**1. Introduction**

Rapid growth of human society and subsequent need of energy is driving the manipulation of non-renewable sources in nature leading to depletion of the same. This is simultaneous with the increasing threats such as global warming, energy shortage, air pollution etc. Standardization of our life style and drastic change in dependence on electricity, demanding urgent need for high efficiency energy conversion and storage. Batteries and supercapacitors are excellent means of electrical energy conversion and storage including solar cells [1, 2].

Conventional condensers or capacitors utilize dielectric materials, e.g., ceramics, polymers which are non-conducting in nature, exhibit the capacitance in the range of pico to microfarad. Typically, anodic metal oxides mostly of Ta, Al, Nb are used in electrochemical capacitors which widen the capacity from micro to millifarad level. Recently, supercapacitors are devised involving energy mechanisms; electric double-layer capacitance (EDLC) and pseudocapacitance. Charge separation at electrode/electrolyte interface results in EDLC and fast, reversible reactions occurring on solid electrode surface leads generation of pseudocapacitance. RuO2 and IrO2 noble metals exhibit superior specific capacitance value of about 750 F/g but at the same time hazardous and non-economical. For this reason, oxides of transition

metals, e.g., CoOx, MnOx, and NiOx are extensively being studied as supercapacitor electrodes [2, 3].
