Tin(II) Antimonates with Adjustable Compositions: Effects of Band-Gaps and Nanostructures on Visible-Light-Driven Photocatalytic H ₂ Evolution

A series of tin(II)-antimonate photocatalysts with varied Sn content were prepared by altering the ion-exchange time and reaction temperature to control their physicochemical properties, especially their band-gaps and nanostructures. Furthermore, the effect of these catalysts on visible-light-driven photocatalytic H ₂-evolution was also investigated. With an increase in Sn content, the narrowed band-gaps enhanced the absorption of photons to excite the photogenerated charge carriers. A decrease in nanocrystal size approaching stoichiometric compositions impeded the recombination of the photogenerated charge carriers; the increased surface areas and pore volumes, owing to the nanostructural transformation, accelerated the redox reactions. Consequently, the photocatalytic activities gradually improved and the highest rate was observed for stoichiometric Sn ₂Sb ₂O ₇. As a result, the as-prepared tin(II) antimonates-especially Sn ₂Sb ₂O ₇-were confirmed to be stable and efficient photocatalysts for visible-light-driven H ₂ evolution. Moreover, the activities of these photocatalysts could be improved by tuning their physicochemical properties to jointly optimize all of the processes in the photocatalytic reaction.