Small but mighty:Empowering sodium/potassium-ion battery performance with S-doped SnO_(2) quantum dots embedded in N,S codoped carbon fiber network

SnO_(2) has been extensively investigated as an anode material for sodium-ion batteries(SIBs)and potassium-ion batteries(PIBs)due to its high Na/K storage capacity,high abundance,and low toxicity.However,the sluggish reaction kinetics,low electronic conductivity,and large volume changes during charge and discharge hinder the practical applications of SnO_(2)-based electrodes for SIBs and PIBs.Engineering rational structures with fast charge/ion transfer and robust stability is important to overcoming these challenges.Herein,S-doped SnO_(2)(S-SnO_(2))quantum dots(QDs)(≈3 nm)encapsulated in an N,S codoped carbon fiber networks(S-SnO_(2)-CFN)are rationally fabricated using a sequential freeze-drying,calcination,and S-doping strategy.Experimental analysis and density functional theory calculations reveal that the integration of S-SnO_(2) QDs with N,S codoped carbon fiber network remarkably decreases the adsorption energies of Na/K atoms in the interlayer of SnO_(2)-CFN,and the S doping can increase the conductivity of SnO_(2),thereby enhancing the ion transfer kinetics.The synergistic interaction between S-SnO_(2) QDs and N,S codoped carbon fiber network results in a composite with fast Na+/K+storage and extraordinary long-term cyclability.Specifically,the S-SnO_(2)-CFN delivers high rate capacities of 141.0 mAh g^(−1) at 20 A g^(−1) in SIBs and 102.8 mAh g^(−1) at 10 A g^(−1) in PIBs.Impressively,it delivers ultra-stable sodium storage up to 10,000 cycles at 5 A g^(−1) and potassium storage up to 5000 cycles at 2 A g^(−1).This study provides insights into constructing metal oxide-based carbon fiber network structures for high-performance electrochemical energy storage and conversion devices.

Enhanced reversible hydrogen storage properties of wrinkled graphene microflowers confined LiBH_(4) system with high volumetric hydrogen storage capacity

LiBH_(4)with high hydrogen storage density,is regarded as one of the most promising hydrogen storage materials.Nevertheless,it suffers from high dehydrogenation temperature and poor reversibility for practical use.Nanoconfinement is effective in achieving low dehydrogenation temperature and favorable reversibility.Besides,graphene can serve as supporting materials for LiBH_(4)catalysts and also destabilize LiBH_(4)via interfacial reaction.However,graphene has never been used alone as a frame material for nanoconfining LiBH_(4).In this study,graphene microflowers with large pore volumes were prepared and used as nanoconfinement framework material for LiBH_(4),and the nanoconfinement effect of graphene was revealed.After loading 70 wt%of LiBH_(4) and mechanically compressed at 350 MPa,8.0 wt% of H2 can be released within 100 min at 320C,corresponding to the highest volumetric hydrogen storage density of 94.9 g H2 L^(-1)ever reported.Thanks to the nanoconfinement of graphene,the rate-limiting step of dehydrogenation of nanoconfined LiBH_(4) was changed and its apparent activation energy of the dehydrogenation(107.3 kJ mol^(-1))was 42%lower than that of pure LiBH_(4).Moreover,the formation of the intermediate Li_(2)B_(12)H_(12) was effectively inhibited,and the stable nanoconfined structure enhanced the reversibility of LiBH_(4).This work widens the understanding of graphene's nanoconfinement effect and provides new insights for developing high-density hydrogen storage materials.

