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|Title:||Thermal evolution of cobalt hydroxides: A comparative study of their various structural phases|
|Authors:||Xu, Z.P. |
|Source:||Xu, Z.P.,Zeng, H.C. (1998-11). Thermal evolution of cobalt hydroxides: A comparative study of their various structural phases. Journal of Materials Chemistry 8 (11) : 2499-2506. ScholarBank@NUS Repository.|
|Abstract:||Through an atmosphere-controlled method, a new phase of hydrotalcite-like Co hydroxide with mixed valent states has been synthesised, along with preparations of known α and β phases. Structural and thermal behaviours of all the Co hydroxides have been compared. Three major stages of decomposition are found: (i) 149-164°C for dehydration of interlayer water, (ii) 185-197°C and (iii) 219-222°C for dehydroxylation of hydrotalcite- and brucite-like phases, respectively. Intercalated nitrate anions in hydrotalcite-like phases decompose largely during stage (ii). The oxide Co3O4 starts to form at temperatures as low as 165°C especially for hydrotalcite-like phases. An intermediate compound, HCoO2, which is formed thermally, decomposes at 258-270°C. The Co3O4 oxide converts into CoO at 842-858 and 935-948°C respectively in nitrogen and air, which is much lower than the previously reported range of 1000-1200°C. Surface areas of calcined samples are found to be proportional to the intercalated anion content. The catalytic activity of the resultant Co3O4 oxides with nitrous oxide is 7.2-8.2 mmol N2O g-1 h-1 at 375°C, which is comparable to some reported active catalyst systems.|
|Source Title:||Journal of Materials Chemistry|
|Appears in Collections:||Staff Publications|
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