Hydrogenation of CO2 to methanol is attracting enormous attention because of its importance in industrial applications and also in utilization of CO2 to reduce the emission of greenhouse gas to the atmosphere. Formate (HCOO) synthesis is an important but slow step in the methanol synthesis and suggested to take place by the Eley-Rideal (ER) mechanism. Since formate synthesis and decomposition are reverse reactions to each other, investigation of desorbed CO2 from formate decomposition must give useful information to enhance the formate synthesis process. We performed ab initio molecular dynamics (AIMD) simulations to elucidate the dynamics (translational, rotational, and vibrational) of desorbed CO2 as a product of formate decomposition on Cu(111). We used vdW density functionals (vdW-DFs). The calculated translational energies using vdW-DFs are in the range of 0.08-0.18 eV, in reasonable agreement with the experimental estimation (0.10 eV). The calculated CO2 rotational energy, vibrational energy of desorbed CO2 bending and symmetric stretching modes are 0.11 eV, 0.26 eV and 0.04 eV, respectively. The vibrational energy of desorbed CO2 bending mode is twice larger than the translational energy. From the present results, we theoretically predict that the reaction rate of formate synthesis should be enhanced if the bending vibrational mode of CO2 is excited rather than the translational, rotational, and/or stretching modes. Accordingly, our study could provide useful guidance in controlling the initial impinged CO2 energy in formate synthesis reaction.

Vibrationally excitated CO2 desorbed from decomposition of formate on Cu(111)

255th National Meeting (2018)

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