Metal-Organic Framework Enabling Poly(Vinylidene Fluoride)-Based Polymer Electrolyte for Dendrite-Free and Long-Lifespan Sodium Metal Batteries

Sodium dentrite formed by uneven plating/stripping can reduce the utilization of active sodium with poor cyclic stability and,more importantly,cause internal short circuit and lead to thermal runaway and fire.Therefore,sodium dendrites and their related problems seriously hinder the practical application of sodium metal batteries(SMBs).Herein,a design concept for the incorporation of metal-organic framework(MOF)in polymer matrix(polyvinylidene fluoride-hexafluoropropylene)is practiced to prepare a novel gel polymer electrolyte(PH@MOF polymer-based electrolyte[GPE])and thus to achieve high-performance SMBs.The addition of the MOF particles can not only reduce the movement hindrance of polymer chains to promote the transfer of Na^(+)but also anchor anions by virtue of their negative charge to reduce polarization during electrochemical reaction.A stable cycling performance with tiny overpotential for over 800 h at a current density of 5 mA cm^(-2)with areal capacity of 5 mA h cm^(-2)is achieved by symmetric cells based on the resulted GPE while the Na_(3)V_(2)O_(2)(PO_(4))_(2)F@rGO(NVOPF)|PH@MOF|Nacell also displays impressive specific cycling capacity(113.3 mA h g^(-1)at 1 C)and rate capability with considerable capacity retention.

Nano-Ni-Induced Electronic Modulation of MoS_(2) Nanosheets Enables Energy-Saving H_(2) Production and Sulfide Degradation

Electrocatalytic hydrogen evolution and sulfion(S^(2-))recycling are promising strategies for boosting H_(2)production and removing environmental pollutants.Here,a nano-Ni-functionalized molybdenum disulfide(MoS_(2))nanosheet was assembled on steel mesh(Ni-MoS_(2)/SM)for use in sulfide oxidation reaction-assisted,energy-saving H_(2)production.Experimental and theoretical calculation results revealed that anchoring nano-Ni on high-surface-area slack MoS_(2)nanosheets not only optimized catalyst adsorption of polysulfides but also played an important role in promoting hydrogen evolution reaction kinetics by absorbing OH_(ad),thereby greatly enhancing the catalytic performance toward sulfide oxidation reaction and hydrogen evolution reaction.Meanwhile,the Ni/MoS^(2-)based hydrogen evolution reaction+sulfide oxidation reaction system achieved nearly 100%hydrogen production efficiency and only consumed 61%less power per kWh than the oxygen evolution reaction+hydrogen evolution reaction system,which suggested our proposed Ni-MoS_(2)and novel hydrogen production system are promising for sustainable energy production.

Effects of Reaction Temperature on Microstructure and Advanced Pseudocapacitor Properties of NiO Prepared via Simple Precipitation Method

Morphology-controlled synthesis and large-scale self-assembly of nanoscale building blocks into complex nanoarchitectures is still a great challenge in nanoscience. In this work, various porous NiO nanostructures are obtained by a simple ammonia precipitation method and we find that the reaction temperature has a significant impact on their microstructures. Nanoflowers and nanoflakes have been obtained at 0 and50, while, weakly self-assembly nanoflowers with nanoflakes are formed at 20. In order to understand the process-structure-property relationship in nanomaterial synthesis and application, the as-prepared NiO is used as supercapacitor electrode materials, and evaluated by electrochemical measurement. The experimental results indicate that the material obtained at lower temperature has higher pseudocapacitance, the specific capacitance of 944, 889 and 410 F/g are reached for the materials prepared at 0, 20 and 50 and further calcined at 300, respectively. While the material obtained at higher temperature has excellent rate capacity. This offers us an opportunity searching for exciting new properties of NiO, and be useful for fabricating functional nanodevices.

Engineering the high-entropy phase of Pt-Au-Cu nanowire for electrocatalytic hydrogen evolution

Hydrogen economy,as the most promising alternative energy system,relies on the hydrogen production through sustainable water splitting which in turn relies on the high efficiency electrocatalysts.PtAuCu A1-phase alloy has been predicted to be a promising electrocatalyst for the hydrogen evolution.As such preferred phase of Pt-Au-Cu is not thermodynamically favored,herein,we stabilize PtAuCu alloy by engineering the high-entropy phase in the form of nanowire.Density functional theory(DFT)calculations indicate that,in comparison with the ordered phase and segregated phases with discrete hydrogen binding energy,the high-entropy phase provides a diverse combination of site composition to continuously tune the hydrogen binding energy,and thus generate a series of highly active sites for the hydrogen evolution.Reflecting the theoretical prediction,electrochemical tests show that the A1-phase PtAuCu nanowire significantly outperforms its nanoparticle counterpart with phase segregation,toward the electrocatalysis of hydrogen evolution,offering one of the best hydrogen evolution electrocatalysts.

