Stabilized fabrication of anatase-TiO2/FeS2 (pyrite) semiconductor composite nanocrystals for enhanced solar light-mediated photocatalytic degradation of methylene blue

Jamshaid Rashid; Sahar Saleem; Saif Ullah Awan; A Iqbal; Rajeev Kumar; M A Barakat; Muhammad Arshad; Muhammad Zaheer; Mohsin Rafique; M Awad

doi:10.1039/c8ra02077a

Stabilized fabrication of anatase-TiO₂/FeS₂ (pyrite) semiconductor composite nanocrystals for enhanced solar light-mediated photocatalytic degradation of methylene blue

RSC Adv. 2018 Mar 27;8(22):11935-11945. doi: 10.1039/c8ra02077a. eCollection 2018 Mar 26.

Authors

Jamshaid Rashid¹, Sahar Saleem¹, Saif Ullah Awan², A Iqbal³, Rajeev Kumar⁴, M A Barakat^{4

5}, Muhammad Arshad⁶, Muhammad Zaheer⁷, Mohsin Rafique⁸, M Awad⁹

Affiliations

¹ Catalysis for Environment and Energy Laboratory, Department of Environmental Science, Faculty of Biological Sciences, Quaid-i-Azam University Islamabad 45320 Pakistan jrashid@qau.edu.pk jamshaidrashid@gmail.com.
² Department of Electrical Engineering, NUST College of Electrical and Mechanical Engineering, National University of Science and Technology (NUST) Islamabad Pakistan.
³ Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology Sector H-12 Islamabad 44000 Pakistan.
⁴ Department of Environmental Sciences, Faculty of Meteorology, Environment and Arid Land Agriculture, King Abdulaziz University Jeddah 21589 Saudi Arabia.
⁵ Central Metallurgical R&D Institute Helwan 11421 Cairo Egypt.
⁶ National Centre for Physics, Nano-Science and Technology Department, Quaid-i-Azam University Islamabad Pakistan.
⁷ Department of Chemistry, SBA School of Science and Engineering, Lahore University of Management Sciences (LUMS) Lahore 54792 Pakistan.
⁸ Center for Micro and Nano Devices (CMND), COMSATS Institute of Information Technology Islamabad 45550 Pakistan.
⁹ UNEP-TONGJI Institute of Environment for Sustainable Development, College of Environmental Sciences and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University Shanghai China 200092.

Abstract

A novel visible light active TiO₂/FeS₂ semiconductor photocatalyst was synthesized by a simple wet chemical process. X-ray diffraction (XRD) was used to analyze the anatase TiO₂ and pyrite structures in FeS₂/TiO₂ nanocrystals. Scanning electron microscopy (SEM) confirmed the spherical morphology of composite nanocrystals. X-ray photoelectron spectroscopy (XPS) identified the Fe²⁺, S^1-, Ti⁴⁺, and O^2- oxidation states of relevant species. Energy dispersive X-ray (EDX) analysis was performed for compositional analysis. The measured band gap of the TiO₂/FeS₂ nanocomposite system was 2.67 eV, which is smaller than un-doped TiO₂ (3.10 eV) and larger than FeS₂ (1.94 eV). The photocatalytic activity of TiO₂/FeS₂ was significantly higher than pure FeS₂ for degrading methylene blue (MB) under solar light irradiation due to the increase in visible light absorption, reduction in band gap energy, and better election-hole pair separation. The photocatalytic degradation of MB was investigated under the influence of solution pH, dye concentrations, and varied catalyst dosage. The optimum degradation (100%) of MB was observed in 180 min and the photocatalysis of MB reduced as the dye concentrations in the solution increased from 15 to 75 mg L^-1. These results prove that the TiO₂/FeS₂ nanocomposite has the stability, recycling, and adaptability for its practical application as a visible light photocatalyst for wastewater treatment. TiO₂/FeS₂ showed increased degradation of the organic pollutant; which is confirmed by the increased rate of chemical reaction following pseudo first-order reaction kinetics with the highest rate constant value of 0.0408 m^-1 having highest R ² value of 0.9981.