Experimental procedure Fig xA Schematic diagram of the

3.2.2. Mn–Co/TiO2
Fig. 4. FTIR spectra of the adsorption of NH3 on Mn–Co/TiO2 catalyst.Figure optionsDownload full-size imageDownload as PowerPoint slide
By purging at increasing temperature, the two bands of NH4+ ions decreased quickly and disappeared at 473 K. In contrast, the bands at 1218 and 1194 cm−1 due to coordinated ammonia increased firstly in intensity, passed through CK-636 maximum at 473 K, and then decreased at higher temperature, finally disappeared until 673 K. The increase of coordinated NH3 was accompanied by depletion of NH4+ at 473 K, this can be interpreted in terms of the lower thermal stability of NH4+ ions, when heating, it tends to desorbing, migrating to Lewis sites and adsorbed as coordinated NH3. The reaction could be described as reaction (3)[11]. These results suggest that the Brønsted acid sites adsorbed NH4+ could act as “reservoir” of actively coordinated NH3 species.equation(3)NH3 (g) + H+ = NH4+ (ads) = NH3 (ads) + H+