Vertically-aligned Co3O4 arrays on Ni foam as monolithic structured catalysts for CO oxidation: effects of morphological transformationElectronic supplementary information (ESI) available: The experimental section, experimental scheme for the in situ Raman experiment and the recycling and stability of NAs-8. See DOI: 10.1039/c8nr00147b

• Main Authors: Mo, Shengpeng, Li, Shuangde, Ren, Quanming, Zhang, Mingyuan, Sun, Yuhai, Wang, Bangfen, Feng, Zhentao, Zhang, Qi, Chen, Yunfa, Ye, Daiqi
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c8nr00147b

A generic hydrothermal synthesis route has been successfully designed and utilized to in situ grow highly ordered Co 3 O 4 nanoarray (NA) precursors on Ni substrates, forming a series of Co 3 O 4 nanoarray-based monolithic catalysts with subsequent calcination. The morphology evolution of Co 3 O 4 nanostructures which depends upon the reaction time, with and without CTAB or NH 4 F is investigated in detail, which is used to further demonstrate the growth mechanism of Co 3 O 4 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, H 2 -TPR, XPS, Raman spectroscopy and in situ Raman spectroscopy. As a proof of concept application, core-shell Co 3 O 4 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 (O ads ). It is confirmed that CO oxidation on the surface of Co 3 O 4 can proceed through the Langmuir-Hinshelwood mechanism via using in situ Raman spectroscopy. It is expected that the in situ synthesis of well-defined Co 3 O 4 monolithic catalysts can be extended to the development of environmentally-friendly and highly active integral materials for practical industrial catalysis. Advanced Co 3 O 4 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.