Surface-confined Pt-based catalysts for strengthening oxygen reduction performance

Developing highly efficient catalysts for the oxygen reduction reaction (ORR) is a key to the fabrication of commercially viable fuel cell devices for future energy applications. Considerable progress has been made to reduce Pt usage and improve performance of the Pt catalysts by modulating exposed facets of Pt nanocrystals and combining Pt with other metals to generate bimetallic nanocrystals with structures in the form of alloys, core-shells, branches or anisotropies. Apart from the above methods, confining Pt-based nanoparticles (NPs) surfaces with elaborately selected layers such as polymers, silicon or carbons can also lead to an optimized Pt electronic structure, which is beneficial to ORR process. In this minireview, we summarize the recent advancements in the area of surface-confined Pt-based electrocatalysts for ORR with emphasis on introducing the design strategies and synthesis methodologies. The integration of these catalysts into ORR operations and the resulting performance as well as the strengthening mechanisms is also discussed. Meanwhile, the insights into the research directions are proposed in order to shed light on the future development of surface-confined Pt-based ORR catalysts.     

Effect of supporting materials on the electrocatalytic activity,stability and selectivity of noble metal-based catalysts for oxygen reduction and hydrogen evolution reactions

Carbonaceous and alternative supporting materials for platinum(Pt) and palladium(Pd) have been explored for the cathodic electrocatalysis in low-temperature fuel cells. Pd and Pt are widely used for catalysis owing to their remarkable electrocatalytic activity toward water splitting and fuel cell reactions. Supporting materials play a paramount role in defining electrocatalytic properties such as durability, selectivity, and activity. The conventional supporting material such as carbon black is unable to fit all the requirements under the severe operating conditions of fuel cells due to its poor corrosion resistance and limited mass transport of fuels to active catalyst sites. Nowadays the scientific research is being concentrated on devising different altered carbonic and carbonfree supporting materials for catalysts to improve the catalytic activity, stability, and selectivity of noble metal electrocatalysts. Lately, Pt, Pd and their alloy catalysts supported on modified carbonaceous and carbon-free materials have attracted solid interest owing to their prominent characteristics contributing to the remarkable fuel cell efficacy. Therefore, it is reasonable to explore this theme, regarding a variety of supporting materials,their advantages, drawbacks and future perspectives. In this mini-review, we selectively summarize recent advancements on several types of key supporting materials: carbon(graphene, carbon nanotubes, mesoporous carbon, and doped carbon nanostructures), non-carbon(transition metals oxides, borides, nitrides, and carbides)and hybrid nanocomposites.     

Applications of M/N/C analogue catalysts in PEM fuel cells and metal-air/oxygen batteries: Status quo,challenges and perspectives

To meet the sharp increase in demand for clean and renewable energy, it is necessary to develop new energy-conversion and storage technologies, such as proton exchange membrane fuel cells (PEMFCs) and metal-air/oxygen batteries (MABs). Due to the sluggish reaction kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in the cathodes of PEMFCs and MABs, significant amounts of precious metal catalysts need to be used, driving up the cost of fuel cells and MABs and thereby hindering their commercialization on a large scale. Transition metal and nitrogen co-doped carbonaceous catalysts (M/N/C) have high catalytic activity towards the ORR and OER once the catalysts are modified with certain promoters/additives. In addition, M/N/C catalysts can be prepared from abundant, inexpensive materials, making their cost negligible compared with precious metal catalysts, a development that would efficiently decrease the cost of PEMFCs and MABs. In last decade, numerous researchers have attempted to realize these applications of M/N/C catalysts, and some exciting results have been achieved, making these promising replacements for precious metal catalysts. However, some serious problems and significant challenges remain. In this paper, we review the research on the application of M/N/C analogue catalysts in PEMFCs and MABs in the last 10 years, indicate the remaining challenges, and suggest the future research directions.     

