The preset invention is a hierarchically-structured carbon microbead and method for forming the microbead utilizing hydrothermal carbonization of a biomass/catalyst mixture to produce partially carbonized amorphous microspheres, wherein the biomass is an inexpensive material containing a high oxygen content component (e.g., sugar, starch, alcohol), and the catalyst is a metal or metal-containing compound, preferably a transition metal compound, and more specifically a transition metal selected from Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt. Subsequently, a heat treatment is performed where the amorphous microspheres are heated to a temperature that is sufficiently high so as to result in carbonization, graphitization, and production of a carbonaceous coating or shell on the core of the microbead.