Ag nanowires as precursors to synthesize novel Ag-CeO2 nanotubes for H2 production by methanol reforming

Novel Ag-CeO2 nanotubes were synthesized by the precipitation method based on preformed Ag NW added as active phase precursors. This nanotubular material was used as catalysts to evaluate the methanol reforming reaction for H-2 production. Nanotubular structures with an external diameter from 120 to 280 nm and internal diameter from 40 to 80 nm were identified by electron microscopy techniques. These nanostructures were mainly composed of CeO2 nanoparticles (similar to 11 nm). The X-ray powder diffraction patterns of the Ag-CeO2 nanotubes showed diffraction peaks characteristic of the cubic structure of the CeO2 and metallic Ag. No diffraction peaks corresponding to those of the Ce-Ag alloys or other impurities were found in these samples. The catalytic activity was improved as the nanotubes concentration was increased in the catalysts. However, the H-2 production was diminished, so, an increase in the Ag particle size promotes the methanol combustion, decreasing hydrogen production and increasing the water formation as well as the CO2 production. It seems that the Ag is the phase mainly responsible of hydrogen production although the large particles reduce the CO formation. (C) 2012 Elsevier B. V. All rights reserved.