Metallophthalocyanines deposited on different CNTs are denoted as MPc/X, where M is the metal and X refers to SWCNTs or the average diameter (in nm) of the MWCNTs (Supplementary Fig. and). Scanning TEM energy-dispersive X-ray spectroscopy (STEM-EDS) mapping shows a uniform distribution of N and Co along the SWCNT surface (Fig. ). In aberration-corrected HAADF-STEM (Fig. ), the bright spots marked with red circles further verify the uniformly dispersed Co sites. The Raman spectra for CoPc and various bare and CoPc-decorated CNTs can be found in Supplementary Fig. and .