Abstract
Nanocluster formation of a metallic platinum (Pt) coating, on manganese oxide inorganic membranes impregnated with multiwall carbon nanotubes (K-OMS-2/MWCNTs), applied by reactive spray deposition technology (RSDT) is discussed. RSDT applies thin films of Pt nanoclusters on the substrate; the thickness of the film can be easily controlled. The K-OMS-2/MWCNTs fibers were enclosed by the thin film of Pt. X-ray diffraction (XRD), scanning electron microscopy/X-ray energy dispersive spectroscopy (SEM/XEDS), focus ion beam/scanning electron microscopy (FIB/SEM), transmission electron microscopy (TEM), and X-ray 3D micro-tomography (MicroXCT) which have been used to characterize the resultant Pt/K-OMS-2/MWCNTs membrane. The non-destructive characterization technique (MicroXCT) resolves the Pt layer on the upper layer of the composite membrane and also shows that the membrane is composed of sheets superimposed into stacks. The nanostructured coating on the composite membrane material has been evaluated for carbon monoxide (CO) oxidation. The functionalized Pt/K-OMS-2/MWCNTs membranes show excellent conversion (100%) of CO to CO2 at a lower temperature 200℃ compared to the uncoated K-OMS-2/MWCNTs. Moreover, the Pt/K-OMS-2/MWCNTs membranes show outstanding stability, of more than 4 days, for CO oxidation at 200℃.
Highlights
Manganese oxide K-octahedral molecular sieve (OMS)-2 is a porous mixed-valent metal oxide with applications in catalysis [1,2,3], environmental remediation [4], sorption processes [5], and microbial fuel cells [6]
Peaks for face centered cubic metallic Pt can be observed after deposition by reactive spray deposition technology (RSDT) [Figure 2(b) Pt/K-OMS-2/MWCNTs]. 1.17 wt % of metallic platinum was loaded in the composite membrane
The Pt precursor deposited on the K-OMS-2/MWCNTs membrane material was completely and successfully transformed into crystalline metallic Pt coating as depicted by the X-ray diffraction pattern, Figure 2
Summary
Manganese oxide K-OMS-2 is a porous mixed-valent metal oxide with applications in catalysis [1,2,3], environmental remediation [4], sorption processes [5], and microbial fuel cells [6]. Deposition of metals on K-OMS-2 membranes, in the open atmosphere, using a flame synthesis process has not been explored. This process constitutes a new cost-effective route to functionalize the inexpensive inorganic membrane and thereby incorporate new functionalities leading to improved performance in: capacitance, adsorption, and control over conversion and selectivity in catalysis. A simple, fast, and new deposition technique has been employed for the formation of a conformal, homogeneous coating of Pt on inorganic K-OMS-2 impregnated with MWCNTs (i.e., the membrane substrate). RSDT is a direct, dry flame based synthesis process and is configured to deposit directly onto a KOMS-2/MWCNT composite membrane [11,12,13,14,15,16]. The time of flight, zone temperature profile, stand-off distance, and locations of the quench are critical to formation of the desired metal and morphology [19]
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