Characterization of new catalysts prepared by in-situ activation of Ce₅₀Ni_50-xAu_x intermetallic compounds for CO oxidation

In this study, catalysts for CO oxidation were prepared through in-situ activation of Ce₅₀Ni_50-xAu_x intermetallic compounds and characterized; these included Ce₅₀Ni₅₀ and Ce₅₀Ni₄₅Au₅. Ribbon samples of intermetallic compounds were fabricated by single-roller melt spinning and then ground into powders for subsequent analysis. XRD patterns of the compounds were indexed as orthorhombic symmetry and no second phase was detected within the limits of low XRD resolution, indicating a homogeneous nature. Among the catalysts evaluated, the metal-oxide complex consisting of Ni–Au and CeO₂, synthesized from the in-situ activation of Ce₅₀Ni₄₅Au₅ compounds, showed a better catalytic activity for CO oxidation. In the presence of CO, Ce oxidation is thermodynamically favored while Ni oxidation is inhibited. The catalyst of the metal-oxide complex prepared from the Ce₅₀Ni₄₅Au₅ compound revealed the CO conversions of 28.1%, 76.3%, 96.3% and 97.1% at reaction temperatures of 100 °C, 150 °C, 200 °C and 250 °C, respectively. SEM results revealed that a large quantity of fine Au–Ni particles were distributed on the CeO₂ support after thermal treatment, which contributed to the high CO conversion over the Ce₅₀Ni₄₅Au₅ compound at temperatures below 200 °C. Compared with the results in the literature, the high catalytic activity of the Ce₅₀Ni₄₅Au₅ intermetallic compound, with a low Au loading of 7.6 wt% and a low surface area of 1.1 m²/g, displayed the most beneficial characteristics for practical applications.