ZnSn(OH)6 Nanocubes and Octahedra Displaying Facet-Dependent Behaviors for Use in Piezocatalysis

Size-tunable ZnSn(OH)6 nanocubes and octahedra have been synthesized at low temperatures of 10–70 °C. Slight size- and shape-related lattice constant differences can be observed in their synchrotron X-ray diffraction (XRD) patterns. Careful high-resolution transmission electron microscopy (HR-TEM) analysis reveals recognizable variations in the lattice point patterns between nanocubes and octahedra. These lattice variations can produce very large property changes. Expectedly, their band gaps display size and facet dependence. A {111}-exposed ZnSn(OH)6 octahedron shows good electrical conductivity, but a {100}-terminated cube is insulative. Octahedra also present notably higher piezoelectric and ferroelectric responses than cubes do. Synchrotron XRD data reveal a relatively large hydroxyl group displacement and dissimilar bond lengths between cubes and octahedra to support the emergence of piezoelectric responses. Remarkably, while octahedra are highly piezocatalytically active toward rhodamine B decomposition, cubes can be inert. Scavenger tests indicate that hydroxyl radicals are the active species in the piezocatalysis. This work demonstrates again that seemingly minute but extended shape-related lattice variations within crystals can produce very large property differences, which affect their applications.