Distinguished from commonly used Fe2O3 and Fe3O4,a three-dimensional multilevel macromicro-mesoporous structure of FeC2O4/graphene composite has been prepared as binderfree electrode for supercapacitors.The as-prepare...Distinguished from commonly used Fe2O3 and Fe3O4,a three-dimensional multilevel macromicro-mesoporous structure of FeC2O4/graphene composite has been prepared as binderfree electrode for supercapacitors.The as-prepared materials are composed of macroporous graphene and microporous/mesoporous ferrous oxalate.Generally,the decomposition voltage of water is 1.23 V and the practical voltage window limit is about 2 V for asymmetric supercapacitors in aqueous electrolytes.When FeC2O4/rGO hydrogel was used as the negative electrode and a pure rGO hydrogel was used as the positive electrode,the asymmetrical supercapacitor voltage window raised to 1.7 V in KOH(1.0 mol/L)electrolyte and reached up to 2.5 V in a neutral aqueous Na2SO4(1.0 mol/L)electrolyte.Correspondingly it also exhibits a high performance with an energy density of 59.7 Wh/kg.By means of combining a metal oxide that owns micro-mesoporous structure with graphene,this work provides a new opportunity for preparing high-voltage aqueous asymmetric supercapacitors without addition of conductive agent and binder.展开更多
The application of direct methanol fuel cells （DMFC） is hampered by high cost, low activity, and poor CO tolerance by the Pt catalyst. Herein, we designed a fancy 3D hybrid by anchoring tungsten nitride （WN） nanop...The application of direct methanol fuel cells （DMFC） is hampered by high cost, low activity, and poor CO tolerance by the Pt catalyst. Herein, we designed a fancy 3D hybrid by anchoring tungsten nitride （WN） nanoparticles （NPs）, of about 3 nm in size, into a 3D carbon nanotube-reduced graphene oxide framework （CNT-rGO） using an assembly route. After depositing Pt, the contacted and strongly coupled Pt-WN NPs were formed, resulting in electron transfer from Pt to WN. The 3D Pt-WN/CNT-rGO hybrid can be used as a bifunctional electrocatalyst for both methanol oxidation reaction （MOR） and oxygen reduction reaction （ORR）. In MOR, the catalysts showed excellent CO tolerance and a high mass activity of 702.4 mA.mgpt-1, 2.44 and 3.81 times higher than those of Pt/CNT-rGO and Pt/C（JM） catalysts, respectively. The catalyst also exhibited a more positive onset potential （1.03 V）, higher mass activity （151.3 mA.mgpt-1）, and better cyclic stability and tolerance in MOR than ORR. The catalyst mainly exhibited a 4e-transfer mechanism with a low peroxide yield. The high activity was closely related to hybrid structure. That is, the 3D framework provided a favorable path for mass-transfer, the CNT-rGO support was favorable for charge transfer, and strongly coupled Pt-WN can enhance the catalytic activity and CO-tolerance of Pt. Pt-WN/CNT-rGO represents a new 3D catalytic platform that is promising as an electrocatalyst for DMFC because it can catalyze both ORR and MOR in an acidic medium with good stability and highly efficient Pt utilization.展开更多
The commercial application of lithium(Li)metal anode is hindered by the growth of Li dendrites.Here,we develop a multidimensional composite struc-ture composed of Co3O4/NiO heterojunction particles and reduced graphen...The commercial application of lithium(Li)metal anode is hindered by the growth of Li dendrites.Here,we develop a multidimensional composite struc-ture composed of Co3O4/NiO heterojunction particles and reduced graphene oxide(rGO)nanosheets,that allows Li to nucleate and deposit selectively in one direction.Among,two transition metal oxides(TMOs)without lit-hiophilicity are transformed into lithiophilic species due to the rich phase boundaries and high Li adsorption energies on interfaces,which can provide uniform active sites and reduce nucleation overpotential for Li deposition.Meanwhile,the rGO substrate with high electrical conductivity and large spe-cific surface area can form a conductive network between TMOs and alleviate volume expansion caused by Li deposition.Benefitting from the synergistic effect of the heterojunctions and carbon substrate,the Co_(3)O_(4)/NiO-rGO regu-lates the local current density and enables the dendrite-free Li plating/stripping behavior.At a current density of 1 mA cm^(-2),the Li metal anode with the Co_(3)O_(4)/NiO-rGO host exhibits remarkable electrochemical performance,consistently maintaining high Coulombic efficiency(>93.8%)over 1000 cycles.Additionally,the full cells matched with LiFePO_(4)cathode also display high rate capability of 130 mAh g^(-1)at 1 C and stable cycling life over 500 cycles.展开更多
基金supported by the National Natural Science Foundation of China (No.51673180 and No. 51673180)
文摘Distinguished from commonly used Fe2O3 and Fe3O4,a three-dimensional multilevel macromicro-mesoporous structure of FeC2O4/graphene composite has been prepared as binderfree electrode for supercapacitors.The as-prepared materials are composed of macroporous graphene and microporous/mesoporous ferrous oxalate.Generally,the decomposition voltage of water is 1.23 V and the practical voltage window limit is about 2 V for asymmetric supercapacitors in aqueous electrolytes.When FeC2O4/rGO hydrogel was used as the negative electrode and a pure rGO hydrogel was used as the positive electrode,the asymmetrical supercapacitor voltage window raised to 1.7 V in KOH(1.0 mol/L)electrolyte and reached up to 2.5 V in a neutral aqueous Na2SO4(1.0 mol/L)electrolyte.Correspondingly it also exhibits a high performance with an energy density of 59.7 Wh/kg.By means of combining a metal oxide that owns micro-mesoporous structure with graphene,this work provides a new opportunity for preparing high-voltage aqueous asymmetric supercapacitors without addition of conductive agent and binder.
