Vertically-aligned Co3O4 arrays on Ni foam as monolithic structured catalysts for CO oxidation: effects of morphological transformation. Issue 16 (16th April 2018) - Mo, Shengpeng
Abstract : Advanced Co3 O4 nanoarray-based monolithic catalysts with a stable structure and morphology can be successfully designed and utilized to in situ grow on Ni substrates, which were investigated for catalytic CO oxidation. Abstract : A generic hydrothermal synthesis route has been successfully designed and utilized to in situ grow highly ordered Co3 O4 nanoarray (NA) precursors on Ni substrates, forming a series of Co3 O4 nanoarray-based monolithic catalysts with subsequent calcination. The morphology evolution of Co3 O4 nanostructures which depends upon the reaction time, with and without CTAB or NH4 F is investigated in detail, which is used to further demonstrate the growth mechanism of Co3 O4 nanoarrays with different morphologies. CO is chosen as a probe molecule to evaluate the catalytic performance over the synthesized Co-based oxide catalysts, and the effect of morphological transformation on the catalytic activity is further confirmed via using TEM, H2 -TPR, XPS, Raman spectroscopy and in situ Raman spectroscopy. As a proof of concept application, core–shell Co3 O4 NAs-8 presenting hierarchical nanosheets@nanoneedle arrays with a low density of nanoneedles exhibits the highest catalytic activity and long-term stability due to its low-temperature reducibility, the lattice distortion of the spinel structure and the abundance of surface-adsorbed oxygen (Oads ). It is confirmed that CO oxidation on the surface of Co3 O4 can proceed through the Langmuir–Hinshelwood mechanism via using in situ Raman spectroscopy. It is expected that the in situ synthesis of well-defined Co3 O4 monolithic catalysts can be extended to the development of environmentally-friendly and highly active integral materials for practical industrial catalysis.