New insights into the role of active copper species in CuO/Cryptomelane catalysts for the CO-PROX reaction

Nominally different Cu contents have been loaded on synthetic Cryptomelane oxide and the resulting CuO/Cryptomelane catalysts have been tested in the CO-PROX reaction. Catalytic activity was assessed in terms of the tunable synergistic interaction between copper and cryptomelane. This work entails the use of conventional characterization techniques such as XRD, Raman, FE-SEM, XPS with complementary DFT simulation. Additionally, it is reported for the first time, in-situ Work Function measurements of CO and O-2 interaction in CuO/Cryptomelane catalysts. Results reveal the strong influence of the interfacial properties on CuO/Cryptomelane reducibility, where Cu+ species are formed by means of redox interplay between Cu+2/Cu+ and Mn3+/ Mn4+. The optimal performance is achieved by the efficient participation of two active species: (1) Cu+ from an intimate MnOx contact, providing the active sites for CO oxidation; and (2) surface Cu+ species stabilized in CuO bulky particles for the efficient O-2 refilling.