Theoretical study of the water-gas shift reaction on a Au/hematite model catalyst

FUENTE SILVIA A; ZUBIETA C.; FERULLO RICARDO M; PATRICIA G. BELELLI

TOPICS IN CATALYSIS

SPRINGER/PLENUM PUBLISHERS

Lugar: New York; Año: 2019

1022-5528

Using the density functional theory, the mechanism of the water?gas shift reaction has been investigated employing a modelcatalyst formed by a Au5 cluster supported on the Fe-terminated (0001) face of hematite (α-Fe2O3), to better understandthe role played by the metal?oxide interface in this reaction. Our results indicate that the Au5/hematite model catalyst hasa good performance to catalyze the reaction following the so-called adsorptive mechanism. The presence of Au favors thedevelopment of the reaction due mainly to the following factors: (i) H2O dissociates very easily at the metal?oxide interfaceproducing OH species; (ii) CO adsorbs strongly on a Au site nearby the position of OH; (iii) the hydroxycarbonyl intermediate (HOCO) is formed at the interface from CO and OH with a low activation barrier; and (iv) after hydrogen releasing,CO2 is desorbed with relative facility from the interface region. The formation of H2 is the stage of the whole reaction thatmore energy demands; however, this process is favored if one hydrogen atom comes directly from HOCO, instead of fromtwo hydrogen atoms bound to surface oxygen anions.