OMS-2
catalysts exhibit excellent selective catalytic reduction
(SCR) activity at low temperature but weak H2O resistance
restricts its industrial application. To remarkably improve the water
resistance of Mn-based catalysts is a key technical problem. In this
work, the H2O endurance and self-cleaning properties of
OMS-2 catalysts are remarkably improved by the facile process, construction
of hydrophobic coating. The performance of the hydrophobic layer on
the bulk OMS-2 catalyst surface could be effectively controlled by
adjusting the polydimethylsiloxane (PDMS) vapor deposition temperature.
It is discovered that the 200 °C catalyst obtained super hydrophobic
properties and formed with a contact angle of 160.3°, which not
only exhibited satisfactory NH3-SCR activity at low temperatures
(140–300 °C) but also dramatically improved H2O endurance and self-cleaning performance. Moreover, the mechanism
of improving H2O resistance and stability of the 200 °C
catalyst was investigated in detail through a series of characterizations.
Although the SCR activity of the 200 °C catalyst decreased slightly
because of the combination of some active species (Oα and Mn3+) with PDMS, the H2O passivation of
the active species was eliminated. The advantage of self-cleaning
was confirmed by the analysis of surface species and simulation experiments,
which could avoid the accumulation of intermediates on the surface
and promote the stability of the OMS-2 catalyst for NH3-SCR at low temperature. This method of constructing special coating
might be a huge step to remarkably improve the H2O endurance
properties of the catalyst and provided a new concept for future industrial
application.
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