原位电化学扫描探针显微镜技术在电催化领域的应用进展

在电化学界面,电催化过程通常包括电子转移、吸附和脱附、静电相互作用、溶剂化及去溶剂化等多步过程,深入理解电催化反应机理极具挑战性.对纳米结构电化学界面(电极)处电催化过程的深入理解十分有助于阐明电催化反应机理和设计高性能电催化剂材料.电催化活性通常与电催化剂表面局域化的活性位点密切有关.在反应条件下,电催化反应过程的研究极大依赖于高分辨表征技术.经典的宏观电化学表征方法仅可以提供不同界面位点的平均信息,很难分辨一些特殊结构位点(如缺陷、晶界、边缘位点)的相关重要电化学信息.原位电化学扫描探针显微镜技术,包括电化学扫描隧道显微镜(EC-STM)、电化学原子力显微镜(EC-AFM)、扫描电化学显微镜(SECM)及扫描电化学池显微镜(SECCM),能够在纳米及原子尺度研究电催化反应过程,弥补了宏观表征方法的不足,为探究构效关系和解析电催化反应机理提供了机遇.本文介绍了各种扫描显微技术的基本原理、特点及优劣势,并且概述了各项技术在电催化领域研究的重大进展.EC-STM和EC-AFM能够原位表征电催化过程中的纳米尺度表面结构演变及吸附/脱附过程,但无法直接测量局部电化学活性(法拉第电流).通过SECM和SECCM可以检测微区电化学信号,并获得电化学通量和电化学反应动力学信息,可作为EC-STM和EC-AFM的补充技术.结合二者的优势,进一步介绍了双探针结合技术(SECM-AFM,SECM-STM,SECM-SICM及SECM-SECCM)的原理和关键电催化应用.随后,从揭示构效关系、结构演变/稳定性、反应物或中间物的吸附、反应路径和选择性等角度,总结了这些原位电化学扫描探针显微镜技术在电催化领域(析氢反应、氢氧化反应、析氧反应、氧还原反应及CO_(2)还原反应)的最新研究进展.最后,对原位电化学扫描探针显微镜技术在电催化领域研究的挑战及未来发展进行了展望.

Synergistic“Anchor‑Capture”Enabled by Amino and Carboxyl for Constructing Robust Interface of Zn Anode

While the rechargeable aqueous zinc-ion batteries(AZIBs)have been recognized as one of the most viable batteries for scale-up application,the instability on Zn anode–electrolyte interface bottleneck the further development dramatically.Herein,we utilize the amino acid glycine(Gly)as an electrolyte additive to stabilize the Zn anode–electrolyte interface.The unique interfacial chemistry is facilitated by the synergistic“anchor-capture”effect of polar groups in Gly molecule,manifested by simultaneously coupling the amino to anchor on the surface of Zn anode and the carboxyl to capture Zn^(2+)in the local region.As such,this robust anode–electrolyte interface inhibits the disordered migration of Zn^(2+),and effectively suppresses both side reactions and dendrite growth.The reversibility of Zn anode achieves a significant improvement with an average Coulombic efficiency of 99.22%at 1 mA cm^(−2)and 0.5 mAh cm^(−2)over 500 cycles.Even at a high Zn utilization rate(depth of discharge,DODZn)of 68%,a steady cycle life up to 200 h is obtained for ultrathin Zn foils(20μm).The superior rate capability and long-term cycle stability of Zn–MnO_(2)full cells further prove the effectiveness of Gly in stabilizing Zn anode.This work sheds light on additive designing from the specific roles of polar groups for AZIBs.

Rational Design of Robust and Universal Aqueous Binders to Enable Highly Stable Cyclability of High-Capacity Conversion and Alloy-Type Anodes

The development of high-performance binders is a simple but effective approach to address the rapid capacity decay of high-capacity anodes caused by large volume change upon lithiation/delithiation.Herein,we demonstrate a unique organic/inorganic hybrid binder system that enables an efficient in situ crosslinking of aqueous binders(e.g.,sodium alginate(SA)and carboxymethyl cellulose(CMC))by reacting with an inorganic crosslinker(sodium metaborate hydrate(SMH))upon vacuum drying.The resultant 3D interconnected networks endow the binders with strong adhesion and outstanding self-healing capability,which effectively improve the electrode integrity by preventing fracturing and exfoliation during cycling and facilitate Li^(+)ion transfer.SiO anodes fabricated from the commercial microsized powders with the SA/0.2SMH binder maintain 1470 mAh g^(-1)of specific capacity at 100 mA g^(-1)after 200 cycles,which is 5 times higher than that fabricated with SA binder alone(293 mAh g^(-1)).Nearly,no capacity loss was observed over 500 cycles when limiting discharge capacity at 1500 mAh g^(-1).The new binders also dramatically improved the performance of Fe_(2)O_(3),Fe_(3)O_(4),NiO,and Si electrodes,indicating the excellent applicability.This finding represents a novel strategy in developing high-performance aqueous binders and improves the prospect of using high-capacity anode materials in Li-ion batteries.

Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives

The rapid advance of mild aqueous zinc-ion batteries(ZIBs)is driving the development of the energy storage system market.But the thorny issues of Zn anodes,mainly including dendrite growth,hydrogen evolution,and corrosion,severely reduce the performance of ZIBs.To commercialize ZIBs,researchers must overcome formidable challenges.Research about mild aqueous ZIBs is still developing.Various technical and scientific obstacles to designing Zn anodes with high stripping efficiency and long cycling life have not been resolved.Moreover,the performance of Zn anodes is a complex scientific issue determined by various parameters,most of which are often ignored,failing to achieve the maximum performance of the cell.This review proposes a comprehensive overview of existing Zn anode issues and the corresponding strategies,frontiers,and development trends to deeply comprehend the essence and inner connection of degradation mechanism and performance.First,the formation mechanism of dendrite growth,hydrogen evolution,corrosion,and their influence on the anode are analyzed.Furthermore,various strategies for constructing stable Zn anodes are summarized and discussed in detail from multiple perspectives.These strategies are mainly divided into interface modification,structural anode,alloying anode,intercalation anode,liquid electrolyte,non-liquid electrolyte,separator design,and other strategies.Finally,research directions and prospects are put forward for Zn anodes.This contribution highlights the latest developments and provides new insights into the advanced Zn anode for future research.

Porous Carbon Architecture Assembled by Cross-Linked Carbon Leaves with Implanted Atomic Cobalt for High-Performance Li-S Batteries

The practical application of lithium-sulfur batteries is severely hampered by the poor conductivity,polysulfide shuttle effect and sluggish reaction kinetics of sulfur cathodes.Herein,a hierarchi-cally porous three-dimension(3D)carbon architecture assembled by cross-linked carbon leaves with implanted atomic Co-N4 has been deli-cately developed as an advanced sulfur host through a SiO_(2)-mediated zeolitic imidazolate framework-L(ZIF-L)strategy.The unique 3D architectures not only provide a highly conductive network for fast electron transfer and buffer the volume change upon lithiation-delithi-ation process but also endow rich interface with full exposure of Co-N4 active sites to boost the lithium polysulfides adsorption and conversion.Owing to the accelerated kinetics and suppressed shuttle effect,the as-prepared sulfur cathode exhibits a superior electrochemical perfor-mance with a high reversible specific capacity of 695 mAh g^(−1) at 5 C and a low capacity fading rate of 0.053%per cycle over 500 cycles at 1 C.This work may provide a promising solution for the design of an advanced sulfur-based cathode toward high-performance Li-S batteries.

Inner Co Synergizing Outer Ru Supported on Carbon Nanotubes for Efficient pH-Universal Hydrogen Evolution Catalysis

Exploring highly active but inexpensive electrocatalysts for the hydrogen evolution reaction(HER)is of critical importance for hydrogen production from electrochemical water splitting.Herein,we report a multicomponent catalyst with exceptional activity and durability for HER,in which cobalt nanoparticles were in-situ confined inside bamboo-like carbon nanotubes(CNTs)while ultralow ruthenium loading(~2.6μg per electrode area~cm^(−2))is uniformly deposited on their exterior walls(Co@CNTsǀRu).The atomic-scale structural investigations and theoretical calculations indicate that the confined inner Co and loaded outer Ru would induce charge redistribution and a synergistic electron coupling,not only optimizing the adsorption energy of H intermediates(ΔGH*)but also facilitating the electron/mass transfer.The as-developed Co@CNTsǀRu composite catalyst requires overpotentials of only 10,32,and 63 mV to afford a current density of 10 mA cm^(−2) in alkaline,acidic and neutral media,respectively,representing top-level catalytic activity among all reported HER catalysts.The current work may open a new insight into the rational design of carbon-supported metal catalysts for practical applications.

