Comparative review of corrosion-resistant coatings on metal bipolar plates of proton exchange membrane fuel cells

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.

Fast and Balanced Charge Transport Enabled by Solution-Processed Metal Oxide Layers for Efficient and Stable Inverted Perovskite Solar Cells

Metal oxide charge transport materials are preferable for realizing long-term stable and potentially low-cost perovskite solar cells(PSCs).However,due to some technical difficulties(e.g.,intricate fabrication protocols,high-temperature heating process,incompatible solvents,etc.),it is still challenging to achieve efficient and reliable all-metal-oxide-based devices.Here,we developed efficient inverted PSCs(IPSCs)based on solution-processed nickel oxide(NiO_(x))and tin oxide(SnO_(2))nanoparticles,working as hole and electron transport materials respectively,enabling a fast and balanced charge transfer for photogenerated charge carriers.Through further understanding and optimizing the perovskite/metal oxide interfaces,we have realized an outstanding power conversion efficiency(PCE)of 23.5%(the bandgap of the perovskite is 1.62 eV),which is the highest efficiency among IPSCs based on all-metal-oxide charge transport materials.Thanks to these stable metal oxides and improved interface properties,ambient stability(retaining 95%of initial PCE after 1 month),thermal stability(retaining 80%of initial PCE after 2 weeks)and light stability(retaining 90%of initial PCE after 1000 hours aging)of resultant devices are enhanced significantly.In addition,owing to the low-temperature fabrication procedures of the entire device,we have obtained a PCE of over 21%for flexible IPSCs with enhanced operational stability.

Metal-organic frameworks with mixed-ligands strategy as heterogeneous nucleation center to assist crystallization for efficient and stable perovskite solar cells

Deep-level defects and random oriented configuration in perovskite crystallization process would cause the nonradiative recombination and further affect the performance of perovskite solar cells(PSCs).Herein,two metal-organic frameworks(MOFs)with tunable Lewis-base passivation sites have been constructed(Cd-Httb and Cd-Httb-BDC,Httb=5-(4-(1H-1,2,4-triazole-1-yl)benzyl)-1h-tetrazole,BDC=1,4-dicarboxybenzene)to eliminate deep-level defects and simultaneously as nanostructured heterogeneous nucleation seed to assist the growth of large-grained perovskite films.Compared with the control and Cd-Httb,Cd-Httb-BDC designed with mix-ligands strategy exhibited the enhanced inducted effect on the crystallization and nucleation of high-quality perovskite films during annealing process.Consequently,the resultant Cd-Httb-BDC-modified device achieved higher power conversion efficiency(PCE)(22.18%)than the control(20.89%)and Cd-Httb(21.56%).Meanwhile,the unencapsulated Cd-Httb-BDC-modified device still maintained 90%of initial PCE after 1500 h in ambient conditions and exhibited enhanced thermal stability(85℃ in N_(2) atmosphere).This work presented a successful example of mixligands strategy on construction of high-quality MOF-assisted perovskite films for high-efficient and stable PSCs.

Multicomponent mixed metallic hierarchical ZnNi@Ni@PEDOT arrayed structures as advanced electrode for high-performance hybrid electrochemical cells