A high-durability aqueous Cu-S battery assisted by pre-copper electrochemistry

Although research interest in aqueous metal-sulfur batteries(AMSs)has surged due to their intrinsic low cost and high capacity,the practical application of AMSs remains a considerable challenge because of the restrictive cycling stability.To circumvent this issue,we propose an innovative and simple pre-copper strategy to realize a high-durability aqueous Cu-S battery.The precopper strategy can effectively promote a stable metal dissolution/deposition,compensate for charge carriers,and facilitate reaction kinetics during the subsequent process.As a result,the aqueous Cu-S battery when coupled with S-decorated porous Ti_(3)C_(2)(S-d-Ti_(3)C_(2))exhibits excellent electrochemical performance,delivering a highly reversible capacity of 1805.4 mAh·g^(-1)in the initial cycle at 0.8 A·g^(-1),impressive cycling stability with 90.2%capacity retention over 800 cycles,and ultralow polarization~0.08 V even at a high current density of 3.1 A·g^(-1).The findings obtained in this work could pave the way for the design of highperformance sulfur-based aqueous batteries,which fill the vacancy of the necessary metal anode,delivering merits in both cost and cycle life.

MoP nanoparticles with a P-rich outermost atomic layer embedded in N-doped porous carbon nanofibers： Self-supported electrodes for efficient hydrogen generation

Despite being pursued for a long time, hydrogen production via water splitting is still a huge challenge mainly due to a lack of durable and efficient catalysts. Molybdenum phosphide （MOP） is theoretically capable of efficient hydrogen evolution reaction （HER） catalysis, however, there is still room for further improvement in its performance. Herein, we propose a design for MoP with a P-rich outermost atomic layer for enhancing HER via complementary theoretical and experimental validation. The correlation of computational results suggests that the P-terminated surface of MoP plays a crucial role in determining its high-efficiency catalytic properties. We fabricated a P-rich outermost atomic layer of MoP nanoparticles by using N-doped porous carbon （MoP@NPCNFs） to capture more P on the surface of MoP and limit the growth of nanoparticles. Further, the as-prepared material can be directly employed as a self-supported electrocatalyst, and it exhibits remarkable electrocatalytic activity for HER in acidic media; it also reveals excellent long-term durability for up to 5,000 cycles with negligible loss of catalytic activity.

Interfacial engineering of Ni/V2O3 for hydrogen evolution reaction

Electrocatalytic water splitting offers a sustainable route for hydrogen production,enabling the clean and renewable alternative energy system of hydrogen economy.The scarcity and high-cost of platinum-group-metal(PGM)materials urge the exploration of high-performance non-PGM electrocatalysts.Herein,a unique hierarchical structure of NiA/2O3 with extraordinary electrocatalytic performance(e.g.t overpotentials as low as 22 mV at 20 mA·cm^-2 and 94 mV at 100 mA·cm^-2)toward hydrogen evolution reaction in alkaline electrolyte(1 M KOH)is reported.The investigation on the hierarchical NiA/2O3 with a bimodal size-distribution also offers insight of interfacial engineering that only proper NiA/2O3 interface can effectively improve H20 adsorption,H20 dissociation as well as H adsorption,for an efficient hydrogen production.

Analysis of graphene-like activated carbon derived from rice straw for application in supercapacitor

Activated carbons with large surface area, abundant microporosity and low cost are the most commonly used electrode materials for energy storage devices. However, activated carbons are conventionally made from fossil precursors, such as coal and petroleum, which are limited resources and easily aggregate large block in high temperature carbonization processes. In this novel work, we examined the use of rice straw as a potential alternative carbon source precursor for the production of graphene-like active carbon. A very slack activated carbon with ultra-thin two-dimensional （2D） layer structure was prepared by our proposed approach in this work, which includes a pre-treatment process and potassium hydroxide activation at high temperatures. The obtained active carbon derived from rice straw exhibited a capacitance of 255 Fig at 0.5 A/g, excellent rate capability, and long cycling capability （98% after 10,000 cycles）.