In the past few years, more and more efforts have been made on designing novel and efficient semiconductor-based heterojunction photocatalyst to maximize the capture and conversion efficiency of solar energy. In this work, unique TiO2 hollow sub-microspheres (THSs) and ZnIn2S4 (ZIS) flower-like microspheres were combined through a facile hydrothermal method and novelly applied in photocatalytic metronidazole (MTZ) degradation. The effects of THSs on the physicochemical properties and photocatalytic performance of ZIS were systemically investigated, and the optimal weight ratio of THS and ZIS in the composite was found. Furthermore, various technologies such as photoluminescence (PL), surface photovoltage spectra (SPS) and electrochemical impedance spectra (EIS) were used to verify the intimate contact and highly-efficient charge-carriers transfer between THS and ZIS components. The underlying photocatalysis mechanism was also carefully surveyed and proposed through hydroxyl radicals (center dot OH) monitoring and radical trapping experiments. (C) 2016 Elsevier B.V. All rights reserved.