查看更多>>摘要：The practical energy density of lithium-sulfur batteries(LSBs)is seriously limited by the high elec-trolyte-to-sulfur ratios(E/S).The E/S can be reduced by employing hosts with easy-to-infiltrate structure that ensures the uniform distribution of a lean electrolyte and high catalytic activity that can suppress"shuttle effect"via accelerating the slow conversion of soluble polysulfides to insoluble sulfides.Among the easy-to-infiltrate structures,the three-dimensional-ordered macroporous(3DOM)structure is easier to scale preparation and more suitable for the existing industrial processes.However,it is difficult to obtain the 3 DOM with(1)high penetrability due to the high viscosity of frequently-used organic polymer precursors and(2)high catalytic activity due to the low confinement effect,meaning that uniformly dispersed small-sized catalytic materials are difficult to load on 3DOM.Herein,using carbon dots(CDs)with both organic and inorganic properties as a precursor and aggregation limiting agent,a 3DOM host with high penetrability and homodispersed Ni particles of small sizes(Ni-CDs-3DOM)was synthesized.In this host:(1)CDs precursor with suitable viscosity can improve the penetrability.(2)CDs can effectively inhibit the agglomeration of Ni particles.(3)Uniformly dispersed small-size Ni particles offer high-efficiency catalytic activity toward sulfur reactions.Con-sequently,the Ni-CDs-3DOM/sulfur cathode exhibits high sulfur utilization and stable cycling performance even under high sulfur loading(5.5 mg·cm-2)and low E/S(6.5 μl·mg-1).This work indicates the usefulness of CDs in constructing hosts for LSBs with high energy density.
查看更多>>摘要：Forming an ultrathin conducting layer on a fluorinated carbon(CFx)surface for reducing severe elec-trochemical polarization in lithium/fluorinated carbon pri-mary batteries(Li/CFx)remains a considerable challenge for achieving batteries with excellent rate capability.Herein,CFx was modified by using acetylene/argon mix-ture plasma combined with MnO2 particles.The CFx/C/MnO2 composite effectively reduced the voltage hysteresis and improved the electrochemical performance of Li/CFx.The excellent rate performance of CFx/C/MnO2 was due to the high electrochemical activity provided by the atomic-scale conductive carbon layer and ultrafine MnO2 particles.Compared with pristine CFx,the charge transfer resistance of the optimized CFx/C/MnO2 decreased from 218.5 to 48.2 Ω,the discharge rate increased from 2C to 10C,and the power density increased from 3.11 to 13.44 kW·g-1.The intrinsic reason for the enhanced rate performance was attributed to the fact that the ultrathin carbon layer acted as a conductive bridge to reduce the voltage hysteresis at the initial stage of the Li/CFx discharge,and the high electro-chemical activity of the ultrafine MnO2 particles provided a faster lithium-ion diffusion rate.
查看更多>>摘要：Hard carbon(HC)is broadly recognized as an exceptionally prospective candidate for the anodes of sodium-ion batteries(SIBs),but their practical implemen-tation faces substantial limitations linked to precursor factors,such as reduced carbon yield and increased cost.Herein,a cost-effective approach is proposed to prepare a coal-derived HC anode with simple pre-oxidation followed by a post-carbonization process which effectively expands the d002 layer spacing,generates closed pores and increases defect sites.Through these modifications,the resulting HC anode attains a delicate equilibrium between plateau capacity and sloping capacity,showcasing a remarkable reversible capacity of 306.3 mAh·g-1 at 0.03 A·g-1.Fur-thermore,the produced HC exhibits fast reaction kinetics and exceptional rate performance,achieving a capacity of 289 mAh·g-1 at 0.1 A·g-1,equivalent to～94.5％of that at 0.03 A·g-1.When implemented in a full cell configu-ration,the impressive electrochemical performance is evi-dent,with a notable energy density of 410.6 Wh·kg-1(based on cathode mass).In short,we provide a straight-forward yet efficient method for regulating coal-derived HC,which is crucial for the widespread use of SIBs anodes.
