Surface-binding through polyfunction groups of Rhodamine B on composite surface and its high performance photodegradation

The proper adsorption sites of Rh B depending on the phases of composites significantly enhance photodegradation activity under visible light. •The composites ZnS/In(OH)3/In2S3 were hydrothermally prepared.•Rhodamine B dye was effectively degraded by the composite under the visible light irradiation.•The three function groups of Rhodamine B bind on the composites ZnS/In(OH)3/In2S3.•The proper adsorption mode and site of Rhodamine B effectively suppress the combination of carrier.•A new degradation path of Rhodamine B on ZnS/In(OH)3/In2S3 is found. A kind of novel composite ZnS/In(OH)3/In2S3 is synthesized using zinc oxide nanoplates as zinc raw material during hydrothermal process. Although the obtained samples are composited of ZnS and In(OH)3 and In2S3 phase, the samples possess different structure, morphology and optical absorption property depending on molar ratio of raw materials. Zeta potential analysis indicates different surface electrical property since various content and particle size of the phases. The equilibrium adsorption study confirms the composite ZnS/In(OH)3/In2S3 with surface negative charge is good adsorbent for Rhodamine B (Rh B) dye. In addition, the degradation of Rh B over the samples with surface negative charge under visible light (λ≥420nm) is more effective than the samples with surface positive charge. The samples before and after adsorbing Rh B molecule are examined by FTIR spectra and Zetasizer. It is found that the three function groups of Rh B molecule, especially carboxyl group anchors to surface of the sample through electrostatic adsorption, coordination and hydrogen-bond. It contributes to rapid transformation of photogenerated electron to conduction band of In(OH)3 and suppresses the recombination of photogenerated carrier. The possible adsorption modes of Rh B are discussed on the basis of the experiment results.