Hydrogen Production by Catalytic Reforming of Gaseous Hydrocarbons (Methane &; LPG)

Hydrogen has been attracting great interest as a major energy source in near future. The lack of an infrastructure has led to a research effort to develop fuel processing technology for production of hydrogen. In this review, we are reporting the catalytic reforming of gaseous hydrocarbons carried out in our research group, covering dry-reforming of CH₄, tri-reforming of CH₄, the electrocatalytic reforming of CH₄ by CO₂ in the SOFC (solid oxide fuel cell) system and steam reforming of LPG. Especially, we have focused on our work, though the related work from other researchers is also discussed wherever necessary. It was found that tri-reforming of CH₄ over NiO–YSZ–CeO₂ catalyst was more desirable than dry-reforming of CH₄ due to higher reforming activity and less carbon formation. The synthesis gas produced by tri-reforming of CH₄ can be used for the production of dimethyl ether, Fischer–Tropsch synthesis fuels and high valued chemicals. To improve the problem of deactivation of catalyst due to carbon formation in the dry reforming of CH_4, the internal reforming of CH₄ by CO₂ in SOFC system with NiO–YSZ–CeO₂ anode catalyst was suggested for cogeneration of a syngas and electricity. It was found that Rh-spc-Ni/MgAl catalyst showed long term stability for 1,100 h in the steam reforming of LPG under the tested conditions. The addition of Rh to spc-Ni/MgAl catalyst restricted the deactivation of catalyst due to carbon formation in the steam reforming of LPG and diesel under the tested conditions. The result suggested that the developed reforming catalysts can be used in the reforming process of CH₄, LNG and LPG for application to hydrogen station and fuel processor system.     

Stability Investigations on a Pt@HGS Catalyst as a Model Material for Fuel Cell Applications: The Role of the Local pH

Increasing the resistance of catalysts against electrochemical degradation is one of the key requirements for the wider use of Proton Exchange Membrane Fuel Cells (PEMFCs). Here, we study the degradation of one entity of a highly stable catalyst, Pt@HGS, on a nanoelectrode under accelerated mass transport conditions. We find that the catalyst degrades more rapidly than expected based on previous ensemble measurements. Corroborated by identical location transmission electron microscopy and catalyst layer experiments, we deduce that locally different pH values are likely the reason for this difference in stability. Ultimately, this work provides insights into the actual conditions present in a PEMFC and raises questions about the applicability of accelerated stress tests usually performed to evaluate catalyst stability, particularly when they are performed in half-cell setups under inert gas.     

PREPARATION AND PROPERTIES OF SPAES-TiO_2 HYBRID MEMBRANES FOR DIRECT METHANOL FUEL CELL

Sulfonated poly(arylene ether sulfone)(SPAES) copolymer with degree of sulfonation of 1.0 was synthesized and characterized.A series of SPAES-TiO_2 hybrid membranes with various contents of nano-sized TiO_2 particles were prepared and characterized through sol-gel reactions.Scanning electron microscopy(SEM) images indicated the TiO_2 particles were well dispersed within polymer matrix.These composite membranes were evaluated for proton exchange membranes(PEMs) in direct methanol fuel cell(DMFC).These mem...     

基于微梯形弹光晶体的大光程差PEM研究

针对目前基于弹光调制器(photoelastic modulator,PEM)的傅里叶变换光谱测量技术(PEM-FTS)的光谱分辨率低,并且PEM调制光程差有限、多次反射对入射光斑大小要求高且光能利用率低等缺点。提出一种基于微梯形八角结构弹光晶体的大光程差PEM方法。通过改进弹光晶体结构,使其为微梯形八角结构,两个通光面略微成一定夹角,该结构PEM不仅可以有效提高PEM调制的最大光程差,而且对入射光斑要求较小。理论推导分析了该PEM的最大调制光程差,并推导得出任意角、任意位置入射时PEM的最大调制光程差公式;通过多物理场耦合仿真软件COMSOL Multiphysics 4.3a对PEM的振动模态和应力分布进行分析;结合PEM的最大调制光程差和光能利用率,分析了寻找最佳入射角的方法。设计加工该PEM,其中弹光晶体选用硒化锌晶体,压电晶体选用压电石英晶体。采用波长为632.8 nm的氦氖激光进行实验分析,实验结果显示,在相同驱动电压下,该PEM的最大调制光程差是普通PEM的19.25倍,与理论仿真的相对误差为1.3%。     