Engineering multicomponent nanomaterials as an electrode with rationalized ordered structures is a promising strategy for fulfilling the high-energy storage needs of supercapacitors(SCs).Even now,the fundamental barrier to utilizing hydroxides/hydroxyl carbonates is their poor electrochemical performance,resulting from the significantly poor electrical conductivity and sluggish charge storage kinetics.Hence,a multilayered structural approach is primarily and successfully used to construct electrodes as one of the efficient approaches.This method has made it possible to develop well-ordered nanostructured electrodes with good performance by taking advantage of tunable approach parameters.Herein,we report the design of multilayered heterostructure porous zinc-nickel nanosheets@nickel flakes hydroxyl carbonates and/or hydroxides integrated with conductive PEDOT fibrous network(i.e.,ZnNi@Ni@PEDOT) via facile synthesis methods.The combined hybrid electrode acquires the features of high electrical conductivity from one part and various valance states from another one to develop a well-organized nanosheet/flake/fibrous-like heterostructure with decent mechanical strength,creating robust synergistic results.Thus,the designed binder-free ZnNi@Ni@PEDOT electrode delivers a high areal capacity value of 1050.1 μA h cm^(-2) at 3 mA cm^(-2) with good cycling durability,significantly outperforming other individual electrodes.Moreover,its feasibility is also tested by constructing a hybrid electrochemical cell(HEC).The assembled HEC exhibits a high areal capacity value of 783.8 μA h cm^(-2) at5 mA cm^(-2).and even at a high current density of 100 mA cm^(-2)(484.6 μA h cm^(-2)),the device still retains a rate capability of 61,82%,Also,the HEC shows maximum energy and power densities of0.595 mW h cm^(-2) and 77.23 mW cm^(-2),respectively,along with good cycling stability.The obtained energy storage capabilities effectively power various electronic components.These results provide a viable and practical way to construct a positive electrode with innovative heterostructures for highperformance energy storage devices and profoundly influence the development of electrochemical SCs.

Understanding of the Relationship between the Properties of Cu(In,Ga)Se_(2) Solar Cells and the Structure of Ag Network Electrodes

The relation between the structure of the silver network electrodes and the properties of Cu(In,Ga)Se_(2)(CIGS)solar cells is systemically investigated.The Ag network electrode is deposited onto an Al:ZnO(AZO)thin film,employing a self-forming cracked template.Precise control over the cracked template's structure is achieved through careful adjustment of temperature and humidity.The Ag network electrodes with different coverage areas and network densities are systemically applied to the CIGS solar cells.It is revealed that predominant fill factor(FF)is influenced by the figure of merit of transparent conducting electrodes,rather than sheet resistance,particularly when the coverage area falls within the range of 1.3–5%.Furthermore,a higher network density corresponds to an enhanced FF when the coverage areas of the Ag networks are similar.When utilizing a thinner AZO film,CIGS solar cells with a surface area of 1.0609 cm^(2)exhibit a notable performance improvement,with efficiency increasing from 10.48%to 11.63%.This enhancement is primarily attributed to the increase in FF from 45%to 65%.These findings underscore the considerable potential for reducing the thickness of the transparent conductive oxide(TCO)in CIGS modules with implications for practical applications in photovoltaic technology.

Mitigated reaction kinetics between lithium metal anodes and electrolytes by alloying lithium metal with low-content magnesium

Lithium(Li)metal is regarded as a promising anode candidate for high-energy-density rechargeable batteries.Nevertheless,Li metal is highly reactive against electrolytes,leading to rapid decay of active Li metal reservoir.Here,alloying Li metal with low-content magnesium(Mg)is proposed to mitigate the reaction kinetics between Li metal anodes and electrolytes.Mg atoms enter the lattice of Li atoms,forming solid solution due to the low amount(5 wt%)of Mg.Mg atoms mainly concentrate near the surface of Mg-alloyed Li metal anodes.The reactivity of Mg-alloyed Li metal is mitigated kinetically,which results from the electron transfer from Li to Mg atoms due to the electronegativity difference.Based on quantitative experimental analysis,the consumption rate of active Li and electrolytes is decreased by using Mgalloyed Li metal anodes,which increases the cycle life of Li metal batteries under demanding conditions.Further,a pouch cell(1.25 Ah)with Mg-alloyed Li metal anodes delivers an energy density of 340 Wh kg^(-1)and a cycle life of 100 cycles.This work inspires the strategy of modifying Li metal anodes to kinetically mitigate the side reactions with electrolytes.

