Data associated with "The Dependence of CNT Aerogel Synthesis on Sulfur-driven Catalyst Nucleation Processes and a Critical Catalyst Particle Mass Concentration" File contains raw data from Scanning Mobility Particle Sizer (SMPS) measurements, used to generate particle size distributions and mass concentrations illustrated in Figures 1 and 3 in the publication XPS data used to generate Figure 2 is included Raw data used to generate figures in the Supplementary data file include: Geometric Mean Diameter and Geometric Standard Deviation data (S1) Raw data from Scanning Mobility Particle Sizer (SMPS) measurements (S3, S6) Minimum mass concentration data (S5)