High-loading, ultrafine Ni nanoparticles dispersed on porous hollow carbon nanospheres for fast (de)hydrogenation kinetics of MgH_(2)

Magnesium hydride(MgH2) is one of the most promising hydrogen storage materials for practical application due to its favorable reversibility, low cost and environmental benign;however, it suffers from high dehydrogenation temperature and slow sorption kinetics.Exploring proper catalysts with high and sustainable activity is extremely desired for substantially improving the hydrogen storage properties of MgH2. In this work, a composite catalyst with high-loading of ultrafine Ni nanoparticles(NPs) uniformly dispersed on porous hollow carbon nanospheres is developed, which shows superior catalytic activity towards the de-/hydrogenation of MgH2. With an addition of 5wt% of the composite, which contains 90 wt% Ni NPs, the onset and peak dehydrogenation temperatures of MgH2are lowered to 190 and 242 ℃, respectively. 6.2 wt% H2is rapidly released within 30 min at 250 ℃. The amount of H2that the dehydrogenation product can absorb at a low temperature of 150 ℃ in only 250 s is very close to the initial dehydrogenation value. A dehydrogenation capacity of 6.4wt% remains after 50 cycles at a moderate cyclic regime, corresponding to a capacity retention of 94.1%. The Ni NPs are highly active,reacting with MgH2and forming nanosized Mg2Ni/Mg2NiH4. They act as catalysts during hydrogen sorption cycling, and maintain a high dispersibility with the help of the dispersive role of the carbon substrate, leading to sustainably catalytic activity. The present work provides new insight into designing stable and highly active catalysts for promoting the(de)hydrogenation kinetics of MgH2.

Reversible Magnesium Metal Anode Enabled by Cooperative Solvation/Surface Engineering in Carbonate Electrolytes

Magnesium metal anode holds great potentials toward future high energy and safe rechargeable magnesium battery technology due to its divalent redox and dendrite-free nature. Electrolytes based on Lewis acid chemistry enable the reversible Mg plating/stripping,while they fail to match most cathode materials toward highvoltage magnesium batteries. Herein,reversible Mg plating/stripping is achieved in conventional carbonate electrolytes enabled by the cooperative solvation/surface engineering. Strongly electronegative Cl from the MgCl_(2) additive of electrolyte impairs the Mg…O = C interaction to reduce the Mg^(2+) desolvation barrier for accelerated redox kinetics,while the Mg^(2+)-conducting polymer coating on the Mg surface ensures the facile Mg^(2+) migration and the e ective isolation of electrolytes. As a result,reversible plating and stripping of Mg is demonstrated with a low overpotential of 0.7 V up to 2000 cycles. Moreover,benefitting from the wide electrochemical window of carbonate electrolytes,high-voltage(> 2.0 V) rechargeable magnesium batteries are achieved through assembling the electrode couple of Mg metal anode and Prussian blue-based cathodes. The present work provides a cooperative engineering strategy to promote the application of magnesium anode in carbonate electrolytes toward high energy rechargeable batteries.

Synthesis of a ternary amide LixKy（NH2）x+y and a novel Li3K（NH2）4–xMgH2 combination system for hydrogen storage

The ternary amides LiK2(NH2)3, LiK(NH2)2, and Li3 K(NH2)4 are successfully synthesized by ball milling mixtures of LiNH2 and KNH2, and the hydrogen storage properties of Li3K(NH2)4–xMgH2(x = 1, 2, 3,4) are systematically investigated. The Li3K(NH2)4–2 Mg H2 sample displays optimized hydrogen storage properties, releasing 6.37 wt% of hydrogen in a two-stage reaction with an onset temperature of 60 °C.The first dehydrogenation stage exhibits good reaction kinetics and thermodynamic properties because of a lower activation energy and appropriate enthalpy change. After full dehydrogenation at 130 °C, the Li3K(NH2)4–2 MgH2 sample absorbs 3.80 wt% of H2 below 160 °C in a variable temperature hydrogenation mode. Mechanistic investigations indicate that Li3 K(NH2)4 reacts with Mg H2 to produce Mg(NH2)2, LiH,and KH during ball milling. In the heating process, Mg(NH2)2 first reacts with Li H to form Li2 Mg2 N3 H3 and Li NH2, while KH works as a catalyst, and then, KH reacts with Li2Mg2N3H3 and Li NH2 to generate a new K-containing compound.

