硼氢化钠制氢技术在质子交换膜燃料电池中的研究进展

硼氢化钠储氢量高达10.6%,安全、无爆炸危险,携带和运输方便;供氢系统设备简单,启动速度快,产氢速度可调,因此是一个非常良好的氢载体,是为质子交换膜燃料电池供氢的理想储氢介质。硼氢化钠供氢系统也已逐步应用于质子交换膜燃料电池电源中。介绍了这种制氢方式的几项关键技术：硼氢化钠水解制氢催化剂、硼氢化钠制氢反应器、氢气净化系统等在质子交换膜燃料电池中的研究进展,并指出了今后的研究发展方向。     

Co-B合金在NaBH4现场催化制氢中的应用研究

采用溶液法制备了Co-B前驱物,并经过不同温度的处理得到了一系列的Co-B合金.对Co-B合金的结构表征发现,随着热处理温度的增加,Co-B前驱物经历了一个由非晶态向晶态的转变过程,同时比表面呈逐渐下降的趋势.X射线衍射结果表明,CoxB合金在400℃下生成了CoB、Co、α-Co的混合相,并在温度升高到600℃以上完全转化为立方晶系的金属Co.在500℃下处理的Co-B合金,其主相为高活性的CoB,因而具有最佳的催化活性,在催化NaBH4的水解反应时每克催化剂可得到近3.0L/min的制氢速率.     

固定式质子交换膜燃料电池的天然气重整制氢

介绍了固定式质子交换膜燃料电池用氢气的各种天然气重整方法,其中包括水蒸气重整法、自热重整法和化学闭合燃烧法。同时简述了氢气进一步纯化的水煤气变换反应、选择氧化、变压吸附和气体膜分离脱一氧化碳的方法。通过上述重整和提纯的处理,最终能制备出满足固定式质子交换膜燃料电池要求的氢气。     

仿蜂巢微通道分叉结构的甲醇重整制氢

针对甲醇蒸汽的微通道重整催化反应过程,建立了三维稳态多组分传输反应模型;利用数值模拟分析,分别研究了平行阵列微通道和仿蜂巢分叉微通道在Zn_Cr/CeO₂/ZrO₂催化剂下的反应情况。通过双速率模型考察这两种流道中操作条件对甲醇蒸汽重整制氢输运规律的影响,发现这两种微通道反应器均可促进甲醇转化率和氢气产率的提高。与常规平行微通道的比较发现,仿蜂巢分叉微通道内反应气流动所需的泵功较小;在相同的加热面积下所能吸收的热量更大,而且更有利于反应器内温度的均匀分布,从而提高甲醇的转化率、减小出口CO的含量。研究结果表明,仿蜂巢分叉微通道结构具有较好的重整制氢综合性能,并可改善氢气产出的品质。     

质子交换膜电解水制氢技术的发展现状及展望

氢能是支撑起智能电网和可再生能源发电规模化的最佳能源载体,而电解水制氢是实现制氢规模化的重要途径。在多种电解水制氢技术中,质子交换膜电解水技术由于具备电流密度大、产氢纯度高、响应速度快等优势,吸引了科学界和工业界的广泛重视。本文首先介绍了质子交换膜电解池的结构组成以及各组成的主要作用,对比分析了碱性电解池、固体氧化物电解池与质子交换膜电解池的技术差异,并结合电解水析氢反应以及析氧反应的机理阐释,分别介绍了两步半反应的常用催化剂;然后,从最初的实验室研究阶段到目前兆瓦级别的质子交换膜电解水系统,回顾了该技术的发展历程以及应用现状;其次,从制氢成本、电堆性能及电堆寿命等多角度分析目前该技术面临的瓶颈问题;最后,根据质子交换膜电解池的技术优势,并针对上游间歇性可再生能源的需求以及和下游产业的联合应用,对其未来前景进行了展望。     

质子交换膜水电解制氢技术现状与展望

介绍了氢气来源以及不同水电解制氢技术发展现状,聚焦质子交换膜水电解面临的膜材料、催化剂等技术瓶颈及发展态势,梳理分析了国内外质子交换膜水电解制氢技术应用新方向.     

质子交换膜燃料电池技术的发展动向

目前 ,燃料电池技术已经从实验室研究逐渐走向规模化、实用化的开发 ,其研发模式也由单纯的科研机构研究转向政府、企业和科研机构三者的结合。本文评述了燃料电池尤其是质子交换膜燃料电池的应用和研发状况。简介了国际国内燃料电池领域内政府的支持和推动 ,以及企业的开发情况。并提出了燃料电池在普及中所面临的关键问题     

硼氢化钠水解制氢用铂基催化剂的研究

选用2种高比表面的碳载体,采用浸渍法制备了担载量为20%的铂基催化剂.经表征20%Pt/乙炔黑的孔径主要分布在2.5～5nm之间,孔径小并且分布集中;而20%Pt/珍珠碳的孔径除少量分布在2.5～5 nm之间外,大部分孔径分布在20～60nm,分布范围较宽.在20min内,20% Pt/珍珠碳和20%Pt/乙炔黑的平均制氢速率分别为1.9 L/min和2.3 L/min,当氢的利用率为100%时,可分别为功率为308W和373 W的质子交换膜燃烧电池持续供氢.     

质子交换膜燃料电池技术的发展及应用

概述了质子交换膜燃料电池(PEMFC)的发展历史和现状,并对其应用前景进行了展望;对质子交换膜燃料电池的膜、膜电极、电催化剂和双极板等关键技术进行了简要介绍。     

甲醇氧化重整制氢工艺条件的研究

在Cr-Zn氧化物催化剂上考察了各种工艺条件对甲醇氧化重整(POX)制氢过程的影响.正交实验表明:对甲醇的转化率、氢气的选择率、氢产率和产物中CO、CO2的浓度影响显著程度为反应温度>氧醇比>水醇比.该催化剂无需预还原可直接使用,反应压力选择在0.3～0.5 MPa,合适的反应温度为650～700 K,氧醇比0.15～0.20,水醇比约1.0.     

PBI‐Based Polymer Membranes for High Temperature Fuel Cells – Preparation,Characterization and Fuel Cell Demonstration

Proton exchange membrane fuel cell (PEMFC) technology based on perfluorosulfonic acid (PFSA) polymer membranes is briefly reviewed. The newest development in alternative polymer electrolytes for operation above 100 °C is summarized and discussed. As one of the successful approaches to high operational temperatures, the development and evaluation of acid doped polybenzimidazole (PBI) membranes are reviewed, covering polymer synthesis, membrane casting, acid doping, physicochemical characterization and fuel cell testing. A high temperature PEMFC system, operational at up to 200 °C based on phosphoric acid‐doped PBI membranes, is demonstrated. It requires little or no gas humidification and has a CO tolerance of up to several percent. The direct use of reformed hydrogen from a simple methanol reformer, without the need for any further CO removal, has been demonstrated. A lifetime of continuous operation, for over 5000 h at 150 °C, and shutdown‐restart thermal cycle testing for 47 cycles has been achieved. Other issues such as cooling, heat recovery, possible integration with fuel processing units, associated problems and further development are discussed.     

Method for Increasing the Humidity in Polymer Electrolyte Membrane Fuel Cell

The water content within the polymer electrolyte membrane is essential to have good proton conduction and high efficiency of a fuel cell system. In this paper a new technique to increase the fuel cell efficiency acting on the internal humidity will be presented. In order to understand the potentialities and the limitations of such technique, the method was studied in a theoretical approach and then applied on a proton exchange membrane fuel cell (1 kW PEMFC) that supplies the energy for the traction of a prototype vehicle, which took part in the last Shell Eco‐marathon competition. Finally has been verified that the membrane water content is related to the hydrogen consumption and for some applications (e.g., military single‐use equipment), the “filling” method could be advantageous over humidified system and non‐humidified systems. To ensure the proper success of the procedure it is also applied the differential method to fault detection.     

How good are the Electrodes we use in PEFC?

Basically, companies and laboratories implement production methods for their electrodes on the basis of experience, technical capabilities and commercial preferences. But how does one know whether they have ended up with the best possible electrode for the components used? What should be the (i) optimal thickness of the catalyst layer? (ii) relative amounts of electronically conducting component (catalyst, with support – if used), electrolyte and pores? (iii) “particle size distributions” in these mesophases? We may be pleased with our MEAs, but could we make them better? The details of excellently working MEA structures are typically not a subject of open discussion, also hardly anyone in the fuel cell business would like to admit that their electrodes could have been made much better. Therefore, we only rarely find (far from systematic) experimental reports on this most important issue. The message of this paper is to illustrate how strongly the MEA morphology could affect the performance and to pave the way for the development of the theory. Full analysis should address the performance at different current densities, which is possible and is partially shown in this paper, but vital trends can be demonstrated on the linear polarization resistance, the signature of electrode performance. The latter is expressed through the minimum number of key parameters characterizing the processes taking place in the MEA. Model expressions of the percolation theory can then be used to approximate the dependence on these parameters. The effects revealed are dramatic. Of course, the corresponding curves will not be reproduced literally in experiments, since these illustrations use crude expressions inspired by the theory of percolation on a regular lattice, whereas the actual mesoscopic architecture of MEA is much more complicated. However, they give us a flavour of reserves that might be released by smart MEA design.     

A Quaternary Polybenzimidazole Membrane for Intermediate Temperature Polymer Electrolyte Membrane Fuel Cells

A quaternary ammonium polybenzimidazole (QPBI) membrane was synthesized for applications in intermediate temperature (100–200 °C) hydrogen fuel cells. The QPBI membrane was imbibed with phosphoric acid to provide suitable proton conductivity. The proton conductivity of the membrane was 0.051 S cm^–1 at 150 °C with the PA acid loading level of 3.5 PRU (amount of H₃PO₄ per repeat unit of polymer QPBI). The QPBI membrane was characterized in terms of composition, structure and morphology by NMR, FTIR, SEM, and EDX. The fuel cell performance with the membrane gave peak power densities of 440 and 240 mW cm^–2 using oxygen and air, respectively, at 175 °C.     

Preparation of KOH‐doped PVA/PSSA Solid Polymer Electrolyte for DMFC: The Influence of TiO2 and PVP on Performance of Membranes

The development of low cost alkaline anion solid exchange membranes requires high ionic conductivity, low liquid uptake, strong mechanical properties and chemical stability. PVA/PSSA blends cross‐linked with glutaraldehyde and decorated with titanium dioxide nanoparticles introduce advantages relative to the pristine membrane of PVA and PVA/PVP membranes due to their improved electrical response and low methanol uptake/ swelling ratio allowing their use in alkaline direct methanol fuel cells.     

Design and Implementation of Fuel Cell and Photovoltaic Panel-Supported Ozonation System

It is normal for a produced agricultural product or food to be transported to distances far from where it is produced. However, it is important to keep the product fresh in this transportation. There are many methods used to extend the life of the food during transport. The chemical method is the most used. However, the chemical method is harmful to human health. One of the methods used for storing, preserving and transporting agricultural products is ozonation and air conditioning. In this study, a system was designed to extend the life of the product in the storage and transport of food products. With the developed system, temperature, relative humidity and ozone were produced and their amounts were controlled according to the type of product being carried. In the design, polymer exchange membrane fuel cell was used for the required oxygen. The energy requirement of the system was provided by a photovoltaic panel to get rid of the generator dependency on supplied electrical power. The applicability of the system to refrigerated vehicles, especially those used in food transportation, was examined.     

Use of Segmented Cell Operated in Hydrogen Recirculation Mode to Detect Water Accumulation in PEMFC

Adequate water management is crucial to increase stability and durability of Polymer Electrolyte Membrane Fuel Cells. In this paper, a test rig suitable for water balance and nitrogen crossover studies was built around a hydrogen‐air segmented cell and used to indirectly assess flooding or drying conditions in specific zones of the active cell area. In particular, the anode of the segmented cell was operated in recirculation mode with continuous water removal. Current density distribution (CDD) diagrams were obtained for different anode operating parameters, namely, the recirculated gas flow rate, anode pressure, and time between purges. Water accumulation at the electrodes was assessed from CDD diagrams and confirmed using water balance and flow‐patterns calculations. It was concluded that lower recirculation flow rates led to flooding due to decreased water removal capabilities at the anode. For higher recirculation flow rates, drying was observed in one zone of the cell but homogeneous CDD in the other. Finally, the use of partially segment bipolar plates was proposed to increase the in‐plane electrical resistance between adjacent segments. The partial segmentation increased the segment to segment in‐plane electrical resistance between 14 and 21% and decreased the through‐plane to in‐plane resistance ratio by 17%.     

Consumption and Efficiency of a Passenger Car with a Hydrogen/Oxygen PEFC based Hybrid Electric Drivetrain

The main factors for reducing the consumption of a vehicle are reduction of curb weight, air drag and increase in the drivetrain efficiency. Highly efficient drivetrains can be developed based on PEFC technology and curb weight may be limited by an innovative vehicle construction. In this paper, data on consumption and efficiency of a four‐place passenger vehicle with a curb weight of 850 kg and an H₂/O₂ fed PEFC/Supercap hybrid electric powertrain are presented. Hydrogen consumption in the New European Driving Cycle is 0.67 kg H₂/100 km, which corresponds to a gasoline equivalent consumption of 2.5 l/100 km. When including the energy needed to supply pure oxygen, the calculated consumption increases from 0.67 to 0.69–0.79 kg H₂/100 km, depending on the method of oxygen production.     

Glycerol Reforming for Hydrogen Production: A Review

Glycerol, which is obtained as a by‐product in biodiesel production, represents a candidate source of hydrogen that is renewable. Its conversion into hydrogen can be achieved by a reforming process. In this article, the glycerol reforming reaction is reviewed. Different reforming processes for hydrogen production, viz. steam, aqueous, and autothermal reforming, are described in brief. The thermodynamic analyses, which enable comparison with experimental studies, are considered. A discussion on experimental investigations over several catalysts is presented, too. Many reaction pathways are possible and some of them are dependent on the properties of the catalyst used. Generally, Ni, Pt, and Ru catalysts facilitate hydrogen production. The same catalysts are also effective for the reforming reaction of ethanol – another renewable resource for hydrogen. While ethanol steam reforming has been comprehensively reviewed by now, an overview on glycerol reforming is still missing. In this paper, an evaluation of the published studies is given to close this gap.     

Synthesis and Characterization of a New Fluorine‐Containing Polybenzimidazole (PBI) for Proton‐Conducting Membranes in Fuel Cells

A new type of fluorine‐containing polybenzimidazole, namely poly(2,2′‐(2,2′‐bis(trifluoromethyl)‐4,4′‐biphenylene)‐5,5′‐bibenzimidazole) (BTBP‐PBI), was developed as a candidate for proton‐conducting membranes in fuel cells. Polymerization conditions were experimentally investigated to achieve high molecular weight polymers with an inherent viscosity (IV) up to 1.60 dl g^–1. The introduction of the highly twisted 2,2′‐disubstituted biphenyl moiety into the polymer backbone suppressed the polymer chain packing efficiency and improved polymer solubility in certain polar organic solvents. The polymer also exhibited excellent thermal and oxidative stability. Phosphoric acid (PA)‐doped BTBP‐PBI membranes were prepared by the conventional acid imbibing procedure and their corresponding properties such as mechanical properties and proton conductivity were carefully studied. The maximum membrane proton conductivity was approximately 0.02 S cm^–1 at 180 °C with a PA doping level of 7.08 PA/RU. The fuel cell performance of BTBP‐PBI membranes was also evaluated in membrane electrode assemblies (MEA) in single cells at elevated temperatures. The testing results showed reliable performance at 180 °C and confirmed the material as a candidate for high‐temperature polymer electrolyte membrane fuel cell (PEMFC) applications.