The mass transport and ohmic losses in proton exchange membrane fuel cells(PEMFCs)is significantly influenced by the channel to rib width ratio(CRWR),particularly when accounting for the interfacial contact resistance...The mass transport and ohmic losses in proton exchange membrane fuel cells(PEMFCs)is significantly influenced by the channel to rib width ratio(CRWR),particularly when accounting for the interfacial contact resistance between bipolar plates(BPs)and gas diffusion layers(GDLs)(ICRBP-GDL).Both the determination of the optimal CRWR value and the development of an efficient flow field structure are significantly influenced by ICRBP-GDLs.To investigate this,three-dimensional numerical models were developed,revealing that selecting an optimal CRWR tailored to specific ICRBP-GDL values can effectively balance mass transport and ohmic losses.Building on this insight,a novel island two-dimensional flow field design is proposed,demonstrating the ability to enhance oxygen transport to the catalyst layer(CL)and achieve a more uniform oxygen distribution without increasing ohmic losses.Compared to conventional straight and serpentine flow fields,the island flow field improves output power density by 4.5%and 3.5%,respectively,while reducing the liquid water coverage ratio by 30%.Additionally,the study identifies optimal CRWR values for conventional flow fields corresponding to ICRBP-GDLs of 2.5,5,10,20,and 40 mΩ·cm^(2) as 1.5,1.5,1.0,0.67,and 0.43,respectively.For the island flow field,the optimal CRWRs are consistently smaller-1.5,1.0,0.67,0.43,and 0.43-due to its superior mass transfer capability.This work provides a valuable framework for optimizing flow field designs to achieve improved PEMFC performance.展开更多
Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)va...Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)values of prepared thermally conductive polymer composites are still difficult to achieve expectations,which has become the bottleneck in the fields of thermally conductive polymer composites.Aimed at that,based on the accumulation of the previous research works by related researchers and our research group,this paper proposes three possible directions for breaking through the bottlenecks:(1)preparing and synthesizing intrinsically thermally conductive polymers,(2)reducing the interfacial thermal resistance in thermally conductive polymer composites,and(3)establishing suitable thermal conduction models and studying inner thermal conduction mechanism to guide experimental optimization.Also,the future development trends of the three above-mentioned directions are foreseen,hoping to provide certain basis and guidance for the preparation,researches and development of thermally conductive polymers and their composites.展开更多
To improve the thermal conductivity of polymeric composites, the numerous interfacial thermal resistance （ITR） inside is usually considered as a bottle neck, but the direct measurement of the ITR is hardly reported....To improve the thermal conductivity of polymeric composites, the numerous interfacial thermal resistance （ITR） inside is usually considered as a bottle neck, but the direct measurement of the ITR is hardly reported. In this paper, a sandwich structure which consists of transducer/high density polyethylene （HDPE）/sapphire is prepared to study the interface characteristics. Then, the ITRs between HDPE and sapphire of two samples with different HDPE thickness values are measured by time-domain thermoreflectance （TDTR） method and the results are -- 2 × 10-7 m2.K.W-1. Furthermore, a model is used to evaluate the importance of ITR for the thermal conductivity of composites. The model＇s analysis indicates that reducing the ITR is an effective way of improving the thermal conductivity of composites. These results will provide valuable guidance for the design and manufacture of polymer-based thermally conductive materials.展开更多
The ideal composite electrolyte for the pursued safe and high-energy-density lithium metal batteries(LMBs)is expected to demonstrate peculiarity of superior bulk conductivity,low interfacial resistances,and good compa...The ideal composite electrolyte for the pursued safe and high-energy-density lithium metal batteries(LMBs)is expected to demonstrate peculiarity of superior bulk conductivity,low interfacial resistances,and good compatibility against both Li-metal anode and high-voltage cathode.There is no composite electrolyte to synchronously meet all these requirements yet,and the battery performance is inhibited by the absence of effective electrolyte design.Here we report a unique"concentrated ionogel-in-ceramic"silanization composite electrolyte(SCE)and validate an electrolyte design strategy based on the coupling of high-content silane-conditioning garnet and concentrated ionogel that builds well-percolated Li+transport pathways and tackles the interface issues to respond all the aforementioned requirements.It is revealed that the silane conditioning enables the uniform dispersion of garnet nanoparticles at high content(70 wt%)and forms mixed-lithiophobic-conductive LiF-Li3N solid electrolyte interphase.Notably,the yielding SCE delivers an ultrahigh ionic conductivity of 1.76 X 10^(-3)S cm^(-1)at 25℃,an extremely low Li-metal/electrolyte interfacial area-specific resistance of 13Ωcm^(2),and a distinctly excellent long-term 1200 cycling without any capacity decay in 4.3 V Li‖LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM523)quasi-solid-state LMB.This composite electrolyte design strategy can be extended to other quasi-/solid-state LMBs.展开更多
[Background and purposes]Proton exchange membrane fuel cells(PEMFCs),which convert hydrogen energy directly into electrical energy and water,have received overwhelming attention,owing to their potential to significant...[Background and purposes]Proton exchange membrane fuel cells(PEMFCs),which convert hydrogen energy directly into electrical energy and water,have received overwhelming attention,owing to their potential to significantly reduce energy consumption,pollution emissions and reliance on fossil fuels.Bipolar plates are the major part and key component of PEMFCs stack,which provide mechanical strength,collect and conduct current segregate oxidants and reduce agents.They contribute 70-80%weight and 20-30%cost of a whole stack,while significantly affecting the power density.There are three types plates,including metal bipolar plate,graphite bipolar plate and composite bipolar plate.Stainless steel bipolar plates,as one of metal bipolar plate,exhibit promising manufacturability,competitive cost and durability among various metal materials.However,stainless steel would be corroded in the harsh acid(pH 2-5)and humid PEMFCs environment,whereas the leached ions will contaminate the membrane.In addition,the passivated film formed on the surface will increase the interfacial contact resistance(ICR).In order to improve the corrosion resistance and electrical conductivity of steel bipolar plates,surface coatings are essential.Metal nitride coatings,metal carbide coatings,polymer coatings and carbon-based coatings have been introduced in recent years.Carbon-based coatings,mainly including a-C(amorphous Carbon),Ta-C(Tetrahedral amorphous carbon)and DLC(diamond-like carbon),have attracted considerable attention from both academia and industry,owing to their superior performance,such as chemical inertness,mechanical hardness and electrical conductivity.However,Ta-C films as protective coating of PEMFCs have been rarely reported,due to the difficulty in production for industrial application.In this paper,multi-layer Ta-C composite films were produced by using customized industrial-scale vacuum equipment to address those issues.