A relaxor ferroelectric polymer exhibits record electromechanical performance, including the largest electrostrain of −13.4%, the highest elastic energy density of 3.1 J cm−3 and the best energy conversion efficiency of 0.5, among the known ferroelectric polymers. Notably, the excellent electromechanical responses are realized under much lower fields than those of ferroelectric polymers.
We
present a facile selective dissolution method for the surface
modification of SmMn2O5 mullite (SMO) to increase
the exposed sites for NO oxidation on the premise of excellent thermal
stability. Surface Sm cations are partially removed during the treatment
(SMO-H), leading to the exposure of B-site cations with higher electronegativity
and oxygen vacancies. Under laboratory-simulated diesel combustion
conditions, the SMO-H exhibits higher NO oxidation activity than the
SMO and is comparable to that of the Pt/Al catalyst under a gas hourly
space velocity (GHSV) of 120 000 mL g–1 h–1. In addition, the SMO-H possesses good thermal and
steam stability during a 50 h test at 300 °C. X-ray absorption
spectroscopy (XAS) and electron paramagnetic resonance (EPR) spectroscopy
results reveal that the SMO-H presents more Mn4+O6 octahedral groups and oxygen vacancies than the SMO. In situ diffuse
reflectance infrared Fourier transform spectroscopy (DRIFTS), near-ambient
pressure X-ray photoelectron spectroscopy (NAP-XPS), and density functional
theory (DFT) calculations show that the valence of surface Mn decreased
after NO capture up to 300 °C and fulfilled the adsorption procedure
as nitrite and/or nitrate species when O2 is involved in
the flue gas. The results indicate that Mn-terminated surface rather
than Sm-terminated one is the major adsorption site for NO.
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