Evolution of microstructure induced by calcination in leached Al-Cu-Fe quasicrystal and its effects on catalytic activity

Effects of calcination on catalytic activity for steam reforming of methanol (SRM) over an Al-Cu-Fe quasicrystal (QC) leached with NaOH aq. have been investigated in terms of microstructure with X-ray diffraction and transmission electron microscope (TEM). Calcination at 600 °C in air drastically improved the catalytic activity of the leached QC. TEM observations on cross-section of the samples revealed that cubic Cu _x Fe _3-x-y Al _y O₄ spinel was formed at the outermost layer of the leached QC after calcinations. Prior to the catalytic reaction, the Cu _x Fe_3-x-y Al _y O₄ spinel decomposed to a composite where fine Cu nanoparticles dispersed in (Fe,Al)₃O₄ matrix under H₂ treatment at 300 °C. Drastic increase in catalytic activity is responsible for the fine Cu nanoparticles in the composite. The Cu nanoparticles sit along the same orientation with (Fe,Al)₃O₄, e.g., Cu [013]//(Fe,Al) ₃O₄ [013] and Cu [200]//(Fe,Al)₃O₄ [400]. This orientation relationship may stabilize the Cu nanoparticles through a bonding of Cu-O-Fe.