Highly stable N-containing polymer-based Fe/Nx/C electrocatalyst for alkaline anion exchange membrane fuel cell applications

A cost-effective electrocatalyst with high activity and stability was developed. The Fe-Nx and pyridinic-N active sites were embedded in nitrogen-doped mesoporous carbon nanomaterial by carbonization at high temperature. The electrocatalyst exhibited excellent electrochemical performance for the oxygen reduction reaction, with high onset potential and half-wave potential values (E_onset = 1.10 ?V and E_1/2 ?= ?0.944 ?V) than 20 ?wt % Pt/C catalyst (1.04 and 0.910 ?V). The mass activity of the Schiff base network (SNW) based SNW-Fe/N/C@800° electrocatalyst (0.64 ?mA ?mg^?1 @ 1 ?V) reached about half of the commercial Pt/C electrocatalyst (1.35 ?mA ?mg^?1 @ 1 ?V). The electrocatalyst followed the 4-electron transfer mechanism due to very low hydrogen peroxide yield (H₂O₂ ?< ?1.5%) was obtained. In addition, this electrocatalyst with dual active sites showed high stability during cyclic voltammetry and chronoamperometry measurements. More importantly, the electrocatalyst also demonstrated the power density of 266 ?mW ?cm^?2 in the alkaline anions exchange membrane fuel cell (AEMFC) test, indicating its prospective application for fuel cells.     

Cu改性直接甲醇燃料电池Pd/C阴极催化剂的电催化性能

用铜做掺杂元素,采用浸渍法以活性炭为载体制备了贵金属载量为20%的Pd-Cu/C系列直接甲醇燃料电池阴极催化剂,比较了4种不同Cu含量催化剂的电催化性能。采用ICP和X射线衍射分析了催化剂中金属元素的比例以及Cu掺杂对Pd/C催化剂晶体结构的影响。结果表明:催化剂中Pd与Cu的物质的量之比与预设值相近,Pd和Cu基本被全部还原;Pd-Cu/C催化剂为面心立方结构,元素铜的加入使催化剂的Pd-Pd间距缩小,从而HO2 ads和OO键能更好地吸附在催化剂金属表面;当采用NaBH4为还原剂,Pd与Cu物质的量比为3∶1时,催化剂(Pd3Cu/C)的平均粒径为3.4 nm,催化剂的催化性能最好,电化学活性表面积EAS达到38.9m2/gPd,电化学性能较Pd/C催化剂有很大提高,接近Pt/C商用催化剂。     

Present status and future prospect of design of Pt–cerium oxide electrodes for fuel cell applications

In the research field of proton exchange membrane fuel cells, the design of electrocatalytic activities on Pt-oxide promoter in the anode side has attracted attention for improvement of CO tolerance of Pt in anode side and a lowering of large over-potential loss of the oxygen reduction reaction on the cathode in the fuel cells. In the Pt-oxide promoter series, Pt–CeOx/C is one of the unique systems. It is because the unique behavior of CeOx such as electrochemical redox reaction between Ce3t and Ce4t in the anodic and cathodic reactions of fuel cell is observed. The present short review gives an overview of the recent works for improvement of the CO tolerance of Pt in the Pt–CeOx/C anodes and enhancement of the oxygen reduction reaction activity on Pt in the Pt–CeOx/C cathodes for fuel cell application. To show the design paradigm for fabrication of high quality Pt–CeOx/C electrodes, the authors re-introduced parts of our research results to highlight the important role of interface structure of Pt–CeOx based on the ultimate analysis results. The usefulness of the combined approach of microanalysis and the processing route design is presented.     

燃料电池混合动力轿车控制策略与参数优化

以某国产经济型轿车为平台,对其动力总成进行了燃料电池混合动力驱动系统的虚拟改装．为提高其整车的经济性和动力性,使用ADVISOR软件对整车性能进行仿真分析,研究了燃料电池混合动力驱动系统开关控制模式和功率跟随控制模式的特性,确定功率跟随控制模式为适合该车型的控制策略．分析了4种典型驱动工况下不同混合动力度的整车经济性及动力性,其中50％的混合动力度是适用于该车型燃料电池混合动力驱动系统最优配置．在此最优配置下,以最小氢气燃料消耗为目标,优化主减速比、燃料电池的最大和最小工作功率以及蓄电池的充电功率,得到了燃料电池混合动力系统的最佳工作点．     

Platinum-supported mesoporous carbon (Pt/CMK-3) as anodic catalyst for direct methanol fuel cell applications: The effect of preparation and deposition methods

