Surfaces and Interfaces 22 (2021) 100808 Available online 12 November 2020 2468-0230/© 2020 Elsevier B.V. All rights reserved. Tuning of Photocatalytic Performance of CeO 2 -Fe 2 O 3 Composite by Sn-doping for the Effective Degradation of Methlene Blue (MB) and Methyl Orange (MO) dyes Athira Krishnan * , Pillai Vinitha Vishwanathan , A. Chithra Mohan , R. Panchami , Sruthy Viswanath , Abhirami V. Krishnan Department of Chemistry, Amrita Vishwa Vidyapeetham, Amritapuri, Kerala 690 525, India ABSTRACT One of the major class of pollutants used among textiles, medicines, plastics are organic dyes. Water pollution due to the industrial exhaust of large amount of these colouring materials are a major threat to our environment. Conventional methods of water treatment are not effective as these chemicals are not easily degradable. Sn-doped 1:2 CeO 2 -Fe 2 O 3 nanocomposite with varying Sn content was prepared by thermal decomposition method for effcient degradation of MB and MO dyes under visible light. The phase composition and morphology were controlled by varying Sn content. 5% Sn doped 1:2 CeO 2 -Fe 2 O 3 nanocomposite achieved nearly complete degradation for 10-50 mg/L MO solution and the maximum degradation effciency obtained for MB solution is 93.54- 94.65 % for 10-30 mg/L MB solution. The optimized photocatalyst degraded MO more effciently than MB solution. A smaller crystallite size of 12 nm was obtained. Incorporation of Sn 4+ ions in CeO 2 lattice improved the catalytic activity of CeO 2 -Fe 2 O 3 composite by altering the fermi level of CeO 2, facilitating charge separation. The infuence of factors such as, exciton generation under solar irradiation, charge recombination rate, surface charge availability were illustrated. The long term stability and reusability of the catalyst composite towards photo degradation reaction unveil the industrial signifcance of the metal oxide composite. 1. Introduction Urbanization and rapid growth of industries have a major role in environmental pollution. Most of these environmental pollutants that have a damaging effect on our ecology are discharged directly into the natural streams. These pollutants include oils, chemicals, metal scraps, vegetable waste, radioactive waste etc. A considerable part of the water pollution is contributed by the dyes, form an integral part of our life which give color to various materials from textiles, paper, leather tan- ning, hair coloring, cosmetic, photochemical cells, and furniture in- dustries [1–4]. Dyeing industries use more than one hundred thousand dyes which are commercially available. Every year, approximately 15% of these non-biodegradable dyes are discharged into water bodies by the industries [5-8]. The major concern is the carcinogenic nature of chemically active dyes in the industrial waste water and it also causes low photosynthetic activity of aquatic bodies, as these dyes will block the sunlight pene- tration and reduce the oxygen dissolution [9,10].The diffcult and complex task is the removal of color from the waste water. Most prob- lematic dyes to be eradicated are acid dyes which are bright in color and water soluble [11,12]. The waste produced during the production of dyes constitutes both the organic and inorganic contaminants that are hazardous to the environment [13-19].The color and dye compound concentration cannot be removed by physio-chemical treatments such as coagulation, membrane process etc [20-23]. Developing technologies for the effec- tive elimination of dyes have been found as a fast growing research area of industrial signifcance. Among the many methods established for dye degradation, chemical treatments such as chlorination, ozonation; physical methods such as adsorption, degradation by adsorption on microbial biomass or enzymatic degradation and photocatalysis were demonstrated as fascinating tools in the area. Dye degradation by pho- tocatalysis is attractive in terms of energy effciency in decontamination of polluted environment. The photocatalytic dye degradation by semi- conductors such as metal oxides, nitrides, sulfdes etc are found to be effective, economic and satisfy international environmental standards. [24-26]. Metal oxides such as TiO 2 , ZnO, CeO 2 , CuO, Fe 3 O 4 , Fe 2 O 3 , BiVO 4 etc are established for their photo catalytic activity for water splitting re- action, degradation of different organic pollutants etc [6-9,16,18,27]. Catalysis by metal oxides under solar irradiation is mainly limited by large band gap, low charge transfer effciency, less resistance to * Corresponding author. E-mail address: athikrishnan91@gmail.com (A. Krishnan). Contents lists available at ScienceDirect Surfaces and Interfaces journal homepage: www.sciencedirect.com/journal/surfaces-and-interfaces https://doi.org/10.1016/j.surfn.2020.100808 Received 22 September 2020; Received in revised form 23 October 2020; Accepted 8 November 2020