Strong metal-support interactions are known to enhance the selectivity of platinum catalysts supported on reducible oxides for selective partial hydrogenation catalysis. Using crotonaldehyde hydrogenation as a model reaction, we investigate the mechanism of enhanced selectivity by platinum-cerium oxide catalysts. Results show that surface reaction kinetics are strongly dependent on the mesoscale morphology of cerium oxide nanocubes deposited on a planar platinum surface. Electron microscopy shows that oxide nanocubes form 2-dimensional aggregates during deposition, giving rise to two distinct platinum-cerium oxide interfaces: 1) the nanoscale interface defined by the boundary between an individual cerium oxide nanocube and the platinum catalyst and 2) the mesoscale interface defined by the boundary around an aggregate of nanoparticles and the surrounding clean platinum surface. Kinetic studies reveal that activity for selective hydrogenation of crotonaldehyde to crotyl alcohol scales with the larger, mesoscale interface. Using ambient pressure XPS, we investigate the mechanism of this support effect. Results show that cerium oxide reduction by H spillover is insensitive to the mesoscale morphology of cerium oxide nanocubes. Further we find that platinum decoration by reduced ceria is not observed under the reaction conditions tested. We discuss the nature of the active site and possible reaction mechanisms in light of these findings.<br/>

Platinum-cerium oxide catalysts studied by ambient pressure X-ray photoelectron spectroscopy

256th National Meeting (2018)

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