Although noble-metal based materials (IrO₂ and RuO₂) are regarded state-of-the-art catalysts for oxygen evolution reaction (OER), their high price, long-term instability, and scarcity have fueled the search for alternative materials that are relatively cheaper and highly abundant in nature and which can be used for the development of electrolyzers that are suitable for hydrogen production. The present work reports the development and application of a new hybrid catalyst derived from the thermal treatment of a mixture of graphene nanoribbons (GNR) and nickel pyrophosphate (β-Ni₂P₂O₇); the proposed hybrid material was found to present remarkably improved properties which include easy charge transfer, high electroactive surface area, high activity, and effective resistance to corrosion in OER in alkaline medium. The combination of highly dispersed β-Ni₂P₂O₇-30 wt% in direct contact with GNR-70 wt%, coupled with the application of thermal treatment – which ensured some enrichment of Ni in the GNiPy350N catalyst, contributed toward the production of an efficient material with excellent and stable OER activity in alkaline conditions. Compared to the state-of-the-art IrO₂ (300 mV), the GNiPy350N catalyst required an overpotential of approximately 320 mV to reach the current density of 10 mA cm⁻² when immobilized on carbon paper electrode.

The aim of this study is to compare the electrochemical behaviour of graphene-based materials of different origin, e.g., commercially available graphene nanosheets from two producers and reduced graphene oxide (rGO) towards the oxygen reduction reaction (ORR) using linear sweep voltammetry, rotating disc electrode and rotating ring-disc electrode methods. We also investigate the effect of catalyst ink preparation using two different solvents (2-propanol containing OH⁻ ionomer or N,N-dimethylformamide) on the ORR. The graphene-based materials are characterised by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Clearly, the catalytic effect depends on the origin of graphene material and, interestingly, the electrocatalytic activity of the catalyst material for ORR is lower when using the OH⁻ ionomer in electrode modification. The graphene electrodes fabricated with commercial graphene show better ORR performance than rGO in alkaline solution.