Toward enhanced alkaline hydrogen electrocatalysis with transition metal‐functionalized nitrogen‐doped carbon supports

Superior catalyst supports are crucial to developing advanced electrocatalysts toward heterogeneous catalytic reactions.Herein,we systematically investigate the role of transition metal‐functionalized N‐doped carbon nanosheets(M‐N‐C,M=Mn,Fe,Co,Ni,Cu,Mo,and Ag)as the multifunctional electrocatalyst supports toward hydrogen evolution/oxidation reactions(HER/HOR)in alkaline media.The results demonstrate that all the M‐N‐C nanosheets,except Cu‐N‐C and Ag‐N‐C,can promote the alkaline HER/HOR electrocatalytic activity of Pt by accelerating the sluggish Volmer step,among which Mn plays a more significant role.Analyses reveal that the promotion effect of M‐N‐C support is closely associated with the electronegativity of the metal dopants and the relative filling degree of their d‐orbitals.For one,the metal dopant in M‐N‐C with smaller electronegativity would provide more electrons to oxygen and hence tune the electronic structure of Pt via the M‐O‐Pt bonds at the interface.For another,the transition metal in M‐N4 moieties with more empty d orbitals would hybridize with O 2p orbitals more strongly that promotes the adsorption of water/hydroxyl species.The results demonstrate the conceptual significance of multifunctional supports and would inspire the future development of advanced electrocatalysts.

First-row transition metal compounds for aqueous metal ion batteries

In recent years,a series of aqueous metal ion batteries(AMIBs)has been developed to improve the safety and cost-efficiency of portable electronics and electric vehicles.However,the significant gaps in energy density,power density,and cycle stability of AMIBs directly hinder them from replacing the currently widely used non-aqueous metal ion batteries,which stems from the lack of reasonable configuration and performance optimization of electrode materials.First-row transition metal compounds(FRTMCs),with the advantages of optional voltage ranges(from low to high),adjustable crystal structures(layered and tunnel types with large spacing),and designable morphology(multi-dimensional nanostructures),are widely used to construct high-performance AMIBs.However,no comprehensive review papers were generated to highlight their specific and significant roles in AMIBs.In this review,we first summarize the superiority and characteristics of FRTMCs in AMIBs.Then,we put forward control strategies of FRTMCs from subsurface engineering to inner construction to promote capacitance control and diffusion control energy storage.After that,the electrochemical performance of the FRTMCs regulation strategies in AMIBs is reviewed.Finally,we present potential directions and challenges for further enhancements of FRTMCs in AMIBs.The review aims to provide an in-depth understanding of regulation strategies for enhancing energy storage to build high-performance AMIBs that meet practical applications.

