BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:SIZE AND SHAPE DEPENDANCY OF CO ADSORPTION ON Pd14 AND Pd55 NANOCL USTERS: DFT AND FTIR STUDIES DTSTART;VALUE=DATE-TIME:20160705T090000Z DTEND;VALUE=DATE-TIME:20160705T100000Z DTSTAMP;VALUE=DATE-TIME:20260808T225442Z UID:indico-contribution-1255@indico.inp.nsk.su DESCRIPTION:Speakers: Yury Rusalev (Southern Federal University)\nPalladiu m is a very effective catalyst for the oxidation of CO. This reaction is v ery important for reducing automotive and industrial emissions and conside red to be a good model for fundamental studies of transition metal catalys ts. It is known that different types of facets as well as size and shape o f a metal nanoparticle have an effect on catalyst properties. The scope of our work is to investigate how the reactivity of Pd nanoparticles towards CO oxidation depends on their size and shape. The keys to the solution ar e ab-initio DFT calculations in combination with in-situ FTIR spectroscopy . For theoretical part\, we have chosen the set of Pd clusters of differen t size and respective shape. After optimization of their geometry\, the ad sorbed CO molecules were relaxed at the top-on positions of cluster surfac e. That allowed us to generate IR spectra to be compared with experimental ones of CO adsorbed on Pd nanoparticles. In order to be closer to the ind ustrial-type processes\, a special setup allowing in-situ FTIR measurement s was designed as well. \n In our theoretical studies we used both molec ular orbital (ADF-2014) and periodic band structure (VASP 5.2) DFT calcula tion schemes to model small metallic Pd clusters. The basis in calculation s was chosen as Triple Zeta with one polarization function and frozen core . We used standard GGA approximation within PBE scheme. Occupations steep est descend method was used for better geometry convergence. All the param eters mentioned above with Scalable SCF gave good convergence in all crite ria. The cutoff energy for periodic plane wave pseudopotential simulation was set to 400eV. The cell around Palladium clusters was constructed as a cubic one with 30 nm edge. A single K-point was used in simulation.\nIn th is work we constructed and optimized geometry of Pd14 and Pd55 clusters wi th octahedral symmetry. The relaxed interatomic distances (Angstom) of Pal ladium 55 cluster with CO molecules placed on top hollow sites of Pd obtai ned by both ADF and VASP DFT calculation schemes are presented in Table 1. \n\nTable 1. The relaxed interatomic distances (Å) of Pd-55 cluster with CO\n\n ADF VASP 5.2\n\n Pd-C 2.052 2.042\n C-O 1. 198 1.200\n\nIR spectra for different configurations were obtained dur ing the calculation. For example main peaks are at 2107 and 503 cm-1.\nBot h CO adsorption and oxidation on Pd nanoparticles have been studied extens ively with different experimental techniques [R1]. It is assumed that reac tion of CO oxidation follows a Langmuir-Hinshelwood mechanism [R2]\, where both reactants\, CO and O2\, adsorb on the catalyst surface prior to reac tion between the adsorbed species to form CO2. There were also found some differences in the kinetics among the (111)\, (110)\, and (100) planes in studies on single crystals of Pd [R3]. Significant number of experimental studies of CO adsorption on surface of Pd have been performed by using Dif fuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). DRIFTS is a useful technique for probing catalysts at catalytically relevant temp eratures and pressures without intense sample preparation [R4]. \nOur expe rimental setup for in-situ DRIFT studies of CO adsorption on Pd nanopartic les as main components includes Vertex 70 FTIR spectrometer\, Praying Mant is Diffuse Reflection Accessory equipped with Low and High Temperature Rea ction Chambers and a two-channel gas mixing system assembled by using the Swagelok tube fittings.\n\n\nReferences\n\n[R1] Janos Szanyi\, W. Kevin Ku hn\, and D. Wayne Goodman J. Phys. Chem. 1994\, 98\, 2978-2981\n[R2] Oh\, S.H.\; Fisher\, G. B.\; Carpenter\, J. E.\; Goodman\, D. W. J. Catal. 198 6\, 100\, 360\n[R3] Xu\, X.\; Szanyi\,J.\; Goodman\, D. W. Catal. Today\, 1994\,. 21\, 57.\n[R4] Griffiths\, P. R.\; Haseth\, J. A. d. Fourier Trans form Infrared Spectrometry\, 2nd ed.\; John Wiley & Sons: New York\, 2007. \n\nhttps://indico.inp.nsk.su/event/3/contributions/1255/ LOCATION:Budker INP 2nd and 3rd floors URL:https://indico.inp.nsk.su/event/3/contributions/1255/ END:VEVENT END:VCALENDAR