Trace Amount of SnO₂-Decorated ZnSn(OH)₆ as Highly Efficient Photocatalyst for Decomposition of Gaseous Benzene: Synthesis, Photocatalytic Activity, and the Unrevealed Synergistic Effect between ZnSn(OH)₆ and SnO₂

Abstract

It is still a challenge to develop a high-performance photocatalyst for the abatement of aromatic compounds like benzene (C 6 H 6 ), which has been regarded as a priority hazardous volatile organic compound substance in the indoor atmosphere. Zinc hydroxystannate (ZnSn(OH) 6, ZHS) is a promising material for this application. However, the key structural features that are responsible for the high activity are still ambiguous. To address this issue, a series of ZHS with different surface properties were hydrothermally synthesized by varying the treatment temperature and the solution pH. Although ZHS can be readily synthesized under a mild reaction condition (temp 90–120 °C, pH 4–10), most of the samples were contaminated by a trace amount of low-crystallized SnO 2 . Pristine ZHS can only be produced in a strong alkaline solution (pH 13). The sample prepared at 120 °C in a pH 10 solution shows the highest activity for the degradation of gaseous C 6 H 6 and an efficiency almost 6 times higher than P25 (TiO 2 ). More importantly, no obvious deactivation of the sample and the formation of stable deposits were observed in a long-term reaction for 48 h. Although the SnO 2 amount is quite small and bare ZHS shows almost no activity, both of them are indispensable for the degradation of C 6 H 6 . SnO 2 and ZHS can be understood as photoactive sites to produce charge carriers and preferential sites for the adsorption of O 2, H 2 O, and C 6 H 6, respectively. A synergistic effect between SnO 2 and ZHS in the formation of active radicals and the degradation of C 6 H 6 accounts for the high performance of the SnO 2 -decorated ZHS.