Activation of O2 on CeO2 nanoparticle surfaces by electron transfer

BRITES HELÚ, MARIELA A.; NORTON, ANGELA; BOSCOBOINIK, J. ANIBAL; STACCHIOLA, DARIO J.; COLLINS, SEBASTIAN E.; CALAZA, FLORENCIA C.

Charlotte, NC (Virtual)

Conferencia; 67th American Vacuum Society Symposium; 2021

American Vacuum Society (AVS)

It is well known that VOCs being recognized as major responsible for the increase in global air pollution. Catalytic combustion is an efficient technology for the abatement of VOC, which are oxidized over a catalyst at temperatures much lower than those of the thermal process. Specifically, gold supported catalysts on CeO have shown a great performance in the oxidation of CO, methanol, toluene, etc. Besides, it is important to clarify the role of the support in such reaction. Ceria has the key property of high oxygen storage capacity which originates in its ability to rapidly switch from Ce+3 to Ce+4 oxidation states as the environment changes from reducing to oxidizing and vice versa. Its redox behaviour is influenced by the substituent lattice groups that could be incorporated during different catalyst pretreatments and could affect the oxidation of VOC. This could be understood as the influence of oxygen vacancies and/or absorbed or coadsorbed H on the activation of oxygen molecules. The latter leads to the formation of superoxide and peroxide molecules on the surface, which could in principle be highly reactive towards oxidation of organic molecules.In this context, we study, by IR spectroscopy (DRIFTS) and mass spectrometry (MS), the interaction of O2 with the modified CeO2 based material, by creating vacancies following different treatments in reducing environments. The possible role of the vacancies and/or presence of H atoms in the electron transfer from the surface to the oxygen molecule is discussed. Using AP-XPS we are able to prove that the surface/near surface of CeOx presents a charging effect which could be due to accumulated charge/electrons which then transfer to O2. Preliminary results showing reactivity of these activated molecular oxygen species (super- and peroxides) are presented regarding the catalytic oxidation of CO.