High-grade hydrogen for use in fuel-cell powered devices appears to be the answer to future energy demands. Active and inexpensive catalysts for the low-temperature water-gas shift (WGS) reaction (CO+H2O→H2+CO2) −used to decrease the CO concentration in the H2 produced from steam hydrocarbon reforming− are sought. Ni-CeO2 systems were shown to be active and selective catalysts for the WGS and ethanol reforming (ESR) reactions. 1-3 The difficulties in characterizing the surface structure of powder catalysts and in identifying the active sites −essential for rational catalysts design− have motivated the preparation/creation of experimental/theoretical model Ni/CeO2(111) catalysts at low Ni loadings. 3-5 Here, the emphasis is put on theoretical density-functional theory (DFT) studies and special attention is given to the effects of ceria as catalyst support. We compare Ni adatoms on CeO2(111), pyramidal Ni4 particles with one Ni atom not in contact with the support, and extended Ni(111) and CeO2(111) surfaces. We discuss the chemisorption properties for C, CO, and H2O and the activation barriers for H2O dissociation as a crucial step in the WGS reaction. The theoretical results are combined with ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and catalytic tests for WGS.

This work has been supported by the MINECO-Spain (CTQ2012-32928), the Ministry of Education of the Czech Republic (LH11017), and the U.S. Department of Energy (DE-AC02-98CH10886, DEAC02-05CH11231). J.C. acknowledges support by the Ramón y Cajal Fellowship, the Marie Curie Career Integration Grant FP7-PEOPLE-2011-CIG: Project NanoWGS. The COST action CM1104 is gratefully acknowledged.

Trabajo presentado en el 250th ACS National Meeting, celebrado en Boston (Estados Unidos) del 16 al 20 de agosto de 2015.

Peer Reviewed