[Methods]Multiple layered Ta-C coatings were prepared by using PIS624 equipment,which assembled filtered cathodic arc evaporation,ion beam and magnetron sputtering into one equipment,while SS304 and silicon specimens were used as substrate for testing and analysis.Adhesion layer and intermediate layer were deposited by using magnetron sputtering at deposition temperature of 150℃and pressure of 3×10^(−1) Pa,while the sputtering current was set to be 5 A and bias power to be 300 V.The Ta-C layer was coated at arc current of 80-100 A,bias voltage of 1500 V and gas flow of 75 sccm.A scanning electron microscope(CIQTEK SEM3200)was used to characterize surface morphology,coating structure and cross-section profile of the coatings.Raman spectrometer(LabRam HR Evolution,HORIBA JOBIN YVON)was used to identify the bonding valence states.Electrochemical tests were performed by using an electrochemical work station(CHI760,Shanghai Chenhua Instrument Co.,Ltd.),with the traditional three electrode system,where saturated Ag/AgCl and platinum mesh were used as the reference electrode and counter electrode,respectively.All samples were mounted in plastic tube and sealed with epoxy resin,with an exposure area of 2.25 cm^(2),serving as the working electrode.Electrochemical measurements were carried out in simulated PEMFCs cathode environment in 0.5 mol·L^(−1) H_(2)SO_(4)+5 ppm F−solution,at operating temperature of 70℃.As the cathode environment was harsher than the anode environment,all the samples are stabilized at the open-circuit potential(OCP)for approximately 30 min before the EIS measurements.ICR between bipolar plates and GDL was a key parameter affecting performance of the PEMFCs stack.The test sample sandwiched between 2 pieces of carbon paper(simulate gas diffusion layer,GDL)was placed between 2 gold-plated copper electrodes at a compaction pressure of 1.4 MPa,which was considered to be the conventional compaction pressure in the PEMFCs.Under the same conditions,the resistance of a single carbon paper was measured as well.The ICR was calculated according to the formula ICR=1/2(R2−R1)×S,where S was the contact area between GDL and coated stainless steel BPPs.All data of ICR were measured three times for averaging.[Results]The coatings deposited by filtered cathodic arc technology were compact and smooth,which reduced coating porosity and favorable to corrosion resistance.The coating thickness of adhesion and intermediate layers were 180 nm,while the protective Ta-C coating thickness was about 300 nm,forming multiple coating to provide stronger protection for metal bipolar plates.Cr,Ti,Nb and Ta coatings were selected as adhesion layers for comparison.According to electrochemical test,Ta and Nb coatings have higher corrosion resistance.However,Ta and Nb materials would be costly when they are used for mass production.Relatively,Cr and Ti materials were cost effective.Hence,a comprehensive assessment was indispensable to decide the materials to be selected as adhesion layer.Ta-TiN and Ti-TiN combined adhesion and intermediate layer exhibited stronger corrosion resistance,with the corrosion current to be less than 10^(−6) A·cm^(−2).Ta-C protective coating deposited by using filtered cathodic arc technology indicated displayed higher corrosion resistance,with the average corrosion density to be about 1.26×10^(−7) A·cm^(−2).Ta-C coating also shown larger contact angle,with the highest hydrophobicity,which was one of the important advantages for Ta-C,in terms of corrosion resistance.According to Raman spectroscopy,the I(D)/I(G)=549.8/1126.7=0.487,with the estimated fraction of sp^(3) bonding to be in the range of 5154%.The intermediate layer TiN has higher conductivity than the CrN layer.Considering cost,corrosion performance and ICR result,the Ti-TiN layer combination is recommended for industrial scale application.[Conclusions]Multiple layer coating structure of Ta-C film had stronger corrosion resistance;with more than 50%sp^(3) content,while it also had larger water contact angle and higher corrosion resistance than DLC film.The filtered arcing deposition technology was able to make the film to be more consistent and stable than normal arcing technology in terms of the preparation of Ta-C.The coating displayed corrosion density of 1.26×10^(−7) A·cm^(−2) and ICR of less than 5 mΩ·cm^(2),far beyond technical target of 2025 DOE(US Department of Energy).This indicated that the mass-production scale coating technology for PEMFC bipolar plates is highly possible.展开更多
To enhance the corrosion resistance and electrical conductivity, the surface of 316L stainless steel was modified by the ion implantation of Mo. By investigating various accelerating voltages and implantation doses, i...To enhance the corrosion resistance and electrical conductivity, the surface of 316L stainless steel was modified by the ion implantation of Mo. By investigating various accelerating voltages and implantation doses, it was found that the corrosion resistance of stainless steel was enhanced by 50%-80% and the surface conductivity by 15%-28% at most. The minimum stabilized current density is 0.72 μA/cm^(2). This is due to the formation of a Cr and Mo riched modified layer on the surface of the stainless steel. Mo oxides synergize with Cr oxides in the form of a solid solution to enhance the corrosion resistance of passivation films on the stainless steel surface. The optimum parameters were Cr in the proportion of 6%-8% and Mo in the proportion of 4%-5%.展开更多
The interfacial thermal resistance(ITR)at material interfaces has emerged as a critical factor in the thermal management of micro/nanoelectronic devices and composite materials.Using non-equilibrium molecular dynamics...The interfacial thermal resistance(ITR)at material interfaces has emerged as a critical factor in the thermal management of micro/nanoelectronic devices and composite materials.Using non-equilibrium molecular dynamics simulations,we systematically investigate how simulation parameters affect the calculated ITR in Si/Ge heterojunctions.Our results demonstrate that the ITR decreases with increasing system length L_(sys)and thermal bath length L_(bath).We identify linear relationships between ITR and the inverse of both L_(sys)and L_(bath),enabling reliable extrapolation to infinite-system values.While the thermostat coupling constantτshows a negligible influence on ITR,excessively large values(τ>5 ps)compromise temperature control accuracy.Spectral analysis reveals that these size effects primarily originate from mid-to-low-frequency phonons(<6 THz),whose long mean free paths make their transport particularly sensitive to system dimensions.This work establishes fundamental guidelines for parameter selection in interfacial thermal transport simulations,while providing new insights into phonon-interface interactions.The findings offer valuable implications for thermal design in high-power devices and composite materials,where accurate ITR prediction is crucial for performance optimization.展开更多
Solid-state electrolytes in rechargeable all-solidstate Li-metal batteries,which have better safety and higher specific capacity than conventional rechargeable Liion batteries with liquid electrolytes,are limited by t...Solid-state electrolytes in rechargeable all-solidstate Li-metal batteries,which have better safety and higher specific capacity than conventional rechargeable Liion batteries with liquid electrolytes,are limited by the low Li-ion conductivity of the solid electrolyte and the large electrolyte/electrode interfacial resistance.Here,we report a new rhombohedral NAS ICON structure Li1.4Sr0.2Hf1.8(PO4)3 with a high Li-ion conductivity of 1.62×10-5 S·cm-1 at 25℃,and its conductivity can be improved to 3.4×10-5 S·cm-1 after the densification of the pellet by hot pressing.Li1.4Sr0.2Hf1.8(PO4)3 coated by a thin layer of polymer electrolyte showed a stable lowimpedance dendrite-free plating/stripping process in a symmetric Li/Li cell for 100 h;moreover,the Li1.4Sr0.2Hf1.8(PO4)3 electrolyte had a small interfacial resistance in all-solid-state Li/LiFePO4 cell,which allows a high Coulombic efficiency and good cycling of the cell.展开更多