Platinum-supported ordered mesoporous carbon catalysts were prepared employing colloidal platinum reduced by four different reducing agents, viz., paraformaldehyde, sodium borohydride, ethylene glycol and hydrogen, and deposited over ordered mesoporous carbon (CMK-3) synthesized by silica hard template (SBA-15). The resulting platinum nanoparticles supported mesoporous carbon, designated as Pt/CMK-3, catalysts were tested for the electocatalytic oxidation of methanol. The effect of the various reduction methods on the influence of particle size vis- a-vis on the electrocatalytic effect is investigated. All the catalysts were systematically characterized by XRD, BET and TEM. The results of the synthetic methods, characterization techniques and the electrocatalytic performance indicate that the Pt/CMK-3 catalysts are superior to that prepared with activated carbon (Pt/AC) as well as with that of the commercial platinumsupported carbon catalyst (Pt/E-TEK). In particular, the catalyst, Pt/CMK-3, prepared using paraformaldehyde reduced platinum showed much higher activity and long-term stability as compared to the other reducing methods.     

硫酸化改性对TiO2负载的铈基脱硝催化剂的活性及抗碱金属性能的影响

采用浸渍法对TiO₂负载的铈基催化剂进行了硫酸化改性,同时制备了未经硫酸化改性的催化剂与之对比,通过X射线衍射（XRD）、比表面积测试（BET）、氢气程序升温还原（H₂-TPR）、X射线光电子能谱（XPS）和吡啶红外光谱（Py-IR）等一系列手段对催化剂进行了表征。结果表明,硫酸化改性不仅能够增加催化剂表面的化学吸附氧的含量,提高催化剂的氧化还原性,而且还能极大地丰富催化剂表面的布朗斯特酸位点和路易斯酸位点,以此来增加催化剂的酸性,使得催化剂的低温活性有所提升并拓宽其温度窗口。此外,硫酸化改性为铈基催化剂表面增加了额外的超强酸位点,使催化剂在受到碱金属的毒害后,仍有大量的酸位能得以保留,能够维持对NH₃的吸附,进行催化反应循环,极大地提升催化剂的抗碱金属性能。     

微生物燃料电池La_(0.7)Sr_(0.3)CoO_3/PANI阴极催化剂的制备及催化性能

采用原位聚合法合成了La0.7Sr0.3CoO3/PANI复合材料微生物燃料电池(MFC)阴极催化剂。通过X射线衍射(XRD)、红外光谱(FT-IR)和扫描电子显微镜(SEM)对所制备催化剂进行结构和微观形貌表征。采用循环伏安法(CV)和交流阻抗法(EIS)对复合材料进行电化学性能的分析。结果表明,聚苯胺(PANI)含量的差异导致催化剂的活性有较大区别,在磷酸盐缓冲溶液中含PANI质量分数为6%的La0.7Sr0.3CoO3/PANI催化剂表现出了良好的活性。将所制备催化剂应用于单室微生物燃料电池阴极,结果显示,PANI质量分数为6%的La0.7Sr0.3CoO3/PANI对应MFC的最大功率密度258.91mW/m2,相应开路电压达642.7mV。这表明La0.7Sr0.3CoO3/PANI催化剂具有显著的催化活性,为需求有效MFC阴极催化剂材料提供了新途径。     

直接甲醇燃料电池管状阴极的制备与性能

以管状金属钛网为支撑体,采用浸涂工艺在其外表面依次制备了气体扩散层、Pt/C催化层和Nafion 膜,制得管状阴极,并分析了影响电池性能的因素.研究结果表明,采用浆液浸涂工艺制备的阴极气体扩散层与催化层,均具有有利于气体传质和电化学反应的多孔结构.随着阴极催化剂载量的增加,单电池的性能也逐渐提高.当Pt载量为4.3 mg/cm2时,常温下以空气作为氧化剂,电池功率密度峰值约为12.3 mW/cm2,而同样的电池,在60 ℃下以氧气作为氧化剂,则可以达到40.0 mW/cm2,这表明温度和氧化剂种类与催化剂载量一样,是影响电池性能的重要因素.电池经约100 h工作时间后进行的等电压放电试验结果表明,该管状Ti基阴极的电化学稳定性优良.     

