Fig. 4: Mapping reaction front propagation in H2 oxidation on Rh.
a in situ PEEM image during an ongoing kinetic transition from the inactive to the active steady state on metallic Rh (T = 483 K, pO2 = 7.7 × 10−7 mbar, pH2 = 9.2 × 10−7 mbar) and a magnified ROI (15 × 50 µm2); b consecutive PEEM snapshots (10 s interval) for the ROI marked in a and respective intensity profiles for the front propagation on metallic Rh; c the corresponding front velocity map of metallic Rh, the colour scale is placed on the right; d and e are analogous to b and c, but for the oxidised Rh surface (T = 483 K, pO2 = 7.7 × 10−7 mbar, pH2 = 2.4 × 10−6 mbar); f front velocity difference for selected domains of the oxidised Rh surface relative to metallic Rh. Squares: measured values; the shaded area illustrates the trend; g velocity difference map, the colour scale (numerically corresponding to the ordinate in f), is placed on the right; h crystallographic orientations (Miller indices) of the Rh(hkl) domains indicated in g.
