The oxygen reduction reaction (ORR) is the rate-limiting reaction in the cathode side of fuel cells. In the quest for alternatives to Pt-electrodes as cathodes in ORR, appropriate transition metal oxide-based electrocatalysts are needed. In the present work, we have synthesized Co₃O₄ and CoO/Co₃O₄ nanostructures using flame spray pyrolysis (FSP), as electrocatalysts for ORR in acidic and alkaline media. A detailed study of the effect of (Co-oxide)/Pt ratio on ORR efficiency shows that the present FSP-made Co-oxides are able to perform ORR at very low-Pt loading, 0.4% of total metal content. In acid medium, an electrode with (5.2% Pt + 4.8% Co₃O₄), achieved the highest ORR performance (J_max = 8.31 mA/cm², E_1/2 = 0.66 V). In alkaline medium, superior performance and stability have been achieved by an electrode with (0.4%Pt + 9.6% (CoO/Co₃O₄)) with ORR activity (J_max = 3.5 mA/cm², E_1/2 = 0.08 V). Using XRD, XPS, Raman and TEM data, we discuss the structural and electronic aspects of the FSP-made Co-oxide catalysts in relation to the ORR performance. Cyclic voltammetry data indicate that the ORR process involves active sites associated with Co³⁺ cations at the cobalt oxide surface. Technology-wise, the present work demonstrates that the developed FSP-protocols, constitutes a novel scalable process for production of co-oxides appropriate for oxygen reduction reaction electrodes.

The utilization of plasmonic nanomaterials in catalytic technologies is an emerging research field with foreseeable applications in energy-catalytic technologies. On this front, the coupling of plasmonic nanomaterials with molecular catalysts is a newly approached, thus far unexploited field, that we discuss herein. In the present mini review, we contrast the case where the plasmonic particle itself is the catalytic center against the case where the plasmonic particle acts as a co-catalyst for an operational catalytic system. In the first part, we present an outline of the key phenomena in nanoplasmonics, and their potential implications in catalytic processes. The concepts of hot electrons, hot holes, and the dynamics of their generation and transfer are reviewed, as are the contribution of near-field and photothermal effects to catalytic processes. All these plasmonic-phenomena are then discussed in conjunction with representative catalytic systems from the literature.