Hydrogen energy,whether in generation plants or utilization facilities,plays a decisive role in the mission to achieve net-zero greenhouse gas emissions,all to minimize pollution.The growing demand for clean energy ca...Hydrogen energy,whether in generation plants or utilization facilities,plays a decisive role in the mission to achieve net-zero greenhouse gas emissions,all to minimize pollution.The growing demand for clean energy carrier steadily accelerates the development of hydrogen production processes,and therein proton exchange membrane(PEM)water electrolysis is deemed a promising long-term strategy for hydrogen preparation and collection.This review retrospects recent developments and applications of bipolar plates(BPs)as key components in PEM fuel cells and water electrolysers.The main content includes multifaceted challenges in the R&D or fabrication of BPs and potential future trends have also been proposed.Specific details cover the BPs matrix(metallic materials and carbon composites)and the surface coating types(metal and compound coatings,carbon-based coatings,and polymer coatings),as well as the influence of flow field design for mass transport.Long-term development and feasible researches of BPs are prospected.Especially in the following aspects:(1)Structural and functional integration of components,such as material fabrication and flow field geometry optimization using 3D printing technology;(2)Introduction of environment-friendly renewable energy for hydrogen production;(3)Research on hydrogen energy reversible systems;(4)Composition optimization of surface coatings based on computational materials science and(5)systematic design expected to evolve into the next generation of BPs.展开更多
Garnet-structured ceramic electrolyte Li_(6.75)La_(3)Zr_(1.75)Ta_(0.25)O_(12)(LLZTO)attracts significant consideration in solid-state Li metal batteries due to its wide electrochemical window and favorable compatibili...Garnet-structured ceramic electrolyte Li_(6.75)La_(3)Zr_(1.75)Ta_(0.25)O_(12)(LLZTO)attracts significant consideration in solid-state Li metal batteries due to its wide electrochemical window and favorable compatibility with Li metal.However,the deployment of LLZTO is severely hampered by poor contact between LLZTO and Li metal anode.In this paper,an ultra-thin Al-Si interface buffer layer(10 nm)is constructed on LLZTO by a magnetron sputtering method,which allows superior wetting of Li onto the LLZTO surface due to the alloying reaction between the Al-Si layer and Li metal.The resulting Li/Al-Si coated LLZTO(ASL)/Li symmetrical cell delivers an interfacial resistance of 15.0Ωcm^(-2),which is much lower than that of 1140.3Ωcm^(-2)for the bare LLZTO symmetrical cell.Moreover,the Li/ASL/Li symmetrical cells exhibit stable plating/striping performance(800 h)with small voltage hysteresis at 1.0 mA cm^(-2).Besides,the full cell with LiFePO_(4)cathode reveals a high capacity of 124.1 mA h g^(-1)after 600 cycles at 0.5C with a lowcapacity decay of 0.032%per cycle.We believe this work will facilitate the development of solid-state rechargeable batteries.展开更多
Despite the enormous interest in inorganic/polymer composite solid-state electrolytes(CSEs)for solid-state batteries(SSBs),the underlying ion transport phenomena in CSEs have not yet been elucidated.Here,we address th...Despite the enormous interest in inorganic/polymer composite solid-state electrolytes(CSEs)for solid-state batteries(SSBs),the underlying ion transport phenomena in CSEs have not yet been elucidated.Here,we address this issue by formulating a mechanistic understanding of bi-percolating ion channels formation and ion conduction across inorganic-polymer electrolyte interfaces in CSEs.A model CSE is composed of argyrodite-type Li_6PS_5Cl(LPSCl)and gel polymer electrolyte(GPE,including Li~+-glyme complex as an ion-conducting medium).The percolation threshold of the LPSCl phase in the CSE strongly depends on the elasticity of the GPE phase.Additionally,manipulating the solvation/desolvation behavior of the Li~+-glyme complex in the GPE facilitates ion conduction across the LPSCl-GPE interface.The resulting scalable CSE(area=8×6(cm×cm),thickness~40μm)can be assembled with a high-mass-loading LiNi_(0.7)Co_(0.15)Mn_(0.15)O_(2)cathode(areal-mass-loading=39 mg cm~(-2))and a graphite anode(negative(N)/positive(P)capacity ratio=1.1)in order to fabricate an SSB full cell with bi-cell configuration.Under this constrained cell condition,the SSB full cell exhibits high volumetric energy density(480 Wh L_(cell)~(-1))and stable cyclability at 25℃,far exceeding the values reported by previous CSE-based SSBs.展开更多
78Li_(2)S-22P_(2)S_(5) are sulfide electrolytes with high lithium-ion conductivity and wide electrochemical windows in the Li_(2)S-P_(2)S_(5) system,making them attractive solid electrolytes for ASSLBs.However,the rol...78Li_(2)S-22P_(2)S_(5) are sulfide electrolytes with high lithium-ion conductivity and wide electrochemical windows in the Li_(2)S-P_(2)S_(5) system,making them attractive solid electrolytes for ASSLBs.However,the role and potential of 78Li_(2)S-22P_(2)S_(5) solid electrolytes over a wide temperature range are still not fully understood.Therefore,we constructed solid-state batteries with NCM622 as the positive electrode and 78Li_(2)S-22P_(2)S_(5) glass-ceramics as the electrolyte to investigate in depth the differences in battery performance over a wide temperature range and their intrinsic mechanisms.The in-situ impedance and relaxation time distribution (DRT) demonstrated the electrochemical stability of the electrolyte over a wide temperature range,while the in-situ stacking pressure observed a large volume change during cycling at 60℃,leading to local solid-solid contact failure and poor cycling stability.This study provides insight into the advantages and problems of 78Li_(2)S-22P_(2)S_(5) in the wide temperature range as well as a basis for the construction of ASSLBs with high energy density and long cycle life.展开更多
The history and current status of materials data activities from handbook to database are reviewed, with introduction to some important products. Through an example of prediction of interfacial thermal resistance base...The history and current status of materials data activities from handbook to database are reviewed, with introduction to some important products. Through an example of prediction of interfacial thermal resistance based on data and data science methods, we show the advantages and potential of material informatics to study material issues which are too complicated or time consuming for conventional theoretical and experimental methods. Materials big data is the fundamental of material informatics. The challenges and strategy to construct materials big data are discussed, and some solutions are proposed as the results of our experiences to construct National Institute for Materials Science（NIMS） materials databases.展开更多
