Speaker
Description
Indium oxide (In2O3) has recently received considerable attention in the catalysis community due to its unexpectedly high selectivity in the hydrogenation of CO2 to methanol.1 Metal deposition onto In2O3 substantially promotes the activity, while the selectivity remains close to that of bare In2O3 independent of the metal used.2,3 To get insight into the metal/In2O3 interaction and the role of the metal/oxide interface in the CO2 hydrogenation reaction, we performed Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) study of “inverse” model catalysts prepared by In oxide deposition onto a Ru(0001) substrate. The In2O3(111) film grows on Ru(0001) via the Volmer-Weber growth mode, forming bulk-like In2O3(111) islands from the onset. NAP-XPS measurements of the In2O3(111) films of various film thickness revealed the formation of metallic In species at 200 - 280°C in pure H2 and CO2 + H2 atmosphere if In2O3 partially covers the Ru surface, and not on the dense films. The In(0) formation is assisted by facile H2 dissociation on the Ru surface, and H ad-atoms react at the interface to In2O3. XPS results obtained for the reference system prepared by direct In deposition onto the partially covered films show that metallic In formed in the H2 atmosphere remains at the In2O3/Ru interface and do not migrate onto Ru to form a surface alloy.