氧调节原生负极-固态电解质界面层助力高稳定性固态钠金属电池

Solid-state sodium metal batteries utilizing inorganic solid electrolytes(SEs)hold immense potentials such as intrinsical safety,high energy density,and environmental sustainability.However,the interfacial inhomogeneity/instability at the anode-SE interface usually triggers the penetration of sodium dendrites into the electrolyte,leading to short circuit and battery failure.Herein,confronting with the original nonuniform and high-resistance solid electrolyte interphase(SEI)at the Na-Na_(3)Zr_(2)Si_(2)PO_(12)interface,an oxygen-regulated SEI innovative approach is proposed to enhance the cycling stability of anode-SEs interface,through a spontaneous reaction between the metallic sodium(containing trace amounts of oxygen)and the Na_(3)Zr_(2)Si_(2)POi_(2)SE.The oxygen-regulated spontaneous SEI is thin,uniform,and kinetically stable to facilitate homogenous interfacial Na^+transportation,Benefitting from the optimized SEI,the assembled symmetric cell exhibits an ultra-stable sodium plating/stripping cycle for over 6600 h under a practical capacity of 3 mAh cm^(-2).Qua si-sol id-state batteries with Na_(3)V_(2)(PO_(4))_(3)cathode deliver excellent cyclability over 500 cycles at a rate of 0.5 C(1 C=117 mA cm^(-2))with a high capacity retention of95.4%.This oxygen-regulated SEI strategy may offer a potential avenue for the future development of high-energy-density solid-state metal batteries.

Pt single atoms coupled with Ru nanoclusters enable robust hydrogen oxidation for high-performance anion exchange membrane fuel cells

The sluggish reaction kinetics of alkaline hydrogen oxidation reaction(HOR)is one of the key challenges for anion exchange membrane fuel cells(AEMFCs).To achieve robust alkaline HOR with minimized cost,we developed a single atom-cluster multiscale structure with isolated Pt single atoms anchored on Ru nanoclusters supported on nitrogen-doped carbon nanosheets(Pt1-Ru/NC).The well-defined structure not only provides multiple sites with varied affinity with the intermediates but also enables simultaneous modulation of different sites via interfacial interaction.In addition to weakening Ru–H bond strength,the isolated Pt sites are heavily involved in hydrogen adsorption and synergistically accelerate the Volmer step with the help of Ru sites.Furthermore,this catalyst configuration inhibits the excessive occupancy of oxygen-containing species on Ru sites and facilitates the HOR at elevated potentials.The Pt1-Ru/NC catalyst exhibits superior alkaline HOR performance with extremely high activity and excellent CO-tolerance.An AEMFC with a 0.1 mg·cmPGM^(−2)loading of Pt1-Ru/NC anode catalyst achieves a peak powder density of 1172 mW·cm^(−2),which is 2.17 and 1.55 times higher than that of Pt/C and PtRu/C,respectively.This work provides a new catalyst concept to address the sluggish kinetics of electrocatalytic reactions containing multiple intermediates and elemental steps.

Fabrication pressures and stack pressures in solid-state battery

Solid-state batteries(SSBs)have received widespread attention with their high safety and high energy density characteristics.However,solid-solid contacts in the internal electrode material and the electrode material/solid electrolyte(SE)interfaces,as well as the severe electrochemo-mechanical effects caused by the internal stress due to the volume change of the active material,these problems hinder ion/electron transport within the SSBs,which significantly deteriorates the electrochemical performance.Applying fabrication pressures and stack pressures are effective measures to improve solid-solid contact and solve electrochemo-mechanical problems.Herein,the influences of different pressures on cathode material,anode material,SEs,and electrode/SEs interface are briefly summarized from the perspective of interface ion diffusion,transmission of electrons and ions in internal particles,current density and ion diffusion kinetics,and the volume changes of Li^(+)stripping/plating based on two physical contact models,and point out the direction for the future research direction of SSBs and advancing industrialization by building the relationship between pressures and SSBs electrochemistry.

Single-atom materials:The application in energy conversion

Single-atom materials(SAMs)have become one of the most important power sources to push the field of energy conversion forward.Among the main types of energy,including thermal energy,electrical energy,solar energy,and biomass energy,SAMs have realized ultra-high efficiency and show an appealing future in practical application.More than high activity,the uniform active sites also provide a convincible model for chemists to design and comprehend the mechanism behind the phenomenon.Therefore,we presented an insightful review of the application of the single-atom material in the field of energy conversion.The challenges(e.g.,accurate synthesis and practical application)and future directions(e.g.,machine learning and efficient design)of the applications of SAMs in energy conversion are included,aiming to provide guidance for the research in the next step.

