Ultrafine Fe/Fe3C decorated on Fe-N_(x)-C as bifunctional oxygen electrocatalysts for efficient Zn-air batteries

Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.

Development of Metal and Metal-Based Composites Anode Materials for Potassium-Ion Batteries

Potassium-ion batteries(KIBs)are considered the next powerful potential generation energy storage system because of substantial potassium resource availability and similar characteristics with lithium.Unfortunately,the actual application of KIBs is inferior to that of lithium-ion batteries(LIBs),in which the fi nite energy density,ordinary circular life,and underdeveloped fabrication technique dominate the key constraints.Various works have recently been directed to growing novel anode electrodes with superior electrochemical capability.Noticeably,metals/metal oxides materials(e.g.,Sb,Sn,Zn,SnO_(2),and MoO_(2))have been widely investigated as KIBs anodes because of high theoretical capacity,suggesting outstanding promise for high-energy KIBs.In this review,the latest research of metals/metal oxides electrodes for potassium storage is summarized.The major strategies to control the electrochemical property of metals/metal oxides electrodes are discussed.Finally,the future investigation foreground for these anode electrodes has been proposed.

Recycle spent graphite to defect-engineered,high-power graphite anode

Graphite is a dominant anode material for lithium-ion batteries(LIBs)due to its outstanding electrochemical performance.However,slow lithium ion(Li+)kinetics of graphite anode restricts its further application.Herein,we report that high-temperature shock(HTS)can drive spent graphite(SG)into defect-rich recycled graphite(DRG)which is ideal for high-rate anode.The DRG exhibits the charging specific capacity of 323 mAh/g at a high current density of 2 C,which outperforms commercial graphite(CG,120 mAh/g).The eminent electrochemical performance of DRG can be attributed to the recovery of layered structure and partial remaining defects of SG during ultrafast heating and cooling process,which can effectively reduce total strain energy,accelerate the phase transition in thermodynamics and improve the Li+diffusion.This study provides a facile strategy to guide the re-graphitization of SG and design high performance battery electrode materials by defect engineering from the atomic level.

Ni_(3)S_(2)@NiWO_(4)nanoarrays towards all-solid-state hybrid supercapacitor with record-high energy density

The rational design and synthesis of hybrid-type electrode nanomaterials are significant for their diverse applications,including their potential usage as high-efficiency nanoarchitectures for supercapacitors(SCs)as a class of promising energy-storage systems for powering next-generation electric vehicles and electronic devices.Here,we reported a facile and controllable synthesis of core-shell Ni_(3)S_(2)@NiWO_(4)nanoarrays to fabricate a freestanding electrode for hybrid SCs.Impressively,the as-prepared freestanding Ni_(3)S_(2)@NiWO_(4)electrode presents an ultrahigh areal capacity of 2032μA h cm^(-2)at 5 mA cm^(-2),and a capacity retention of 63.6%even when the current density increased up to 50 mA cm^(-2).Remarkably,the Ni_(3)S_(2)@NiWO_(4)nanoarraybased hybrid SC delivers a maximum energy density of 1.283 mW h cm^(-2)at 3.128 mW cm^(-2)and a maximum power density of 41.105 mW cm^(-2)at 0.753 mW h cm^(-2).Furthermore,the hybrid SC exhibits a capacity retention of 89.6%even after continuous 10,000 cycles,proving its superior stability.This study provides a facile pathway to rationally design a variety of core-shell metal nanostructures for high-performance energy storage devices.

Stable confinement of Fe/Fe_(3)C in Fe,N-codoped carbon nanotube towards robust zinc-air batteries

Catalytic oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)have garnered great attention as the key character in metal-air batteries.Herein,we developed a superior nonprecious bifunctional oxygen electrocatalyst,fabricated through spatial confinement of Fe/Fe_(3)C nanocrystals in pyridinic N and Fe-Nx rich carbon nanotubes(Fe/Fe_(3)C-N-CNTs).During ORR,the resultant electrocatalyst exhibits positive onset pote ntial of 1.0 V(vs.RHE),large half-wave potentials of 0.88 V(vs.RHE),which is more positive than Pt/C(0.98 V and 0.83 V,respectively).Remarkably,Fe/Fe_(3)C-N-CNTs exhibits outstanding durability and great methanol tolerance,exceeding Pt/C and most reported nonprecious metal-based oxygen reduction electrocatalysts.Moreover,Fe/Fe_(3)C-N-CNTs show a markedly low potential at j=10 mA/cm^(2),small Tafel slopes and extremely high stability for OER.Impressively,the Fe/Fe_(3)C-N-CNTs-based Zn-air batteries demonstrate high power density of 183 mW/cm^(2)and robust charge/discharge stability.It is revealed that the spatial confinement effect can impede the aggregation and corrosion of Fe/Fe_(3)C nanocrystals.Meanwhile,Fe/Fe_(3)C and Fe-Nx play synergistic effect on boosting the ORR/OER activity,which provides an important guideline for construction of inexpensive nonprecious metal-carbon hybrid nanomaterials.