Methods of manufacturing a carbon structure including exposing a carbon fiber substrate to oxygen at a first predetermined temperature and activating the carbon fiber substrate by exposure to oxygen at a second predetermined temperature. A catalyst including palladium is deposited on the activated carbon fiber substrate. The deposited catalyst on the carbon fiber structure is exposed to a hydrocarbon at a third predetermined temperature to grow carbon structures thereon. The carbon structures grown can be multimodal in nature with structures that are nano-scale and/or submicron-scale.