Mesoporous NiCo_2O_4@MnO_2 nanoneedle arrays as electrode materials for supercapacitor grown on a conductive nickel foam were prepared by a facile hydrothermal route. The interconnected mesoporous structure of the NiC...Mesoporous NiCo_2O_4@MnO_2 nanoneedle arrays as electrode materials for supercapacitor grown on a conductive nickel foam were prepared by a facile hydrothermal route. The interconnected mesoporous structure of the NiCo_2O_4 nanoneedle arrays provides a large specific surface area for charge storage.The electrochemically active MnO_2 nanoparticles covered on the surface of NiCo_2O_4 nanoneedle result in a favorable synergistic storage effect because of charge redistribution at the NiCo_2O_4|MnO_2 interface,which reduces the interfacial polarization and facilitates ion diffusion. The initial specific capacitance of NiCo_2O_4@MnO_2(S2) is 1001 F g^(-1) at current density of 15 A g^(-1). The capacity retention of S2 is about87.4% after 4000 cycles, and the specific capacitance of S2 electrode only decreases from 1001 F g^(-1) to736 F g^(-1) even after 10,000 cycles. The first-principles calculations show that a chemical bonding between the NiCo_2O_4 and MnO_2 is not only helpful for stabilizing the composites but also leads to a charge redistribution at the interface, which may lead to a smaller interfacial polarization and thus beneficial for the interfacial capacity. The excellent electrochemical performance of NiCo_2O_4@MnO_2 composites(S2)can be ascribed to the high surface area, unique architecture, MnO_2 nanoparticle modification, reduced charge transfer resistance and stable interface between NiCo_2O_4 and MnO_2. The simple material synthesis and architectural design strategy provides new insights in opportunities to exhibit promising potential for practical application in energy storage.展开更多
A porous nanocrystalline NiCo_2O_4 compound electrode was obtained.The morphology of the electrode was controlled by altering the concentration of precipitant (NaOH solution).The electrode was consisted of metal subst...A porous nanocrystalline NiCo_2O_4 compound electrode was obtained.The morphology of the electrode was controlled by altering the concentration of precipitant (NaOH solution).The electrode was consisted of metal substrate (Ni) and porous nanocrystalline NiCo_2O_4 film which was stacked by homosized and pretty regular hexagonal nanoparticles,with thinner than 50 nm and about 200 nm in diameter.The electrode exhibits good electrochemical properties compared with Ni electrode.展开更多
Up to this date,researchers are still facing difficulties to expand the technology of direct methanol fuel cells(DMFCs) because of the high overpotential required to oxidize the methanol and its relatively poor perfor...Up to this date,researchers are still facing difficulties to expand the technology of direct methanol fuel cells(DMFCs) because of the high overpotential required to oxidize the methanol and its relatively poor performance due to CO poisoning of the leading-high cost anode catalyst.In line with this,we have successfully modified the morphological structure and composition of low cost cobalt based-metal oxides,MCo_2O_4(M = Zn and Ni),with the simple and noble use of polyvinyl pyrrolidone(PVP) as growth modifier and surface stabilizer during the synthesis of nanoparticles in our previous reports,which shown high electrocatalytic activity and strong stability.Due to the good performance of our PVP modified MCo_2O_4 towards pseudocapacitor and oxygen evolution reaction applications,we decided to extend our research study to methanol oxidation reaction.Remarkably,PVP modified Ni Co_2O_4 electrode directly grown on nickel foam substrate via a simple hydrothermal process exhibited better performance compared with PVP modified ZnCo_2O_4 and NiCo_2O_4 without PVP.It had obtained a remarkably low onset potential of 0.285 V and high current density of 280 m A cm^(-2),and shown great stability and high poison tolerance during a continuous CV cycling and Chronoamperometry test,which attained high efficiency of 86.86%and 98.52%,respectively.These positive results of PVP modified Ni Co_2O_4 electrode towards MOR might be attributed to its hierarchical 3 D nanostructures with highly mesoporous surface and large surface area which may have provided numerous electroactive sites,and the exceptional corrosion stability of Ni Co_2O_4 electrode in alkaline solution.展开更多
