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5 years ago

Graphene Composites with Cobalt Sulfide: Efficient Trifunctional Electrocatalysts for Oxygen Reversible Catalysis and Hydrogen Production in the Same Electrolyte

Graphene Composites with Cobalt Sulfide: Efficient Trifunctional Electrocatalysts for Oxygen Reversible Catalysis and Hydrogen Production in the Same Electrolyte
Ligui Li, Zhenghua Tang, Nan Wang, Xiongwu Kang, Dengke Zhao, Shaowei Chen
Nitrogen and sulfur-codoped graphene composites with Co9S8 (NS/rGO-Co) are synthesized by facile thermal annealing of graphene oxides with cobalt nitrate and thiourea in an ammonium atmosphere. Significantly, in 0.1 m KOH aqueous solution the best sample exhibits an oxygen evolution reaction (OER) activity that is superior to that of benchmark RuO2 catalysts, an oxygen reduction reaction (ORR) activity that is comparable to that of commercial Pt/C, and an overpotential of only −0.193 V to reach 10 mA cm−2 for hydrogen evolution reaction (HER). With this single catalyst for oxygen reversible electrocatalysis, a potential difference of only 0.700 V is observed in 0.1 m KOH solution between the half-wave potential in ORR and the potential to reach 10 mA cm−2 in OER; in addition, an overpotential of only 450 mV is needed to reach 10 mA cm−2 for full water splitting in the same electrolyte. The present trifunctional catalytic activities are markedly better than leading results reported in recent literature, where the remarkable trifunctional activity is attributed to the synergetic effects between N,S-codoped rGO, and Co9S8 nanoparticles. These results highlight the significance of deliberate structural engineering in the preparation of multifunctional electrocatalysts for versatile electrochemical reactions. Nitrogen and sulfur-codoped graphene composites with Co9S8 nanoparticles (NS/rGO-Co) are facilely prepared by thermal annealing of graphene oxides with cobalt nitrate and thiourea in an ammonium atmosphere. Electrochemical measurements confirm the efficient trifunctional activities toward oxygen reversible catalysis as well as hydrogen production in a water electrolyzer with a single NS/rGO-Co catalyst in the same alkaline electrolyte.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/smll.201701025

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