Modular Preparation of Graphene-Based Functional Architectures through Two-Step Organic Reactions: Towards High-Performance Energy Storage

Graphene-based materials have recently attracted much attention due to their extraordinary physical and chemical properties, which make them attractive candidates for many technological applications in sensing, optoelectronics, catalysis, and energy storage. Their chemical functionalization is key to tuning their properties. Herein, a novel two-step synthetic approach, which enables a high degree of covalent functionalization of graphene oxide (GO) is devised, thereby making the facile attachment of various robust functional molecules possible. Such a process relies initially on the grafting of an ethylenediamine linker followed by a second step consisting of the condensation reaction between aldehyde and amine groups to form imine bonds. As test beds, two kinds of graphene-based functional systems, namely, porphyrin-modified GO and ferrocene-modified GO, are prepared. Such hybrid systems are characterized by various spectroscopic and microscopic techniques. The degree of functionalization is quantified as the attachment of one porphyrin or ferrocene unit to every 34 or 77 carbon atoms of the GO scaffold, respectively, which is much higher than that of values obtained upon using various established chemical approaches to functionalize GO, such as condensation, cycloaddition, or coupling reactions. For the first time, the reduced form of ferrocene-modified GO was employed as an electrode material in supercapacitors, showing a specific capacitance of 127 F g(-1) at a current density of 1 A g(-1), with capacitance retention of about 93 % after 5000 cycles at the same current density; this demonstrates great potential for application in high-performance energy-storage devices.