基金We gratefully acknowledge the support of this research by the Key Program of the National Natural Science Foundation of China （No. 21031001）, the National Natural Science Foundation of China （Nos. 21371053, 21571054, and 21401048）, Program for Innovative Research Team in University （No. IRT-1237）, Special Research Fund for the Doctoral Program of Higher Education of China （No. 20112301110002）, the Natural Science Foundation of Heilongjiang Province （No. QC2014C007）, China Postdoctoral Science Foundation funded project （No. 2015T80374）, and Excellent Youth Foundation of Heilongjiang University.
文摘The application of direct methanol fuel cells （DMFC） is hampered by high cost, low activity, and poor CO tolerance by the Pt catalyst. Herein, we designed a fancy 3D hybrid by anchoring tungsten nitride （WN） nanoparticles （NPs）, of about 3 nm in size, into a 3D carbon nanotube-reduced graphene oxide framework （CNT-rGO） using an assembly route. After depositing Pt, the contacted and strongly coupled Pt-WN NPs were formed, resulting in electron transfer from Pt to WN. The 3D Pt-WN/CNT-rGO hybrid can be used as a bifunctional electrocatalyst for both methanol oxidation reaction （MOR） and oxygen reduction reaction （ORR）. In MOR, the catalysts showed excellent CO tolerance and a high mass activity of 702.4 mA.mgpt-1, 2.44 and 3.81 times higher than those of Pt/CNT-rGO and Pt/C（JM） catalysts, respectively. The catalyst also exhibited a more positive onset potential （1.03 V）, higher mass activity （151.3 mA.mgpt-1）, and better cyclic stability and tolerance in MOR than ORR. The catalyst mainly exhibited a 4e-transfer mechanism with a low peroxide yield. The high activity was closely related to hybrid structure. That is, the 3D framework provided a favorable path for mass-transfer, the CNT-rGO support was favorable for charge transfer, and strongly coupled Pt-WN can enhance the catalytic activity and CO-tolerance of Pt. Pt-WN/CNT-rGO represents a new 3D catalytic platform that is promising as an electrocatalyst for DMFC because it can catalyze both ORR and MOR in an acidic medium with good stability and highly efficient Pt utilization.
基金Beijing Outstanding Young Scientists Program,Grant/Award Number:BJJWZYJH01201910007023Guangdong Key Laboratory of Battery Safety,Grant/Award Number:2019B121203008+1 种基金National Natural Science Foundation of China,Grant/Award Numbers:51972030,51772030,52002022S&T Major Project of Inner Mongolia Autonomous Region of China,Grant/Award Number:2020ZD0018。
文摘The commercial application of lithium(Li)metal anode is hindered by the growth of Li dendrites.Here,we develop a multidimensional composite struc-ture composed of Co3O4/NiO heterojunction particles and reduced graphene oxide(rGO)nanosheets,that allows Li to nucleate and deposit selectively in one direction.Among,two transition metal oxides(TMOs)without lit-hiophilicity are transformed into lithiophilic species due to the rich phase boundaries and high Li adsorption energies on interfaces,which can provide uniform active sites and reduce nucleation overpotential for Li deposition.Meanwhile,the rGO substrate with high electrical conductivity and large spe-cific surface area can form a conductive network between TMOs and alleviate volume expansion caused by Li deposition.Benefitting from the synergistic effect of the heterojunctions and carbon substrate,the Co_(3)O_(4)/NiO-rGO regu-lates the local current density and enables the dendrite-free Li plating/stripping behavior.At a current density of 1 mA cm^(-2),the Li metal anode with the Co_(3)O_(4)/NiO-rGO host exhibits remarkable electrochemical performance,consistently maintaining high Coulombic efficiency(>93.8%)over 1000 cycles.Additionally,the full cells matched with LiFePO_(4)cathode also display high rate capability of 130 mAh g^(-1)at 1 C and stable cycling life over 500 cycles.
