Co/Co₉S₈@S,N-doped porous graphene sheets derived from S, N dual organic ligands assembled Co-MOFs as superior electrocatalysts for full water splitting in alkaline media

Highlights: • S, N dual organic ligands were used to construct Co-MOFs on GO sheets at room temperature. • Co/Co₉S₈@S,N-doped porous graphene sheets were derived from [email protected] • Co/Co₉S₈@SNGS-1000 demonstrated bifunctional catalytic activities of OER and HER. Here we report the synthesis of Co/Co₉S₈ core-shell structures anchored onto S, N co-doped porous graphene sheets (Co/Co₉S₈@SNGS) from thiophene-2,5-dicarboxylate (Tdc) and 4,4ˊ-bipyridine (Bpy) dual organic ligands assembled Co-based metal-organic frameworks (Co-MOFs) in situ grown on graphene oxide sheets ([email protected]) by a room-temperature solution reaction. S-containing Tdc and N-containing Bpy not only trigger the growth of Co-MOFs nanocrystals with a fixed S/N atomic ratio of 1:2.4 on GO sheets in the presence of Co²⁺ in H₂O/NaOH system, but also provide S, N doping sources in the pyrolysis process of Co-MOFs to form Co/Co₉S₈ core-shell structure and S, N co-doping in graphene. The results demonstrate that the obtained Co/Co₉S₈@SNGS at 1000 °C (Co/Co₉S₈@SNGS-1000) by pyrolysis of [email protected] exhibits superiorly bifunctional catalytic activities of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 0.1 M KOH electrolyte, affording an overpotential of 290 mV for OER at a current density of 10 mA cm⁻² and 350 mV for HER at a current density of 20 mA cm⁻². The OER activity of Co/Co₉S₈@SNGS-1000 is slightly better than that of commercial RuO₂ catalyst, simultaneously, Co/Co₉S₈@SNGS-1000 also exhibits good HER activity. As electrode material for full water splitting in 0.1 M KOH solution, the Co/Co₉S₈@SNGS-1000 electrodes exhibit O₂ and H₂ generation efficiencies of 2.48 and 4.87 μmol min⁻¹ respectively, at an applied potential of 1.58 V (vs. RHE) under the given time range, affording nearly 100% Faradaic yield during electrocatalytic water splitting to produce O₂ and H₂.