide materials. The stability results indicated no significant deactivation even after four successive re-uses in RhB photodegradation. Furthermore, the rate of ˙OH radical formation during UV irradiation was also tracked to investigate the mechanism of RhB photodegradation. The same trend was also observed on comparing the photoactivity and rate of ˙OH radical formation. Thus, it can be proposed that the mechanism of RhB degradation catalyzed by the as-synthesized materials followed an indirect oxidation of the dye by ˙OH radicals formed over the photocatalyst during UV irradiation, instead of direct electron transfer between dye and photocatalyst because there was no remarkable adsorption of the dye onto the photocatalyst surface.