Fe-N_(x) sites coupled with core-shell FeS@C nanoparticles to boost the oxygen catalysis for rechargeable Zn-air batteries

The development of efficient single-atom catalysts(SACs) for the oxygen reduction reaction(ORR)remains a formidable challenge,primarily due to the symmetric charge distribution of metal singleatom sites(M-N_(4)).To address such issue,herein,Fe-N_(x) sites coupled synergistic catalysts fabrication strategy is presented to break the uniform electronic distribution,thus enhancing the intrinsic catalytic activity.Precisely,atomically dispersed Fe-N_(x) sites supported on N/S-doped mesoporous carbon(NSC)coupled with FeS@C core-shell nanoparticles(FAS-NSC@950) is synthesized by a facile hydrothermal reaction and subsequent pyrolysis.Due to the presence of an in situ-grown conductive graphitic layer(shell),the FeS nanoparticles(core) effectively adjust the electronic structure of single-atom Fe sites and facilitate the ORR kinetics via short/long-range coupling interactions.Consequently,FAS-NSC@950displays a more positive half-wave potential(E_(1/2)) of 0.871 V with a significantly boosted ORR kinetics(Tafel slope=52.2 mV dec^(-1)),outpacing the commercial Pt/C(E_(1/2)=0.84 V and Tafel slope=54.6 mV dec^(-1)).As a bifunctional electrocatalyst,it displays a smaller bifunctional activity parameter(ΔE) of 0.673 V,surpassing the Pt/C-RuO_(2) combination(ΔE=0.724 V).Besides,the FAS-NSC@950-based zincair battery(ZAB) displays superior power density,specific capacity,and long-term cycling performance to the Pt/C-Ir/C-based ZAB.This work significantly contributes to the field by offering a promising strategy to enhance the catalytic activity of SACs for ORR,with potential implications for energy conversion and storage technologies.

Continuous nitrogen-doped carbon nanotube matrix for boosting oxygen electrocatalysis in rechargeable Zn-air batteries

Developing robust oxygen electrocatalyst with high-performance is very significant for practical rechargeable Zn-air battery.We report herein the preparation of three-dimensional continuous nanocarbon network composed of interconnected nitrogen-doped carbon nanotubes and its application as oxygen electrocatalysis in rechargeable Zn-air battery.Except the excellent electrochemical bifunctionality,this carbon nanotube matrix also delivers an impressive battery performance.Specifically,an opencircuit voltage of 1.50 V as well as a high power density of 220 m W cm^(-2) with remarkable cycling stability for 1600 h is achieved in the rechargeable Zn-air battery.The study not only provides an efficient bifunctional oxygen electrocatalyst but more importantly may pave significant concepts in designing robust electrode for long-life rechargeable Zn-air battery and other energy technologies.

Direct growth of ordered N-doped carbon nanotube arrays on carbon fiber cloth as a free-standing and binder-free air electrode for flexible quasi-solid-state rechargeable Zn-Air batteries

The development of an air electrode that is flexible in physical property and highly active and durable at different geometric status for both oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)is of crucial importance for the rational design of flexible rechargeable Zn-air batteries(ZABs).Considering their good elasticity,high conductivity,and superior thermal and chemical stability,carbon nanotubes have been widely used as a catalyst support in various electrocatalysts,while oxide or metal nanoparticles have been frequently deposited on the carbon nanotube substrate to perform as the active materials.Considering the poor contact between active materials and carbon nanotubes may introduce a challenge for long-term operating stability,in particular in flexible devices,pure carbon electrocatalyst is highly appreciated.Herein,a free-standing air electrode with cobalt nanoparticles encapsulated N-codoped carbon nanotube arrays uniformly grown on the surface of carbon fiber cloth is developed by a two-step in situ growth method.Such a carbon-based electrode shows outstanding activity for both ORR and OER.The flexible ZAB with such air electrode shows superior flexibility and stability working under extreme bending conditions.Moreover,the polarization and round-trip efficiency for the flexible battery is 0.67 V and 64.4%at 2 mA/cm2,respectively,even after being operated for 30 hours.This study provides a feasible way to design all carbon-based free-standing and flexible electrode and enlightens the electrode design for flexible energy conversion/storage devices.

