Plasma-assisted synthesis of Co3O4-based electrocatalysts on Ni foam substrates for the oxygen evolution reaction

Electrocatalytic oxygen evolution reaction (OER) plays a key role in sustainableenergy conversion and storage, but is severely hampered by the lack ofefficient catalysts, whose development remains a critical and challenging issue.Herein, it is reported for the first time that pure and Fe2O3-containing Co3O4-based OER electrocatalysts are grown on highly porous Ni foams by plasmaenhanced-chemical vapor deposition and/or radiofrequency sputtering. Thanksto the inherent advantages of cold plasma synthesis routes, Ni foam supportsare efficiently infiltrated by Co3O4 nanostructures and eventually nanosizedFe2O3, allowing a fine-tuning of their mutual content, nano-organization, andoxygen defectivity. For Co3O4-Fe2O3 systems, these issues enable current densitiesup to ca. 120 mA cm-2 at 1.79 V versus the reversible hydrogen electrode,an overpotential of ca. 350 mV at 10 mA cm-2 and a Tafel slope as low as60 mV dec-1, favorably comparing with literature values for most cobalt-basedOER catalysts reported so far. Such features, accompanied by a good timestability, represent an important goal for eventual practical applications andcandidate the proposed fabrication route as a valuable tool for the design ofefficient electrocatalysts with precisely engineered properties and based onnaturally abundant transition elements.