Boosting High-Voltage Practical Lithium Metal Batteries with Tailored Additives

The lithium(Li)metal anode is widely regarded as an ideal anode material for high-energy-density batteries.However,uncontrolled Li dendrite growth often leads to unfavorable interfaces and low Coulombic efficiency(CE),limiting its broader application.Herein,an ether-based electrolyte(termed FGN-182)is formulated,exhibiting ultra-stable Li metal anodes through the incorporation of LiFSI and LiNO3 as dual salts.The synergistic effect of the dual salts facilitates the formation of a highly robust SEI film with fast Li+transport kinetics.Notably,Li||Cu half cells exhibit an average CE reaching up to 99.56%.In particular,pouch cells equipped with high-loading lithium cobalt oxide(LCO,3 mAh cm^(-2))cathodes,ultrathin Li chips(25μm),and lean electrolytes(5 g Ah-1)demonstrate outstanding cycling performance,retaining 80%capacity after 125 cycles.To address the gas issue in the cathode under high voltage,cathode additives 1,3,6-tricyanohexane is incorporated with FGN-182;the resulting high-voltage LCO||Li(4.4 V)pouch cells can cycle steadily over 93 cycles.This study demonstrates that,even with the use of ether-based electrolytes,it is possible to simultaneously achieve significant improvements in both high Li utilization and electrolyte tolerance to high voltage by exploring appropriate functional additives for both the cathode and anode.

12.6μm-Thick Asymmetric Composite Electrolyte with Superior Interfacial Stability for Solid-State Lithium-Metal Batteries

Solid-state lithium metal batteries(SSLMBs)show great promise in terms of high-energy-density and high-safety performance.However,there is an urgent need to address the compatibility of electrolytes with high-voltage cathodes/Li anodes,and to minimize the electrolyte thickness to achieve highenergy-density of SSLMBs.Herein,we develop an ultrathin(12.6μm)asymmetric composite solid-state electrolyte with ultralight areal density(1.69 mg cm^(−2))for SSLMBs.The electrolyte combining a garnet(LLZO)layer and a metal organic framework(MOF)layer,which are fabricated on both sides of the polyethylene(PE)separator separately by tape casting.The PE separator endows the electrolyte with flexibility and excellent mechanical properties.The LLZO layer on the cathode side ensures high chemical stability at high voltage.The MOF layer on the anode side achieves a stable electric field and uniform Li flux,thus promoting uniform Li^(+)deposition.Thanks to the well-designed structure,the Li symmetric battery exhibits an ultralong cycle life(5000 h),and high-voltage SSLMBs achieve stable cycle performance.The assembled pouch cells provided a gravimetric/volume energy density of 344.0 Wh kg^(−1)/773.1 Wh L^(−1).This simple operation allows for large-scale preparation,and the design concept of ultrathin asymmetric structure also reveals the future development direction of SSLMBs.

Fe-N-C core-shell catalysts with single low-spin Fe(Ⅱ)-N_(4)species for oxygen reduction reaction and high-performance proton exchange membrane fuel cells

Fe-N-doped carbon materials(Fe-N-C)are promising candidates for oxygen reduction reaction(ORR)relative to Pt-based catalysts in proton exchange membrane fuel cells(PEMFCs).However,the intrinsic contributions of Fe-N_(4)moiety with different chemical/spin states(e.g.D1,D2,D3)to ORR are unclear since various states coexist inevitably.In the present work,Fe-N-C core-shell nanocatalyst with single lowspin Fe(Ⅱ)-N_(4)species(D1)is synthesized and identified with ex-situ ultralow temperature Mossbauer spectroscopy(T=1.6 K)that could essentially differentiate various Fe-N_(4)states and invisible Fe-O species.By quantifying with CO-pulse chemisorption,site density and turnover frequency of Fe-N-C catalysts reach 2.4×10^(-9)site g^(-1)and 23 e site~(-1)s^(-1)during the ORR,respectively.Half-wave potential(0.915V_(RHE))of the Fe-N-C catalyst is more positive(approximately 54 mV)than that of Pt/C.Moreover,we observe that the performance of PEMFCs on Fe-N-C almost achieves the 2025 target of the US Department of Energy by demonstrating a current density of 1.037 A cm^(-2)combined with the peak power density of 0,685 W cm^(-2),suggesting the critical role of Fe(Ⅱ)-N_(4)site(D1).After 500 h of running,PEMFCs still deliver a power density of 1.26 W cm^(-2)at 1.0 bar H_(2)-O_(2),An unexpected rate-determining step is figured out by isotopic labelling experiment and theoretical calculation.This work not only offers valuable insights regarding the intrinsic contribution of Fe-N_(4)with a single spin state to alkaline/acidic ORR,but also provides great opportunities for developing high-performance stable PEMFCs.

