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

Published online: 04 Feb 2016 *

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