质子交换膜燃料电池Pt/C电催化剂的制备研究

采用浸渍还原法 ,用H2 [PtCl6]制备了高分散的纳米级碳载铂 (Pt/C)电催化剂 .探讨了搅拌方式、H2 [PtCl6]浓度、反应温度、碳的热处理等因素对电催化剂性能的影响 .得到了较适宜的制备工艺 .     

直接甲醇燃料电池测控系统的研制

根据直接甲醇燃料电池性能测试和运行工艺参数的需要,设计了在线实时监控系统,硬件采用瑞博华公司的数据采集器AD8201用于实时的监测电池系统的运行参数和性能,通过开关量控制甲醇热压的加热设备,来稳定电池的运行温度,测量的具体参数有电流、电压和温度,并用二维视图显示在计算机屏幕上,软件采用VB设计实现。     

燃料电池汽车开发及产业化的关键技术研究

燃料电池电动汽车技术是当今世界上正在进行研究的一项高新技术,文章介绍了燃料电池电动汽车的动力系统和燃料电池系统的基本结构和工作原理。从燃料电池电动汽车的车身和底盘设计、燃料电池系统、驱动电机系统、电控系统以及系统优化等方面,分析了燃料电池电动汽车开发及产业化需要解决的关键技术,同时提出了相应的技术路线和对策。     

固体氧化物燃料电池系统仿真分析与控制

固体氧化物燃料电池（SOFC）系统是一个非线性、多变量和强耦合的系统,很难用传统的建模方法来建立。本文基于BP神经网络的方法,利用MATLAB/Simulink平台构建SOFC系统模型,并在该模型的基础上增加PID控制,实现了闭环控制系统的分析。实验结果表明,该模型预测精度高,由预测模型得出的温度数据与实际数据的绝对误差为0.011%,增加的PID控制算法具有很强的抗干扰能力。     

直接甲醇燃料电池的阳极进料系统及控制策略

直接甲醇燃料电池(direct methanol fuel cells,DMFC)的甲醇燃料的利用关系到系统的能量密度,是其微型化亟待解决的问题。为了提高甲醇利用率和提高系统的能量密度,必须采用必要的进料系统和控制策略。该文从主动和被动两类系统总结了面向直接甲醇燃料电池的关键系统组件和相关的控制策略,从系统工程的角度加以分析,总结了DMFC用甲醇传感器和系统控制的设计开发思想,并指出电池型化学传感器将是DMFC用甲醇传感器的主要开发方向,系统需采用脉冲式进料和混合动力方式以适应不同模式的负载。自呼吸电堆需采用基于化学势为推动力的被动式进料方式。采用空载自升温模式有助于缩短启动时间。     

Gas-based reduction of vanadium titano-magnetite concentrate: behavior and mechanisms

The reduction of vanadium titano-magnetite pellets by H₂-CO at temperatures from 850 to 1050℃ was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_H2/(V_H2 + V_CO) on the metallization degree were studied. The results showed that pre-oxidation played a substantial role in the reduction of vanadium titano-magnetite pellets. During the reduction process, the metallization degree increased with increasing temperature and increasing V_H2/(V_H2 + V_CO). The phase transformation of pre-oxidized vanadium titano-magnetite pellets during the reduction process under an H₂ atmosphere and a CO atmosphere was discussed, and the reduced samples were analyzed by scanning electron microscopy (SEM) in conjunction with back scatter electron (BSE) imaging. The results show that the difference in thermodynamic reducing ability between H₂ and CO is not the only factor that leads to differences in the reduction results obtained using different atmospheres. Some of Fe_3-xTi_xO₄ cannot be reduced under a CO atmosphere because of the densification of particles' structure and because of the enrichment of Mg in unreacted cores. By contrast, a loose structure of particles was obtained when the pellets were reduced under an H₂ atmosphere and this structure decreased the resistance to gas diffusion. Moreover, the phenomenon of Mg enrichment in unreacted cores disappeared during H₂ reduction. Both the lower resistance to gas diffusion and the lack of Mg enrichment facilitated the reduction of vanadium titano-magnetite.     

车用燃料电池发动机控制系统与协调控制研究

介绍了燃料电池发动机的基本结构和特点,设计了实用的控制系统,并阐述了各个子系统的工作原理和控制策略,根据其自身特性和运行工况,提出了燃料电池发动机各子系统的协调控制方法,获得了较好的控制效果。