Hexagonal microrods architectured MoO 3 thin film for supercapacitor application R. B. Pujari 1 • V. C. Lokhande 2 • V. S. Kumbhar 1 • N. R. Chodankar 1 • Chandrakant D. Lokhande 1 Received: 15 October 2015 / Accepted: 29 November 2015 Ó Springer Science+Business Media New York 2015 Abstract Hexagonal microrods containing MoO 3 thin films are synthesized by simple, low cost and scalable chemical bath deposition approach with acidification of ammonium molybdate ([NH 4 ]6Mo 7 O 24 Á4H 2 O). The struc- tural and morphological analyses are carried out through X-ray diffraction and field emission scanning electron microscopy (FE-SEM) respectively. Hexagonal microrods of width *5 lm and length of *20–50 lm are manifested in FE-SEM analysis. Supercapacitive tests of electrode are performed with cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) techniques in 1 M Na 2 SO 4 elec- trolyte. The highest specific capacitance of 194 Fg -1 is obtained from CV study. The energy and power densities of 7.33 Wh kg -1 and 1200 W kg -1 , respectively are obtained from GCD study. An electrochemical impedance spectroscopic study is also carried out. 1 Introduction Clean, sustainable energy harvesting and its storage are the burning issues of the world. Rapid growth in consumption of energy has influenced world economy and environment by high increasing population and industrialization. Effective energy storage system should combine features of relatively higher energy density, good power ability, long life, environment friendly, and low cost. The super- capacitors among the all energy storage systems attracted large attention owing to their high power density and cycling stability over battery and high energy density over traditional capacitors. Therefore, supercapacitors are uti- lized to bridge the gap between battery and capacitor [1, 2] and classified as electrochemical double layer capacitors (EDLCs) and pseudocapacitors. In EDLCs, reversible adsorption mechanism of charge storage occurs and redox reaction mechanism facilitates charge storage in pseudo- capacitor [3]. EDLC materials (known for their high surface area property compared with pseudocapacitive materials) have been used are graphene oxide [3, 4], carbon nano tubes (CNTs) [5, 6] etc., but low energy density and complicated process of synthesis made limitation on carbon derivatives applications [1, 2]. Pseudocapacitive metal oxides like RuO 2 [7], MnO 2 [8, 9], NiO [10], MoO 3 [11, 12] etc. show multiple oxidation states useful for redox reactions. Out of these, MoO 3 has versatile applications in various fields as smart windows [13], catalysts [14, 15], supercapacitor [16], sensors [17], optical devices [18] etc. MoO 3 has three forms as, a-MoO 3 , which is thermodynamically stable phase with orthorhombic crystal structure; b-MoO 3 and h-MoO 3 are metastable phases with monoclinic and hexagonal crystal structures, respectively [19–22]. In lit- erature, MoO 3 is described as a layered structure of Mo–O octahedron. These layers are connected by weak van der Waals force containing van der Waals gaps of few A ˚ [11, 18]. These gaps can be utilized by intercalation and de- intercalation of electrolyte ions while charging and dis- charging of MoO 3 electrode. It has gathered a wide interest as a candidate for supercapacitor application owing to ease of fabrication, non-toxicity in nature, and low cost of fabrication as compared to RuO 2 [7]. & Chandrakant D. Lokhande l_chandrakant@yahoo.com 1 Thin Film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004, M.S., India 2 Department of Electronics and Computer Engineering, Chonnam National University, 300 Yongbong-Dong, Puk-Gu, Gwangju 500-757, South Korea 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-015-4160-3