Tailoring structural properties of carbon via implanting optimal co nanoparticles in n-rich carbon cages toward high-efficiency oxygen electrocatalysis for rechargeable zn-air batteries

Rational construction of carbon-based materials with high-efficiency bifunctionality and low cost as the substitute of precious metal catalyst shows a highly practical value for rechargeable Zn-air batteries(ZABs)yet it still remains challenging.Herein,this study employs a simple mixing-calcination strategy to fabricate a high-performance bifunctional composite catalyst composed of N-doped graphitic carbon encapsulating Co nanoparticles(Co@NrC).Benefiting from the core-shell architectural and compositional advantages of favorable electronic configuration,more exposed active sites,sufficient electric conductivity,rich defects,and excellent charge transport,the optimal Co@NrC hybrid(Co@NrC-0.3)presents outstanding catalytic activity and stability toward oxygen-related electrochemical reactions(oxygen reduction and evolution reactions,i.e.,ORR and OER),with a low potential gap of 0.766 V.Besides,the rechargeable liquid ZAB assembled with this hybrid electrocatalyst delivers a high peak power density of 168 mW cm^(−2),a small initial discharge-charge potential gap of 0.45 V at 10 mA cm^(−2),and a good rate performance.Furthermore,a relatively large power density of 108 mW cm^(−2) is also obtained with the Co@NrC-0.3-based flexible solid-state ZAB,which can well power LED lights.Such work offers insights in developing excellent bifunctional electrocatalysts for both OER and ORR and highlights their potential applications in metal-air batteries and other energy-conversion/storage devices.

Rechargeable Zn-air batteries initiated by nickel–cobalt bimetallic selenide

A Zn-air battery is a potential next-generation energy storage device owing to its extremely high theoretical energy density. Currently, it is important to explore non-precious metal electrocatalysts with high electroactivity and stability in the oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) for the development of Zn-air batteries. In this work, porous(Ni,Co)Se2 nanosheets were synthesized by selenizing Ni Co2O4 nanosheets. By regulating the conductivity and morphology of the sample, the prepared porous(Ni,Co)Se2 nanosheets show enhanced electrocatalytic activity for OER and ORR compared to Ni Co2O4 nanosheets. The aqueous Zn-air battery using porous(Ni,Co)Se2 nanosheets as the air cathode exhibits superior charge and discharge performance(1.98 V for charging and 1.17 V for discharging), high specific capacity(770 m Ah/g), and excellent cycle stability(140 h). These results indicate that the porous(Ni,Co)Se2 nanosheets are suitable as a bifunctional electrocatalyst for future Zn-air batteries.

Co/Ni dual-metal embedded in heteroatom doped porous carbon core-shell bifunctional electrocatalyst for rechargeable Zn-air batteries

Rational construction of highly efficient and cheap bifunctional electrocatalysts to boost both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)is extremely essential for the wide application of rechargeable metal-air battery.In this work,we design a core-shell structural catalyst of CoNi dual-metal embedded in nitrogen doped porous carbon(NPC,CoNi@NPC),which is developed via the pyrolysis of CoNiMOFs,assisting by mesoporous SiO_(2) to effectively inhibit the aggregation of metal sites.Consequently,the asprepared CoNi@NPC manifests good ORR activity with half-wave potential up to 0.77 V.Specifically,the CoNi@NPC gives a very low OER over-potential of merely 101 mV in 6 M KOH along with high stability,outperforming the commercial Pt/C-RuO_(2).Moreover,the home-made zinc air battery with CoNi@NPC air cathode demonstrates excellent stability over long-term charging–discharging test,and delivers the maximum power density of 224 mW cm^(-2).The enhanced high performance of CoNi@NPC bifunctional catalyst for both ORR and OER can be ascribed to its unique core-shell structure and strong synergistic effect between the dual-bimetal active sites and the heteroatom doped carbon.This work opens a new avenue for the rational design of nonprecious metal bifunctional catalysts for rechargeable metal-air battery.

