Contents lists available at ScienceDirect Materials Science in Semiconductor Processing journal homepage: www.elsevier.com/locate/mssp Study on structural, morphological, electrochemical and corrosion properties of mesoporous RuO 2 thin films prepared by ultrasonic spray pyrolysis for supercapacitor electrode application B.Y. Fugare, B.J. Lokhande ⁎ School of Physical Sciences, Solapur University, Solapur 413255, Maharashtra, India ARTICLE INFO Keywords: Ruthenium oxide (RuO 2 ) Mesoporous Ultrasonic spray pyrolysis Corrosion Energy and power ABSTRACT RuO 2 samples were deposited on stainless steel at 723 K by an ultrasonic spray pyrolysis technique using 0.005 M RuCl 3 .nH 2 O as a precursor solution. XRD analysis confirms the amorphous nature of the deposited samples. Raman studies confirm the formation of RuO 2 phase. SEM, AFM and HRTEM morphologies illustrate uniform spherical granular type morphology of hydrophilic nature. BET study confirms mesoporous nature. RuO 2 phase formation is also confirmed by using XPS analysis. All electrochemical characterizations of the as deposited electrodes were carried out in 0.5 M H 2 SO 4 electrolyte. Optimized electrode shows maximum specific capacitance 2192 F/g at 2 mV/sec. The achieved maximum values of specific energy (SE) specific power (SP) and columbic efficiency (η) calculated by using galvanostatic charge-discharge method are 61.12 Wh/Kg, 114.94 kW/Kg and 72.34% respectively. The obtained corrosion rate is ~ 0.1171(mm/year) which is very less than reported values. 1. Introduction In the developed countries, there is a huge need to store the electric energy and transfer it to the power supplies. For the storage purpose supercapacitor offers a very high specific capacitance in a small pack up for the fulfillment of the need of power supplies. It stores energy using faradic (redox) and non faradic (electric double layer) reaction me- chanisms. Reported precursor materials which have high potential window should be able to get redox reversibility between various oxi- dation states [1,2]. Various transition metal oxides (TMO) and con- ducting polymer materials are the examples of such a materials [3–6]. Among these TMOs, ruthenium oxide is one of the most excellent promising material for supercapacitor electrode application due to its wide potential window, multi oxidation states, mixed electro-protonic conductivity, high porosity [7,8]. As per literature, amorphous ruthe- nium oxide (RuO 2 ) exhibits high specific capacitance [9]. Several re- ports are there to improve the specific capacitance of RuO 2 , but not on the reproducibility it for high specific capacitance. The achievement of good reproducibility and high specific capacitance is strongly depends on the method of preparation and surface morphology of the deposited material [10]. Till now, RuO 2 samples have been synthesized by various methods like electro deposition [11], sol-gel [12], e- beam evaporation [13], ultrasonic spray pyrolysis [14,15], etc. Among them, ultrasonic spray pyrolysis (USP) is one capable of producing metal oxide thin films even at low decomposition temperature, useful for large surface area coat- ings and exhibits high adherency at only one step. USP technique is computer controlled, simple in operation, cost effective, gives re- producibility and have control over various operative parameters such as spray rate, concentration of precursor and decomposition tempera- ture. In the present investigation, RuO 2 samples were prepared by using USP and were analyzed for structural, morphological, electrochemical and corrosion properties to get suited as an electrode material for ultra supercapacitor. 2. Experimental In the deposition of RuO 2 samples by USP, 50 ml 0.005 M aqueous solution of Rucl 3 :xH 2 O (Sd Fine, 99.9%) AR grade was prepared in double distilled water. Well-polished (using emery paper) stainless steel (SS-304) plates having dimension 1.5 × 5 cm 2 were used as a sub- strates. Prepared solution was sprayed at the rate 10 ml/min, using compressed air as a carrier gas at the flow rate of 12 L min -1 onto the pre-heated SS substrates kept at 673 K, which was the optimized de- composition temperature in our previous work [16]. The substrate to nozzle distance was kept constant at 22 cm and X-Y movement of nozzle http://dx.doi.org/10.1016/j.mssp.2017.07.016 Received 5 April 2017; Received in revised form 10 June 2017; Accepted 15 July 2017 ⁎ Corresponding author. E-mail address: bjlokhande@yahoo.com (B.J. Lokhande). Materials Science in Semiconductor Processing 71 (2017) 121–127 1369-8001/ © 2017 Elsevier Ltd. All rights reserved. MARK