A theoretical exploratory study of low-energy (1-2 eV) electron catalysis in the CO2+H-2 -> HCOOH gas phase process

It is shown that electron capture by a reactant may catalyze condensation r eactions that otherwise would require higher activation energies in the neu tral state. Two competitive processes have been examined in the CO2H2 syste m: (a) CO2 + H-2 --> HCOOH, (b) CO + H2O --> HCOOH, of which only (a) is li kely to occur through electron activation. Upon electron capture (threshold around 1 eV), bent hot CO2 reacts with Hz via a stepwise path, leading to formic acid with an overall activation energy close to 2 eV (neutral activa tion energy 3.17 eV). In the 2 eV energy range, a close contact (HCOO-...H- .) complex is formed. After electron detachment, a diradical (HCOO. + H-.) system results which spontaneously yields HCOOH. The electron is re-emitted with approximately its initial energy so that it can be regarded as a true catalyst for this reaction. (C) 2000 Elsevier Science B.V. All rights rese rved.