Biomass-derived carbon doping to enhance the current carrying capacity and flux pinning of an isotopic Mg^(11)B_(2)superconductor

Low activation isotopic boron(11B)based magnesium diboride(Mg^(11)B_(2))superconductors doped with biomass-derived activated carbon were synthesized using11B and magnesium powder via solid-state reaction.The effect of carbon doping on the lattice structure and superconducting properties of Mg^(11)B_(2)bulks were evaluated using X-ray powder diffraction,high resolution transmission electron microscopy,scanning electron microscopy and magnetization measurements.Precise refinement of structural parameters indicates successful substitution of carbon in Mg^(11)B_(2)bulks.The critical current density(Jc)of carbon doped Mg^(11)B_(2)synthesized at 650℃was enhanced more than two times compared with the pure Mg^(11)B_(2)bulk.Similar improvement was observed for the Mg^(11)B_(2)bulks heat-treated at 800℃.This enhancement is due to successful substitution of biomass-derived carbon with high surface area into Mg^(11)B_(2)lattice.The flux pinning mechanism of pure and doped Mg^(11)B_(2)bulks were investigated using the Dew-Hughes model.This study provides information regarding enhancement of the Jc of low activation Mg^(11)B_(2)superconductors suitable for next-generation fusion magnets.

Photovoltaic-powered supercapacitors for driving overall water splitting:A dual-modulated 3D architecture

Due to the growing demand for clean and renewable hydrogen fuel,there has been a surge of interest in electrocatalytic water-splitting devices driven by renewable energy sources.However,the feasibility of self-driven water splitting is limited by inefficient connections between functional modules,lack of highly active and stable electrocatalysts,and intermittent and unpredictable renewable energy supply.Herein,we construct a dualmodulated three-dimensional(3D)NiCo_(2)O_(4)@NiCo_(2)S_(4)(denoted as NCONCS)heterostructure deposited on nickel foam as a multifunctional electrode for electrocatalytic water splitting driven by photovoltaic-powered supercapacitors.Due to a stable 3D architecture configuration,abundant active sites,efficient charge transfer,and tuned interface properties,the NCONCS delivers a high specific capacity and rate performance for supercapacitors.A twoelectrode electrolyzer assembled with the NCONCS as both the anode and the cathode only requires a low cell voltage of 1.47 V to achieve a current density of 10 mA cm^(−2) in alkaline electrolyte,which outperforms the state-of-the-art bifunctional electrocatalysts.Theoretical calculations suggest that the generated heterointerfaces in NCONCS improve the surface binding capability of reaction intermediates while regulating the local electronic structures,which thus accelerates the reaction kinetics of water electrolysis.As a proof of concept,an integrated configuration comprising a two-electrode electrolyzer driven by two series-connected supercapacitors charged by a solar cell delivers a high product yield with superior durability.

A functionalized separator enables dendrite-free Zn anode via metal-polydopamine coordination chemistry

Designing a multifunctional separator with abundant ion migration paths is crucial for tuning the ion transport in rocking-chair-type batteries.Herein,a polydopamine-functionalized PVDF(PVDF@PDA)nanofibrous membrane is designed to serve as a separator for aqueous zinc-ion batteries(AZIBs).The functional groups(OH and NH)in PDA facilitate the formation of Zn O and Zn N coordination bonds with Zn ions,homogenizing the Zn-ion flux and thus enabling dendrite-free Zn deposition.Moreover,the PVDF@PDA separator effectively inhibits the shuttling of V-species through the formation of V-O coordination bonds.As a result,the Zn/NH_(4)V_(4)O_(10) battery with the PVDF@PDA separator exhibits enhanced cycling stability(92.3%after 1000 cycles at 5 A g^(-1))and rate capability compared to that using a glass fiber separator.This work provides a new avenue to design functionalized separators for high-performance AZIBs.

Photo-enhanced rechargeable high-energy-density metal batteries for solar energy conversion and storage

Solar energy is considered the most promising renewable energy source.Solar cells can harvest and convert solar energy into electrical energy,which needs to be stored as chemical energy,thereby realizing a balanced supply and demand for energy.As energy storage devices for this purpose,newly developed photo-enhanced rechargeable metal batteries,through the internal integration of photovoltaic technology and high-energy-density metal batteries in a single device,can simplify device configuration,lower costs,and reduce external energy loss.This review focuses on recent progress regarding the working principles,device architectures,and performances of various closed-type and open-type photo-enhanced rechargeable devices based on metal batteries,including Li/Zn-ion,Li-S,and Li/Zn-I_(2),and Li/Zn-O_(2)/air,Li-CO_(2),and Na-O_(2) batteries.In addition to provide a fundamental understanding of photo-enhanced rechargeable devices,key challenges and possible strategies are also discussed.Finally,some perspectives are provided for further enhancing the overall performance of the proposed devices.

Synthesis of Fe-doped carbon hybrid composed of CNT/flake-like carbon for catalyzing oxygen reduction

Carbon-based materials with tunable properties have emerged as promising candidates to replace Pt-based catalysts for accelerating oxygen reduction reaction(ORR)in fuel cells or metal-air batteries.In this work,we constructed a carbon hybrid which consists of one-dimensional(1D)carbon nanotubes and flake-like carbons by pyrolysis of leaf-like metal-organic frameworks.The optimal hybrid electrocatalyst of Fe_(7%)-L-CNT-900 possesses the desired features for ORR,including active Fe species,high degree of graphitization,large specific surface area,and hierarchical porous structures.Consequently,Fe_(7%)-L-CNT900 performs a high electrocatalytic activity for ORR with a half-wave potential of 0.88 V,which is comparable to that of Pt/C(20 wt.%).This strategy provides an insight into the investigation of highly efficient and low-cost composite electrocatalyst for oxygen reduction reaction.

Porous Metal Nanocrystal Catalysts:Can Crystalline Porosity Enable Catalytic Selectivity?

Catalytic selectivity is a central issue in the efficiency of catalytic processes.A large number of strategies have been developed to improve the catalytic selectivity of metal catalysts at the atomic and molecular levels,for instance,alloying secondary elements,fabricating metal-support interactions,and introducing surface ligands.Recently,macro/mesoscopic pores and cavities have been demonstrated as an alternative route to promote catalytic selectivity of metal nanocrystal catalysts.The promotion effects of continuous crystalline porosity include(1)more catalytically active sites that accelerate the favorable catalytic routes to targeted products,(2)confined spaces that increase the retention time of key intermediates and remarkably promote the selective catalysis toward desired products,and(3)an optimized electronic structure and coordination environment of active metal sites that tailor the reaction trends of selective catalysis toward desired products.In this minireview,we summarize recent advances in porosity-enabled catalytic selectivity of metal nanocrystal catalysts with focused discussions of CO_(2) reduction electrocatalysis and selective hydrogenation reactions.The mechanisms that allow for the continuous porosity that enables the catalytic selectivity of metal nanocrystal catalysts are discussed in detail.We end this minireview by proposing current challenges and offering future opportunities in this research field.