α-Bi2O3/β-Ni(OH)2 composites: Effective solar light photocatalysts for organic pollutants degradation

Abstract α-Bi2O3/β-Ni(OH)2 composites exhibited perfect photocatalytic properties for organic pollutants degradation under sunlight irradiation. Pure α-Bi2O3 and β-Ni(OH)2 were prepared by coprecipitation method and then mechanically mixed in different proportions to form α-Bi2O3/β-Ni(OH)2 composites. The XRD and FTIR analyses have well emphasized the formation of monoclinic α-Bi2O3 and hexagonal β-Ni(OH)2 phases with high crystallinity. The SEM micrographs of α-Bi2O3 and β-Ni(OH)2 powders displayed a rod and sheet shaped grains, respectively. The band gap of the pure α-Bi2O3 was estimated to be 2.87 eV. Pure β-Ni(OH)2 revealed three absorption bands in the UV–visible light region. α-Bi2O3/β-Ni(OH)2 composites have a more intense absorption in the visible light region compared to pure α-Bi2O3 sample. Modification of α-Bi2O3 by β-Ni(OH)2 induced a superior photocatalytic activity especially at β-Ni(OH)2 content of 12 wt% in α-Bi2O3 (BN-12 composite). This composite showed high efficiencies of 99%, 96%, 91% and 90% for methylene blue, Congo red, methyl orange and 4-niropheniol degradation in 80, 80, 180 and 300 min under sunlight irradiation, respectively. The remarkable photocatalytic activity of the α-Bi2O3/β-Ni(OH)2 composite was attributed to the new states in charge separation, charge transportation and the intensive absorption of visible light. α-Bi2O3/β-Ni(OH)2 composite (BN-12) has a great potential in removing of cationic and anionic dyes beside phenolic compounds from wastewater.