Stability of hydroxy-formate species at a Pb(110) surface

Chemisorbed surface hydroxy-formate species on Pb(110), formed by reacting gaseous HCOOH with pre-adsorbed atomic oxygen, yields O(1s) and C(1s) photoelectron peaks at 531.3 and 288.3 eV, respectively. The three desorption features can be assigned as multilayer HCOOH at 190 K, a monolayer formic acid at 230 K and a metastable state (hydroxy-formate) at 300 K. Heating the overlayer in vacuum to 450 K results in removal of all surface hydroxyl although the higher temperature peak which corresponds to the recombination of surface protons with formate species remains stable. The formate species desorbs partially from the metal surface with extensive decomposition as shown by a large C(1s) residue at ∼285.0 eV.