Original Research Paper Photocatalytic properties of Au/Fe 2 O 3 nano-composites prepared by co-precipitation Maneesha Mishra, Hani Park, Doo-Man Chun ⇑ School of Mechanical Engineering, University of Ulsan, Ulsan 680749, South Korea article info Article history: Received 23 April 2015 Accepted 20 November 2015 Available online xxxx Keywords: Fe 2 O 3 Co-precipitation Photocatalytic property Nanocomposites abstract Nano-composites of Au/Fe 2 O 3 with different Au concentrations were prepared by a co-precipitation method. The microstructure and phase analysis of the nano-composites were carried out by X-ray diffrac- tion (XRD) and scanning electron microscopy (SEM). The compositions of the powders were confirmed by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Band gaps of the powders were analyzed by UV–Vis spectroscopy. The photocatalytic property of the nano- composites was analyzed for methylene blue (MB) degradation and the powders with 0.5 mol of Au show the best photocatalytic degradation efficiency toward methylene blue dye. Evaluation of the reaction con- ditions for Au(0.5)/Fe 2 O 3 was also carried out at different process conditions such as reaction tempera- ture, light intensity, and pH. Ó 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. 1. Introduction Limited availability of nonrenewable energy sources has direc- ted the focus of researchers toward photocatalytic materials, mate- rials that use solar radiation. Photocatalytic materials have applications in various fields such as water splitting for hydrogen production [1–3], removal of organic and inorganic pollutants from water [4–6] as well as from air [7–9], deactivation of microorgan- isms from water [10,11] and artificial photosynthesis [12,13], self cleaning applications [14,15] and solar cells [16,17]. An ideal photocatalyst should have good photoactivity, should be able to absorb near ultraviolet (UV) or visible (Vis) wavelengths of light, must be biologically and chemically inert, inexpensive and non-toxic and must resist photo corrosion. There are many semiconductors that are photocatalytic such as CdS, ZnS, TiO 2 , ZnO, SnO 2 and WO 3 . Most of these oxides have an absorption edge only in the UV region which limits the range of the solar spectrum in which they are useful. Although sulfides and nitrides have a lower band gap than oxides, the stability of these materials in an aqueous medium is a major disadvantage. Compared to other photocatalytic materials, Fe 2 O 3 has a lower band gap (2.0 eV), which allows 40% of solar radiation to be uti- lized. Due to its lower band gap, it has a band edge in the visible range. Fe 2 O 3 is stable in most aqueous solutions (pH > 3), and is one of the least expensive semiconductor materials available. The valence band (VB) edge of Fe 2 O 3 is lower than the water oxidation potential, which makes Fe 2 O 3 a potential candidate material for water splitting applications to produce hydrogen (H 2 ). Disadvan- tages of Fe 2 O 3 include a high recombination rate and low hole dif- fusion length (2–4 nm) [18,19]. The basic mechanism behind the photocatalytic properties of Fe 2 O 3 is as follows [20]. Fe 2 O 3 ! Fe 2 O 3 ðe  þ h þ Þ h þ þ H 2 O ! HO Å þ H þ O 2 þ e ! O 2 O 2 þ 2H þ þ e  ! H 2 O 2 HO Å þ H 2 O 2 ! HOO Å þ H 2 O HOO Å þ Fe 3þ ! Fe 2þ þ H þ þ O 2 Fe 2þ þ H 2 O 2 ! HO Å þ OH  HO Å þ Dye ! Dye oxd Many methods have been adapted to improve photocatalytic properties, including synthesizing materials in different morpho- logical nano-structure forms [21–24], doping with different mate- rials [25,26], forming composites [27–29] and preparing hetero structures [30–33]. All these techniques help to improve the pho- tocatalytic properties of the photocatalyst by increasing the surface area and lowering the recombination effect of electrons (e  ) and holes (h + ). Addition of noble metals is one useful technique to improve the photocatalytic properties of materials. Adding metals http://dx.doi.org/10.1016/j.apt.2015.11.009 0921-8831/Ó 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. ⇑ Corresponding author. E-mail address: dmchun@ulsan.ac.kr (D.-M. Chun). Advanced Powder Technology xxx (2015) xxx–xxx Contents lists available at ScienceDirect Advanced Powder Technology journal homepage: www.elsevier.com/locate/apt Please cite this article in press as: M. Mishra et al., Photocatalytic properties of Au/Fe 2 O 3 nano-composites prepared by co-precipitation, Advanced Powder Technology (2015), http://dx.doi.org/10.1016/j.apt.2015.11.009