Modifying the electronic and chemical properties by doping heterogeneous cations is another powerful approach to promote the activities of Co3O4. Potassium, as an electron donor for the capacity of sticking and dissociation of dioxygen, would lower the formation energy of oxygen vacancy and make the surface more reactive according to a “low-valence dopant effect”. A convenient and mild method based on the interaction between K-Co to boost the catalysis of oxygen-transfer in oxidation of carbon monoxide, vinyl chloride (VC) and methane to represent different reaction temperature zone. The conversion temperatures shifted towards much lower values (shown in Table 1), which was even more active than noble metal catalysts. XPS confirmed a change of electronic state of cobalt, and more Co3+ was exposed on Co3O4(K) surface. The valence band spectra of Co3O4 and Co3O4(K) are shown that electron binding energy shifted to a lower value closed to the Fermi level for the Co3O4(K) sample. Both the weakening of Co-O bond and abundance of surface Co3+ were thought to expedite the formation of oxygen vacancies causing the oxygen easier to activate and migrate on Co3O4(K). Mars-van Krevelen process was generally proposed as Co3O4-related oxidation reaction mechanism. By the modification of K, the Co-O bond was weakened making the Mars-van Krevelen process enhanced.

Introducing trace potassium as the electronic and structural modifier to enhance the oxidation of Co3O4 catalyst

254th National Meeting (2017)

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