Synthesis and hydrogenation of formate on Cu(100) at high pressures

In the commercial methanol catalyst, which consists mainly of copper particles highly dispersed on ZnO, copper is believed to be the active component. In order to address this role, the fundamental steps of the methanol synthesis have been investigated on a well defined Cu(100) single crystal under UHV conditions using x-ray photoelectron spectroscopy, low-energy electron diffraction, high-resolution electron energy-loss spectroscopy, temperature programmed desorption and high pressure facilities. The adsorption and desorption of H2, CO2, and HCOO (formate) were studied and it was proved that formate, which is believed to be an important intermediate in the methanol synthesis, can indeed be formed by exposing the Cu(100) crystal to a 2.3 bar mixture of H2 and CO2. The kinetics of this reaction step were studied in detail as a function of temperature. The activation energy was determined to be 55.6 kJ/mol. Further hydrogenation of the formate was found to be possible under high pressure conditions. The activation energy for this process was found to be 82 kJ/mol.