Synthesis and decomposition of formate on Cu(111) and Cu(110) surfaces: Structure sensitivity

The kinetics of both the formate synthesis of hydrogenation of ${\mathrm{CO}}_{\mathrm{2}}$ and the formate decomposition has been studied on clean Cu(111) and Cu(110) surfaces using in situ infrared reflection absorption spectroscopy. It has been found that the formate synthesis does not depend on the surface structure of copper between Cu(111) and Cu(110). The activation energies for the initial formation rate of formate species on Cu(111) and Cu(110) have been determined to be 56.6±4.8 and 59.8±4.1 ${\mathrm{kJ mol}}^{\mathrm{-1}}$ , respectively. On the other hand, the activation energy and the pre-exponential factor for the formate decomposition on Cu(111) are widely different from those on Cu(110), indicating that the decomposition of the formate species depends on the Cu surface structure. The position of the neighboring Cu atom is considered to be important for the kinetics of the decomposition since the transition state of the formate decomposition may pass through by the OCO plane vibration toward the surface.