The graded AlGaN:Si back barrier can form the majority of three-dimensional electron gases(3DEGs)at the GaN/graded AlGaN:Si heterostructure and create a composite two-dimensional(2D)-three-dimensional(3D)channel in Al...The graded AlGaN:Si back barrier can form the majority of three-dimensional electron gases(3DEGs)at the GaN/graded AlGaN:Si heterostructure and create a composite two-dimensional(2D)-three-dimensional(3D)channel in AlGaN/GaN/graded-AlGaN:Si/GaN:C heterostructure(DH:Si/C).Frequency-dependent capacitances and conductance are measured to investigate the characteristics of the multi-temperature trap states of in DH:Si/C and AlGaN/GaN/GaN:C heterostructure(SH:C).There are fast,medium,and slow trap states in DH:Si/C,while only medium trap states exist in SH:C.The time constant/trap density for medium trap state in SH:C heterostructure are(11μs-17.7μs)/(1.1×10^13 cm^-2·eV^-1-3.9×10^13 cm^-2·eV^-1)and(8.7μs-14.1μs)/(0.7×10^13 cm^-2·eV^-1-1.9×10^13 cm^-2·eV^-1)at 300 K and 500 K respectively.The time constant/trap density for fast,medium,and slow trap states in DH:Si/C heterostructure are(4.2μs-7.7μs)/(1.5×10^13 cm^-2·eV^-1-3.2×10^13 cm^-2·eV^-1),(6.8μs-11.8μs)/(0.8×10^13 cm^-2·eV^-1-2.8×10^13 cm^-2·eV^-1),(30.1μs-151μs)/(7.5×10^12 cm^-2·eV^-1-7.8×10^12 cm^-2·eV^-1)at 300 K and(3.5μs-6.5μs)/(0.9×10^13 cm^-2·eV^-1-1.8×10^13 cm^-2·eV^-1),(4.9μs-9.4μs)/(0.6×10^13 cm^-2·eV^-1-1.7×10^13 cm^-2·eV^-1),(20.6μs-61.9μs)/(3.2×10^12 cm^-2·eV^-1-3.5×10^12 cm^-2·eV^-1)at 500 K,respectively.The DH:Si/C structure can effectively reduce the density of medium trap states compared with SH:C structure.展开更多
The advancement of sodium-ion batteries is impeded by challenges such as sluggish ion kinetics and structural instability,particularly in nitride and telluride-based anodes.Herein,a novel multiheterostructured composi...The advancement of sodium-ion batteries is impeded by challenges such as sluggish ion kinetics and structural instability,particularly in nitride and telluride-based anodes.Herein,a novel multiheterostructured composite,MoN/CoTe/NiTe_(2)@NCNTs,was rationally designed by integrating multiple electroactive phases,conductive networks,and hierarchical frameworks into a unified architecture.Unlike conventional binary heterostructures,this ternary system leverages multi-phase synergy to construct extensive interfacial charge redistribution zones,enhancing both structural stability and Na~+ diffusion kinetics.The multidimensional framework ensures structural robustness and buffers volume fluctuations during electrochemical cycling.In half-cell tests,the composite delivers a high reversible capacity of 375.7 mAhg^(-1) at 0.2 A g^(-1),retaining 230.1 mAhg^(-1) after 1000 cycles at 2.0 A g^(-1), demonstrating excellent cycling stability.Even at a high current density of 10.0 A g^(-1),a remarkable capacity of 197.7 mAh g^(-1) is maintained.In full-cell configuration,the MoN/CoTe/NiTe_(2)@NCNTs//Na_(3)V_(2)(PO_4)_(3) system achieves a competitive energy density of 146.9 Wh kg^(-1) and excellent cycling stability with an average capacity degradation rate of <0.11 % per cycle over 500 cycles.Combined density functional theory calculations and ex-situ characterizations reveal a phase-dependent sodium storage mechanism,where intercalation dominates at MoN-rich sites and conversion reactions occur at CoTe/NiTe_(2) domains,supported by interfacial charge redistribution.This work offers a promising strategy for designing advanced multi-heterostructured materials and provides valuable insights into the practical application of highperformance sodium-ion batteries.展开更多
