Synthesis and Shape Control of Ag8SnS6 Submicropyramids with High Surface Energy

Orthorhombic Ag8SnS6 submicropyramids with high surface energy have been synthesized by the solventless method. The four outer surfaces are ((4) over bar 11), (112), (21 $$(1) over bar) and (4 $(1) over bar $3) lattice planes according to scanning electron microscopy, transmission electron microscopy, high resolution TEM, fast Fourier transform analyses, and angle measurements. Such morphology agrees well with the crystallographic symmetry requirement of the space group Pna2(1) of orthorhombic Ag8SnS6. Effects of polar washing solvent, reaction temperature, and time that influence the morphology are systematically investigated. Interestingly, the as-synthesized Ag8SnS6 submicropyramids exhibit superior photocatalytic activity to commercial P25 TiO2 under visible light, which may owe to the high surface energy.