Band-gap-energy-adjustable and noble-metal-free modified NiS-ZnxCd1-xS for highly efficient visible-light-driven Cr6+ photoreduction in alkaline wastewater. (March 2021)

• Record Type: Journal Article
• Authors: Wang, Linjuan; Zan, Ling
• Is Part Of: Journal of physics and chemistry of solids. Volume 150(2021)
• Publication Date: 2021-03
• Subjects: Photocatalytic -- Zn0.25Cd0.75S nanoparticles -- NiS co-catalyst -- Environmental remediation -- Electron transfer; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2020.109893
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Industrial wastewater containing heavy metal ions can cover the full pH range according to the manufacturing process. Alkaline wastewater treatment is still a great challenge because Cr 6+ therein has a more negative reduction potential (Cr2 O7 2− + 14H + + 6e − = 2Cr 3+ + 7H2 O (ECr 6+ (Cr2O7 2− /Cr 3+ ) = E θ − RT nF ln [ OH ] − ) than in acid solution, in which it can be easily reduced by numerous reagents. In this study, weakly alkaline Cr 6+ solution has been used to simulate weakly alkaline industrial wastewater, and a reagent capable of excellent reduction efficiency therein has been developed. A series of band-gap-energy-adjustable NiS-Zn x Cd1- x S composites has been synthesized by a one-pot hydrothermal method. A more negative conduction band position for Zn x Cd1- x S has been achieved by doping and changing the amount of Zn 2+ ions to ensure a superior photoreduction ability. All modified samples show excellent photocatalytic efficiency. For example, the reduction efficiency of 10%NiS–Zn0.25 Cd0.75 S sample is threefold higher than that of Zn0.25 Cd0.75 S and sixfold higher than that of CdS when deployed at a catalytic level for 30 min. Multiple characterization methods have been applied, and the results show that the improved efficiency can be ascribed to intimate contact between Zn0.25 Cd0.75 S and NiS. Photoluminescence (PL) and photocurrent measurements and electrochemical impedance spectroscopy (EIS) further elucidate the catalytic mechanism and imply an enhanced charge-carrier separation efficiency between Zn0.25 Cd0.75 S and NiS. Graphical abstract: Image 1 Highlights: A series of Zn x Cd1- x S composites were synthesized through a facile one-pot method. NiS-Zn0.25 Cd0.75 S composites show a high efficiency of photocatalytic. Intimate contacts were observed between Zn0.25 Cd0.75 S and NiS by XPS. PL, photocurrent, and EIS measurements elucidated the photocatalytic mechanism.