The fabrication of bifunctional electrocatalysts for hydrogen and oxygen evolution in aqueous environment has far-reaching significance.Especially,reasonable interface process regulation toward heterogeneous composite...The fabrication of bifunctional electrocatalysts for hydrogen and oxygen evolution in aqueous environment has far-reaching significance.Especially,reasonable interface process regulation toward heterogeneous composites can make full use of the active sites and improve the electrocatalytic activity.In this study,we designed and synthesized NiS_(2)-MoS_(2)-based heterogeneous composites as efficient and stable electrocatalysts for hydrogen and oxygen evolution in alkaline electrolyte.The heterostructure was obtained by one-step hydrothermal ulfurization operation towards polymolybdate-based metal-organic complex.The composition and nanostructures can be tailored by modulating experiment parameter,realizing the phase-controlled synthesis and interface regulation:(1)High-percentage of 1T-MoS_(2)can be achieved via selecting appropriate vulcanization time and thiourea concentration,benifiting for the higher electroconductivity and more active sites;(2)Regular and orderly vulcanization time promotes the gradual growth and aggregation of nanosheets;(3)The existence of nickel hydroxide improves the electrocatalytic stability for oxygen production performance.The optimized heterogeneous interfaces provide sufficient active sites and accelerate electron transfer.Consequently,the optimal heterogeneous nanosheets present low overpotentials of 33 and 122 m V at the catalytic current densities of 10 m A/cm2for HER and OER,respectively.展开更多
基金the National Key Research and Development Program of China(Grant No.2018YFB1802100)the Natural Science Foundation of Shaanxi Province,China(Grant Nos.2020JM-191 and 2018HJCG-20)+2 种基金the National Natural Science Foundation of China(Grant Nos.61904135,61704124,and 61534007)the China Postdoctoral Science Foundation(Grant Nos.2018M640957 and 2019M663930XB)the Wuhu and Xidian University Special Fund for Industry-University-Research Cooperation,China(Grant No.XWYCXY-012019007).
文摘The graded AlGaN:Si back barrier can form the majority of three-dimensional electron gases(3DEGs)at the GaN/graded AlGaN:Si heterostructure and create a composite two-dimensional(2D)-three-dimensional(3D)channel in AlGaN/GaN/graded-AlGaN:Si/GaN:C heterostructure(DH:Si/C).Frequency-dependent capacitances and conductance are measured to investigate the characteristics of the multi-temperature trap states of in DH:Si/C and AlGaN/GaN/GaN:C heterostructure(SH:C).There are fast,medium,and slow trap states in DH:Si/C,while only medium trap states exist in SH:C.The time constant/trap density for medium trap state in SH:C heterostructure are(11μs-17.7μs)/(1.1×10^13 cm^-2·eV^-1-3.9×10^13 cm^-2·eV^-1)and(8.7μs-14.1μs)/(0.7×10^13 cm^-2·eV^-1-1.9×10^13 cm^-2·eV^-1)at 300 K and 500 K respectively.The time constant/trap density for fast,medium,and slow trap states in DH:Si/C heterostructure are(4.2μs-7.7μs)/(1.5×10^13 cm^-2·eV^-1-3.2×10^13 cm^-2·eV^-1),(6.8μs-11.8μs)/(0.8×10^13 cm^-2·eV^-1-2.8×10^13 cm^-2·eV^-1),(30.1μs-151μs)/(7.5×10^12 cm^-2·eV^-1-7.8×10^12 cm^-2·eV^-1)at 300 K and(3.5μs-6.5μs)/(0.9×10^13 cm^-2·eV^-1-1.8×10^13 cm^-2·eV^-1),(4.9μs-9.4μs)/(0.6×10^13 cm^-2·eV^-1-1.7×10^13 cm^-2·eV^-1),(20.6μs-61.9μs)/(3.2×10^12 cm^-2·eV^-1-3.5×10^12 cm^-2·eV^-1)at 500 K,respectively.The DH:Si/C structure can effectively reduce the density of medium trap states compared with SH:C structure.
