Carbon Surface Crowding and Subsurface Traffic Jam as Drivers for Methane Oxidation Activity and Selectivity on Palladium Surfaces

Separating how surface and subsurface species affect catalytic function is a challenging task in heterogeneous catalysis, particularly when deposition and segregation take place at reaction conditions. Here, we report on an operando approach to establish surface/subsurface/function correlations. Using temperature modulations we oscillate carbon deposition and segregation over a Pd catalyst. Catalytic composition and function are monitored during methane oxidation with time- and depth-resolved spectroscopy coupled with Fourier analysis. Hereby, we show that the surface coverage of carbon drives partial oxidation to CO, while the subsurface carbon controls the overall methane turnover. Also, we show that a carbon traffic jam in the subsurface leads to a shifting selectivity from H ₂ to H ₂ O formation.