Weakly chemisorbed ammonia species at a Cu(110) surface

Abstract

Non-dissociative adsorption of ammonia on a Cu(110) surface leads to the formation of two distinct entities between 80 and 298K. A single XP N(ls) peak at 401 eV and the VEEL spectra characterize the alpha ammonia species which is primarily physically coordinated to surface sites via diverse types of hydrogen bonds. The beta picture is clearly evident by the persistent R-xy mode at 410 cm(-1). Direct interaction between the 'monolayer' and most of the 'overlayer' NH3 groups reduces the Bronsted acidity of surface copper atoms. No N-H bond rupture occurs prior to the transformation of the beta pattern back into the form and an ammonia-free surface is regenerated eventually.