基金financially supported by the program of the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT, and Future planning (grant number 2022R1A4A1034312, 2023R1A2C1007413)the Commercialization Promotion Agency for R&D Outcomes (COMPA) grant funded by the Korean Government (Ministery of Science and ICT) (RS2023-00304764)。
文摘The advancement of sodium-ion batteries is impeded by challenges such as sluggish ion kinetics and structural instability,particularly in nitride and telluride-based anodes.Herein,a novel multiheterostructured composite,MoN/CoTe/NiTe_(2)@NCNTs,was rationally designed by integrating multiple electroactive phases,conductive networks,and hierarchical frameworks into a unified architecture.Unlike conventional binary heterostructures,this ternary system leverages multi-phase synergy to construct extensive interfacial charge redistribution zones,enhancing both structural stability and Na~+ diffusion kinetics.The multidimensional framework ensures structural robustness and buffers volume fluctuations during electrochemical cycling.In half-cell tests,the composite delivers a high reversible capacity of 375.7 mAhg^(-1) at 0.2 A g^(-1),retaining 230.1 mAhg^(-1) after 1000 cycles at 2.0 A g^(-1), demonstrating excellent cycling stability.Even at a high current density of 10.0 A g^(-1),a remarkable capacity of 197.7 mAh g^(-1) is maintained.In full-cell configuration,the MoN/CoTe/NiTe_(2)@NCNTs//Na_(3)V_(2)(PO_4)_(3) system achieves a competitive energy density of 146.9 Wh kg^(-1) and excellent cycling stability with an average capacity degradation rate of <0.11 % per cycle over 500 cycles.Combined density functional theory calculations and ex-situ characterizations reveal a phase-dependent sodium storage mechanism,where intercalation dominates at MoN-rich sites and conversion reactions occur at CoTe/NiTe_(2) domains,supported by interfacial charge redistribution.This work offers a promising strategy for designing advanced multi-heterostructured materials and provides valuable insights into the practical application of highperformance sodium-ion batteries.
基金financially supported by the National Natural Science Foundation of China(Nos.22271021,21971024)Liao Ning Revitalization Talents Program(No.XLYC1902011)Research Foundation of Education Bureau of Liaoning Province(No.LJKQZ20222290)。
文摘The fabrication of bifunctional electrocatalysts for hydrogen and oxygen evolution in aqueous environment has far-reaching significance.Especially,reasonable interface process regulation toward heterogeneous composites can make full use of the active sites and improve the electrocatalytic activity.In this study,we designed and synthesized NiS_(2)-MoS_(2)-based heterogeneous composites as efficient and stable electrocatalysts for hydrogen and oxygen evolution in alkaline electrolyte.The heterostructure was obtained by one-step hydrothermal ulfurization operation towards polymolybdate-based metal-organic complex.The composition and nanostructures can be tailored by modulating experiment parameter,realizing the phase-controlled synthesis and interface regulation:(1)High-percentage of 1T-MoS_(2)can be achieved via selecting appropriate vulcanization time and thiourea concentration,benifiting for the higher electroconductivity and more active sites;(2)Regular and orderly vulcanization time promotes the gradual growth and aggregation of nanosheets;(3)The existence of nickel hydroxide improves the electrocatalytic stability for oxygen production performance.The optimized heterogeneous interfaces provide sufficient active sites and accelerate electron transfer.Consequently,the optimal heterogeneous nanosheets present low overpotentials of 33 and 122 m V at the catalytic current densities of 10 m A/cm2for HER and OER,respectively.