Heteroatom anchors Fe-Mn dual-atom catalysts with bi-functional oxygen catalytic activity for low-temperature rechargeable flexible Zn-air batteries

M-N-C(M=Fe,Co,Ni,etc.) catalyst owns high catalytic activity in the oxygen catalytic reaction which is the most likely to replace the Pt-based catalysts.But it is still a challenge to further increase the active site density.This article constructs the high-efficiency FeMn-N/S-C-1000 catalyst to realize ORR/OER bifunctional catalysis by hetero-atom,bimetal(Fe,Mn) doped simultaneously strategy.When evaluated it as bi-functional electro-catalysts,FeMn-N/S-C-1000 exhibits excellent catalytic activity(E_(1/2)=0.924 V,E_(j=10)=1.617 V) in alkaline media,outperforms conventional Pt/C,RuO_(2) and most non-precious-metal catalysts reported recently,Such outstanding performance is owing to N,S co-coordinated with metal to form multi-types of single atom,dual atom active sites to carry out bi-catalysis.Importantly,nitrite poison test provides the proof that the active sites of FeMn-N/S-C are more than that of single-atom catalysts to promote catalytic reactions directly.To better understand the local structure of Fe and Mn active sites,XAS and DFT were employed to reveal that FeMn-N_5/S-C site plays the key role during catalysis.Notably,the FeMn-N/S-C-1000 based low-temperature rechargeable flexible Zn-air also exhibits superior discharge performance and extraordinary durability at-40℃.This work will provide a new idea to design diatomic catalysts applied in low-temperature rechargeable batteries.

Reinforcing oxygen electrocatalytic activity via selective dualphase heterointerface engineering for rechargeable Zn-air batteries

Dual-phase heterointerface electrocatalysts(DPHE)constructed by oxygen reduction reaction(ORR)-and oxygen evolution reaction(OER)-active elements exhibit excellent bifunctional activity and long-term durability due to the abundant interface exposure and synergistic catalytic effect.Herein,low-dimensional N-doped graphene nanoribbons(N-GNRs)coupling with ultrathin CoO nanocomposites(N-GNRs/CoO)were controllably fabricated through a facile two-step approach using synthesized Co(OH)_2 nanosheet as CoO precursor.Density functional theory(DFT)calculations and experimental characterizations prove that the formation of interface between N-GNRs and CoO can induce local charge redistribution,contributing to the improvement of catalytic activity and stability.The optimal N-GNRs/CoO DPHE possesses hierarchically porous architectures and presents outstanding bifunctional activities with a small potential gap of 0.729 V between the potential at 10 mA·cm^(-2)for OER and the halfwave potential for ORR,which outperforms Pt/C+IrO_(2)and the majority of noble-metal-free bifunctional catalysts.Liquid-and solid-state rechargeable Zn-air batteries assembled with N-GNRs/CoO as the cathode also display high peak power density and fantastic cycle stability,superior to that of benchmark Pt/C+IrO_(2)catalyst.It is anticipated to offer significant benefits toward high activity,stability and mechanical flexibility bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries.

A perspective on the key factors of safety for rechargeable magnesium batteries

Rechargeable Mg batteries(RMBs)have become one of the best subsitutes for lithium-ion batteries due to the high volumetric capacity,abundant resources,and uniform plating behavior of Mg metal anode.However,the safety hazard induced by the formation of high-modulue Mg dendrites under a high current density(10 mA cm^(-1))was still revealed in recent years.It has forced researchers to re-examine the safety of RMBs.In this review,the intrinsic safety factors of key components in RMBs,such as uneven plating,pitting and flammability of Mg anode,heat release and crystalline water decomposition of cathode,strong corrosion,low oxidition stability and flammability of electrolytes,and soforth,are systematacially summarized.Their origins,formation mechanisms,and possible safety hazards are deeply discussed.To develop high-performance Mg anode,current strategies including designing artificial SEI,three-dimensional substrates,and Mg alloys are summarized.For practical electrolytes,the configurations of boron-centered anions and simple Mg salts and the functionalized solvent with high boiling point and low flammability are suggested to comprehensively design.In addition,the future study should more focus on the investigation on the thermal runaway and decomposition of cathode materials and separa-tors.This review aims to provide fundamental insights into the relationship between electrochemistry and safety,further promoting the sustainable development of RMBs.

