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 (Co-MOFs@GO) 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 Co-MOFs@GO 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.

ESCALAB 250 X-ray photoelectron spectrometer equipped with Al Ka1,2 monochromatized radiation at 1486.6 eV X-ray source. The surface area and porosity of samples were measured by a surface area and porosity anyalyzer. Raman spectra of the samples were recorded on a LabRAM HR 800 confocal microscope Raman system using an Ar ion laser operating at 632nm. Thermogravimetric analysis curve of the sample was obtained from 25℃ to 1100℃ by SDT Q600 at a heating rate of 10 ℃ min-1 in N2 atmosphere. The produced O2 and H2 from full water splitting were determined by a gas chromatograph(CEL-GSOA-7GC7920, Beijing China Eduaction Au-light Co., Ltd).