Adsorption and Reactions of Formic Hydrazide on Cu(100) and O/Cu(100) Surfaces

Abstract

Adsorption and reactions of formic hydrazide on Cu(100) and O/Cu(100) are explored using temperature-programmed reaction/desorption (TPR/D) and reflection-absorption infrared spectroscopy (RAIRS) under ultra-high vacuum In the case of Cu(100) at 120 K formic hydrazide exists in multiple adsorption forms including (1) HC(O)-NH-NH2 and (2) HC(OH)=N=N?HO (or -HC(OH)-N≡N?HO) The first form possesses a carbonyl group with a measured infrared peak at 1642 cm-1 The second adsorption structure is generated from the transformation of the first one involving H-migration and N-H bond elongation (or breakage) and has infrared adsorption of 2094 cm-1 Hydrogen bonding exists between the adsorbed molecules Thermal decomposition of formic hydrazide on Cu(100) generates the products of H2 N2 H2O CON2H2 CO2 CO and NO N2 (239 K) H2O (239 K) and H2 (245 K) evolve below 300 K Between 250 K and 300 K an intermediate of HC(OH)N2 is present on the surface Upon heating to 365 K this intermediate is desorbed into vacuum likely in the form of H-C(O)-N=NH Eventually other unidentified surface species containing C O and N atoms further react to generate CO2 CO and NO at higher temperatures In the formic hydrazide/O/Cu(100) study the observed infrared absorption frequencies are similar to those of Cu(100) Moreover the thermal reaction of the adsorbed formic hydrazide produces the same products as those on Cu(100) However the amounts of the products are relatively small which may be due to the following reasons: (1) In the adsorption process of formic hydrazide the molecules approaching the O/Cu(100) surface may be blocked by the preadsorbed oxygen atoms and decrease in the possibility of adsorption due to steric and/or electrostatic repulsion (2) The preadsorbed oxygen atoms possibly occupy the active sites and therefore suppress the reaction of adsorbed formic hydrazide

Date of Award	2020
Original language	English
Supervisor	Jong-Liang Lin (Supervisor)