Methanol decomposition on palladium catalysts may provide hydrogen for direct methanol fuel cells. The understanding of this process also can provide insight into its reverse reaction, i.e., synthesis of methanol directly from syngas. One of the challenges is the palladium poisoned by the presence of carbon monoxide at low temperature (<250 °C).
In a combined scanning tunneling microscopy (STM), DFT and temperature-programmed desorption (TPD) study, Flytzani-Stephanopoulos and Sykes found that isolated Pd1 atoms alloyed with the Cu(111) surface showed high selective hydrogenation of styrene and acetylene.1 In this work, site-isolated Pd1 catalysts protected by atomic layer deposition (ALD) oxide thin films were used as the platform for methanol decomposition. STEM, XAFS and carbon monoxide adsorption DRIFTS confirmed the presence of isolated Pd1 sites which showed tuneable thermal stability depending on the thickness of ALD. In-situ Pd XANES revealed the surface coverage of H2 and CO on Pd surface. The Pd1 catalyst performance is found to be dependent on the oxide thin film thickness, type of oxide and promoters.
(1) Kyriakou, G.; Boucher, M. B.; Jewell, A. D.; Lewis, E. A.; Lawton, T. J.; Baber, A. E.; Tierney, H. L.; Flytzani-Stephanopoulos, M.; Sykes, E. C. H., Isolated Metal Atom Geometries as a Strategy for Selective Heterogeneous Hydrogenations. Science 2012, 335, 1209-1212.