Water–gas shift activity of Au and Cu nanoparticles supported on molybdenum oxides

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2008-02, Vol.281 (1), p.59-65
• Main Authors: Rodríguez, J.A., Liu, P., Hrbek, J., Pérez, M., Evans, J.
• Format: Article
• Language: English
• Subjects: Carbon monoxide; Catalysis; Chemistry; CO oxidation; Colloidal state and disperse state; Copper; Exact sciences and technology; General and physical chemistry; Gold; Hydrogen production; Molybdenum oxides; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Water; Water–gas shift
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2007.07.032

The water–gas shift (WGS, CO + H 2O → H 2 + CO 2) reaction was studied on a series of gold/molybdena and copper/molybdena surfaces. Films of MoO 2 were grown by exposing a Mo(1 1 0) substrate to NO 2 at 1000 K. Then, Au and Cu nanoparticles were deposited on the oxide surfaces and their WGS activity was measured in a reaction cell ( P CO = 20 Torr; P H 2 O = 10   Torr ; T = 575–650 K). Although bulk metallic Au is inactive as a catalyst for the WGS and worthless in this respect when compared to bulk metallic Cu, Au nanoparticles supported on MoO 2 are a little bit better catalysts than Cu nanoparticles. The WGS activity of the Au and Cu nanoparticles supported on MoO 2 is five to eight times larger than that of Cu(1 0 0). The apparent activation energies are 7.2 kcal/mol for Au/MoO 2, 7.8 kcal/mol for Cu/MoO 2, and 15.2 kcal/mol for Cu(1 0 0). The Cu/MoO 2 surfaces have a catalytic activity comparable to that of Cu/CeO 2(1 1 1) surfaces and superior to that of Cu / ZnO ( 0   0   0   1 ¯ ) surfaces. Post-reaction surface characterization indicates that the admetals in Au/MoO 2 and Cu/MoO 2 remain in a metallic state, while there is a minor MoO 2 → MoO 3 transformation. Formate- and/or carbonate-like species are present on the surface of the catalysts. DFT calculations indicate that the oxide support in Au/MoO 2 and Cu/MoO 2 is directly involved in the WGS process.