Novel hierarchical architectures of Sb^sub 2^WO^sub 6^: template-free hydrothermal synthesis and photocatalytic reduction property for azo compound

Novel hierarchical architectures of Sb^sub 2^WO^sub 6^ are synthesized successfully by a simple hydrothermal process without any organic solvent or surfactant. The physicochemical properties of the as-prepared products are characterized in detail. Interestingly, the morphologies of Sb^sub 2^WO^sub 6^ could be selectively controlled by adjusting pH values of the reactive solutions. The tuft-like, cockscomb-like, and flower-like hierarchical architectures are obtained at pH = 1, 3, and 5, respectively. Based on the time-dependent experimental results, a possible growth mechanism is proposed, which reasonably follows a synergy interaction of reaction-crystallization and dissolution-recrystallization processes. The photocatalytic activities of the novel hierarchical Sb^sub 2^WO^sub 6^ are evaluated by the decomposition of azo compounds for the first time. Results show that the as-prepared samples exhibit the excellent photocatalytic activity and universality for the reduction of azo compounds. The conversion of methyl orange reaches 98 % after 140 min of light irradiation. HPLC-MS indicates that the selectivity of 4-aminobenzene sulfonic acid is over 99 %.[PUBLICATION ABSTRACT]