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.