查看更多>>摘要：Calcium-ion batteries(CIBs)have generated intense interest due to the growing demand for safer,cheaper,and large-scale energy storage systems.However,their development is still in its infancy,owing to the lack of suitable cathodes for sustaining reversible Ca2+intercala-tion/deintercalation.Herein,layered H2V3O8(HVO)with Zn2+pre-insertion(ZHVO)is reported as a high-rate and highly durable cathode material for CIBs.The existence of Zn2+and H2O pillars could expand the interlayer spacing up to 1.8 nm,which is favorable for the diffusion of bulky Ca2+.The formation of Zn-O bonds facilitates electron transfer and enhances electrical conduction.Consequently,the ZHVO cathode achieves superior capacity performance(213.9 mAh·g-1 at 0.2 A·g-1)and long lifespan(78.3％for 1,000 cycles at 5 A·g-1)compared to pristine HVO.Density functional theory(DFT)calculations revealed that Zn2+moved during Ca2+intercalation,thereby reducing the diffusion energy barrier and facilitating Ca2+diffusion.Finally,a safe aqueous calcium ion cell was successfully assembled.
查看更多>>摘要：To effectively address energy challenges,it is crucial to explore efficient and stable bifunctional non-precious metal catalysts.In this study,a Mo-doped nickel-iron layered double hydroxide with flower-cluster archi-tecture was successfully prepared by a one-step hydrothermal method,which demonstrated a good water splitting performance.After an appropriate amount of Mo doping,some lattice distortions in the material provided reactive sites for the adsorption and conversion of inter-mediates,thus optimising the charge distribution of the material.Moreover,the multidimensional void structures formed after doping had a larger specific surface area and accelerated the penetration of the electrolyte,which sig-nificantly improved the activity of the catalyst in alkaline media.At 10 mA.cm-2,the hydrogen and oxygen evolu-tion overpotentials of Mo-doped nickel-iron double hydroxides(Mo-NiFe LDH/NF-0.2)were 167 and 220 mV,respectively,with an excellent durability up to 24 h.When the Mo-NiFe LDH/NF-0.2 catalyst was used as the cathode and anode of an electrolytic cell,the catalyst achieved a current density of 10 mA.cm-2 at an applied voltage of 1.643 V.This study provides a novel approach for designing excellent bifunctional electrocatalysts con-taining nonprecious metals.
查看更多>>摘要：Herein,the successful preparation of a single-atom catalyst V-N-C using vanadium-doped zeolitic imi-dazolate framework(ZIF)-8 as a precursor is reported.The experimental results showed that the V-N-C had a good promoting effect on the hydrogen storage performance of MgH2,and the optimal addition amount of V-N-C was 10 wt％.The hydrogenation and dehydrogenation apparent activation energies of 10 wt％V-N-C-catalyzed MgH2 were reduced by 44.9 and 53.5 kJ·mol-1,respectively,compared to those of additive-free MgH2.The 10 wt％V-N-C-catalyzed MgH2 could reabsorb 5.92 wt％of hydro-gen in 50 min at 150 ℃,with a capacity retention rate of 99.1％after 30 cycles of hydrogen absorption and des-orption.Mechanism analysis showed that V-N-C was partially transformed into VN and metallic V when it was milled with MgH2;the in-situ-formed VN and metallic V played an important role in improving the hydrogen storage performance of MgH2.This approach provides a potential solution for obtaining high-performance Mg-based hydro-gen storage materials through synergistic interactions between V,N and C.
查看更多>>摘要：Constructing heterostructures has proved to be a successful strategy to fabricate electrocatalysts with high efficiency for water splitting.However,the structure evo-lution in alkaline hydrogen evolution reaction lacks investigation and the specific active center remains dis-putable.Herein,we take the well-designed Ni3S2@VO2 heterostructures as a model to investigate the electrocat-alytic activity and the surface reconstruction process of heterostructure catalysts in alkaline electrolyte.The Ni3S2@VO2 heterostructures,with Ni3S2 nanorods as the core and VO2 nanoflakes as the shell,coupled with the high conductive Ni3S2,the hydrophilic VO2 and modulated electronic structures at the interfaces,exhibited prominent activity and superior stability at various current densities.Further,the ex-situ characterizations confirmed that the surface reconstruction from Ni3S2@VO2 into Ni3S2@amorphous-Ni(OH)2 in alkaline media could opti-mize the water dissociation barrier and exposed large active area,thereby contributing to improved electrocatalytic performance.Our study not only introduces novel high-performance electrocatalysts for hydrogen evolution reaction(HER),but also provides a new avenue for re-examining hetero-structural catalysts in alkaline solutions.
