A surface study on model Pd(111) catalyst modified with boron

Abstract

A number of studies have been devoted to borided Group VIII metals as selective hydrogenation catalysts. The present results are a first attempt to characterize formation and behaviour of Pd(111)-B modified surface. The Pd(111) sample was exposed (UHV, 300 K) to diborane, B 2H 6, and subsequently investigated by LEED, AES and TDS. (1) The dissociative B 2H 6 adsorption resulted in hydrogen and boron ad- and absorption; the B concentration in the Pd(111) surface layer was determined from AES. (2) The distinct O 2-induced surface segregation of B absorbed in Pd(111) ( T⩾ 600 K, 2 × 10 −6 < p O 2 < 1 × 10 −5 Pa) was stable B x O y adspecies was forming. (3) The presence of both kinds of borided Pd surfaces in catalytic systems has been discussed.