基金financially supported by the National Natural Science Foundation of China (nos. 51774002 and 21773060)Anhui Provincial Science Fund for Excellent Young Scholars (no. gxyqZD2016066)
文摘Mesoporous NiCo_2O_4@MnO_2 nanoneedle arrays as electrode materials for supercapacitor grown on a conductive nickel foam were prepared by a facile hydrothermal route. The interconnected mesoporous structure of the NiCo_2O_4 nanoneedle arrays provides a large specific surface area for charge storage.The electrochemically active MnO_2 nanoparticles covered on the surface of NiCo_2O_4 nanoneedle result in a favorable synergistic storage effect because of charge redistribution at the NiCo_2O_4|MnO_2 interface,which reduces the interfacial polarization and facilitates ion diffusion. The initial specific capacitance of NiCo_2O_4@MnO_2(S2) is 1001 F g^(-1) at current density of 15 A g^(-1). The capacity retention of S2 is about87.4% after 4000 cycles, and the specific capacitance of S2 electrode only decreases from 1001 F g^(-1) to736 F g^(-1) even after 10,000 cycles. The first-principles calculations show that a chemical bonding between the NiCo_2O_4 and MnO_2 is not only helpful for stabilizing the composites but also leads to a charge redistribution at the interface, which may lead to a smaller interfacial polarization and thus beneficial for the interfacial capacity. The excellent electrochemical performance of NiCo_2O_4@MnO_2 composites(S2)can be ascribed to the high surface area, unique architecture, MnO_2 nanoparticle modification, reduced charge transfer resistance and stable interface between NiCo_2O_4 and MnO_2. The simple material synthesis and architectural design strategy provides new insights in opportunities to exhibit promising potential for practical application in energy storage.
文摘A porous nanocrystalline NiCo_2O_4 compound electrode was obtained.The morphology of the electrode was controlled by altering the concentration of precipitant (NaOH solution).The electrode was consisted of metal substrate (Ni) and porous nanocrystalline NiCo_2O_4 film which was stacked by homosized and pretty regular hexagonal nanoparticles,with thinner than 50 nm and about 200 nm in diameter.The electrode exhibits good electrochemical properties compared with Ni electrode.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) - Grants funded by the Ministry of Trade,Industry and Energy (MOTIE) (No.20174010201160)the National Research Foundation of Korea (NRF) - Grant funded by the Ministry of Education (No.20090093816),Republic of Korea
文摘Up to this date,researchers are still facing difficulties to expand the technology of direct methanol fuel cells(DMFCs) because of the high overpotential required to oxidize the methanol and its relatively poor performance due to CO poisoning of the leading-high cost anode catalyst.In line with this,we have successfully modified the morphological structure and composition of low cost cobalt based-metal oxides,MCo_2O_4(M = Zn and Ni),with the simple and noble use of polyvinyl pyrrolidone(PVP) as growth modifier and surface stabilizer during the synthesis of nanoparticles in our previous reports,which shown high electrocatalytic activity and strong stability.Due to the good performance of our PVP modified MCo_2O_4 towards pseudocapacitor and oxygen evolution reaction applications,we decided to extend our research study to methanol oxidation reaction.Remarkably,PVP modified Ni Co_2O_4 electrode directly grown on nickel foam substrate via a simple hydrothermal process exhibited better performance compared with PVP modified ZnCo_2O_4 and NiCo_2O_4 without PVP.It had obtained a remarkably low onset potential of 0.285 V and high current density of 280 m A cm^(-2),and shown great stability and high poison tolerance during a continuous CV cycling and Chronoamperometry test,which attained high efficiency of 86.86%and 98.52%,respectively.These positive results of PVP modified Ni Co_2O_4 electrode towards MOR might be attributed to its hierarchical 3 D nanostructures with highly mesoporous surface and large surface area which may have provided numerous electroactive sites,and the exceptional corrosion stability of Ni Co_2O_4 electrode in alkaline solution.
