Reducible metal oxides (RMOs) represent an important category of catalysts with many applications due to their interesting properties in redox reactions, which aroused massive research interests in the past decades. Mechanistic studies have discovered the importance of vacancy generation in RMO catalysis. It is generally accepted that removal of lattice oxygen from RMO surface would generate a vacancy site and neighbor cations being partially reduced with redistribution of excess electrons in the empty orbitals, which are more energetic and act as active sites in catalysis. Despite of the importance and many research efforts, a generic theory for depicting RMO catalysis that would help mechanism understanding and guide catalyst materials research still lacks. Herein we report a new theory model that considers both work function (W) parameter and oscillation of work function (ΔW) during RMO catalysis. After introducing ΔW as one additional responsible parameter, the RMO activity property can be more accurately described using these material descriptors. Through study of CO oxidation as a model reaction and integration of experimental measurements and DFT simulations of RMO catalysis, we demonstrate effectiveness of W and ΔW as descriptor parameters and an inverted volcano correlation with the RMO activity property. The findings of work function and the oscillation as governing structural parameters provide a plausible theory to understand RMO catalysis and guide the catalyst research.

Oscillation of work function during reducible metal oxide catalysis and correlation with the activity property

ACS Fall 2021

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