Graphene is a two-dimensional material that can be folded into diverse and yet interesting nanostructures like macro-scale paper origami.Folding of graphene not only makes different morphological configurations but al...Graphene is a two-dimensional material that can be folded into diverse and yet interesting nanostructures like macro-scale paper origami.Folding of graphene not only makes different morphological configurations but also modifies their mechanical and thermal properties.Inspired by paper origami,herein we studied systemically the effects of creases,where sp^(2)to sp^(3)bond transformation occurs,on the thermal properties of graphene origami using molecular dynamics(MD)simulations.Our MD simulation results show that tensile strain reduces(not increases)the interfacial thermal resistance owing to the presence of the crease.This unusual phenomenon is explained by the micro-heat flux migration and stress distribution.Our findings on the graphene origami enable the design of the next-generation thermal management devices and flexible electronics with tuneable properties.展开更多
To improve the corrosion resistance and surface electrical conductivity of AISI 430 stainless steel （430 SS） as bipolar plates for proton exchange membrane fuel cells （PEMFCs） used in marine environment, a tungste...To improve the corrosion resistance and surface electrical conductivity of AISI 430 stainless steel （430 SS） as bipolar plates for proton exchange membrane fuel cells （PEMFCs） used in marine environment, a tungsten alloying layer has been successfully prepared on 430 SS substrate via the plasma surface diffusion alloying technique. The tungsten- modified （W-modified） 430 SS displays a 7-8 Ixm tungsten alloying layer with a body-centered-cubic structure. The W-modified surface also shows a better hydrophobicity with contact angle of 93.5~ and a lower interfacial contact resistance compared with the untreated 430 SS. The potentiodynamic and potentiostatic polarization and electrochemical impedance spectroscopy measurements show that the corrosion resistance of 430 SS is obviously improved in simulated PEMFC environment （0.05 M H2SO4 ＋ 2 ppm HF ＋ 0.01 M NaC1 solution at 70℃）, after the plasma surface diffusion alloying process.展开更多
In order to use stainless steel as bipolar plate for PEMFC, electrochemical behavior of a high Cr and Ni austenitic stainless steel was studied in the solutions containing different concentration of H2SO4 and 2 mg...In order to use stainless steel as bipolar plate for PEMFC, electrochemical behavior of a high Cr and Ni austenitic stainless steel was studied in the solutions containing different concentration of H2SO4 and 2 mg·L-1 F-, and interfacial contact resistance was measured after corrosion tests. The experimental results show that the passive current density lowers with decreasing the concentration of H2SO4. The interfacial contact resistance between carbon paper and passive film formed in the simulated PEMFC environment is higher than the goal of bipolar plate for PEMFC. Surface conductivity should be further reduced by surface modification.展开更多
While boron nitride(BN) is widely recognized as the most promising thermally conductive filler for rapidly developing high-power electronic devices due to its excellent thermal conductivity and dielectric properties,a...While boron nitride(BN) is widely recognized as the most promising thermally conductive filler for rapidly developing high-power electronic devices due to its excellent thermal conductivity and dielectric properties,a great challenge is the poor vertical thermal conductivity when embedded in composites owing to the poor interracial interaction causing severe phonon scattering.Here,we report a novel surface modification strategy called the "self-modified nanointerface" using BN nanocrystals(BNNCs) to efficiently link the interface between BN and the polymer matrix.Combining with ice-press assembly method,an only 25 wt% BNembedded composite film can not only possess an in-plane thermal conductivity of 20.3 W m-1K-1but also,more importantly,achieve a through-plane thermal conductivity as high as 21.3 W m-1K-1,which is more than twice the reported maximum due to the ideal phonon spectrum matching between BNNCs and BN fillers,the strong interaction between the self-modified fillers and polymer matrix,as well as ladder-structured BN skeleton.The excellent thermal conductivity has been verified by theoretical calculations and the heat dissipation of a CPU.This study provides an innovative design principle to tailor composite interfaces and opens up a new path to develop high-performance composites.展开更多
Alkaline hydrazine liquid fuel cells(AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts.Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction...Alkaline hydrazine liquid fuel cells(AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts.Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction(ORR),the surface density of the active site is very low and the catalyst layer should be thick to acquire the necessary number of catalytic active sites.With this thick catalyst layer,it is important to have an optimum pore structure for effective reactant conveyance to active sites and an interface structure for faster charge transfer.Herein,we prepare a Fe-N-C catalyst with magnetite particles and hierarchical pore structure by steam activation.The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses.Based on a systematic characterization,we found that hierarchical pore structures improve the catalyst utilization efficiency of the AHFCs,and magnetite nanoparticles act as surface modifiers to reduce the interracial resistance between the electrode and the ion-exchange membrane.展开更多
Bipolar plates are a multifunctional component of PEMFC. Comparing with the machined graphite and stainless steels, the plain carbon steel is a very cheap commercial metal material. In this paper, the possibility of a...Bipolar plates are a multifunctional component of PEMFC. Comparing with the machined graphite and stainless steels, the plain carbon steel is a very cheap commercial metal material. In this paper, the possibility of applying the plain carbon steels in the bipolar plate for PEMFC was exploited. In order to improve the corrosion resistance of the low carbon steel in the PEMFCs′ environments, two surface modification processes was developed and then the electrochemical performances and interfacial contact resistance (ICR) of the surface modified plate of plain carbon steel were investigated. The results show that the surface modified steel plates have good corrosion resistance and relatively low contact resistance, and it may be a candidate material as bipolar plate of PEMFC.展开更多
In the realm of proton exchange membrane fuel cells(PEMFCs),the bipolar plates(BPs)are indispensable and serve pivotal roles in distributing reactant gases,collecting current,facilitating product water removal,and coo...In the realm of proton exchange membrane fuel cells(PEMFCs),the bipolar plates(BPs)are indispensable and serve pivotal roles in distributing reactant gases,collecting current,facilitating product water removal,and cooling the stack.Metal BPs,characterized by outstanding manufacturability,cost-effectiveness,higher power density,and mechanical strength,are emerging as viable alternatives to traditional graphite BPs.The foremost challenge for metal BPs lies in enhancing their corrosion resistance and conductivity under acidic conditions,necessitating the application of various coatings on their surfaces to ensure superior performance.This review summarizes and compares recent advancements in the research of eight distinct types of coatings for BPs in PEMFCs,including noble metal,carbide,ni-tride,and amorphous carbon(a-C)/metal compound composite coatings.The various challenges encountered in the manufacturing and fu-ture application of these coatings are also delineated.展开更多
基金the financial support of Natural Science Foundation of Hunan Province(2023JJ40261).
文摘The mass transport and ohmic losses in proton exchange membrane fuel cells(PEMFCs)is significantly influenced by the channel to rib width ratio(CRWR),particularly when accounting for the interfacial contact resistance between bipolar plates(BPs)and gas diffusion layers(GDLs)(ICRBP-GDL).Both the determination of the optimal CRWR value and the development of an efficient flow field structure are significantly influenced by ICRBP-GDLs.To investigate this,three-dimensional numerical models were developed,revealing that selecting an optimal CRWR tailored to specific ICRBP-GDL values can effectively balance mass transport and ohmic losses.Building on this insight,a novel island two-dimensional flow field design is proposed,demonstrating the ability to enhance oxygen transport to the catalyst layer(CL)and achieve a more uniform oxygen distribution without increasing ohmic losses.Compared to conventional straight and serpentine flow fields,the island flow field improves output power density by 4.5%and 3.5%,respectively,while reducing the liquid water coverage ratio by 30%.Additionally,the study identifies optimal CRWR values for conventional flow fields corresponding to ICRBP-GDLs of 2.5,5,10,20,and 40 mΩ·cm^(2) as 1.5,1.5,1.0,0.67,and 0.43,respectively.For the island flow field,the optimal CRWRs are consistently smaller-1.5,1.0,0.67,0.43,and 0.43-due to its superior mass transfer capability.This work provides a valuable framework for optimizing flow field designs to achieve improved PEMFC performance.
基金National Natural Science Foundation of China(51773169 and 51973173)Guangdong Basic and Applied Basic Research Foundation(2019B1515120093)+2 种基金Technological Base Scientific Research ProjectsNatural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province(2019JC-11)Polymer Electromagnetic Functional Materials Innovation Team of Shaanxi Sanqin Scholars.
文摘Rapid development of energy,electrical and electronic technologies has put forward higher requirements for the thermal conductivities of polymers and their composites.However,the thermal conductivity coefficient(λ)values of prepared thermally conductive polymer composites are still difficult to achieve expectations,which has become the bottleneck in the fields of thermally conductive polymer composites.Aimed at that,based on the accumulation of the previous research works by related researchers and our research group,this paper proposes three possible directions for breaking through the bottlenecks:(1)preparing and synthesizing intrinsically thermally conductive polymers,(2)reducing the interfacial thermal resistance in thermally conductive polymer composites,and(3)establishing suitable thermal conduction models and studying inner thermal conduction mechanism to guide experimental optimization.Also,the future development trends of the three above-mentioned directions are foreseen,hoping to provide certain basis and guidance for the preparation,researches and development of thermally conductive polymers and their composites.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51373184 and 51206167)the National Plan for Science&Technology Support,China(Grant No.2014BAC03B05)the National Basic Research Program of China(Grant Nos.2014CB931803 and 2012CB933801)
文摘To improve the thermal conductivity of polymeric composites, the numerous interfacial thermal resistance （ITR） inside is usually considered as a bottle neck, but the direct measurement of the ITR is hardly reported. In this paper, a sandwich structure which consists of transducer/high density polyethylene （HDPE）/sapphire is prepared to study the interface characteristics. Then, the ITRs between HDPE and sapphire of two samples with different HDPE thickness values are measured by time-domain thermoreflectance （TDTR） method and the results are -- 2 × 10-7 m2.K.W-1. Furthermore, a model is used to evaluate the importance of ITR for the thermal conductivity of composites. The model＇s analysis indicates that reducing the ITR is an effective way of improving the thermal conductivity of composites. These results will provide valuable guidance for the design and manufacture of polymer-based thermally conductive materials.
基金supported by the Key Program for International Science and Technology Cooperation Projects of the Ministry of Science and Technology of China(2021YFE0109700)Technical Innovation and Application Development Project of Chongqing(Z20230084)+7 种基金Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure(SKL202106SIC)Chinese National Natural Science Fund(11632004,U1864208)National Science and Technology Major Project(2017-VII-0011-0106)Science and Technology Planning Project of Tianjin(20ZYJDJC00030)Key Program of Research and Development of Hebei Province(202030507040009)Fund for Innovative Research Groups of Natural Science Foundation of Hebei Province(A2020202002)Natural Science Foundation of Chongqing(cstc2021jcyjmsxm X0241)Key Project of Natural Science Foundation of Tianjin(S20ZDF077)
文摘The ideal composite electrolyte for the pursued safe and high-energy-density lithium metal batteries(LMBs)is expected to demonstrate peculiarity of superior bulk conductivity,low interfacial resistances,and good compatibility against both Li-metal anode and high-voltage cathode.There is no composite electrolyte to synchronously meet all these requirements yet,and the battery performance is inhibited by the absence of effective electrolyte design.Here we report a unique"concentrated ionogel-in-ceramic"silanization composite electrolyte(SCE)and validate an electrolyte design strategy based on the coupling of high-content silane-conditioning garnet and concentrated ionogel that builds well-percolated Li+transport pathways and tackles the interface issues to respond all the aforementioned requirements.It is revealed that the silane conditioning enables the uniform dispersion of garnet nanoparticles at high content(70 wt%)and forms mixed-lithiophobic-conductive LiF-Li3N solid electrolyte interphase.Notably,the yielding SCE delivers an ultrahigh ionic conductivity of 1.76 X 10^(-3)S cm^(-1)at 25℃,an extremely low Li-metal/electrolyte interfacial area-specific resistance of 13Ωcm^(2),and a distinctly excellent long-term 1200 cycling without any capacity decay in 4.3 V Li‖LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM523)quasi-solid-state LMB.This composite electrolyte design strategy can be extended to other quasi-/solid-state LMBs.
