Please cite this article in press as: K.P. Madhuri, N.S. John, Supercapacitor application of nickel phthalocyanine nanofibres and its composite with reduced graphene oxide, Appl. Surf. Sci. (2017), https://doi.org/10.1016/j.apsusc.2017.12.021 ARTICLE IN PRESS G Model APSUSC-37891; No. of Pages 9 Applied Surface Science xxx (2017) xxx–xxx Contents lists available at ScienceDirect Applied Surface Science jou rn al h om ep age: www.elsevier.com/locate/apsusc Full Length Article Supercapacitor application of nickel phthalocyanine nanofibres and its composite with reduced graphene oxide K. Priya Madhuri, Neena S. John ∗ Centre for Nano and Soft Matter Sciences, Jalahalli, Bangalore 560013, India a r t i c l e i n f o Article history: Received 5 October 2017 Received in revised form 24 November 2017 Accepted 3 December 2017 Available online xxx Keywords: Nickel phthalocyanine Nanofibres Reduced graphene oxide Supercapacitance a b s t r a c t The combination of double layer capacitor and pseudocapacitor materials are the next generation com- posites for energy storage. Nitrogen enriched species like metal phthalocyanines with metal redox centres may be combined with electrical double layer capacitive carbon materials for improved charge storage. We have explored electrochemical capacitance applications of nickel phthalocyanine (NiPc) nanofibres and its composite with reduced graphene oxide (rGO) synthesized through simple chemical routes. The composite material exhibits a superior specific capacitance, 223.28 Fg −1 at 1 Ag −1 , four fold higher than the individual components and also good stability over continuous cycling for 1000 cycles. The syner- gistic effect of NiPc and rGO with excellent physical interface offers less charge transfer resistance and better charge storage capacity. © 2017 Published by Elsevier B.V. 1. Introduction Metal phthalocyanines (MPcs) constitute a fascinating class of organic semiconductors whose chemical structure is composed of four isoindole units bearing active nitrogen sites bonded to accommodate the metal ion in their central cavity. They possess 18  electrons delocalized around the macrocycle that facilitate charge transport and self-assembly through - stacking. Their versatile optical and electrical properties enable them to be use- ful candidates for solar cells, gas sensors, field effect transistors, electrocatalysis, etc. [1,2]. MPcs are thermally and chemically very stable and hence, can be used in adverse environment like high temperatures, acidic or basic conditions. However, the conductiv- ity of divalent MPcs like NiPc, CuPc falls in the range of 10 −12 Scm −1 [3] and hence, efforts have been made towards achieving improved activity by combining them with conducting carbon materials like carbon nanotubes, reduced graphene oxide (rGO) and porous car- bon structures for varied applications [4,5]. Recent reports have shown that MPcs are also excellent can- didates for charge storage applications. Electrochemical capacitors are of two types, electrical double layer capacitors (EDLC) and pseu- docapacitors. The EDLC systems are the ones that store charges at the electrode and electrolyte interface, while the pseudocapac- itors are the materials that possess charges as a virtue of their ∗ Corresponding author. E-mail addresses: jsneena@cens.res.in, jsneena@gmail.com (N.S. John). redox properties, referred as faradaic process. The combination of EDLC and pseudocapacitors can provide an overwhelming perfor- mance in terms of higher specific capacitance and good cycling stability. There is enormous interest to explore transition metal complexes as potential electrode systems for supercapacitor appli- cations. Among them, nickel complexes have become popular due to the predicted large theoretical specific capacitance (2573 Fg −1 ), well-defined redox behaviour and environmental benignity [6]. Ruan et al. elaborately reviewed nanostructured nickel based mate- rials utilized for superior specific capacitance ranging from 300 to 1100 Fg −1 depending on the specimen structure and prepa- ration approach [7]. Phthalocyanine complexes are exciting for investigation because they also possess nitrogen active sites along with metal centres capable of redox reactions. For combination with EDLC materials, rGO is one of the promising solutions since they possess large surface area with oxygen functional groups for anchoring other materials and a basal plane of conductive carbon network providing - interactions. They can be prepared in bulk amounts through simple chemical routes and thus form a cheap alternative to other expensive carbon materials. The applications of rGO composites cover a broad area in the field of energy, photo- voltaics, bio-imaging, etc. [8–10]. It also has fast electrolyte transfer channels, which are vastly desirable for high power applications. The commercially obtained MPcs are mostly macroscopic needle-like crystals with poor solubility in most of the solvents. Since the electrochemical properties are strongly interface driven, it is important to have a control over the structure and morphology of the electrode material. It will be interesting to tailor the mor- https://doi.org/10.1016/j.apsusc.2017.12.021 0169-4332/© 2017 Published by Elsevier B.V.