Chapter 18 - Metal phthalocyanines and their composites with carbon nanostructures for applications in energy generation and storage

Abstract

This chapter introduces the structure and significance of metal phthalocyanines (MPcs) as molecular materials that form an important class of organic semiconductors and organic electronics. The exotic feature of MPcs is polymorphism wherein the physical properties vary considerably depending on molecular stacking and can be tailored on specific substrates to realize different applications. The important characteristics including optical, electrical, and magnetic properties are directly impacted by structural organization of MPc moieties. The redox rich properties of metal centers and macrocycles along with excellent optical absorption characteristics in solar spectrum render them ideal candidates for various electrochemical, photoelectrochemical applications. The presence of π-electron delocalization in MPcs materials offer an advantage to make composites with π-electron based carbon nanomaterials such as reduced graphene oxide, graphene, and carbon nanotubes to enhance their electronic conductivity required for device-specific applications. A detailed description of the preparation of MPc-carbon composites employing noncovalent interaction and covalent functionalization of either constituent is given with examples in relation with applications. The synergy developed between MPc and carbon materials further offer practical applicability in energy generation, conversion and storage and is enumerated with diverse illustrations. In particular, their applications as hole conductor in organic photovoltaics, electro- and photocatalysts in electrochemical hydrogen evolution, oxygen reduction, carbon dioxide reduction, and finally as pseudocapacitors in charge storage devices are discussed.