Vertically-aligned Co₃O₄ arrays on Ni foam as monolithic structured catalysts for CO oxidation: effects of morphological transformation

Abstract

A generic hydrothermal synthesis route has been successfully designed and utilized to in situ grow highly ordered Co3O4 nanoarray (NA) precursors on Ni substrates, forming a series of Co3O4 nanoarray-based monolithic catalysts with subsequent calcination. The morphology evolution of Co3O4 nanostructures which depends upon the reaction time, with and without CTAB or NH4F is investigated in detail, which is used to further demonstrate the growth mechanism of Co3O4 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 Co3O4 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 Co3O4 can proceed through the Langmuir-Hinshelwood mechanism via using in situ Raman spectroscopy. It is expected that the in situ synthesis of well-defined Co3O4 monolithic catalysts can be extended to the development of environmentally-friendly and highly active integral materials for practical industrial catalysis.

Recent Advances in the Catalytic Oxidation of Volatile Organic Compounds: A Review Based on Pollutant Sorts and Sources

“…985,986 For this reason, extruded materials such as monoliths are ideal structures for supporting catalysts as they are typically exhibit high surface areas and possess numerous parallel channels, which reduces pressure drops across the catalyst bed. They are also highly tunable; monoliths can be produced in many different sizes and shapes, and can be synthesized from lots of different materials, including; metal wires, meshes or foams, [987][988][989][990] metallic or ceramic membrances, 109,991 and cordierite honeycomb materials, 992,993 which have attracted increasing attention due to their high mechanical strength and heat transfer capacity.…”

Enhancing catalytic toluene oxidation over MnO2@Co3O4 by constructing a coupled interface

“…6(c). The peak at about 529.7 eV is ascribed to the lattice oxygen (Olatt) species, and the shoulder peak at the higher binding energy of around 531.5 eV is assigned to the surface-adsorbed oxygen (Oads) species, which are directly associated with the catalytic activity of toluene oxidation [36,37]. In comparison with the cases of pure α-MnO2 and Co3O4-b, the molar ratio of Oads/Olatt in α-MnO2@Co3O4 is notably increased by decorating Co3O4 on α-MnO2, which is favorable to the catalytic oxidation of toluene over the α-MnO2@Co3O4 catalysts.…”

Bimetallic Pt-Co Nanoparticle Deposited on Alumina for Simultaneous CO and Toluene Oxidation in the Presence of Moisture

“…In recent years, with the progress of industrial development and the increased number of vehicles, the concentration of carbon monoxide (CO) and hydrocarbons (HCs) in ambient air is on the rise, causing the frequent occurrence of photochemical smog pollution in some areas and seriously threatening people's health [1][2][3][4][5][6][7][8][9]. However, controlling CO and HCs exhaust emissions can be an important direction to reducing air pollution.…”