A new core–shell Z-scheme heterojunction structured La(OH)${}_3$@In${}_2$S${}_3$ composite with superior photocatalytic performance

Constructing Z-scheme heterojunction photocatalyst with strong redox ability to make for enhanced photocatalytic performance and efficient charge separation is extremely attractive but still underdeveloped. Herein, a Z-scheme heterojunction structured La(OH)${}_3$@In${}_2$S${}_3$ composite (labeled by "LIS") with photocatalytic for the methylene orange (MO) degradation under simulated light irradiation has been developed. The as-prepared LIS, together with commercial La(OH)${}_3$ and pure In${}_2$S${}_3$ fabricated with the identical processing method and starting materials as those of LIS, was characterized by X-ray diffraction, UV–vis diffuse reflectance spectra, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra and electrochemical impedance spectroscopy. The results show the heterojunction of La(OH)${}_3$/In${}_2$S${}_3$ has prolonged the lifetime of the photo-generated carriers. The photocatalytic activity test shows that over only a small amount (0.02 g in 100 ml MO) of LIS, the photodegradation rate of 95% toward MO can be obtained in 90 min, which is about 3.4 times higher than that over pure In${}_2$S${}_3$. The active species trapping experiments indicate that there were four active species playing roles in photodegradation as the following order: e${}^{-}$ = ∙OH < h${}^{+}$< ∙O${}_2$${}^{-}$. A mechanism of Z-scheme heterojunction was proposed and well explained the enhanced photocatalytic performance. This work provides a new cost-effective photocatalyst with high photocatalytic properties.