Figure 2. TEM and TDFNR cobalt particle size analyses.

(a) TEM micrograph of CoCNTA sample (scale bar, 20 nm). (b) Corresponding cobalt particle size distribution, which is calculated from hundreds of Co particles based on the statistical TEM measurements. (c) Cobalt particles numbers per mg of cobalt (N_p  mg_Co⁻¹) in the different particles size ranges as a function of the blocking temperature measured by TDFNR. The number of size ranges is limited to 3 because the smallest particles (<3 nm) observed by TEM cannot be measured at the lowest FNR temperature. The discrepancy observed for the large Co particles (>10 nm) between the TEM and FNR techniques could be attributed to the extremely small area of investigation. The total catalyst weight analysed by FNR is ∼100 mg while that analysed by TEM is less than a nanogram.