Photocatalytic water splitting under visible light by mixed-valence Sn ₃O₄

A mixed-valence tin oxide, (Sn²⁺)₂(Sn ⁴⁺)O₄, was synthesized via a hydrothermal route. The Sn₃O₄ material consisted of highly crystalline {110} flexes. The Sn₃O₄ material, when pure platinum (Pt) was used as a co-catalyst, significantly catalyzed water-splitting in aqueous solution under illumination of visible light (λ > 400 nm), whereas neither Sn²⁺O nor Sn⁴⁺O₂ was active toward the reaction. Theoretical calculations have demonstrated that the co-existence of Sn²⁺ and Sn⁴⁺ in Sn₃O₄ leads to a desirable band structure for photocatalytic hydrogen evolution from water solution. Sn₃O₄ has great potential as an abundant, cheap, and environmentally benign solar-energy conversion catalyst.