Controllable and facile synthesis of nearly monodisperse 18-facet indium hydroxide polyhedra

Abstract

Perfect 18-facet In(OH)₃ polyhedra were successfully synthesized by a simple mixed solvothermal process using NaOH as base source without any surfactant. Electron microscopy images revealed that octadecahedral bcc In(OH)₃ are entirely enclosed by twelve {110} and six {100} facets and follow Euler's rule. A series of controlled experimental results indicated that the appropriate amount of NaOH, optimal volume ratio of absolute ethanol to deionized water and adequate reaction time were the key factors to form the perfect In(OH)₃ octadecahedra. The synergistic effect of high concentration OH⁻ ion and ethanol could change the crystal facet growth habits of bcc In(OH)₃ by increasing the chemical potential of the reaction system and decreasing the viscosity of the reaction medium. The optimized reaction conditions decreased the growth rate along the <110> direction and led to the formation of octadecahedral {110} facets. A plausible formation and growth mechanism were proposed. The photocatalytic property test showed that In(OH)₃ octadecahedra had better H₂ evolution from a methanol aqueous solution than the commercial Degussa P25 TiO₂.