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Changxing, China

Cao X.,Soochow University of China | Yan W.,Soochow University of China | Jin C.,Soochow University of China | Tian J.,Soochow University of China | And 2 more authors.
Electrochimica Acta | Year: 2015

The spinel-type MnCo2O4 is an attractive bifunctional electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the catalytic activity of MnCo2O4 is limited by its poor electronic conductivity. Herein MnCo2O4 coated with conducting polypyrrole (i.e. MCO@PPyhybrid) is synthesized. The obtained MCO@PPy hybrid exhibits excellent electrocatalytic activity for both the ORR and OER, outperforming pristine MCO, PPy and MCO+PPy mixture. The ORR and OER activities of MCO@PPy are comparable to that of the commercial Pt/C (20 wt.%) and RuO2/C (20 wt.%), benchmark electrocatalysts for ORR and OER, respectively. While the stabilities of MCO@PPy hybrid toward both the ORR and OER are much higher than that of Pt/C (20 wt.%) and RuO2/C (20 wt.%), respectively. The PPy coating on the surface of MCO provides a conductive network for fast electron transfer and the coupling between the PPy layer and MCO promotes the transfer of electrons from PPy to MCO, benefiting the ORR and OER. The results reveal the effectiveness of surface modification with conducting polymer on improving the electrocatalytic activity of spinel oxide. © 2015 Elsevier Ltd.All rights reserved. Source


Yan W.,Soochow University of China | Cao X.,Soochow University of China | Ke K.,Chilwee Group | Tian J.,Soochow University of China | And 2 more authors.
RSC Advances | Year: 2015

Monodispersed porous spinel-type cobalt ferrite oxide (CoFe2O4) nanospheres (CFO-ns) directly grown on reduced graphene oxide (rGO) sheets are fabricated by a one-pot solvothermal method. With this special structure of CFO-ns and the covalent coupling between CFO-ns and rGO in the CFO-ns/rGO hybrid, more active sites are exposed and the transport of O2 and electrolyte is faciliated when the CFO-ns/rGO hybrid is employed as an electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The CFO-ns/rGO hybrid demonstrates high catalytic activity for both the ORR and OER. It shows a more positive onset potential of -0.11 V (vs. Ag/AgCl) for the ORR, which is 50 mV higher than that of CFO-ns + rGO physical mixture (-0.16 V). Meanwhile, the onset potential of CFO-ns/rGO hybrid (0.56 V) for the OER is 40 mV lower than that of CFO-ns + rGO mixture (0.60 V). The high activity of the CFO-ns/rGO hybrid is attributed to the special structure of CFO-ns, the covalent coupling between CFO-ns and rGO as well as the suppressed agglomeration of CFO-ns and restacking of rGO in the hybrid. Moreover, the covalent coupling between CFO-ns and rGO endows the hybrid with excellent electrochemical stabilities for both the ORR and OER. © 2016 The Royal Society of Chemistry. Source


Yan W.,Soochow University of China | Cao X.,Soochow University of China | Tian J.,Soochow University of China | Jin C.,Soochow University of China | And 2 more authors.
Carbon | Year: 2016

To expedite the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in electrochemical systems, efficient nonprecious electrocatalysts are highly desired. In this work, a hybrid of CoFe2O4 nanoparticles supported on nitrogen/sulfur dual-doped three-dimensional (3D) reduced graphene oxide networks (CFO/NS-rGO) has been designed and fabricated. The doping of N and S provide the graphene networks with a large amount of defects. Moreover, both N and S doped in reduced graphene oxide play important roles in engineering the covalent coupling between CoFe2O4 and the 3D graphene networks. The covalent coupling between CoFe2O4 and NS-rGO along with the hierarchical porous structure and 3D networks endow the hybrid with a pronounced ORR activity (4-electron pathway), superior OER activity (comparable to that of the state-of-the-art RuO2/C catalyst) and high durability toward both ORR and OER. © 2015 Elsevier Ltd. All rights reserved. Source


Cao X.,Soochow University of China | Zheng X.,Soochow University of China | Tian J.,Soochow University of China | Jin C.,Soochow University of China | And 2 more authors.
Electrochimica Acta | Year: 2016

Efficient nonprecious electrocatalysts with fast kinetics for the the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to improve the efficiency of electrochemical systems such as fuel cells and metal-air battereies. Here, Co9S8 embedded in porous nitrogen-doped carbon (N-C) matrix has been designed and fabricated. The as-fabricated Co9S8/N-C hybrid shows an excellent ORR activity, which is comparable to that of the commercial Pt/C (20 wt.%). Notably, the OER activity of Co9S8/N-C hybrid is superior to that of the RuO2/C (20 wt.%), a benchmark electrocatalyst for OER. The stabilities of Co9S8/N-C hybrid toward ORR and OER are significantly improved as compared to that of Pt/C (20 wt.%) and RuO2/C (20 wt.%), respectively. The synergistic effect of the covalent coupling between Co9S8 and N-C and the porous structure of N-C is responsible for the enhanced catalytic activity and durability of Co9S8/N-C hybrid. © 2016 Elsevier Ltd. All rights reserved. Source

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