In the last few decades, investigations of low-cost, stable, highly active, and fast-synthesizing electrocatalysts for the oxygen evolution and reduction reaction (OER and ORR) have been the main focus of electrochemical examinations. These two reactions are key half-reactions in rechargeable metal–air batteries (MABs) and unitized regenerative fuel cells (URFCs), which are considered eco-friendly and promising energy storage technologies. URFCs can function in two modes: in electrolysis mode, water is split into hydrogen and oxygen via the hydrogen evolution reaction (HER) and OER; in fuel cell mode, hydrogen and oxygen are used to generate electricity and water through the hydrogen oxidation reaction (HOR) and ORR. Similarly, MABs rely on OER and ORR as the primary reactions occurring at the air cathode during charging and discharging cycles. Although noble metal-based catalysts such as iridium or ruthenium oxides (IrO₂/RuO₂) and platinum (Pt) are regarded as standard electrocatalysts for OER and ORR, their use is limited by sluggish kinetics when applied in the opposite reaction—Pt for OER and IrO₂/RuO₂ for ORR.

In this work, Co/rGO was synthesized via chemical synthesis, characterized by scanning electron microscopy, and tested for OER/ORR in alkaline media. The Co/rGO electrodes demonstrated comparable or superior performance to state-of-the-art OER/ORR catalysts, with enhanced stability and cost-effectiveness, highlighting their potential as practical alternatives in metal–air batteries and fuel cells.

Acknowledgments

The authors acknowledge the financial support from the Science Fund of the Republic of Serbia, grant number 250, High-performance NANosize Oxygen Electrodes: transition metals deposited ON reduced graphene oxide vs. high-entropy alloy alternatives-NANO-E-ON (Diaspora: Support for Visits of Diaspora Scientists programme).