Membrane-less MoO_(3-x)@TiO_(2)-bromine battery with excellent rate capability and cyclic stability

Bromine has attracted significant attention as a cathode material for aqueous batteries due to its high reduction potential of 1.05 V(Br_(3)^(-)+2e~-■3Br~-),impressive theoretical specific capacity of 223 mA h g^(-1),and rapid reaction kinetics in the electrolyte.However,searching for compatible anode materials to match with bromine has posed a challenge due to its highly corrosive nature.In this study,we developed oxygen-deficient MoO_(3) with TiO_(2) coating(referred to as MoO_(3-x)@TiO_(2))as an anode material to pair with a bromine cathode in static full batteries.The oxygen deficiency contributes to enhanced electronic and protonic diffusion within the MoO_(3-x)lattice,while the TiO_(2) coating mitigates structural dissolution and proton trapping during cycling.The MoO_(3-x)@TiO_(2) demonstrates fast charge storage kinetics and excellent resistance to bromine corrosion.The impressive compatibility between MoO_(3-x)@TiO_(2) and bromine enables the construction of membrane-less full batteries with exceptional rate capability and cyclic stability.The MoO_(3-x)@TiO_(2)-bromine battery achieves an energy density of70.8 W h kg^(-1)at a power density of 328.1 W kg^(-1),showcasing an impressive long-term cyclic life of 20,000 cycles.Our study provides valuable insights for the development of high-performance aqueous secondary batteries.

In situ formed ultrafine metallic Ni from nickel(Ⅱ) acetylacetonate precursor to realize an exceptional hydrogen storage performance of MgH_(2)-Ni-EG nanocomposite

It has been well known that doping nano-scale catalysts can significantly improve both the kinetics and reversible hydrogen storage capacity of MgH_(2) . However, so far it is still a challenge to directly synthesize ultrafine catalysts(e.g., < 5 nm), mainly because of the complicated chemical reaction processes. Here, a facile one-step high-energy ball milling process is developed to in situ form ultrafine Ni nanoparticles from the nickel acetylacetonate precursor in the MgH_(2) matrix. With the combined action of ultrafine metallic Ni and expanded graphite(EG), the formed MgH_(2)-Ni-EG nanocomposite with the optimized doping amounts of Ni and EG can still release 7.03 wt.% H_(2) within 8.5 min at 300 ℃ after 10 cycles. At a temperature close to room temperature(50 ℃), it can also absorb 2.42 wt.% H_(2) within 1 h. It can be confirmed from the microstructural characterization analysis that the in situ formed ultrafine metallic Ni is transformed into Mg_(2)Ni/Mg_(2)NiH_4 in the subsequent hydrogen absorption and desorption cycles. It is calculated that the dehydrogenation activation energy of the MgH_(2)-Ni-EG nanocomposite is also reduced obviously in comparison with the pure MgH_(2) . Our work provides a methodology to significantly improve the hydrogen storage performance of MgH_(2) by combining the in situ formed and uniformly dispersed ultrafine metallic catalyst from the precursor and EG.

Achieving a novel solvent-free regeneration of LiBH_(4) combining hydrogen storage and production in a closed material cycle

LiBH_(4) has been considered as one of the most promising energy storage materials with its ultrahigh hydrogen capacity,which can supply hydrogen through hydrolysis process or realize hydrogen-to-electricity conversion via anodic oxidation reaction of direct borohydride fuel cells(DBFCs).However,the realization of practical hydrogen applications heavily depends on the effective synthesis of high-purity LiBH_(4) and recycling of the spent fuels(LiBO_(2)·xH_(2)O).The present work demonstrates a convenient and high-efficiency solvent-free strategy for regenerating LiBH_(4) with a maximum yield close to 80%,by retrieving its by-products with MgH_(2) as a reducing agent under ambient conditions.Besides,the hydrogen released from the regeneration course can completely compensate the demand for consumed MgH_(2).The isotopic tracer method reveals that the hydrogen stored in LiBH_(4) comes from both MgH_(2) and coordinated water bound to LiBO_(2).Here,the expensive MgH_(2) can be substituted with the readily available and cost-effective MgH_(2)-Mg mixtures to simplify the regeneration route.Notably,LiBH_(4) catalyzed by CoCl_(2) can stably supply hydrogen to proton exchange membrane fuel cell(PEMFC),thus powering a portable prototype vehicle.By combining hydrogen storage,production and utilization in a closed cycle,this work offers new insights into deploying boron-based hydrides for energy applications.

Hydrogen Production via Hydrolysis and Alcoholysis of Light Metal-Based Materials:A Review

As an environmentally friendly and high-density energy carrier,hydrogen has been recognized as one of the ideal alternatives for fossil fuels.One of the major challenges faced by“hydrogen economy”is the development of efficient,low-cost,safe and selective hydrogen generation from chemical storage materials.In this review,we summarize the recent advances in hydrogen production via hydrolysis and alcoholysis of light-metal-based materials,such as borohydrides,Mg-based and Al-based materials,and the highly efficient regeneration of borohydrides.Unfortunately,most of these hydrolysable materials are still plagued by sluggish kinetics and low hydrogen yield.While a number of strategies including catalysis,alloying,solution modification,and ball milling have been developed to overcome these drawbacks,the high costs required for the“one-pass”utilization of hydrolysis/alcoholysis systems have ultimately made these techniques almost impossible for practical large-scale applications.Therefore,it is imperative to develop low-cost material systems based on abundant resources and effective recycling technologies of spent fuels for efficient transport,production and storage of hydrogen in a fuel cell-based hydrogen economy.

