The constant increase in energy demand combined with our non-renewable fossil fuelbased civilization producing a negative environmental impact (CO2 emission) calls for the development of sustainable energy conversion and storage with a small environmental footprint. Electrochemical technologies such as supercapacitors (SCs) and batteries are emerging as important energy storage devices for electronics, electric vehicles, and smart grids. SCs display remarkable advantages over batteries, such as ultrafast charging, high power dissipation, and extralong cyclelife. Furthermore, they are a cheaper and far more sustainable energy storage technology, since they are carbon-based, not requiring lowabundance elements as batteries do (i.e. lithium, cobalt, or nickel). However, stateoftheart SCs materials are lagging behind Li-ion batteries in energy content by order of magnitude. A lot of research effort is thus focused on increasing the energy content of SCs in order to exploit their advantages in applications requiring energy supply for more extended periods. For this purpose, we have studied methods in order to increase the performance of SCs electrode materials via developing hybrids by combining the densely functionalized graphene derivative (Cyanographene, GCN) with ultra-small nanoparticles of -FeOOH and Fe3S4.The constant increase in energy demand combined with our non-renewable fossil fuelbased civilization producing a negative environmental impact (CO2 emission) calls for the development of sustainable energy conversion and storage with a small environmental footprint. Electrochemical technologies such as supercapacitors (SCs) and batteries are emerging as important energy storage devices for electronics, electric vehicles, and smart grids. SCs display remarkable advantages over batteries, such as ultrafast charging, high power dissipation, and extralong cyclelife. Furthermore, they are a cheaper and far more sustainable energy storage technology, since they are carbon-based, not requiring lowabundance elements as batteries do (i.e. lithium, cobalt, or nickel). However, stateoftheart SCs materials are lagging behind Li-ion batteries in energy content by order of magnitude. A lot of research effort is thus focused on increasing the energy content of SCs in order to exploit their advantages in applications requiring energy supply for more extended periods. For this purpose, we have studied methods in order to increase the performance of SCs electrode materials via developing hybrids by combining the densely functionalized graphene derivative (Cyanographene, GCN) with ultra-small nanoparticles of -FeOOH and Fe3S4.