基金Major Science and technology projects of Anhui Province (202103a05020003)。
文摘[Background and purposes]Proton exchange membrane fuel cells(PEMFCs),which convert hydrogen energy directly into electrical energy and water,have received overwhelming attention,owing to their potential to significantly reduce energy consumption,pollution emissions and reliance on fossil fuels.Bipolar plates are the major part and key component of PEMFCs stack,which provide mechanical strength,collect and conduct current segregate oxidants and reduce agents.They contribute 70-80%weight and 20-30%cost of a whole stack,while significantly affecting the power density.There are three types plates,including metal bipolar plate,graphite bipolar plate and composite bipolar plate.Stainless steel bipolar plates,as one of metal bipolar plate,exhibit promising manufacturability,competitive cost and durability among various metal materials.However,stainless steel would be corroded in the harsh acid(pH 2-5)and humid PEMFCs environment,whereas the leached ions will contaminate the membrane.In addition,the passivated film formed on the surface will increase the interfacial contact resistance(ICR).In order to improve the corrosion resistance and electrical conductivity of steel bipolar plates,surface coatings are essential.Metal nitride coatings,metal carbide coatings,polymer coatings and carbon-based coatings have been introduced in recent years.Carbon-based coatings,mainly including a-C(amorphous Carbon),Ta-C(Tetrahedral amorphous carbon)and DLC(diamond-like carbon),have attracted considerable attention from both academia and industry,owing to their superior performance,such as chemical inertness,mechanical hardness and electrical conductivity.However,Ta-C films as protective coating of PEMFCs have been rarely reported,due to the difficulty in production for industrial application.In this paper,multi-layer Ta-C composite films were produced by using customized industrial-scale vacuum equipment to address those issues.[Methods]Multiple layered Ta-C coatings were prepared by using PIS624 equipment,which assembled filtered cathodic arc evaporation,ion beam and magnetron sputtering into one equipment,while SS304 and silicon specimens were used as substrate for testing and analysis.Adhesion layer and intermediate layer were deposited by using magnetron sputtering at deposition temperature of 150℃and pressure of 3×10^(−1) Pa,while the sputtering current was set to be 5 A and bias power to be 300 V.The Ta-C layer was coated at arc current of 80-100 A,bias voltage of 1500 V and gas flow of 75 sccm.A scanning electron microscope(CIQTEK SEM3200)was used to characterize surface morphology,coating structure and cross-section profile of the coatings.Raman spectrometer(LabRam HR Evolution,HORIBA JOBIN YVON)was used to identify the bonding valence states.Electrochemical tests were performed by using an electrochemical work station(CHI760,Shanghai Chenhua Instrument Co.,Ltd.),with the traditional three electrode system,where saturated Ag/AgCl and platinum mesh were used as the reference electrode and counter electrode,respectively.All samples were mounted in plastic tube and sealed with epoxy resin,with an exposure area of 2.25 cm^(2),serving as the working electrode.Electrochemical measurements were carried out in simulated PEMFCs cathode environment in 0.5 mol·L^(−1) H_(2)SO_(4)+5 ppm F−solution,at operating temperature of 70℃.As the cathode environment was harsher than the anode environment,all the samples are stabilized at the open-circuit potential(OCP)for approximately 30 min before the EIS measurements.ICR between bipolar plates and GDL was a key parameter affecting performance of the PEMFCs stack.The test sample sandwiched between 2 pieces of carbon paper(simulate gas diffusion layer,GDL)was placed between 2 gold-plated copper electrodes at a compaction pressure of 1.4 MPa,which was considered to be the conventional compaction pressure in the PEMFCs.Under the same conditions,the resistance of a single carbon paper was measured as well.The ICR was calculated according to the formula ICR=1/2(R2−R1)×S,where S was the contact area between GDL and coated stainless steel BPPs.All data of ICR were measured three times for averaging.[Results]The coatings deposited by filtered cathodic arc technology were compact and smooth,which reduced coating porosity and favorable to corrosion resistance.The coating thickness of adhesion and intermediate layers were 180 nm,while the protective Ta-C coating thickness was about 300 nm,forming multiple coating to provide stronger protection for metal bipolar plates.Cr,Ti,Nb and Ta coatings were selected as adhesion layers for comparison.According to electrochemical test,Ta and Nb coatings have higher corrosion resistance.However,Ta and Nb materials would be costly when they are used for mass production.Relatively,Cr and Ti materials were cost effective.Hence,a comprehensive assessment was indispensable to decide the materials to be selected as adhesion layer.Ta-TiN and Ti-TiN combined adhesion and intermediate layer exhibited stronger corrosion resistance,with the corrosion current to be less than 10^(−6) A·cm^(−2).Ta-C protective coating deposited by using filtered cathodic arc technology indicated displayed higher corrosion resistance,with the average corrosion density to be about 1.26×10^(−7) A·cm^(−2).Ta-C coating also shown larger contact angle,with the highest hydrophobicity,which was one of the important advantages for Ta-C,in terms of corrosion resistance.According to Raman spectroscopy,the I(D)/I(G)=549.8/1126.7=0.487,with the estimated fraction of sp^(3) bonding to be in the range of 5154%.The intermediate layer TiN has higher conductivity than the CrN layer.Considering cost,corrosion performance and ICR result,the Ti-TiN layer combination is recommended for industrial scale application.[Conclusions]Multiple layer coating structure of Ta-C film had stronger corrosion resistance;with more than 50%sp^(3) content,while it also had larger water contact angle and higher corrosion resistance than DLC film.The filtered arcing deposition technology was able to make the film to be more consistent and stable than normal arcing technology in terms of the preparation of Ta-C.The coating displayed corrosion density of 1.26×10^(−7) A·cm^(−2) and ICR of less than 5 mΩ·cm^(2),far beyond technical target of 2025 DOE(US Department of Energy).This indicated that the mass-production scale coating technology for PEMFC bipolar plates is highly possible.
基金supported by the National Natural Science Foundation of China(22005140)Scientific Research Foundation for the Introduction of Talents by Nanjing Institute of Technology(YKJ201996)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX22_1370).
文摘To enhance the corrosion resistance and electrical conductivity, the surface of 316L stainless steel was modified by the ion implantation of Mo. By investigating various accelerating voltages and implantation doses, it was found that the corrosion resistance of stainless steel was enhanced by 50%-80% and the surface conductivity by 15%-28% at most. The minimum stabilized current density is 0.72 μA/cm^(2). This is due to the formation of a Cr and Mo riched modified layer on the surface of the stainless steel. Mo oxides synergize with Cr oxides in the form of a solid solution to enhance the corrosion resistance of passivation films on the stainless steel surface. The optimum parameters were Cr in the proportion of 6%-8% and Mo in the proportion of 4%-5%.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174276 and 12304059)the Basic and Applied Basic Research Foundation of Guangdong Province(Grant Nos.2024A1515010521,2024A1515012635,and 2022A1515110572).
文摘The interfacial thermal resistance(ITR)at material interfaces has emerged as a critical factor in the thermal management of micro/nanoelectronic devices and composite materials.Using non-equilibrium molecular dynamics simulations,we systematically investigate how simulation parameters affect the calculated ITR in Si/Ge heterojunctions.Our results demonstrate that the ITR decreases with increasing system length L_(sys)and thermal bath length L_(bath).We identify linear relationships between ITR and the inverse of both L_(sys)and L_(bath),enabling reliable extrapolation to infinite-system values.While the thermostat coupling constantτshows a negligible influence on ITR,excessively large values(τ>5 ps)compromise temperature control accuracy.Spectral analysis reveals that these size effects primarily originate from mid-to-low-frequency phonons(<6 THz),whose long mean free paths make their transport particularly sensitive to system dimensions.This work establishes fundamental guidelines for parameter selection in interfacial thermal transport simulations,while providing new insights into phonon-interface interactions.The findings offer valuable implications for thermal design in high-power devices and composite materials,where accurate ITR prediction is crucial for performance optimization.