Remarkable low-temperature hydrogen cycling kinetics of Mg enabled by VH_(x) nanoparticles

Nanoscaled catalysts have attracted much more attention due to their more abundant active sites and better dispersion than their bulky counterparts.In this work,VH_(x) nanoparticles smaller than 10 nm in average size are successfully synthesized by a simple solid-state ball milling coupled with THF washing process,which are proved to be highly effective in enhancing the hydrogen absorption/desorption kinetics of MgH_(2) at moderate temperatures.The nano-VH_(x)-modified MgH_(2) releases hydrogen from 182℃,which is 88℃ lower than additive-free MgH_(2).The release of hydrogen amounts to 6.3 wt%H within 10 min at 230℃ and 5.6 wt%H after 30 min at 215℃ with initial vacuum.More importantly,the dehydro-genated MgH_(2)+10 wt.%nano-VH_(x) rapidly absorbs 5.2 wt%H within 3 min at 50℃ under 50 bar H_(2).It even takes up 4.3 wt%H within 30 min at room temperature(25℃)under 10 bar H_(2),exhibiting supe-rior hydrogenation kinetics to most of the previous reports.Mechanistic analyzes disclose the reversible transformation between V and V-H species during the hydrogen desorption-absorption process.The ho-mogeneously distributed V-based species is believed to act as hydrogen pump and nucleation sites for MgH_(2) and Mg,respectively,thus triggering fast hydrogenation/dehydrogenation kinetics.

Epitaxial interface stabilizing iridium dioxide toward the oxygen evolution reaction under high working potentials

Proton exchange membrane water electrolyzer(PEMWE)driven by renewable electricity is a promising technique toward green hydrogen production,but the corrosive environment and high working potential pose severe challenges for developing advanced electrocatalysts for the oxygen evolution reaction(OER).Although Ir-based materials possess relatively balanced activity and stability for the OER,their dissolution behavior cannot be neglected,in particular under high working potentials.In this work,iridium dioxide(IrO_(2))nanoparticles(NPs)were anchored on the surface of exfoliated h-boron nitride(BN)nanosheets(NSs)toward the OER reaction in acid media.Highly active Ir(V)species were stabilized by the epitaxial interface between IrO_(2)and h-BN,and therefore the IrO_(2)/BN delivered stable performance at increased working potentials,while the activity of bare IrO_(2)NPs without h-BN support decreased rapidly.Also,the smaller lattice spacing of h-BN induced compressive strain for IrO_(2),resulting in improved activity.Our results demonstrate the feasibility of stabilizing highly active Ir(V)species for the OER in acid media by constructing robust interface and provide new possibilities toward designing advanced heterostructured electrocatalysts.

Recent advances in catalyst-modified Mg-based hydrogen storage materials

The storage of hydrogen in a compact,safe and cost-effective manner can be one of the key enabling technologies to power a more sustainable society.Magnesium hydride(MgH_(2))has attracted strong research interest as a hydrogen carrier because of its high gravimetric and volumetric hydrogen densities.However,the practical use of MgH_(2)for hydrogen storage has been limited due to high operation temperatures and sluggish kinetics.Catalysis is of crucial importance for the enhancement of hydrogen cycling kinetics of Mg/MgH_(2)and considerable work has been focused on designing,fabricating and optimizing catalysts.This review covers the recent advances in catalyzed Mg-based hydrogen storage materials.The fundamental properties and the syntheses of MgH_(2)as a hydrogen carrier are first briefly reviewed.After that,the general catalysis mechanisms and the catalysts developed for hydrogen storage in MgH_(2)are summarized in detail.Finally,the challenges and future research focus are discussed.Literature studies indicate that transition metals,rare-earth metals and their compounds are quite effective in catalyzing hydrogen storage in Mg/MgH_(2).Most metal-containing compounds were converted in situ to elemental metal or their magnesium alloys,and their particle sizes and dispersion affect their catalytic activity.The in-situ construction of catalyzed ultrasmall Mg/MgH_(2)nanostructures(<10 nm in size)is believed to be the future research focus.These important insights will help with the design and development of high-performance catalysts for hydrogen storage in Mg/MgH_(2).