Dual-Defect Engineering Strategy Enables High-Durability Rechargeable Magnesium-Metal Batteries

Rechargeable magnesium-metal batteries(RMMBs)are promising next-generation secondary batteries;however,their development is inhibited by the low capacity and short cycle lifespan of cathodes.Although various strategies have been devised to enhance the Mg^(2+)migration kinetics and structural stability of cathodes,they fail to improve electronic conductivity,rendering the cathodes incompatible with magnesium-metal anodes.Herein,we propose a dual-defect engineering strategy,namely,the incorporation of Mg^(2+)pre-intercalation defect(P-Mgd)and oxygen defect(Od),to simultaneously improve the Mg^(2+)migration kinetics,structural stability,and electronic conductivity of the cathodes of RMMBs.Using lamellar V_(2)O_(5)·nH_(2)O as a demo cathode material,we prepare a cathode comprising Mg_(0.07)V_(2)O_(5)·1.4H_(2)O nanobelts composited with reduced graphene oxide(MVOH/rGO)with P-Mgd and Od.The Od enlarges interlayer spacing,accelerates Mg^(2+)migration kinetics,and prevents structural collapse,while the P-Mgd stabilizes the lamellar structure and increases electronic conductivity.Consequently,the MVOH/rGO cathode exhibits a high capacity of 197 mAh g^(−1),and the developed Mg foil//MVOH/rGO full cell demonstrates an incredible lifespan of 850 cycles at 0.1 A g^(−1),capable of powering a light-emitting diode.The proposed dual-defect engineering strategy provides new insights into developing high-durability,high-capacity cathodes,advancing the practical application of RMMBs,and other new secondary batteries.

Engineering single-atom Mn on nitrogen-doped carbon to regulate lithium-peroxide reaction kinetics for rechargeable lithium-oxygen batteries

Precision engineering of catalytic sites to guide more favorable pathways for Li_(2)O_(2) nucleation and decom-position represents an enticing kinetic strategy for mitigating overpotential,enhancing discharge capac-ity,and improving recycling stability of Li-O_(2) batteries.In this work,we employ metal-organic frameworks(MOFs)derivation and ion substitution strategies to construct atomically dispersed Mn-N_(4) moieties on hierarchical porous nitrogen-doped carbon(Mn SAs-NC)with the aim of reducing the over-potential and improving the cycling stability of Li-O_(2) batteries.The porous structure provides more chan-nels for mass transfer and exposes more highly active sites for electrocatalytic reactions,thus promoting the formation and decomposition of Li_(2)O_(2).The Li-O_(2) batteries with Mn SAs-NC cathode achieve lower overpotential,higher specific capacity(14290 mA h g^(-1) at 100 mAg^(-1)),and superior cycle stability(>100 cycles at 200 mA g^(-1))compared with the Mn NPs-NC and NC.Density functional theory(DFT)cal-culations reveal that the construction of Mn-N_(4) moiety tunes the charge distribution of the pyridinic N-rich vacancy and balances the affinity of the intermediates(LiO_(2) and Li_(2)O_(2)).The initial nucleation of Li_(2)O_(2) on Mn SAs-NC favors the O_(2)-→LiO_(2)→Li_(2)O_(2) surface-adsorption pathway,which mitigates the overpoten-tials of the oxygen reduction(ORR)and oxygen evolution reaction(OER).As a result,Mn SAs-NC with Mn-N_(4) moiety effectively facilitates the Li_(2)O_(2) nucleation and enables its reversible decomposition.This work establishes a methodology for constructing carbon-based electrocatalysts with high activity and selectivity for Li-O_(2)batteries.