基金financially supported by the National Natural Science Foundation of China(No.51504127)。
文摘Solid-state electrolytes in rechargeable all-solidstate Li-metal batteries,which have better safety and higher specific capacity than conventional rechargeable Liion batteries with liquid electrolytes,are limited by the low Li-ion conductivity of the solid electrolyte and the large electrolyte/electrode interfacial resistance.Here,we report a new rhombohedral NAS ICON structure Li1.4Sr0.2Hf1.8(PO4)3 with a high Li-ion conductivity of 1.62×10-5 S·cm-1 at 25℃,and its conductivity can be improved to 3.4×10-5 S·cm-1 after the densification of the pellet by hot pressing.Li1.4Sr0.2Hf1.8(PO4)3 coated by a thin layer of polymer electrolyte showed a stable lowimpedance dendrite-free plating/stripping process in a symmetric Li/Li cell for 100 h;moreover,the Li1.4Sr0.2Hf1.8(PO4)3 electrolyte had a small interfacial resistance in all-solid-state Li/LiFePO4 cell,which allows a high Coulombic efficiency and good cycling of the cell.
基金supported by the National Key Research and Development Program of China(No.2021YFB4000101)the National Natural Science Foundation of China(No.52125102)the Fundamental Research Funds for the Central Universities(No.FRF-TP-2021–02C2).
文摘Hydrogen energy,whether in generation plants or utilization facilities,plays a decisive role in the mission to achieve net-zero greenhouse gas emissions,all to minimize pollution.The growing demand for clean energy carrier steadily accelerates the development of hydrogen production processes,and therein proton exchange membrane(PEM)water electrolysis is deemed a promising long-term strategy for hydrogen preparation and collection.This review retrospects recent developments and applications of bipolar plates(BPs)as key components in PEM fuel cells and water electrolysers.The main content includes multifaceted challenges in the R&D or fabrication of BPs and potential future trends have also been proposed.Specific details cover the BPs matrix(metallic materials and carbon composites)and the surface coating types(metal and compound coatings,carbon-based coatings,and polymer coatings),as well as the influence of flow field design for mass transport.Long-term development and feasible researches of BPs are prospected.Especially in the following aspects:(1)Structural and functional integration of components,such as material fabrication and flow field geometry optimization using 3D printing technology;(2)Introduction of environment-friendly renewable energy for hydrogen production;(3)Research on hydrogen energy reversible systems;(4)Composition optimization of surface coatings based on computational materials science and(5)systematic design expected to evolve into the next generation of BPs.
基金supported by the National Natural Science Foundation of China(22209140,52072328,and 52175192)the Incubation Program of Youth Innovation in Shandong Province and Natural Science Foundation of Shandong Province(ZR2022QE059)。
文摘Garnet-structured ceramic electrolyte Li_(6.75)La_(3)Zr_(1.75)Ta_(0.25)O_(12)(LLZTO)attracts significant consideration in solid-state Li metal batteries due to its wide electrochemical window and favorable compatibility with Li metal.However,the deployment of LLZTO is severely hampered by poor contact between LLZTO and Li metal anode.In this paper,an ultra-thin Al-Si interface buffer layer(10 nm)is constructed on LLZTO by a magnetron sputtering method,which allows superior wetting of Li onto the LLZTO surface due to the alloying reaction between the Al-Si layer and Li metal.The resulting Li/Al-Si coated LLZTO(ASL)/Li symmetrical cell delivers an interfacial resistance of 15.0Ωcm^(-2),which is much lower than that of 1140.3Ωcm^(-2)for the bare LLZTO symmetrical cell.Moreover,the Li/ASL/Li symmetrical cells exhibit stable plating/striping performance(800 h)with small voltage hysteresis at 1.0 mA cm^(-2).Besides,the full cell with LiFePO_(4)cathode reveals a high capacity of 124.1 mA h g^(-1)after 600 cycles at 0.5C with a lowcapacity decay of 0.032%per cycle.We believe this work will facilitate the development of solid-state rechargeable batteries.
基金the Basic Science Research Program(2018M3D1A1058744,2021R1A5A6002853,2021R1A2B5B03001615,and 2022M3J1A1085397)through the National Research Foundation of Korea(NRF)grant by the Korean Government(MSIT)provided by KISTI(KSC-2020-CRE-0301)supported by the Hyundai NGV program。
文摘Despite the enormous interest in inorganic/polymer composite solid-state electrolytes(CSEs)for solid-state batteries(SSBs),the underlying ion transport phenomena in CSEs have not yet been elucidated.Here,we address this issue by formulating a mechanistic understanding of bi-percolating ion channels formation and ion conduction across inorganic-polymer electrolyte interfaces in CSEs.A model CSE is composed of argyrodite-type Li_6PS_5Cl(LPSCl)and gel polymer electrolyte(GPE,including Li~+-glyme complex as an ion-conducting medium).The percolation threshold of the LPSCl phase in the CSE strongly depends on the elasticity of the GPE phase.Additionally,manipulating the solvation/desolvation behavior of the Li~+-glyme complex in the GPE facilitates ion conduction across the LPSCl-GPE interface.The resulting scalable CSE(area=8×6(cm×cm),thickness~40μm)can be assembled with a high-mass-loading LiNi_(0.7)Co_(0.15)Mn_(0.15)O_(2)cathode(areal-mass-loading=39 mg cm~(-2))and a graphite anode(negative(N)/positive(P)capacity ratio=1.1)in order to fabricate an SSB full cell with bi-cell configuration.Under this constrained cell condition,the SSB full cell exhibits high volumetric energy density(480 Wh L_(cell)~(-1))and stable cyclability at 25℃,far exceeding the values reported by previous CSE-based SSBs.
基金supported by the National Key Research and Development Program (No. 2021YFB2400300)the National Natural Science Foundation of China (No. 52177214)。
文摘78Li_(2)S-22P_(2)S_(5) are sulfide electrolytes with high lithium-ion conductivity and wide electrochemical windows in the Li_(2)S-P_(2)S_(5) system,making them attractive solid electrolytes for ASSLBs.However,the role and potential of 78Li_(2)S-22P_(2)S_(5) solid electrolytes over a wide temperature range are still not fully understood.Therefore,we constructed solid-state batteries with NCM622 as the positive electrode and 78Li_(2)S-22P_(2)S_(5) glass-ceramics as the electrolyte to investigate in depth the differences in battery performance over a wide temperature range and their intrinsic mechanisms.The in-situ impedance and relaxation time distribution (DRT) demonstrated the electrochemical stability of the electrolyte over a wide temperature range,while the in-situ stacking pressure observed a large volume change during cycling at 60℃,leading to local solid-solid contact failure and poor cycling stability.This study provides insight into the advantages and problems of 78Li_(2)S-22P_(2)S_(5) in the wide temperature range as well as a basis for the construction of ASSLBs with high energy density and long cycle life.
