Carbon nanostructures are formed from a carbon precursor and catalytic templating nanoparticles. Methods for manufacturing carbon nanostructures generally include (1) forming a precursor mixture that includes a carbon precursor and a plurality of catalytic templating particles, (2) carbonizing the precursor mixture to form an intermediate carbon material including carbon nanostructures, amorphous carbon, and catalytic metal, (3) purifying the intermediate carbon material by removing at least a portion of the amorphous carbon and optionally at least a portion of the catalytic metal, and (4) heat treating the purified intermediate carbon material and/or treating the purified intermediate carbon material with a base to remove functional groups on the surface thereof. The removal of functional groups increases the graphitic content of the carbon nanomaterial and decreases its hydrophilicity.