Structure and Photocatalytic Properties of In(OH)₃/InOOH Natural Heterojunction Nanocrystals Prepared by Hydrothermal Synthesis

Abstract

In(OH) 3 /InOOH nanocrystals are synthesized using InCl 3 •4H 2 O as the indium source in the presence of ethylenediamine by a one-step hydrothermal process, and the e ect of synthesis temperature on the morphology, crystallization, structure, and photocatalytic properties of the photocatalysts is investigated. The results show that all the synthesized In(OH) 3 /InOOH samples have granular nanoparticles with a size of 20-30 nm. When the synthesis temperature is lower than 150°C, only the In(OH) 3 phase exists. With increasing synthesis temperature, In(OH) 3 gradually dehydrates to form InOOH to achieve a phase equilibrium between InOOH and In(OH) 3 . The concentration of InOOH is the maximum at 180°C and decreases at 210°C. The photocatalytic activity is evaluated from the degradation of a Rhodamine B solution under ultraviolet light irradiation, which follows the rst-order reaction kinetics. The increase in synthesis temperature can signi cantly improve the photocatalytic performance of In(OH) 3 /InOOH because of the formation of a large number of natural heterojunctions in the nanocrystals, which can enhance ultraviolet light absorption and facilitate charge transfer and separation. The rst-order kinetic constant of the nanocrystals synthesized at 180°C is almost 2.5 times that of the nanocrystals synthesized at 150°C. The active species capture experiments demonstrate that holes and superoxide radicals are the main active species in the photocatalytic systems.