PEM燃料电池内水分布和温度分布的数值模拟

本文建立了一个两相流、非等温、三维模型来研究PEM燃料电池内的传递过程,讨论了其内部水分布和温度分布特性。模拟结果表明水分布和温度分布都不均匀。沿着流动方向阳极侧水浓度逐渐降低,而阴极侧水浓度却不断升高,导致阴极容易形成液态水;在垂直流动方向上,脊下水的浓度和液态水饱和度都高于流道下;不同放电电压下阴极GDL中液态水分布趋势不同。沿流动方向温度逐渐降低,反应气体不足时降低梯度更大;脊下膜电极中温度低于流道下;垂直膜电极方向上最高温度在阴极催化层,放电电压越低,温度梯度越大;相同放电电压下质子交换膜越厚,各处的温度越低,温度梯度也越小。     

Electrocatalytically Active Hollow Carbon Nanospheres Derived from PS‐b‐P4VP Micelles

A facile method using polystyrene‐b‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) micelles is demonstrated to synthesize N/FeN₄‐doped hollow carbon nanospheres (N/FeN₄‐CHNS) with high electrocatalytic activity for oxygen reduction reactions (ORRs). Uniform spherical micelles with PS core and P4VP shell are prepared by exposing PS‐b‐P4VP in a mixture of ethanol/tetrahydrofuran. Pyridinic N in shell cooperates with Fe³⁺ to induce an in situ polymerization of pyrrole. Tuning molecular composition of PS‐b‐P4VP can form hollow carbon spheres with controlled size down to sub‐100 nm that remains challenge using traditional hard template strategies. N/FeN₄‐CHNS possesses a series of desirable properties as electrode materials, including easy fabrication, high reproducibility, large surface area, and highly accessible porous surface. This electrocatalyst exhibits excellent ORR activity (onset potential of 0.976 V vs reversible hydrogen electrode (RHE) and half‐wave potential of 0.852 V vs RHE), higher than that of commercial Pt/C (20 wt%) in an alkaline media, and shows a good activity in an acidic media as well. In addition to its higher stability and methanol tolerance than Pt/C in both alkaline and acidic electrolytes, highly competitive single cell performance is achieved in a proton exchange membrane fuel cell. This work provides a general approach to preparing functionalized small hollow nanospheres based on self‐assembly of block copolymers.     

质子交换膜燃料电池扩散层电阻的实验研究

气体扩散层是质子交换膜燃料电池的重要组件,其与极板之间的接触电阻是燃料电池内阻的重要组成部分,也是导致燃料电池功率损失的重要因素。为了得到扩散层与极板间接触电阻以及扩散层本体电阻,首先在扩散层试样表面溅射厚度为50nm的金属铜,再在实验室搭建的燃料电池压力-位移测试平台上用四点法测得试样的总电阻,而后用斜率-截距法分离了气体扩散层本体电阻和其与极板的接触电阻,计算出了相应的电阻率,得到了压力和接触电阻之间的关系。结果表明,接触电阻随着接触面压强的增大而减小,接触电阻率和接触压强关系满足经验公式ρ=43.39P-0.725。     

燃料电池中质子交换膜干涸的热物理机制

本文首次应用有内热源的多孔介质中流体流动与换热理论,对直接甲醇燃料电池中PEM中的传热过程和干涸 现象进行定量研究。建立了相应的数学物理模型并进行了数值求解。计算结果表明:反映水的热容量和膜的内部产热量的 两个无因次参数D和N是影响PEM中传热的主要因素;水的质量流率小和电流密度过高是造成膜干涸的主要原因。     

Nafion perfluorinated membranes in fuel cells

Increasing global energy requirements, localized power issues and the need for less environmental impact are now providing even more incentive to make fuel cells a reality. A number of technologies have been demonstrated to be feasible for generation of power from fuel cells over the last several years. Proton exchange membranes (PEM) have emerged as an essential factor in the technology race. DuPont has supplied Nafion^® perfluorinated membranes in fuel cells for space travel for more than 35 years and they have played an integral part in the success of recent work in portable, stationary and transportation applications. The basis for PEM fuel cell emergence and DuPont technology utilization will be discussed.