Construction of ultra-stable NiFe armored catalyst for liquid and flexible quasi-solid-state rechargeable Zn-air batteries

The commercial application of non-precious metal-based electrocatalysts is not only limited by the intrinsic activity of the catalysts,but also the stability of the catalysts is extremely important.Herein,we fabricated an ultra-stable NiFe armored catalyst(Ar-NiFe/NC)by a simple secondary pyrolysis strategy.The as-obtained Ar-NiFe/NC electrocatalyst exhibits an excellent bifunctional oxygen electrocatalytic performance with an activity indicatorΔE of 0.74 V vs.reversible hydrogen electrode(RHE).More importantly,the Ar-NiFe/NC electrocatalyst also shows a remarkable operational and storage stability.After accelerated durability test(ADT)cycles,no obvious degradation of oxygen electrocatalytic performance could be observed.In addition,the Ar-NiFe/NC electrocatalyst still exhibits an unbated oxygen electrocatalytic performance comparable to fresh catalysts after three months of air-exposed storage.The assembled liquid and flexible quasi-solid-state rechargeable Zn-air batteries with the Ar-NiFe/NC electrocatalyst exhibit impressive performance.The liquid rechargeable Zn-air batteries possess a high open-circuit voltage(OCV)of 1.43 V and a salient peak power density of 146.40 mW·cm^(−2),while the flexible quasi-solid-state rechargeable Zn-air batteries also exhibit an excellent OCV of 1.60 V and an exciting peak power density of 41.99 mW·cm^(−2).

A comparison study on single metal atoms(Fe,Co,Ni)within nitrogen-doped graphene for oxygen electrocatalysis and rechargeable Zn-air batteries

Single atom catalysts(SACs)with atomically dispersed transition metals on nitrogen-doped carbon supports have recently emerged as highly active non-noble metal electrocatalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),showing great application potential in Zn-air batteries.However,because of the complex structure-performance relationships of carbon-based SACs in the oxygen electrocatalytic reactions,the contribution of different metal atoms to the catalytic activity of SACs in Zn-air batteries still remains ambiguous.In this study,SACs with atomically dispersed transition metals on nitrogen-doped graphene sheets(M-N@Gs,M=Co,Fe and Ni),featured with similar physicochemical properties and M-N@C configurations,are obtained.By comparing the on-set potentials and the maximum current,we observed that the ORR activity is in the order of Co-N@G>Fe-N@G>Ni-N@G,while the OER activity is in the order of Co-N@G>Ni-N@G>Fe-N@G.The Zn-air batteries with Co-N@G as the air cathode catalysts outperform those with the Fe-N@G and Ni-N@G.This is due to the accelerated charge transfer between Co-N@C active sites and the oxygen-containing reactants.This study could improve our understanding of the design of more efficient bifunctional electrocatalysts for Zn-air batteries at the atomic level.

Tuning interface mechanism of FeCo alloy embedded N,S-codoped carbon substrate for rechargeable Zn-air battery

The interface mechanism between catalyst and carbon substrate has been the focus of research.In this paper,the FeCo alloy embedded N,S co-doped carbon substrate bifunctional catalyst(FeCo/S-NC)is obtained by a simple one-step pyrolysis strategy.The experimental results and density functional theory(DFT)calculation show that the formation of FeCo alloy is conducive to promoting electron transfer,and the introduction of S atom can enhance the interaction between FeCo alloy and carbon substrate,thus inhibiting the migration and agglomeration of particles on the surface of carbon material.The FeCo/SNC catalysts show outstanding performance for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).FeCo/S-NC shows a high half-wave potential(E_(1/2)=0.8823 V)for ORR and a low overpotential at 10 mA cm^(-2)(E_(j=10)=299 mV)for OER.In addition,compared with Pt/C+RuO_(2) assembled Zn-air battery(ZAB),the FeCo/S-NC assembled ZAB exhibits a larger power density(198.8 mW cm^(-2)),a higher specific capacity(786.1 mA h g_(zn)~(-1)),and ultra-stable cycle performance.These results confirm that the optimized composition and the interfacial interaction between catalyst and carbon substrate synergistically enhance the electrochemical performance.

