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Co3O4/TiO2 catalysts studied in situ during the preferential oxidation of carbon monoxide: the effect of different TiO2 polymorphs

DOI: 10.1039/D2CY01699K DOI Help

Authors: Thulani M. Nyathi (University of Cape Town) , Mohamed I. Fadlalla (University of Cape Town) , Nico Fischer (University of Cape Town) , Andrew P. E. York (Johnson Matthey Technology Centre) , Ezra J. Olivier (Nelson Mandela University) , Emma K. Gibson (University of Glasgow; UK Catalysis Hub, Research Complex at Harwell) , Peter P. Wells (UK Catalysis Hub, Research Complex at Harwell; University of Southampton; Diamond Light Source) , Michael Claeys (University of Cape Town)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Catalysis Science & Technology , VOL 151

State: Published (Approved)
Published: February 2023
Diamond Proposal Number(s): 19850

Open Access Open Access

Abstract: Co3O4 nanoparticles were supported on different TiO2 polymorphs, namely, rutile, anatase, and a 15[thin space (1/6-em)]:[thin space (1/6-em)]85 mixture of rutile and anatase (also known as P25), via incipient wetness impregnation. The Co3O4/TiO2 catalysts were evaluated in the preferential oxidation of CO (CO-PrOx) in a H2-rich gas environment and characterised in situ using PXRD and magnetometry. Our results show that supporting Co3O4 on P25 resulted in better catalytic performance, that is, a higher maximum CO conversion to CO2 of 72.7% at 200 °C was achieved than on rutile (60.7%) and anatase (51.5%). However, the degree of reduction (DoR) of Co3O4 to Co0 was highest on P25 (91.9% at 450 °C), with no CoTiO3 detected in the spent catalyst. The DoR of Co3O4 was lowest on anatase (76.4%), with the presence of TixOy-encapsulated CoOx nanoparticles and bulk CoTiO3 (13.8%) also confirmed in the spent catalyst. Relatively low amounts of CoTiO3 (8.9%) were detected in the spent rutile-supported catalyst, while a higher DoR (85.9%) was reached under reaction conditions. The Co0 nanoparticles formed on P25 and rutile existed in the fcc and hcp crystal phases, while only fcc Co0 was detected on anatase. Furthermore, undesired CH4 formation took place over the Co0 present in the P25- and rutile-supported catalysts, while CH4 was not formed over the Co0 on anatase possibly due to encapsulation by TixOy species. For the first time, this study revealed the influence of different TiO2 polymorphs (used as catalyst supports) on the chemical and crystal phase transformations of Co3O4, which in turn affect its activity and selectivity during CO-PrOx.

Subject Areas: Chemistry, Materials

Instruments: B18-Core EXAFS

Added On: 07/03/2023 09:11


Discipline Tags:

Physical Chemistry Catalysis Chemistry Materials Science Nanoscience/Nanotechnology

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS)