闭口氢-氧PEM燃料电池非稳态运行研究

建立了闭口氢-氧质子交换膜燃料电池的三维非稳态数学模型,研究了不同操作压力条件下,电池的运行特性及内部各参数的变化情况。结果表明:闭口电池的性能随着运行时间的增加逐渐下降,且阴极侧氧气不足是导致电池衰减的主要原因;在较高的操作压力下,电池可以维持工作更长的时间。

稀土金属助催的甲醇水蒸汽重整制氢催化剂的研究

制备稀土金属离子助催的铜锌基甲醇水蒸汽重整催化剂并分别比较了铜锌和两种以稀土Ce3+,Zr4+为助催剂的铜锌催化剂上甲醇水蒸汽重整制氢的催化性能:在220℃反应条件下,Cu ZnO,Cu ZnO Ce2O3和Cu ZnO ZrO2的甲醇转化率分别为28.1%、37.3%和51.6%,后两个催化剂的氢选择性高达100%,CO的选择性为0.Cu ZnO ZrO2催化剂经60h的运转后,催化剂的性能不变,触氧实验表明该催化剂能满足甲醇燃料电池电动车启动温度低、CO2选择性高的要求.

Theoretical On-Board Hydrogen Redox Electric Power Generator for Infinite Cruising Range Fuel Cell Vehicles

The development of hydrogen redox electric power generators for infinite cruising range electric vehicles represents a true technological breakthrough. Such systems consist of a polymer electrolyte membrane hydrogen electrolytic cell equipped with an electrostatic-induction potential-superposed water electrolytic cell that provides a stoichiometric H2-O2 fuel mixture during operation of the vehicle. This generator functions with zero power input, zero matter input and zero emission due to the so-called ＂zero power input＂ electrostatic-to-chemical energy conversion occurring in the electrolytic cell. Here, theoretical simulations were performed to verify the target performance of such generators, assuming a pair of FC （fuel cell） and electrolytic cell stacks, both of which are commercially available.

石墨炔在电化学储能器件中的应用研究

石墨炔作为一种新型二维碳材料,具有π共轭单元、sp^(2)和sp杂化的碳原子和可调节的孔结构,结构稳定,导电性好,可塑性强。简要介绍了不同类型的石墨炔及其结构,阐述了石墨炔及其衍生物的合成策略,重点综述了石墨炔及石墨炔衍生物在能源领域的研究内容和成果,介绍了石墨炔及其衍生物在锂离子电池、氢-氧燃料电池、钠离子电池、超级电容器和其它一些电化学储能器件及材料上的研究成果。综合分析表明,石墨炔在电化学储能器件方面具有广阔的应用前景。

Catalytic activity of V_(2)CO_(2) MXene supported transition metal single atoms for oxygen reduction and hydrogen oxidation reactions:A density functional theory calculation study

Two-dimensional(2D)MXene and single-atom(SA)catalysts are two frontier research fields in catalysis.2D materials with unique geometric and electronic structures can modulate the catalytic performance of supported SAs,which,in turn,affect the intrinsic activity of 2D materials.Density functional theory calculations were used to systematically explore the potential of O-terminated V2C MXene(V_(2)CO_(2))-supported transition metal(TM)SAs,including a series of 3d,4d,and 5d metals,as oxygen reduction reaction(ORR)and hydrogen oxidation reaction(HOR)catalysts.The combination of TM SAs and V_(2)CO_(2)changes their electronic structure and enriches the active sites,and consequently regulates the intermediate adsorption energy and catalytic activity for ORR and HOR.Among the investigated TM-V_(2)CO_(2)models,Sc-,Mn-,Rh-,and PtMCCh showed high ORR activity,while Sc-,Ti-,V-,Cr-,and Mn-V_(2)CO_(2)exhibited high HOR activity.Specifically,Mn-and Sc-V_(2)CO_(2)are expected to serve as highly efficient and cost-effective bifunctional catalysts for fuel cells because of their high catalytic activity and stability.This work provides theoretical guidance for the rational design of efficient ORR and HOR bifunctional catalysts.

Electrocatalysts development for hydrogen oxidation reaction in alkaline media:From mechanism understanding to materials design

Anion exchange membrane(AEM)fuel cells have gained great attention partially due to the advantage of using non-precious metal as catalysts.However,the reaction kinetics of hydrogen oxidation reaction(HOR)is two orders of magnitude slower in alkaline systems than in acid.To understand the slower kinetics of HOR in base,two major theories have been proposed,such as(1)pH dependent hydrogen binding energy as a major descriptor for HOR;and(2)bifunctional theory based on the contributions of both hydrogen and hydroxide adsorption for HOR in alkaline electrolyte.Here,we discuss the possible HOR mechanisms in alkaline electrolytes with the corresponding change in their Tafel behavior.Apart from the traditional Tafel-Volmer and Heyrovsky-Volmer HOR mechanisms,the recently proposed hydroxide adsorption step is also discussed to illustrate the difference in HOR mechanisms in acid and base.We further summarize the representative works of alkaline HOR catalyst design(e.g.,precious metals,alloy,intermetallic materials,Ni-based alloys,carbides,nitrides,etc.),and briefly describe their fundamental HOR reaction mechanism to emphasize the difference in elementary reaction steps in alkaline medium.The strategy of strengthening local interaction that facilitates both H2 desorption and Hads+OHads recombination is finally proposed for future HOR catalyst design in alkaline environment.

Modelling the Hydrogen Inhibition Effect on Ammonia Decomposition

Recently ammonia has been investigated as a fuel for SOFCs （solid oxide fuel cells）. Ammonia is widely produced and transported globally, and stores hydrogen in its bonds making it an excellent fuel for fuel cells. The high temperature of SOFCs allows for internal decomposition of ammonia. Previous models of ammonia-fed SOFCs treat ammonia decomposition as having first order dependence on ammonia partial pressure, and ignore the effect of hydrogen inhibition. However, research has shown that at low temperatures （≤ 600 ℃） and low ammonia partial pressures, the rate of ammonia decomposition is inhibited by the presence of hydrogen. This hydrogen inhibition effect was studied and implemented in a model of an ammonia decomposition reactor. Results showed that it may significantly decrease the rate of hydrogen generation. This work sets the foundation for more accurate modelling of intermediate temperature ammonia-fed SOFCs.

Highly efficient overall urea electrolysis via single-atomically active centers on layered double hydroxide

Anodic urea oxidation reaction(UOR)is an intriguing half reaction that can replace oxygen evolution reaction(OER)and work together with hydrogen evolution reaction(HER)toward simultaneous hydrogen fuel generation and urea-rich wastewater purification;however,it remains a challenge to achieve overall urea electrolysis with high efficiency.Herein,we report a multifunctional electrocatalyst termed as Rh/Ni V-LDH,through integration of nickel-vanadium layered double hydroxide(LDH)with rhodium single-atom catalyst(SAC),to achieve this goal.The electrocatalyst delivers high HER mass activity of0.262 A mg^(-1) and exceptionally high turnover frequency(TOF)of 2.125 s^(-1) at an overpotential of100 m V.Moreover,exceptional activity toward urea oxidation is addressed,which requires a potential of 1.33 V to yield 10 mA cm^(-2),endorsing the potential to surmount the sluggish OER.The splendid catalytic activity is enabled by the synergy of the Ni V-LDH support and the atomically dispersed Rh sites(located on the Ni-V hollow sites)as evidenced both experimentally and theoretically.The selfsupported Rh/Ni V-LDH catalyst serving as the anode and cathode for overall urea electrolysis(1 mol L^(-1) KOH with 0.33 mol L^(-1) urea as electrolyte)only requires a small voltage of 1.47 V to deliver 100 mA cm^(-2) with excellent stability.This work provides important insights into multifunctional SAC design from the perspective of support sites toward overall electrolysis applications.

Self-healing and highly elastic fluorine-free proton exchange membranes comprised of poly(vinyl alcohol) derivative and phytic acid for durable fuel cells

Fluorine-free proton exchange membranes(PEMs)capable of healing from physical damage are important for PEM fuel cells(PEMFCs)with extended service life and enhanced reliability.Herein,highly elastic fluorine-free PEMs with excellent self-healing ability and high proton conductivity are fabricated through complexation of phytic acid(PA)with sulfonated polyvinyl alcohol(SPVA),followed by subsequent grafting of SPVA with positively charged 4-(1H-imidazol-1-yl)benzenecarbaldehyde(IBZ).Compared with recast Nafion membranes,the as-prepared SPVA-IBZ/PA membranes exhibit an enhanced mechanical strength and elasticity and can spontaneously recover from a^50%strain to their initial states within^30 s at room temperature.Meanwhile,the SPVA-IBZ/PA membranes have a proton conductivity of^0.095 S cm-1at^70°C,which is higher than that of recast Nafion membranes.The hydrogen-powered PEMFCs using the SPVA-IBZ/PA membranes,which show an open circuit voltage of^0.98 V and maximum power density of^609 mW cm-2,exhibit a satisfactory cell performance.Importantly,the SPVA-IBZ/PA membranes can spontaneously heal mechanical damage of several tens of micrometers in size and restore their original proton conductivity and cell performance under the working conditions of PEMFCs.

LDHs derived nanoparticle-stacked metal nitride as interlayer for long-life lithium sulfur batteries

Shuttle effect is one of the most serious disadvantages in lithium-sulfur battery which results in poor cycle performance and hinders the commercialization of Li-S battery.To reduce the dissolution of polysulfides into the electrolyte and prolong the cycling stability,nanoparticle-stacked metal nitride derived from layered double hydroxides(LDHs)as an interlayer was inserted between sulfur cathode and separator to confine polysulfides by physical and chemical interactions.Meanwhile,the surface of metal nitride will form an oxide passivation layer.The passivation layer possesses hydrophilic metal-O group and provides a polar surface for strong binding with polysulfide.What’s more,the nanoparticlesstacked structure could immerge and retain electrolyte well,which could enhance the ability of promoting the electron exchange rate.The sulfur electrode with nanoparticle-stacked metal nitride interlayer has an excellent cycle performance owing to the interactions between metal nitride and polysulfides.The battery delivered an initial capacity of 764.6 m Ahg^(-1) and still possesses a capacity of 477.5 mAhg^(-1) with the retention of 62.4% after 800 cycles.

One-dimensional manganese borate hydroxide nanorods and the corresponding manganese oxyborate nanorods as promising anodes for lithium ion batteries

Novel manganese and boron containing nanomaterials have been investigated for applications in rechargeable lithium ion batteries （L1Bs） in recent years owing since they are more environmentally-benign and more abundant in nature than the materials currently employed. In this study, one-dimensional （1D） Mn3B7O13OH nanorods and MnBO2OH nanorod bundles were controllably fabricated by using NH4HB4O7 and Mn（NO3）2 as reagents via a hydrothermal or solvothermal process, respectively, without any surfactants or templates at 220 ℃. It is interesting to find that both materials are transformed into Mn2OBO3 nanorods/nanorod bundles by subsequent calcination. The formation processes of the above 1D borate containing products were investigated and the as-obtained four kinds of borates were studied as novel anode materials. It was found that the Mn2OBO3 nanorods displayed the best performance among the four borates, delivering an initial discharge capacitiy of 1,172 mAh·g^-1 at 100 mA·g^-1, and 724 mAh.g could be retained after 120 cycles. A full battery composed of a Mn2OBO3 nanorod anode and a commercial LiFePO4 （or LiCoO2） cathode has also been assembled for the first time, which delivered an initial discharge capacity of 949 mAh·g^-1 （779 mAh·g^-1 for LiCoO2）. The excellent cycle and rate performances of the products reveal their potential applications as anodes for LIBs.

ZnO hierarchical aggregates： Solvothermal synthesis and application in dye-sensitized solar cells

ZnO hierarchical aggregates have been successfully synthesized by solvothermal methods through reaction of zinc acetate and potassium hydroxide in methanol solution. The shapes of the aggregates were controlled by varying the ratio of Zn2~ and OH- ions in the reaction system, while the size can be tuned from 2μm to 100 nm. Oriented attachment was found to be the main mechanism of the three-dimensional assembly of small ZnO nanocrystallites into large aggregates. The performance of these aggregates in dye-sensitized solar cells （DSCs） indicated that hierarchical structured photoelectrodes can increase energy conversion efficiency of DSCs effectively when the sizes of aggregates match the wavelengths of visible light.

Aluminum-based materials for advanced battery systems

There has been increasing interest in devel- oping micro/nanostructured aluminum-based materials for sustainable, dependable and high-efficiency electro- chemical energy storage. This review chiefly discusses the aluminum-based electrode materials mainly including A1203, AIF3, AIPO4, AI（OH）3, as well as the composites （carbons, silicons, metals and transition metal oxides） for lithium-ion batteries, the development of aluminum-ion batteries, and nickel-metal hydride alkaline secondary batteries, which summarizes the methodologies, related charge-storage mechanisms, the relationship between nanos- tructures and electrochemical properties found in recent years, latest research achievements and their potential ap- plications. In addition, we raise the relevant challenges in recently developed electrode materials and put forward new ideas for further development of micro/nanostructured aluminum-based materials in advanced battery systems.

Converting biomass into efficient oxygen reduction reaction catalysts for proton exchange membrane fuel cells

It is urgent to develop low-cost but efficient oxygen reduction reaction(ORR)catalysts for the emerging clean energy devices of fuel cells based on proton exchange membrane.Herein,we report a facile method to covert the biomass of black fungus into an efficient ORR catalyst.The black fungus undergoes hydrothermal and pyrolysis processes to transform into carbon-based materials.The as-obtained BF-N-950 catalyst shows prominent ORR catalytic activities in both acidic and alkaline electrolytes with a half-wave potential reaching 0.77 and 0.91 V,respectively.A membrane electrolyte assembly was fabricated with the as-obtained BF-N-950 as the cathode catalyst which shows a high peak power density of255 mW cm^-2.The study shows the potential of converting conventional biomass into low-cost ORR catalyst,which is promising for the fuel cell technology.

The dual role of hydrogen peroxide in fuel cells

Clean and highly efficient energy production has long been sought after, as a way to solve global energy and environmental problems. Fuel cells, which convert the chemical energy stored in fuel directly into electricity, are expected to be a key enabling technology for the pressing energy issues that plague our planet. Fuel cells require oxygen as an oxidant and require oxygen tank containers when used in air-free environments such as outer space and underwater. Hydrogen peroxide has been extensively uti- lized as an alternative liquid oxidant in place of gaseous oxygen. In addition to being an oxidant, hydrogen peroxide can donate electrons in the oxidation reaction to act as a fuel. This article provides an overview of the dual role of hydrogen peroxide in fuel-cell applications, including working principle, system design, and cell performance. Recent innovations and future perspectives of fuel cells that use hydrogen peroxide are particularly emphasized.