Gas-phase coupling of reactive surfaces by oscillating reactant clouds

The collective, global behavior of a heterogeneous catalytic system depends on the effective communication of local reactivity variations to distant points in the system. One particularly efficient mode of communication occurs via partial pressure fluctuations in the gas-phase above the reactive surface. Although gas-phase communication has been implicated in a number of heterogeneous systems, the details of this coupling mechanism are lacking due to experimental difficulties in addressing local variations in surface and gas-phase activity simultaneously. Here, we take advantage of a spatially distributed system of isolated chemical oscillators to investigate the details of gas-phase communication in the 10−3 mbar range. Characterization of local gas-phase oscillations, in parallel with kinetic oscillations on the surface, provides a novel description of the surface/gas-phase interaction under reaction conditions. This analysis further allows for a quantitative estimate of the effective gas-phase coupling length scale observed in surface imaging experiments.

Angular CO uptake associated with kinetic oscillations on a single grain (outlined in white) of a polycrystalline Pt foil. Ultimately, the expanse of the CO adsorption distribution above a single grain will determine the spatial limits for the synchronization of activity on distant grains and in turn global catalyst performance (pO2pO2 = 2.4 × 10−3 mbar, pCO = 1.5 × 10−4 mbar, T = 534 K).Figure optionsDownload high-quality image (50 K)Download as PowerPoint slide