Electro-oxidation Reaction of Methanol over Reducible Ce 1- x - y Ni x Sr y O 2-δ : A Mechanistic Probe of Participation of Lattice Oxygen.

Methanol oxidation reaction crucially depends on the formation of -OOH species over the catalyst's surface. Ni-based catalysts are by far the choice of materials, where the redox couple of Ni 2+ /Ni 3+ facilitates the formation of -OOH species by surface reconstructions. However, it is challenging to oxidize Ni 2+ as it generates charge-transfer orbitals near the Fermi energy level. One possible solution is to substitute Ni 2+ with a reducible oxide support, which will not only facilitate the Ni 2+ → Ni 3+ oxidation but also adsorb oxygenated species like -OOH at a lower potential owing to its oxophilicity. This work shows with the help of structural and surface studies that the reducible CeO 2 support in Ni and Sr co-doped Ce 1- x - y Ni x Sr y O 2-δ solid solution can easily facilitate Ni 2+ → Ni 3+ oxidation as well as evolution of lattice oxygen during the methanol oxidation reaction. While the Ni 3+ species helped in formation of -OOH surface intermediates, the evolved lattice oxygen eased the CO oxidation process in order to bring out the better CO-tolerant methanol oxidation activity over Ce 1- x - y Ni x Sr y O 2-δ . The study shows the unique importance of the electronic interactions between the active site and support and involvement of lattice oxygen in the methanol oxidation reaction.