Abstract
Developing cost-effective electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital in energy conversion and storage applications. Herein, we report a simple method for the synthesis of graphene-reinforced CoS/C nanocomposites and the evaluation of their electrocatalytic performance for typical electrocatalytic reactions. Nanocomposites of CoS embedded in N, S co-doped porous carbon and graphene (CoS@C/Graphene) were generated via simultaneous sulfurization and carbonization of one-pot synthesized graphite oxide-ZIF-67 precursors. The obtained CoS@C/Graphene nanocomposites were characterized by X-ray diffraction, Raman spectroscopy, thermogravimetric analysis-mass spectroscopy, scanning electronic microscopy, transmission electronic microscopy, X-ray photoelectron spectroscopy and gas sorption. It is found that CoS nanoparticles homogenously dispersed in the in situ formed N, S co-doped porous carbon/graphene matrix. The CoS@C/10Graphene composite not only shows excellent electrocatalytic activity toward ORR with high onset potential of 0.89 V, four-electron pathway and superior durability of maintaining 98% of current after continuously running for around 5 h, but also exhibits good performance for OER and HER, due to the improved electrical conductivity, increased catalytic active sites and connectivity between the electrocatalytic active CoS and the carbon matrix. This work offers a new approach for the development of novel multifunctional nanocomposites for the next generation of energy conversion and storage applications.
Highlights
The increasing energy demand together with the potential depletion of fossil fuel-based energy sources has triggered worldwide intense research on renewable energy conversion and storage systems that are highly efficient, low cost and environmentally friendly [1,2]
We developed a simple approach to prepare graphene-reinforced CoS embedded in heteroatoms doped porous carbon via a simultaneous sulfurization and carbonization of one-pot synthesized graphite oxide/ZIF67 composite (GO-zeolitic imidazolate frameworks (ZIFs)-67)
Electrocatalytic performance of the catalysts was evaluated by cyclic voltammograms (CV), linear sweep voltammograms (LSV) and chronoamperometry in a three-electrode electrochemical cell which was connected to a computercontrolled potentiostat (CHI 760D), coupled with a rotating disk electrode (RDE) system
Summary
The increasing energy demand together with the potential depletion of fossil fuel-based energy sources has triggered worldwide intense research on renewable energy conversion and storage systems that are highly efficient, low cost and environmentally friendly [1,2]. It still remains a challenge to effectively support catalytically active species on graphene with uniform distribution so as to improve the performance of the electrocatalyst In this regard, a composite of ZIF derivative and graphene may potentially be promising electrocatalyst with good charge mobility, high surface area and highly dispersed active species for relevant electrocatalytic reactions. Heat treatment of the in situ synthesized GO-ZIFs in H2S atmosphere at high temperature can result in CoS dispersed in N, S co-doped porous carbon and graphene with improved catalytic active sites and electrical conductivity. Compared to the graphene-free sample, the resulting graphene-reinforced CoS/C nanocomposites exhibit multifunctional electrocatalytic performance for ORR, OER and HER with improved activities and good durabilities, due to the increased electrical conductivity, catalytic active sites and connectivity between CoS and carbon/graphene
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