Manufacture, characterization and application of porous metal-fiber sintered felt used as mass-transfer-controlling medium for direct methanol fuel cells

Fabrication, characterization and performance of a porous metal-fiber sintered felt （PMFSF） based on multi-tooth cutting and solid-phase sintering were studied. The PMFSF was used as the anodic methanol barrier in a passive air-breathing direct methanol fuel cell to mitigate the effects of methanol crossover. Compared with the commercial SUS316L felt made of bundle-drawn fibers, this self-made PMFSF has larger pore diameter, polarized pore distribution, irregular fiber shape, rougher surface, lower mass flow resistance and evident hydrophobicity. The results reveal that the use of a PMFSF significantly enhances the cell performance since it helps to maintain a balance between the reactant and product management while depressing methanol crossover. The PMFSF with a porosity of 70% yields the highest cell performance at a methanol concentration of 4 mol/L.

Heterojunction Incorporating Perovskite and Microporous Metal–Organic Framework Nanocrystals for Efficient and Stable Solar Cells

In this paper,we present a facile approach to enhance the efficiency and stability of perovskite solar cells(PSCs)by incorporating perovskite with microporous indium-based metal–organic framework[In12O(OH)16(H2O)5(btc)6]n(In-BTC)nanocrystals and forming heterojunction light-harvesting layer.The interconnected micropores and terminal oxygen sites of In-BTC allow the preferential crystallization of perovskite inside the regular cavities,endowing the derived films with improved morphology/crystallinity and reduced grain boundaries/defects.Consequently,the In-BTC-modified PSC yields enhanced fill factor of 0.79 and power conversion efficiency(PCE)of 20.87%,surpassing the pristine device(0.76 and 19.52%,respectively).More importantly,over 80%of the original PCE is retained after 12 days of exposure to ambient environment(25°C and relative humidity of^65%)without encapsulation,while only about 35%is left to the pristine device.

Improving the stability of metal halide perovskite solar cells from material to structure

Metal halide perovskites(MHPs) are promising photovoltaic(PV) materials owing to their advantages such as high carrier mobility, excellent absorption coefficient, bandgap tenability, long diffusion length,and low material cost. These qualities have increased the efficiency of MHP solar cells to 23.3%. However,MHPs are hindered by a lack of stability. In addition, the applications of MHP solar cells are restricted by the instability of perovskite materials and devices. In this article, the most urgent stability problems faced by perovskite solar cells are identified, and recent progresses in MHPs are enumerated. The factors affecting the stability of perovskite materials and devices are also discussed. We analyzed the thermal and humid stability of perovskite materials in terms of transporting materials and their interface. In view of these recent advances, future works should focus on the large-scale application of MHP solar cells.

Effects of environmental factors on corrosion behaviors of metal-fiber porous components in a simulated direct methanol fuel cell environment

Abstract： To enable the use of metallic components in direct methanol fuel cells （DMFCs）, issues related to corrosion resistance must be considered because of an acid environment induced by the solid electrolyte. In this study, we report the electrochemical behaviors of metal-fiber-based porous sintered components in a simulated corrosive environment of DMFCs. Three materials were evaluated： pure copper, AISI304, and AISI316L. The environmental factors and related mechanisms affecting the corrosion behaviors were analyzed. The results demonstrated that AISI316L exhibits the best performance. A higher SO4^2- concentration increases the risk of material corrosion, whereas an increase in methanol concentration inhibits corrosion. The morphological features of the corroded samples were also characterized in this study.

