Fourier-transform infrared study of the surface properties of cobalt oxides

The surface properties of cobalt oxide after two different pretreatments have been investigated by means of Fourier-transform infrared (FTIR) spectroscopy of adsorbed carbon monoxide, methanol and ammonia. The surface of evacuated Co3O4 exposes CO3+ cations that react rapidly with CO, producing Co2+ and probably CO+, together with carbonate ions. This surface is extremely reactive, and decomposes at room temperature both ammonia and methanol. After mild reduction in hydrogen, CoO is produced. After this treatment the surface exposes Co2+ and even more reduced sites that by contact with CO give small polycarbonyl clusters. This surface adsorbs methanol dissociatively and ammonia molecularly at room temperature.