Imaging the dynamics of catalysed surface reactions by in situ scanning electron microscopy

Analytical methods that provide direct real-space information about the dynamics of catalysed reactions often require simplified model systems and operate under high-vacuum conditions. There is thus a strong need for the development of methods that enable observation of active catalysts under relevant working conditions. Here, in situ scanning electron microscopy is employed to study reaction dynamics and structure–activity correlations on surfaces. High sensitivity to changes in the work function and surface composition enables the detection of monolayers of adsorbed molecular species on metal surfaces, which is used here to visualize catalytic NO2 hydrogenation on platinum. The initiation of reactive behaviours and propagation of reaction fronts, as well as the spillover of activated species revealed in real-time and across a large pressure range, demonstrate the power of in situ scanning electron microscopy as a surface science tool in the study of gas-phase- and temperature-induced processes. In situ studies of catalytic surface reactions are restricted to a small number of analytical techniques. Here, scanning electron microscopy is utilized to visualize the catalytic hydrogenation of nitrogen dioxide on platinum, showing its potential for monitoring reaction dynamics on surfaces.