Surface Science 453 (2000) 103–111 www.elsevier.nl/locate/susc NO and deuterium co-adsorption on the reconstructed Pt(100)-hex surface: a temperature programmed reaction study E.I. Vovk * , M.Yu. Smirnov, D. Zemlyanov 1 Boreskov Institute of Catalysis, Pr. Ak. Lavrentieva, 5, Novosibirsk 630090, Russia Received 16 September 1999; accepted for publication 20 January 2000 Abstract The deuterium adsorption at 270 K on a reconstructed Pt(100)-hex surface covered by NO ads was studied by means of temperature programmed reaction (TPR). In the case of adsorption on a clean Pt(100)-hex surface the saturated D ads coverage is 0.06 ML at P H 2 =6×10−8 mbar, whereas the D ads uptake is enhanced considerably by NO pre-adsorption. First the D ads uptake increases with increasing NO ads coverage, h NO , reaching a maximum at h NO #0.25 ML, and then decreases to zero. This phenomenon is explained as follows. The NO adsorption on the hex surface leads to the formation of 1×1 islands saturated by NO ads and surrounded by the hex phase. The NO ads /1×1 islands are assumed to modify the hex phase adjacent to the island boundaries, adapting this area for deuterium adsorption. TPR in the co-adsorption layer of NO ads and D ads is initiated by D 2 desorption and shows an ‘explosive’ behaviour, manifesting itself in the narrow TPR peaks of N 2 and D 2 O at ~370 K. The NO ads pre-coverage affects the reaction temperature as well. Thus, at NO ads coverage of 0.35–0.40 ML the temperature of the surface explosion increases abruptly by ~15–20 K. At this coverage the NO ads /1×1 islands are supposed to modify the rest of the hex phase so that, after further D 2 adsorption, the surface becomes completely saturated by D ads and NO ads species. A possible mechanism for this is discussed. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Deuterium; Hydrogen molecule; Nitrogen oxides; Platinum; Surface relaxation and reconstruction 1. Introduction propagation of periodic surface concentration waves, and ‘surface explosions’ [1,2]. The Pt(100) The Pt(100) surface is an attractive object for surface can exist in two different structures — a researchers in the field of heterogeneous catalysis reconstructed hexagonal hex phase and an unre- due to the fact that a number of reactions on this constructed 1×1 phase; these can transform into surface, including NO+H 2 , show fascinating each other depending on the temperature and phenomena such as sustained kinetic oscillations, chemical composition of the adsorption layer [3– 5]. The hex and 1×1 surfaces exhibit dramatically * Corresponding author. Fax: +7-3832-343056. different adsorption and catalytic properties. E-mail addresses: vovk@catalysis.nsk.su (E.I. Vovk), The adsorption of hydrogen on unreconstructed dzem@wpi.edu (D. Zemlyanov) Pt(100)-1×1 and reconstructed Pt(100)-hex sur- 1 Present address: Worcester Polytechnic Institute, 100 Institute Road, Worcester, 01609 MA, USA. faces has been studied in detail [6–15]. The adsorp- 0039-6028/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S0039-6028(00)00311-3