查看更多>>摘要：In this study,the double loaded Co-Fe-B@g-C3N4/NF(NF:Ni foam)thin film catalysts were prepared for the first time via chemical deposition method at room temperature.By optimizing the reducing agent concentra-tion to 0.9 mol·L-1,the as-obtained Co-Fe-B@g-C3N4/NF exhibited the twisted ribbon structure with more dis-tinct three-dimensional hierarchy and the smaller particle size,showing the good catalytic property for the hydrolysis of NaBH4 solution.The H2 generation rate of Co-Fe-B@g-C3N4/NF and binary Co-B@g-C3N4/NF under visi-ble light irradiation surpassed the value under natural condition.The apparent activation energy of Co-Fe-B@g-C3N4/NF(45.0 kJ·mol-1)under visible light irradiation was obviously reduced when compared with the natural condition(48.4 kJ·mol-1)and binary Co-B@g-C3N4/NF(60.6 kJ·mol-1)under visible light irradiation.Further-more,the catalytic performance of the optimized Co-Fe-B@g-C3N4/NF thin film catalyst was superior to most of the reported non-noble metal and even noble metal cata-lysts.Hence,it illustrated that the catalytic H2 production performance of Co-Fe-B@g-C3N4/NF thin film was distinctly improved after the introduction of light and multicomponent recombination.
查看更多>>摘要：Efficient electrocatalysts are vital to large-cur-rent hydrogen production in commercial water splitting for green energy generation.Herein,a novel heterophase engineering strategy is described to produce polymorphic CoSe2 electrocatalysts.The composition of the electrocat-alysts consisting of both cubic CoSe2(c-CoSe2)and orthorhombic CoSe2(o-CoSe2)phases can be controlled precisely.Our results demonstrate that junction-induced spin-state modulation of Co atoms enhances the adsorption of intermediates and accelerates charge transfer resulting in superior large-current hydrogen evolution reaction(HER)properties.Specifically,the CoSe2-based heterophase cat-alyst with the optimal c-CoSe2 content requires an over-potential of merely 240 mV to achieve 1,000 mA·cm-2 as well as a Tafel slope of 50.4 mV·dec-1.Furthermore,the electrocatalyst can maintain a large current density of 1,500 mA·cm-2 for over 320 h without decay.The results reveal the advantages and potential of heterophase junction engineering pertaining to design and fabrication of low-cost transition metal catalysts for large-current water splitting.
查看更多>>摘要：Ti-based catalysts are known to improve the hydrogen storage performance of NaAlH4 by facilitating the dissociation/recombination of H-H and Al-H bonds.The catalytic activity of metallic Ti species strongly depends on its particle size and dispersity.Ti clusters and even single atoms are therefore highly desirable,but their controllable fabrication has been highly challenging.Herein,we demonstrate a novel facile sonochemical syn-thesis of a Ti-O clusters featuring single Ti atom catalyst at room temperature.Through reducing TiCl4 by MgBu2 with ultrasound instead of heating as driving force,numerous single Ti atoms coupled with Ti-O clusters with Ti loading on graphene(Ti1/Ti-O@G)up to 22.6 wt％have been successfully obtained.The prepared Ti1/Ti-O@G con-tributes high reactivity and superior catalytic activity,therefore enabling full dehydrogenation of NaAlH4 at 80 ℃ in thermogravimetric mode and re-hydrogenation at 30 ℃ and 10 MPa with 4.9 wt％H2.This fact indicates for the first time that single Ti atom catalyst with high loading is highly effective in catalyzing hydrogen cycling of NaAlH4 at remarkably reduced temperatures.
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