Growth and inhibition of zinc anode dendrites in Zn-air batteries:Model and experiment

Zinc(Zn)-air batteries are widely used in secondary battery research owing to their high theoretical energy density,good electrochemical reversibility,stable discharge performance,and low cost of the anode active material Zn.However,the Zn anode also leads to many challenges,including dendrite growth,deformation,and hydrogen precipitation self-corrosion.In this context,Zn dendrite growth has a greater impact on the cycle lives.In this dissertation,a dendrite growth model for a Zn-air battery was established based on electrochemical phase field theory,and the effects of the charging time,anisotropy strength,and electrolyte temperature on the morphology and growth height of Zn dendrites were studied.A series of experiments was designed with different gradient influencing factors in subsequent experiments to verify the theoretical simulations,including elevated electrolyte temperatures,flowing electrolytes,and pulsed charging.The simulation results show that the growth of Zn dendrites is controlled mainly by diffusion and mass transfer processes,whereas the electrolyte temperature,flow rate,and interfacial energy anisotropy intensity are the main factors.The experimental results show that an optimal electrolyte temperature of 343.15 K,an optimal electrolyte flow rate of 40 ml·min^(-1),and an effective pulse charging mode.

Enhanced bifunctional oxygen electrochemical catalytic performance using La-doped CoFe_(2)O_(4)spinel supported by 3D-G for Zn-air batteries

The preparation of bifunctional catalysts for oxygen reduction(ORR)and oxygen evolution(OER)is crucial for Zn-air batteries.Here,we report a La doped CoFe_(2)O_(4) spinel catalyst supported on threedimensional graphene(3D-G),where La can facilitate electron transfer from Co to Fe,leading to increased electron cloud density in Fe and improved catalytic performance.The redshift of the G peak in the Raman spectra indicates the interaction between theπbond of 3D-G and d orbitals in La_(0.2)CoFe_(1.8)O_(4).La_(0.2)CoFe_(1.8)/3D-G exhibits superior ORR performance(E_(1/2)=0.86 V vs.RHE)and OER performance(E_(j=10)=1.55 V vs.RHE)to CoFe_(2)O_(4)/3D-G(E_(1/2)=0.831 V vs.RHE,E_(j=10)=1.603 V vs.RHE).Furthermore,it demonstrates excellent bifunctional oxygen catalytic performance while maintaining high power density and stability in liquid zinc-air batteries(ZABs)and flexible ZABs(F-ZABs).This work presents a viable strategy for utilizing rare earth element doped spinels to enhance oxygen catalyst and ZABs performance.

Aerophilic Triphase Interface Tuned by Carbon Dots Driving Durable and Flexible Rechargeable Zn‑Air Batteries

Efficient bifunctional catalysts for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)are vital for rechargeable Zn-air batteries(ZABs).Herein,an oxygen-respirable sponge-like Co@C–O–Cs catalyst with oxygen-rich active sites was designed and constructed for both ORR and OER by a facile carbon dot-assisted strategy.The aerophilic triphase interface of Co@C–O–Cs cathode efficiently boosts oxygen diffusion and transfer.The theoretical calculations and experimental studies revealed that the Co–C–COC active sites can redistribute the local charge density and lower the reaction energy barrier.The Co@C–O–Cs catalyst displays superior bifunctional catalytic activities with a half-wave potential of 0.82 V for ORR and an ultralow overpotential of 294 mV at 10 mA cm^(−2) for OER.Moreover,it can drive the liquid ZABs with high peak power density(106.4 mW cm^(−2)),specific capacity(720.7 mAh g^(−1)),outstanding long-term cycle stability(over 750 cycles at 10 mA cm^(−2)),and exhibits excellent feasibility in flexible all-solid-state ZABs.These findings provide new insights into the rational design of efficient bifunctional oxygen catalysts in rechargeable metal-air batteries.

