In-situ synthesis of CN@La(OH)3 nanocomposite for improved the charge separation and enhanced the photocatalytic activity towards Cr(VI) reduction under visible light

Abstract

In this work, we report for the first time a novel graphitic carbon nitride (CN) composited with different weight percentages (5–15%) of La(OH)3 (CN@La(OH)3) for photocatalytic reduction of hexavalent chromium (Cr(VI)) in aqueous solution. In situ fabrication of the CN@La(OH)3 photocatalysts were carried out via a hydrothermal method. The La(OH)3 nanoparticles were deposited onto the surface of CN nanosheets to form heterojunction, as confirmed by series of techniques. Compared to the pure CN and different weight percentages of CN@La(OH)3 nanocomposite, the CN@La(OH)3(10%) nanocomposite exhibited remarkable photocatalytic reduction performance for Cr(VI) under visible light illumination. Such excellent photocatalytic reduction activity ascribed to the more photocatalytic active sites, high visible light harvesting capacity and improved electron-hole separation and transfer efficiency which was confirmed by photocurrent, impedance and photoluminescence results. The photoreduction efficiency and the reduction rate constant was 98.7% and 0.0263 min−1 within 50 min. A possible reaction mechanism for the effective reduction of carcinogenic Cr(VI) is put forward tentatively. Moreover, the developed CN@La(OH)3(10%) nanocomposite also possessed high structural stability and recyclability after five photocatalytic cycles. This work may open up the way into the robust photocatalysis of Cr(VI) in wastewater treatment application.