Superior catalyst supports are crucial to developing advanced electrocatalysts toward heterogeneous catalytic reactions.Herein,we systematically investigate the role of transition metal‐functionalized N‐doped carbon...Superior catalyst supports are crucial to developing advanced electrocatalysts toward heterogeneous catalytic reactions.Herein,we systematically investigate the role of transition metal‐functionalized N‐doped carbon nanosheets(M‐N‐C,M=Mn,Fe,Co,Ni,Cu,Mo,and Ag)as the multifunctional electrocatalyst supports toward hydrogen evolution/oxidation reactions(HER/HOR)in alkaline media.The results demonstrate that all the M‐N‐C nanosheets,except Cu‐N‐C and Ag‐N‐C,can promote the alkaline HER/HOR electrocatalytic activity of Pt by accelerating the sluggish Volmer step,among which Mn plays a more significant role.Analyses reveal that the promotion effect of M‐N‐C support is closely associated with the electronegativity of the metal dopants and the relative filling degree of their d‐orbitals.For one,the metal dopant in M‐N‐C with smaller electronegativity would provide more electrons to oxygen and hence tune the electronic structure of Pt via the M‐O‐Pt bonds at the interface.For another,the transition metal in M‐N4 moieties with more empty d orbitals would hybridize with O 2p orbitals more strongly that promotes the adsorption of water/hydroxyl species.The results demonstrate the conceptual significance of multifunctional supports and would inspire the future development of advanced electrocatalysts.展开更多
The coupling between electrochemically active material and conductive matrix is vitally important for high efficiency lithium ion batteries （LIBs）. By introducing oxygen groups into the nanoporous carbon framework, ...The coupling between electrochemically active material and conductive matrix is vitally important for high efficiency lithium ion batteries （LIBs）. By introducing oxygen groups into the nanoporous carbon framework, we accom- plish sustainably enhanced electrochemical performance for a SnO2/carbon LIB. 2-5 nm SnO2 nanoparticles are hydro- thermally grown in different nanoporous carbon frameworks, which are pristine, nitrogen- or oxygen-doped carbons. Compared with pristine and nitrogen-doped carbon hosts, the SnO2/oxygen-doped activated carbon （OAC） composite ex- hibits a higher discharge capacity of 1,122mAhg^-1 at 500 mA g^-1 after 320 cycles operation and a larger lithium storage capacity up to 680 mAhg-I at a high rate of 2,000 mA g^-1. The exceptional electrochemical performance originated from the oxygen groups, which could act as Lewis acid sites to attract electrons effectively from Sn during the charge process, thus accelerating reversible conversion of Sn to SnO2. Meanwhile, SnO2 nanoparticles are effectively bonded with carbon through such oxygen groups, thus preventing the electrochemical sintering and maintaining the cycling stability of the SnO2/OAC composite anode. The high electrochemical performance, low biomass cost, and facile preparation renders the SnO2/OAC composites a promising candidate for anode materials.展开更多
文摘Superior catalyst supports are crucial to developing advanced electrocatalysts toward heterogeneous catalytic reactions.Herein,we systematically investigate the role of transition metal‐functionalized N‐doped carbon nanosheets(M‐N‐C,M=Mn,Fe,Co,Ni,Cu,Mo,and Ag)as the multifunctional electrocatalyst supports toward hydrogen evolution/oxidation reactions(HER/HOR)in alkaline media.The results demonstrate that all the M‐N‐C nanosheets,except Cu‐N‐C and Ag‐N‐C,can promote the alkaline HER/HOR electrocatalytic activity of Pt by accelerating the sluggish Volmer step,among which Mn plays a more significant role.Analyses reveal that the promotion effect of M‐N‐C support is closely associated with the electronegativity of the metal dopants and the relative filling degree of their d‐orbitals.For one,the metal dopant in M‐N‐C with smaller electronegativity would provide more electrons to oxygen and hence tune the electronic structure of Pt via the M‐O‐Pt bonds at the interface.For another,the transition metal in M‐N4 moieties with more empty d orbitals would hybridize with O 2p orbitals more strongly that promotes the adsorption of water/hydroxyl species.The results demonstrate the conceptual significance of multifunctional supports and would inspire the future development of advanced electrocatalysts.
基金supported by the National High Technology Research and Development Program of China(2012AA053305 and 2014AA052501)the National Natural Science Foundation of China(21506224)
文摘The coupling between electrochemically active material and conductive matrix is vitally important for high efficiency lithium ion batteries （LIBs）. By introducing oxygen groups into the nanoporous carbon framework, we accom- plish sustainably enhanced electrochemical performance for a SnO2/carbon LIB. 2-5 nm SnO2 nanoparticles are hydro- thermally grown in different nanoporous carbon frameworks, which are pristine, nitrogen- or oxygen-doped carbons. Compared with pristine and nitrogen-doped carbon hosts, the SnO2/oxygen-doped activated carbon （OAC） composite ex- hibits a higher discharge capacity of 1,122mAhg^-1 at 500 mA g^-1 after 320 cycles operation and a larger lithium storage capacity up to 680 mAhg-I at a high rate of 2,000 mA g^-1. The exceptional electrochemical performance originated from the oxygen groups, which could act as Lewis acid sites to attract electrons effectively from Sn during the charge process, thus accelerating reversible conversion of Sn to SnO2. Meanwhile, SnO2 nanoparticles are effectively bonded with carbon through such oxygen groups, thus preventing the electrochemical sintering and maintaining the cycling stability of the SnO2/OAC composite anode. The high electrochemical performance, low biomass cost, and facile preparation renders the SnO2/OAC composites a promising candidate for anode materials.
