Hydrogen atom reactions with graphite island edges on Pt(111) surfaces: hydrogenation through Eley-Rideal and hot-atom processes

Graphite islands of various coverages were prepared on Pt(lll) surfaces by thermal decomposition of ethane. The reactions of gaseous H (D) atoms with these islands were investigated at 90 and 380 K substrate temperatures with LEED, AES, TDS and HREELS methods. Armchair and zig-zag edge C atoms at the graphite islands react with H (D) to form monohydride CH (CD) groups with sp(3) type bonding. CH armchair groups decompose at 600 K and CH zig-zag groups at 650 K causing hydrogen desorption via first order processes. H atoms react with C edge atoms through direct Eley-Rideal as well as hot-atom processes, in which H precursors on the bare Pt surface fraction are involved. (C) 1999 Elsevier Science B.V. All rights reserved.