Getting a charge out of microporous oxides: Building a better ultracapacitor

Microporous nickel oxides consisting of nano-sized particles have been utilized as active electrode materials for ultracapacitors. Both the physical adsorption of ions near the charged surface of these particles and surface oxidation/reduction reactions play a role in the capacitative charge storing mechanism. These are therefore appropriately referred to as pseudo-capacitors since they rely on mechanisms in addition to double layer charging in order to store energy. In this study, it has been shown that surface hydration contributes to the formation of an initial compound which participates in the electrochemical reactions of ultracapacitors. The specific capacitance of this material is ranging from 60 to 120 F/g depending upon the types of electrolyte solution used in the ultracapacitor.