Plating current density distribution of lithium metal anodes in pouch cells

The uniformity of current density distribution upon electrodes is one of the most important factors determining the lithium dendrites growth and cycling performance of lithium metal batteries(LMBs). Herein,current density distributions of lithium metal anodes induced by various engineering factors, consisting of uneven cathode, electrolyte distribution, and different tab positions, and their effects on the electrochemical performance are investigated theoretically and experimentally in pouch cells. The deviation of current density in lithium metal anodes ranges from 2.47% to 196.18% due to the different levels of uneven cathode materials. However, the deviation is just 13.60% for different electrolyte thicknesses between cathodes and anodes, even a ten-layer separator in some positions. The maximum deviation for variational tab positions is only 0.17%. The nonuniformity in current density distribution results in severe dendrite growth issues and poor electrochemical performance of LMBs. This work not only confirms the direct correlation between the uneven current density distribution and lithium deposition behaviors, but also points out the decisive effects of cathode surface roughness on current distribution of anodes, to which more attentions should be paid in practical applications of LMBs.

Review： Perspectives on the metallic interconnects for solid oxide fuel cells

The various stages and progress in the development of interconnect materials for solid oxide fuel cells (SOFCs )over the last two decades are reviewed. The criteria for the application of materials as interconnects are highlighted. Interconnects based on lanthanum chromite ceramics demonstrate many inherent drawbacks and therefore are only useful for SOFCs operating around 1000℃. The advance in the research of anode-supported flat SOFCs facilitates the replacement of ceramic interconnects with metallic ones due to their significantly lowered working temperature. Besides, interconnects made of metals or alloys offer many advantages as compared to their ceramic counterpart. The oxidation response and thermal expansion behaviors of various prospective metallic interconnects are examined and evaluated. The minimization of contact resistance to achieve desired and reliable stack performance during their projected lifetime still remains a highly challenging issue with metallic interconnects. Inexpensive coating materials and techniques may play a key role in promoting the commercialization of SOFC stack whose interconnects are constructed of some current commercially available alloys. Alternatively, development of new metallic materials that are capable of forming stable oxide scales with sluggish growth rate and sufficient electrical conductivity is called for.

High efficiency and stable solid-state fiber dye-sensitized solar cells obtained using TiO_(2) photoanodes enhanced with metal organic frameworks

Solid-state fiber dye-sensitized solar cells(SS-FDSSCs) have been the subject of intensive attention and development in recent years. Although this field is only in its infancy, metal–organic frameworks(MOFs) are one such material that has been utilized to further improve the power conversion efficiency of solar cells. In this study, MOF-integrated DSSCs were shown to have potential in the development of solar cell devices with efficiency comparable to or better than that of conventional solar cells. The power conversion efficiency(PCE) of SS-FDSSCs was improved by embedding MOF-801 into a mesoporous-TiO_(2)(mp-TiO_(2)) layer, which was used as a photoanode in SS-FDSSCs, which are inherently flexible. The PCE of the MOF-integrated SS-FDSSCs was 6.50%, which is comparable to that of the reference devices(4.19%).The MOF-801 enhanced SS-FDSSCs decreased the series resistance(R_(s)) value, resulting in effective electron extraction with improved short-circuit current density(J_(SC)), while also increasing the shunt resistance(R_(sh)) value to prevent the recombination of photo-induced electrons. The result is an improved fill factor and, consequently, a higher value for the PCE.

