Adsorption and reaction of HCOOH on K-promoted Pd(100) surfaces

Abstract

The adsorption and reaction of formic acid on clean and K-promoted Pd(100) surfaces have been studied with thermal desorption mass spectrometry (TDS), electron energy loss spectroscopy (EELS), ultraviolet photoelectron spectroscopy (UPS) and work function change. Formic acid adsorbs molecularly on a clean Pd(100) at 90–100 K, and decomposes below 200 K to give CO and H 2. No spectroscopic evidence was found for the intermediate formation of formate. Preadsorbed potassium increased the uptake of formic acid, it altered the product distribution of the surface decomposition and it induced the formation of formate species. It is assumed that formic acid interacts directly with potassium adatoms to give a stable HCOOK like species which decomposes completely only above 400 K. The products of the decomposition, CO, CO 2 and H 2 are strongly stabilized by potassium.