The present work establishes a systematic approach based on the application of in-situ Fourier transform infrared spectroscopy (FTIR) for the investigation of the crystal structure, thermal stability, redox behavior (temperature-programmed reduction/temperature programmed re-oxidation) as well as the catalytic properties of Co3O4 thin films. The syntheses of Co3O4 were achieved by chemical vapor deposition in the temperature range of 400-500°C. The structure analysis of the as-prepared material revealed the presence of two prominent IR bands peaking at 544 cm-1 (v1) and 650 cm-1 (v2) respectively, which originate from the stretching vibrations of the Co-O bond, characteristic of the Co3O4 spinel. The lattice stability limit of Co3O4 was estimated to be above 650°C. The redox properties of the spinel structure were determined by integrating the area under the emission bands v1 and v2 as a function of the temperature. Moreover, Co3O4 has been successfully tested as a catalyst towards complete oxidation of dimethyl ether below 340°C. The exhaust gas analysis during the catalytic process by in situ absorption FTIR revealed that only CO2 and H2O were detected as the final products in the catalytic reaction. The redox behavior suggests that the oxidation of dimethyl ether over Co3O4 follows a Mars-van Krevelen type mechanism. The comprehensive application of in situ FTIR provides a novel diagnostic tool in characterization and performance test of catalysts.
Qualitative characterizations of the structure as well as the quantitative diagnostic of the thermal stability, the redox and catalytic properties of Co3O4 were comprehensively and accurately performed using an in situ FTIR technique. The as-prepared thin film was con-firmed to be Co3O4 spinel. The investigation of the thermal properties shows that, Co3O4 stability limit was obtained above 650°C. The evaluation of redox property indicates that Co3O4 can be easily reduced and oxidized at relatively mild temperature. Co3O4 was used as a catalyst for the total oxidation of DME using an in situ FTIR for the diagnostic of the exhaust gas produced during the catalytic process. Co3O4 thin film exhibited promising performance at low temperature. The in situ FTIR diagnostic of Co3O4 properties performed in this study can be further fine-tuned and extended to other metallic oxides including chromium oxide, nickel oxide, lead oxide, and silicon dioxide. The in situ FTIR technique is con-firmed to be a valuable tool for the efficient study of metal oxide material for a wide range of applications.
