Vibrational identification of the surface reaction intermediates for the dehalogenation of trichloroethene on PdCu(110) alloy

The adsorption and dissociation of trichloroethene (TCE) on PdCu(1 1 0) have been investigated under the view of high resolution electron energy loss spectroscopy (HREELS) and first-principle quantum chemical calculations. At 180 K and after an exposure of 10 L, TCE is physisorbed on the surface. The HREELS spectrum is similar to the gas-phase one, measured by infrared spectroscopy. There are small shifts in the bands of the HREELS spectrum, which also indicate a weak interaction between the molecule and the surface. The chemistry of the TCE dissociation on PdCu(1 1 0) is more complex than the one on Cu(1 1 0). By increasing the surface temperature, a great variety of surface species occurs, as shown by the experimental spectra and confirmed by the calculations. This reaction seems to occur relatively early, at 200 K. At 280 K most of the CCl bonds have been already broken. The decrease of the intensity of the ν CCl stretching vibration and the increase of the intensity of the metalCl vibration are shown to be fingerprints of this process.