Dual-Carbon-Confined SnS Nanostructure with High Capacity and Long Cycle Life for Lithium-ion Batteries

SnS with high theoretical capacity is a promising anode material for lithiumion batteries.However,dramatic volume changes of SnS during repeated discharge/charge cycles result in fractures or even pulverization of electrode,leading to rapid capacity degradation.To solve this problem,we construct a dual-carbon-confined SnS nanostructure(denoted as SnS@C/rGO)by depositing semi-graphitized carbon layers on reduced graphene oxide(rGO)supported SnS nanoplates during high-temperature reduction.The dual carbon of rGO and in situ formed carbon coating confines growth of SnS during the high-temperature calcination.Moreover,during the reversible Li+storage the dual-carbon modification enables good electronic conductivity,relieves the volume effect,and provides double insurance for the electrical contact of SnS even after repeated cycles.Benefiting from the dual-carbon confinement,SnS@C/rGO exhibits significantly enhanced rate capability and cycling stability compared with the bare and single carbon modified SnS.SnS@C/rGO presents reversible capacity of 1029.8 mAh g^(-1)at 0.2 A g^(-1).Even at a high current density of 1 A g^(-1),it initially delivers reversible capacity of 934.0 mAh g^(-1)and retains 98.2%of the capacity(918.0 mAh g^(-1))after 330 cycles.This work demonstrates potential application of dual-carbon modification in the development of electrode materials for high-performance lithium-ion batteries.

Enhanced hydrogen generation from hydrolysis of MgLi doped with expanded graphite

Hydrolysis of Mg-based materials is considered as a potential means of safe and convenient real-time control of H_(2)release,enabling efficient loading,discharge and utilization of hydrogen in portable electronic devices.At present work,the hydrogen generation properties of MgLi-graphite composites were evaluated for the first time.The MgLi-graphite composites with different doping amounts of expanded graphite(abbreviated as EG hereinafter)were synthesized through ball milling and the hydrogen behaviors of the composites were investigated in chloride solutions.Among the above doping systems,the 10 wt.%EG-doped MgLi exhibited the best hydrogen performance in MgCl_(2)solutions.In particular,the 22 h-milled MgLi-10 wt.%EG composites possessed both desirable hydrogen conversion and rapid reaction kinetics,delivering a hydrogen yield of 966 mL H_(2)g^(-1)within merely 2 min and a maximum hydrogen generation rate of 1147 mL H_(2)min^(-1)g^(-1),as opposed to the sluggish kinetics in the EG-free composites.Moreover,the EG-doped MgLi showed superior air-stable ability even under a 75 RH%ambient atmosphere.For example,the 22 h-milled MgLi-10 wt.%EG composites held a fuel conversion of 89%after air exposure for 72 h,rendering it an advantage for Mg-based materials to safely store and transfer in practical applications.The similar favorable hydrogen performance of MgLi-EG composites in(simulate)seawater may shed light on future development of hydrogen generation technologies.

Enhancing (de)hydrogenation kinetics properties of the Mg/MgH_(2) system by adding ANi_(5)(A=Ce,Nd,Pr,Sm,and Y) alloys via ball milling

Magnesium(Mg)-based alloys have already been widely studied as the hydrogen storage materials because of their high reversible hydrogen storage capacity,low cost,light weight,etc.However,the poor de/hydrogenation kinetic properties dramatically hinder the practical applications.In this work,the MgH_(2)-ANi_(5)(A=Ce,Nd,Pr,Sm,and Y) composites were prepared by a high-energy ball milling method.which can effectively refine the particle size thus improving the kinetic properties.Experimental results reveal that the MgH_(2)-ANi_(5) composites mainly consist of Mg_(2)NiH_(4),MgH_(2) and rare earth(RE) hydride,which will be dehydrogenated to form Mg_(2)Ni,Mg and stable RE hydride reversibly.Accordingly,the asmilled MgH_(2)-ANi_(5)(A=Ce,Nd,Pr,Sm,and Y) composites with various A-elements can respectively contribute to a reversible hydrogen storage capacity of 6.16 wt%,5.7 wt%,6.21 wt%,6.38 wt%,and 6.5 wt%at a temperature of 300℃,and show much better kinetic properties in comparison to the pure MgH_(2) without any additive.In-situ formed Mg_(2) Ni and stable RE hydride(such as CeH_(2.73) and YH_(2)) might act as effective catalysts to significantly improve the hydrogen storage properties of MgH_(2).The present work provides a guideline on improving the kinetic properties of the Mg-based hydrogen storage alloys.

Effect of scandium and zirconium alloying on microstructure and gaseous hydrogen storage properties of YFe_(3)

RM_(3) compounds(R=rare earth metals,M=transition metals)have rarely been studied for gaseous hydrogen storage applications because of unfavorable thermodynamics.In this work,the hydrogen storage properties of a single-phase YFe_(3)alloy were improved by non-stoichiometric composition and alloying with Sc and Zr.Only the Y_(1.1-y)Sc_(y)Fe_(3)(y=0.22,0.33)alloys consist of a single rhombohedral phase.The Sc substitution for Y leads to the reduction in the unit cell volume of the YFe_(3)phase,and thus significantly increases the dehydriding equilibrium pressure and decreases the dehydrogenation temperature.The alloy Y_(0.77)Sc_(0.33)Fe_(3)delivers a decomposition enthalpy change of 33.54 kJ/mol and a lowest dehydrogenation temperature of 135℃,in comparison with 38.99 kJ/mol and 165℃ for the alloy Y_(1.1)Fe_(3).The Zr substitution causes a similar thermodynamic destabilization effect,but the composition and microstructure of Y-Zr-Fe alloys need to be further optimized.