Title: CO oxidation over gold nanoparticles on Mg(OH)2 and MgO subjected to different redox treatments

Authors: Eunice Vargas; Elena Smolentseva; Miguel Estrada; Sergio Fuentes; Andrey Simakov; Martin López-Cisneros; Sergey Beloshapkin

Addresses: Facultad de Ingeniería, Arquitectura y Diseño, Universidad Autónoma de Baja California, C.P. 22860, Ensenada, Baja California, Mexico ' Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana a Ensenada, C.P. 22860, Ensenada, Baja California, Mexico ' Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana a Ensenada, C.P. 22860, Ensenada, Baja California, Mexico ' Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana a Ensenada, C.P. 22860, Ensenada, Baja California, Mexico ' Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana a Ensenada, C.P. 22860, Ensenada, Baja California, Mexico ' Posgrado en Ciencia e Ingeniera de Materiales, Universidad Nacional Autónoma de México, Km. 107 Carretera Tijuana a Ensenada, C.P. 22860, Ensenada, Baja California, Mexico ' Materials & Surface Science Institute, University of Limerick, Limerick C.P. V94 T9PX, Ireland

Abstract: CO oxidation over gold nanoparticles (Au NPs) supported on magnesium oxide and magnesium hydroxide was studied at 30ºC during 15 h. Gold (~2.6 wt.%) was supported by deposition precipitation on commercial magnesia followed by thermal treatment of selected samples in hydrogen or in oxygen at different temperatures: 350 or 500°C. The formation of Au NPs during the phase transition of Mg(OH)2 to MgO under either reduction or oxidation was monitored by in situ UV-Visible spectroscopy, online mass analysis and X-ray diffraction (XRD). The Mg(OH)2 to MgO phase transition led to the decapsulation of ∼30% of the gold that had been encapsulated by the Mg(OH)2species during gold deposition from aqueous solution on MgO. The initial activity on CO oxidation was similar for Au NPs supported either on Mg(OH)2 or on MgO, and was practically independent the type of redox pre-treatment. In turn, the catalytic activity decay with reaction time strongly depended on the type of redox pre-treatment, pre-oxidised catalysts being more stable than pre-reduced ones. It was suggested that sample pre-treatment affects activity decay via change of the CO2-catalyst interaction.

Keywords: magnesium hydroxide; magnesium oxide; gold nanoparticles; CO oxidation; high temperature; UV-Vis spectroscopy; carbon monoxide; redox treatment; nanotechnology; catalytic activity.

DOI: 10.1504/IJNT.2016.074535

International Journal of Nanotechnology, 2016 Vol.13 No.1/2/3, pp.208 - 226

Available online: 04 Feb 2016 *

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