Development of non-stoichiometric hybrid Co3S4/Co0.85Se nanocomposites for an evaluation of synergistic effect on the OER performance

Abstract Water electrolysis powered by renewable energy sources to produce green hydrogen is a very promising and sustainable alternative to fossil fuels, as well as one of the best approaches for significantly reducing carbon footprints and controlling pollution. In this study, novel hybrid non-stoichiometric nanocomposite Co3S4/Co0.85Se electrocatalyst materials were synthesized using a simple and one-pot eco-friendly hydrothermal method. The as-prepared samples were characterized using X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) for structural features. Crystalline phases of Co3S4, Co0.85Se, and mixed phases in the hybrid samples were confirmed through XRD. Uniformly distributed agglomerated nanoparticles (30-80 nm) of Co3S4, clearly distinguishable nanoaggregates (20-90 nm) of Co0.85Se, and nanoflakes covered with nanoparticles (30-150 nm) of Co3S4/Co0.85Se were confirmed by FESEM. The synergistic effects of the hybrid nanocomposite due to the combination of Co3S4 (containing two different oxidation states of cobalt) and non-stoichiometric Co0.85Se, was investigated towards the oxygen evolution reaction (OER). The electrocatalytic studies confirmed that the Co3S4/Co0.85Se electrocatalyst exhibited a low overpotential of 362 mV @ +30 mA.cm−2 towards the OER in an alkaline solution in comparison with Co3S4 and Co0.85Se electrocatalysts. Furthermore, a low overpotential of 1.59 V at a high current density and a high electrochemical active surface area (ECSA) of 210 cm2 was achieved due to the combined effects of chemical coupling between the Co3S4 and Co0.85Se. Chronoamperometric studies revealed excellent stability of the hybrid nanocomposite samples with negligible changes in the overpotential, even after 30 hours of testing. The synergetic effect of cobalt chalcogenides due to the nanoscale interaction was confirmed by the enhanced electrocatalytic activity.