Irregularly Shaped NiO Nanostructures for Catalytic Lean Methane Combustion
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Abstract
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NiO nanomaterials prepared using a solid–liquid NH3·H2O precipitation
method (NiO-NSL) were tested in the catalytic combustion of methane.
The NiO-NSL presented a characteristic rod-like nanostructure with a
length of about a few hundred nanometers except for a part of the
nanoparticles. For comparison, the NiO nanomaterials prepared by the
traditional liquid-phase NH3·H2O precipitation method (NiO-NLL) were
tested in the same reaction conditions. NiO-NSL exhibited
significantly higher methane combustion activity than NiO-NLL and
achieved the complete combustion of methane at 390 °C, which was
outstanding in non-noble metal-based catalyst. X-ray photoelectron
spectroscopy (XPS) and hydrogen-temperature-programmed reduction
(H2-TPR) results indicate that the surface Ni2+ content of NiO-NSL
was higher than that of NiO-NLL, and the presence of more Ni2+ might
be responsible for the enhanced activity. DFT calculations prove
that the energy barrier for C–H bond activation on Ni2+ was lower
than that on Ni3+, which was consistent with the higher methane
catalytic combustion activity of NiO-NSL. In addition, when the
precipitating agent was replaced with NaOH and (NH4)2CO3, the
generalization of the solid–liquid precipitation method in the
preparation of the NiO catalysts was also tested. The results show
that the solid–liquid precipitation method proposed in this work was
still applicable when NaOH was used as a precipitant. However, with
the use of (NH4)2CO3 as a precipitant, the methane catalytic activity
of the NiO nanoparticles prepared by the solid–liquid precipitation
method was reduced to a certain extent compared with the traditional
liquid-phase precipitation method. This research can open up a
highly efficient and environmentally friendly method for the
synthesis of methane combustion catalysts.
Keywords
TP Chemical technology