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 ≈120 mA cm−2 at 1.79 V versus the reversible hydrogen electrode, an overpotential of ≈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.