아크 플라즈마 기술을 이용한 삼원촉매 표면의 Pt 열화 특성 향상

Abstract

The objectives of this study are to develop highly dispersed Pt nanoparticles by pulsed Arc plasma deposition (APD) method and to select anchoring materials through quantum chemical calculation (QCC) approach. Arc Plasma deposition method was used to deposit Pt nanoparticles onto gamma alumina based powders from a Pt metal cathode. Deposited Pt nanoparticles exhibited a higher dispersion and thus showed higher catalytic activity for NOx, CO and HC conversion, compared to conventional Pt/Al2O3 catalyst prepared by the impregnation method. Through the first principle calculations Fe and Mn metal aluminate were selected as anchoring materials by considering the lattice constant, surface energy, interfacial energy, wetting angle and adhesion and VASP(Vienna Abinitio Simulation Package) was used as a calculation package. The Fe and Mn aluminate catalysts were prepared by co-gelation precipitation precipitation and impregnation methods indicated the absence of spinel structure. The samples prepared by APD using Pt and Fe targets over alumina support in the presence of oxygen showed better dispersion and hgih thermal stability. Further QCC modeling of electron energy level of PtO2/CeO2, PtO2/Al2O3, PtO2/TiO2 and PtO2/ZrO2 results revealed that the PtO2/CeO2 showed the lowest (-6.645 eV) energy level followed by PtO2/Al2O3 than the others. On the basis of these QCC results, CeO2-Al2O3 support was selected for sample preparation by deposition precipitation and co-precipitation methods. Pt deposited by APD over CeO2-Al2O3 which was prepared by co-precipitation attributed fine dispersion of Pt and PtO2 with high thermal stability. The catalysts were comprehensively characterized by BET-SA(Brunauer Emmett Teller-Surface Area), TEM(transmission electron microscopy), XPS(X-ray Photoelectron Spectroscopy), H2-TPR(temperature programmed reduction) and NO-TPD(temperature programmed desorption) with QMS(Qaudrupole Mass Spectrometer). Thermal stability at 950ºC for 3h under 1% O2 of Pt deposited CeO2-Al2O3 catalysts showed high sintering stability confirmed by TEM images. This may be due to the anchoring effect of CeO2. Moerover, the Pt/CeO2-Al2O3 catalysts showed higher catalytic activity for NOx, CO and HC conversion at low temperature.