Effect of alkali and alkaline earth metal dopants on catalytic activity of mesoporous cobalt oxide evaluated using a model reaction

• Published in: Applied catalysis. A, General General, 2018-04, Vol.555, p.189-195
• Main Authors: Bingwa, Ndzondelelo, Bewana, Semakaleng, Ndolomingo, Matumuene Joe, Mawila, Naphtaly, Mogudi, Batsile, Ncube, Phendukani, Carleschi, Emanuela, Doyle, Bryan P., Haumann, Marco, Meijboom, Reinout
• Format: Article
• Language: English
• Subjects: Alkali metals; Alkalies; Alkaline earth metals; Amorphous materials; Calcium; Catalysis; Catalysts; Catalytic activity; Catalytic converters; Chemical synthesis; Cobalt; Cobalt oxides; Effective kinetics; Inductively coupled plasma mass spectrometry; Kinetics; Leaching; Lithium; Mass spectrometry; Metal dopants; Morin oxidation; Oxidation; Reducible metal oxides; Scanning electron microscopy; Trace elements; Transmission electron microscopy; Transport limitation; X ray photoelectron spectroscopy; X ray powder diffraction; X-ray diffraction
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2018.01.028

[Display omitted] •Synthesis of Co3O4 and doped-Co3O4 catalysts is described.•The Co3O4 catalysts are active in oxidation of morin.•The H2-TPR and XPS analyses confirm electron structure change. Herein we report the synthesis of mesoporous cobalt oxides in pure (Co3O4) and alkali and alkaline earth metal doped form (Li-, Ca-, Cs-, and Na-, K-, and Mg/Co3O4) via the inverse micelle method. The as-prepared materials were characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen sorption (BET), hydrogen-temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). Characterization results suggested that the as-synthesized materials are of amorphous and mesoporous nature. Their catalytic activity was investigated using a model reaction, namely the liquid-phase morin oxidation. Results revealed pure cobalt oxide to be the better catalyst compared to its doped counterparts. The stability of Li/Co3O4 material was investigated exemplarily by recycling and reusing the catalysts for as many as four catalytic cycles. Conversion of morin was complete in all runs and no significant metal leaching could be detected by the use of inductively coupled plasma mass spectrometry (ICP-MS).