Facile four-electrode system synthesis of Pt–Co/graphene composite for efficient electrocatalytic water splitting

Electrolytic water splitting for hydrogen production is considered as one of the promising directions due to its environmental friendliness and high generated hydrogen purity. To address the high overpotential caused by the sluggish kinetics of the oxygen evolution reaction (OER), a modified four-electrode system has been designed to synthesize bifunctional PtCo/graphene (PtCo/G) composites, which feature dual active sites. This method allows for the electrolysis of Pt at a high voltage (30 V) and Co at a lower voltage (10 V), while graphene is prepared through the exfoliation of graphite sheets at the cathode. This process concurrently resolves the issues of differential dissolution voltages between Pt and Co and the poor conductivity of the material, achieving the efficient synthesis of metal/graphene composites. The PtCo/G-2h composite exhibits excellent electrocatalytic activity. In the 0.5 M H 2 SO 4 , the overpotential for hydrogen evolution reaction (HER) at 10 mA cm −2 is 18 mV lower than that of commercial Pt/C catalyst. In 1 M KOH, PtCo/G-2h demonstrates superior electrocatalytic OER activity, with an overpotential at 10 mA cm −2 that is only 2 mV higher than that of the commercial RuO 2 catalyst. As a bifunctional catalyst for water electrolysis, the PtCo/G composites can effectively facilitate the adsorption of OH − ions, and assist in altering the rate-determining step, thus significantly reducing the activation energy (E a ) of the reaction. This work introduces a novel approach for the synthesis of graphene-based materials using a self-designed electrochemical method.