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 sustainable
energy conversion and storage, but is severely hampered by the lack of
efficient 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 plasma
enhanced-chemical vapor deposition and/or radiofrequency sputtering. Thanks
to the inherent advantages of cold plasma synthesis routes, Ni foam supports
are efficiently infiltrated by Co3O4 nanostructures and eventually nanosized
Fe2O3, allowing a fine-tuning of their mutual content, nano-organization, and
oxygen defectivity. For Co3O4-Fe2O3 systems, these issues enable current densities
up 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 as
60 mV dec-1, favorably comparing with literature values for most cobalt-based
OER catalysts reported so far. Such features, accompanied by a good time
stability, represent an important goal for eventual practical applications and
candidate the proposed fabrication route as a valuable tool for the design of
efficient electrocatalysts with precisely engineered properties and based on
naturally abundant transition elements.