Surface-nitrogen removal in NO and N 2O reduction on Pd(1 1 0): Angular distribution studies of desorbing products

Abstract

This paper is a report of angle-resolved product desorption measurements in the course of catalyzed NO and N 2O reduction on Pd(1 1 0). Surface-nitrogen removal processes show different angular distributions, i.e. normally directed N 2 desorption takes place in process (i) 2N(a) → N 2(g). Highly inclined N 2 desorption towards the [0 0 1] direction is induced in process (ii) N 2O(a) → N 2(g) + O(a). N 2O or NH 3 desorption follows the cosine distribution characterizing the desorption after the thermalization in process (iii) N 2O(a) → N 2O(g) or (iv) N(a) + 3H(a) → NH 3(a) → NH 3(g). Thus, a combination of the angular and velocity distributions provides the analysis of most of surface-nitrogen removal processes in the course of catalyzed NO reduction. At temperatures below 600 K, processes (ii) and (iii) dominate and process (iv) is enhanced at H 2 pressures higher than NO. Process (i) contributes significantly above 600 K. Only three processes except for NH 3 formation are operative when CO is used. Only process (ii) was observed in a steady-state N 2O + CO (or H 2) reaction.