In-situ fabrication of noble metal modified (Ce, Zr)O2−δ monolithic catalysts for CO oxidation

Abstract

The CeO2-ZrO2 solid solution ((Ce, Zr)O2) has long been utilized in catalytic industry due to its enhanced oxygen storage/release capacity (OSC/ORC) and outstanding thermal stability. In this study, (Ce, Zr)O2−δ monolithic catalysts are successfully in-situ fabricated on flexible titanium mesh through traditional plasma electrolytic oxidation (PEO) method. The surface Ce, Zr atomic percentages (at.%) of the as-prepared catalysts can be widely tailored through the change of the mass ratio of Ce2(SO4)3 and Zr(SO4)2 in the initial electrolyte during PEO process. XRD test in accompany with Raman study reveals the existence of cubic CeO2, stable/metastable tetragonal phases (t, t′ phases) and Ce, Zr containing amorphous phase in the catalysts. XPS analysis shows the non-stoichiometric feature of the as-prepared monolithic catalysts while the TEM characterization indicates the nanocrystalline nature of the (Ce, Zr)O2−δ catalysts. After noble metal (Au, PdO) modification, the monolithic catalysts show remarkable CO oxidation activities. The PdO/Ce75Zr25 sample shows the best catalytic activity with a lowest CO oxidation temperature of 135 °C. This study establishes an efficient in-situ fabrication strategy toward the preparation of CeO2-ZrO2 solid solution on flexible valve metal substrates with good substrate adherence, which is advantageous and promising for the direct integration of various oxide catalysts toward CO oxidation, TWCs, SCR, etc.