Fig. 1: Structure sensitivity versus structure insensitivity as observed by different spectroscopic techniques.

a, b Structure sensitivity versus structure insensitivity plotted on a linear Y-axis. The influence of the Ni mean particle size on TOF for a CO₂ hydrogenation at 300 °C and b ethene hydrogenation at 150 °C. The Supplementary Information S1 shows alternative plots, and an extensive literature search on both structure sensitive, and insensitive reactions. c, d Operando FT-IR spectra during CO₂ hydrogenation at 300 °C and ethene hydrogenation at 150 °C, respectively for three different mean particle sizes of Ni/SiO₂. X-ray absorption spectra (XAS) with 2 s time resolution obtained upon switching from pure H₂ after reduction, to either CO₂ (e) or ethene (f) hydrogenation. g, h absolute magnitude of change induced by the onset of catalysis (seen in e, f) at the Ni K-edge using the largest Δ, at 8333 eV and the second largest Δ at 8370 eV indicated by the dotted lines in (e, f) and normalized for available surface area, for CO₂ (g) and ethene (h) hydrogenation.