Functionalized Carbon Nanotube Supercapacitor Electrodes: A Review on Pseudocapacitive Materials

Carbon nanotube (CNT) supercapacitor electrodes have been the focus of a large amount of research in the last decade given the high specific surface area, electrical conductivity, and chemical stability that they provide. In addition to the electrochemical double-layer capacitance provided by CNTs, electrodes synthesized with this material can be further functionalized with substances such as conducting polymers, metallophthalocyanines, or metal oxides (including oxides of ruthenium, manganese, nickel, and zinc) that add a faradaic (charge transfer) component to the capacitor known as pseudocapacitance. With relatively little pseudocapacitive material, the performance characteristics of the electrode can be improved dramatically. This review details the various methods, materials, and resulting performance figures of pseudocapacitive functionalization to carbon nanotube supercapacitors presented in recent years.