The particle size dependence of CO oxidation on model planar titania supported gold catalysts measured by parallel thermographic imaging

•A parallel thermographic screen allows measurement of particle size and support effects on model planar catalysts.•The turn over frequency (TOF) of an exothermic reaction can be determined simultaneously on 100 catalysts.•The catalytic activity for CO oxidation of titania supported gold with particle sizes 6 > d/nm > 1.5 has been measured.•A monotonic increase in the TOF is observed with decreasing particle diameter (d) which is proportional to ca. d−1.8.•Calculation of the gold surface area evidences a surface specific activity of the gold which increases as ca. d−4.•The steep rise in activity suggests an electronic perturbation of the gold nano-particles by the substrate.