A robust bifunctional catalyst for rechargeable Zn-air batteries:Ultrathin NiFe-LDH nanowalls vertically anchored on soybeanderived Fe-N-C matrix

ABSTRACT NiFe layered double hydroxide(NiFe-LDH)nanosheets and metal-nitrogen-carbon materials(M-N-C,M=Ni,Fe,Co,etc.)are supreme catalysts in the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)process,respectively.Nevertheless,the monotonic performance and insufficient stability severely hamper their practical application in rechargeable batteries.Herein,we simultaneously combine ultrathin NiFe-LDH nanowalls with renewable soybean-derived Fe-N-C matrix to obtain a hybrid materials(NiFe-LDH/FeSoy-CNSs-A),which exhibits robust catalytic activities for OER(E_(j=10)=1.53 V vs.RHE)and ORR(E_(1/2)=0.91 V vs.RHE),with a top-notch battery parameters and stability in assembled rechargeable Zn-air batteries.Intensive investigations indicate that the vertically dispersed NiFe-LDH nanosheets,Fe-N-C matrix derived from soybean and the strong synergy between them are responsible for the unprecedented OER and ORR performances.The key role of intrinsic N defects involved in the hybrid materials is firstly specified by ultrasoundassisted extraction of soy protein from soybean.The exquisite design can facilitate the utilization of sustainable biomass-derived catalysts,and the mechanism investigations of N defects and oxygenic groups on the structure-activity relationship can stimulate the progress of other functional hybrid electrocatalysts.

Hierarchical mesoporous S,N-codoped carbon nanostructures composed of Co/Co-Cu-S/carbon nanoplate arrays on carbon nanofibers as a self-supported air cathode for long-lasting rechargeable Zn-air batteries

One of the primary roadblocks to widespread applications of rechargeable Zn-air batteries is the durability issue with oxygen reduction and evolution processes(ORR/OER)bifunctional electrocatalysts.We herein report the construction of a selfsupported air cathode for Zn-air batteries made of S,N-codoped porous complex carbon nanostructures of Co/Co-Cu-S/carbon nanoplate arrays and carbon nanofibers(denoted as Co/Co-Cu-S@SNPCP-CFs).The hierarchical heteroatom-doped mesoporous carbon nanohybrids with multiple active species not only provide a high surface-to-volume ratio,exposing more catalytic sites and accelerating the charge and mass transfer,but also boost the activity and durability.The Co/Co-Cu-S@SNPCP-CFs catalyst reveals a small potential gap(ΔE=0.67 V)between the half-wave potential of ORR and OER potential at 10 m A ccm^(-2),demonstrating outstanding bifunctional performance.Furthermore,the rechargeable Zn-air battery made with the as-obtained electrocatalyst exhibits a high-power density of 220 m W cm^(-2)and a long cycling time of over 800 h at 10 m A ccm^(-2),and the flexible solid-state rechargeable Zn-air battery based on Co/Co-Cu-S@SNPCP-CFs self-supporting air cathode also displays a long duration time of over 60 h.

Zinc–Bromine Rechargeable Batteries:From Device Configuration,Electrochemistry,Material to Performance Evaluation

Zinc–bromine rechargeable batteries(ZBRBs)are one of the most powerful candidates for next-generation energy storage due to their potentially lower material cost,deep discharge capability,non-flammable electrolytes,relatively long lifetime and good reversibility.However,many opportunities remain to improve the efficiency and stability of these batteries for long-life operation.Here,we discuss the device configurations,working mechanisms and performance evaluation of ZBRBs.Both non-flow(static)and flow-type cells are highlighted in detail in this review.The fundamental electrochemical aspects,including the key challenges and promising solutions,are discussed,with particular attention paid to zinc and bromine half-cells,as their performance plays a critical role in determining the electrochemical performance of the battery system.The following sections examine the key performance metrics of ZBRBs and assessment methods using various ex situ and in situ/operando techniques.The review concludes with insights into future developments and prospects for high-performance ZBRBs.