基金Project supported by “Materials Research by Information Integration” Initiative(MI2I) project of the Support Program for Starting Up Innovation Hub from Japan Science and Technology Agency(JST)
文摘The history and current status of materials data activities from handbook to database are reviewed, with introduction to some important products. Through an example of prediction of interfacial thermal resistance based on data and data science methods, we show the advantages and potential of material informatics to study material issues which are too complicated or time consuming for conventional theoretical and experimental methods. Materials big data is the fundamental of material informatics. The challenges and strategy to construct materials big data are discussed, and some solutions are proposed as the results of our experiences to construct National Institute for Materials Science（NIMS） materials databases.
基金support by the National Natural Science Foundation of China(Grant Nos.11972171,11502217)the Programs of Innovation and Entrepreneurship of Jiangsu Province+2 种基金the Fundamental Research Funds for the Central Universities(Nos.2452015054,2452017122)China Postdoctoral Science Foundation(No.2015M570854 and 2016T90949)Open Fund of Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education(NUAA)(Grant No.INMD-2019M08)
文摘Graphene is a two-dimensional material that can be folded into diverse and yet interesting nanostructures like macro-scale paper origami.Folding of graphene not only makes different morphological configurations but also modifies their mechanical and thermal properties.Inspired by paper origami,herein we studied systemically the effects of creases,where sp^(2)to sp^(3)bond transformation occurs,on the thermal properties of graphene origami using molecular dynamics(MD)simulations.Our MD simulation results show that tensile strain reduces(not increases)the interfacial thermal resistance owing to the presence of the crease.This unusual phenomenon is explained by the micro-heat flux migration and stress distribution.Our findings on the graphene origami enable the design of the next-generation thermal management devices and flexible electronics with tuneable properties.
基金financially supported by the National Natural Science Foundation of China (Nos. 51479019 and 21476035)Fundamental Research Funds for Central Universities (No. 3132014323)
文摘To improve the corrosion resistance and surface electrical conductivity of AISI 430 stainless steel （430 SS） as bipolar plates for proton exchange membrane fuel cells （PEMFCs） used in marine environment, a tungsten alloying layer has been successfully prepared on 430 SS substrate via the plasma surface diffusion alloying technique. The tungsten- modified （W-modified） 430 SS displays a 7-8 Ixm tungsten alloying layer with a body-centered-cubic structure. The W-modified surface also shows a better hydrophobicity with contact angle of 93.5~ and a lower interfacial contact resistance compared with the untreated 430 SS. The potentiodynamic and potentiostatic polarization and electrochemical impedance spectroscopy measurements show that the corrosion resistance of 430 SS is obviously improved in simulated PEMFC environment （0.05 M H2SO4 ＋ 2 ppm HF ＋ 0.01 M NaC1 solution at 70℃）, after the plasma surface diffusion alloying process.
文摘In order to use stainless steel as bipolar plate for PEMFC, electrochemical behavior of a high Cr and Ni austenitic stainless steel was studied in the solutions containing different concentration of H2SO4 and 2 mg·L-1 F-, and interfacial contact resistance was measured after corrosion tests. The experimental results show that the passive current density lowers with decreasing the concentration of H2SO4. The interfacial contact resistance between carbon paper and passive film formed in the simulated PEMFC environment is higher than the goal of bipolar plate for PEMFC. Surface conductivity should be further reduced by surface modification.
基金the National Natural Science Foundation of China(52173072,51721002 and 52033003)Natural Science Foundation of Shanghai(22ZR1403700).
文摘While boron nitride(BN) is widely recognized as the most promising thermally conductive filler for rapidly developing high-power electronic devices due to its excellent thermal conductivity and dielectric properties,a great challenge is the poor vertical thermal conductivity when embedded in composites owing to the poor interracial interaction causing severe phonon scattering.Here,we report a novel surface modification strategy called the "self-modified nanointerface" using BN nanocrystals(BNNCs) to efficiently link the interface between BN and the polymer matrix.Combining with ice-press assembly method,an only 25 wt% BNembedded composite film can not only possess an in-plane thermal conductivity of 20.3 W m-1K-1but also,more importantly,achieve a through-plane thermal conductivity as high as 21.3 W m-1K-1,which is more than twice the reported maximum due to the ideal phonon spectrum matching between BNNCs and BN fillers,the strong interaction between the self-modified fillers and polymer matrix,as well as ladder-structured BN skeleton.The excellent thermal conductivity has been verified by theoretical calculations and the heat dissipation of a CPU.This study provides an innovative design principle to tailor composite interfaces and opens up a new path to develop high-performance composites.
基金supported by the GIST Research Institute(GRI)grant funded by GIST in 2021supported by the KBSI grants(C140140 and C140110)。
文摘Alkaline hydrazine liquid fuel cells(AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts.Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction(ORR),the surface density of the active site is very low and the catalyst layer should be thick to acquire the necessary number of catalytic active sites.With this thick catalyst layer,it is important to have an optimum pore structure for effective reactant conveyance to active sites and an interface structure for faster charge transfer.Herein,we prepare a Fe-N-C catalyst with magnetite particles and hierarchical pore structure by steam activation.The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses.Based on a systematic characterization,we found that hierarchical pore structures improve the catalyst utilization efficiency of the AHFCs,and magnetite nanoparticles act as surface modifiers to reduce the interracial resistance between the electrode and the ion-exchange membrane.
文摘Bipolar plates are a multifunctional component of PEMFC. Comparing with the machined graphite and stainless steels, the plain carbon steel is a very cheap commercial metal material. In this paper, the possibility of applying the plain carbon steels in the bipolar plate for PEMFC was exploited. In order to improve the corrosion resistance of the low carbon steel in the PEMFCs′ environments, two surface modification processes was developed and then the electrochemical performances and interfacial contact resistance (ICR) of the surface modified plate of plain carbon steel were investigated. The results show that the surface modified steel plates have good corrosion resistance and relatively low contact resistance, and it may be a candidate material as bipolar plate of PEMFC.
基金the support from the Shenzhen Science and Technology Program of China(No.JCYJ20220530161614031)National Natural Science Foundation of China(No.52471094)Shaanxi Coal Chemical Industry Technology Research Institute Co.,Ltd.
文摘In the realm of proton exchange membrane fuel cells(PEMFCs),the bipolar plates(BPs)are indispensable and serve pivotal roles in distributing reactant gases,collecting current,facilitating product water removal,and cooling the stack.Metal BPs,characterized by outstanding manufacturability,cost-effectiveness,higher power density,and mechanical strength,are emerging as viable alternatives to traditional graphite BPs.The foremost challenge for metal BPs lies in enhancing their corrosion resistance and conductivity under acidic conditions,necessitating the application of various coatings on their surfaces to ensure superior performance.This review summarizes and compares recent advancements in the research of eight distinct types of coatings for BPs in PEMFCs,including noble metal,carbide,ni-tride,and amorphous carbon(a-C)/metal compound composite coatings.The various challenges encountered in the manufacturing and fu-ture application of these coatings are also delineated.
