Quantum chemistry and in situ FT ir spectroscopy studies on potential-dependent properties of CO adsorbed on Pt electrodes

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The electronic and vibrational properties of CO adsorbed on Pt electrodes at different potentials have been studied, by using methods of self-consistent-charge discrete variational Xα (SCC-DV-Xα) cluster calculations and in situ FT ir spectroscopy. Two new models have been developed and verified to be successful: (1) using a “metallic state cluster” to imitate a metal (electrode) surface; and (2) charging the cluster and shifting its Fermi level (ϵ f) to simulate, according to the relation of —d ϵ f e d E, quantitatively the variation of the electrode potential ( E). It is shown that the binding of PtCO is dominated by the electric charge transfer of dπ Pt ⇒ 2π * CO, while that of σ CO ⇒ Pt is less important in this binding. The electron occupancy of the 2π * orbital of CO ads weakens the CO bond and decreases the v CO. Variation of E mainly influences the charge transfer process of dπ Pt ⇒ 2π * CO, but hardly influences that of σ CO ⇒ Pt. A linear potential-dependence of v CO has been shown and the calculated d v CO/d E = 35.0 cm −1 V −1. All results of calculations coincide with the ir experimental data.