Review on Metallization Approaches for High-Efficiency Silicon Heterojunction Solar Cells

Crystalline silicon(c-Si)heterojunction(HJT)solar cells are one of the promising technologies for next-generation industrial high-efficiency silicon solar cells,and many efforts in transferring this technology to high-volume manufacturing in the photovoltaic(PV)industry are currently ongoing.Metallization is of vital importance to the PV performance and long-term reliability of HJT solar cells.In this review,we summarize the development status of metallization approaches for highefficiency HJT solar cells.For conventional screen printing technology,to avoid the degradation of the passivation properties of the amorphous silicon layer,a low-temperature-cured(<250℃)paste and process are needed.This process,in turn,leads to high line/contact resistances and high paste costs.To improve the conductivity of electrodes and reduce the metallization cost,multi-busbar,fine-line printing,and low-temperature-cured silver-coated copper pastes have been developed.In addition,several potential metallization technologies for HJT solar cells,such as the Smart Wire Contacting Technology,pattern transfer printing,inkjet/FlexTrailprinting,and copper electroplating,are discussed in detail.B ased on the summary,the potential and challenges of these metallization technologies for HJT solar cells are analyzed.

Toxicity assessment of heavy metals and organic compounds using CellSense biosensor with E.coli

A new strategy using an arnperometric biosensor with Escherichia coli （E. coli） that provides a rapid toxicity determination of chemical compounds is described. The CellSense biosensor system comprises a biological component immobilized in intimate contact with a transducer which converts the biochemical signal into a quantifiable electrical signal. Toxicity assessment of heavy metals using E.coli biosensors could be finished within 30 min and the 50% effective concentrations （ECso） values of four heavy metals were determined. The results shows that inhibitory effects of four heavy metals to E.coli can be ranked in a decreasing order of Hg^2＋ 〉 Cu^2＋ 〉 Zn^2＋ 〉 Ni^2＋, which accords to the results of conventional bacterial counting method. The toxicity test of organic compounds by using CellSense biosensor was also demonstrated. The CellSense biosensor with E. coli shows a good, reproducible behavior and can be used for reproducible measurements.

Review on transition metal compounds based counter electrode for dye-sensitized solar cells

Commercial application of the dye-sensitized solar cells（DSCs） depends on great improvement of the power conversion efficiency and reduction of the fabrication cost. Generally, developing low cost counter electrode catalysts to replace the expensive Pt counter electrode is a feasible path to reduce the production cost of DSCs. In this review article, we summarize the recent progress on the transition metal compound based counter electrode catalysts containing carbides, nitrides, oxides, sulfides, phosphide, selenides, borides, silicide, and telluride toward the regeneration of the traditional iodide redox couple.Moreover, the benefits and drawbacks of each kind of CE catalyst are discussed and the research directions to design new counter electrode catalysts in future research are also proposed.

The effect of transition metal ions (M^(2+)=Mn^(2+),Ni^(2+),Co^(2+),Cu^(2+)) on the chemical synthesis polyaniline as counter electrodes in dye-sensitized solar cells

The effect of transition metal ions(M^(2+)=Mn^(2+),Ni^(2+),Co^(2+),Cu^(2+)) on the chemical synthesis of polyaniline(PANI) used as a platinum-free counter electrode(CE) in dye-sensitized solar cells(DSSCs) was investigated.PANI was synthesized by co-polymerization of aniline in the presence of different transition metal ions by using potassium dichromate in acidic medium. It was found that the ion doping of PANI showed a certain catalytic activity for the regeneration of traditional iodide/triiodide(I^-/I_3^-) redox couples. The power conversion efficiency(η) of PANI CEs doped with Mn^(2+),Ni^(2+),Co^(2+) (4.41%, 2.36% and 2.10%, respectively) were higher than 1.94%, the value measured for PANI CE without doping. Doping with Cu^(2+)decreased the power conversion efficiency of PANI CE(PANI-Cu^(2+) η = 1.41%). The electrical properties of the PANI, PANI-Ni^(2+), PANI-Co^(2+),PANI-Mn^(2+) and PANI-Cu^(2+) were studied by cyclic voltammetry(CV), impedance(EIS), and Tafel polarization curve. The experimental results confirmed that PANI was affected by the doping of different transition metal ions(M^(2+)=Mn^(2+),Ni^(2+),Co^(2+),Cu^(2+)). These results indicate a potential application of ion doped PANI as counter electrode in cost-effective DSSCs.