Metal oxide-doped activated carbons from bakery waste and coffee grounds for application in supercapacitors

The functionalization of sustainable carbon materials and their application in energy storage systems attract more and more relevancy. Bakery waste and spent coffee grounds were chosen as abundant organic residues and found to be suitable starting materials for hydrothermal carbonization and a subsequent chemical activation obtaining carbon contents of > 88%. In situ doping of the hydrochars during carbonization has proven to be a successful method for insertion of Fe2O3-, Fe3O4- and MnO2-Nanoparticles into the carbon matrix, supported by XRD analysis and SEM images. Chemical activation with K2CO3 led to iron contents up to 18% of iron and around 8% of manganese, respectively, in the corresponding activated carbon. Electrochemical characterization revealed overall higher specific capacitance for activated carbons derived from spent coffee grounds, with a highest of 87F*g-1. In contrast, the highest specific capacitance measured for activated carbons originated from bakery waste was 40,3F*g-1.