Infrared spectra of carbon monoxide chemisorbed on metal films: a comparative study of copper, silver, gold, iron, cobalt and nickel

Abstract

Infrared spectra have been obtained of carbon monoxide chemisorbed on very thin metal films deposited at 113 K under ultrahigh vacuum conditions. On iron, cobalt and nickel the spectra are similar to those found with silica-supported metals, but the absorption bands appeared only at high coverage, indicating that only a part of the adsorbed gas is responsible for them. On copper, silver and gold the adsorbed carbon monoxide is infrared active at low coverages, with bands at 2105, 2160 and 2110 cm$^{-1}$ respectively. Only one absorption band occurs on each metal, and on copper and gold the absorbance increases linearly with coverage. The extinction coefficients are 1 $\times $ 10$^{-17}$ and 2 $\times $ 10$^{-17}$ molecule$^{-1}$ cm$^{2}$ on copper and gold respectively. The relations between frequency, surface potential and heat of adsorption on the noble metals are discussed in terms of $\sigma -$ and $\pi $-bonding.