甲醇浓度对被动式自呼吸直接甲醇燃料电池性能的影响

依据单电池测试结果和甲醇传质理论考察了甲醇溶液的浓度对被动式自呼吸直接甲醇燃料电池（DMFC）性能的影响.研究结果表明,电池的法拉第效率和能量转化效率会随着浓度的增大而降低,采用4mol/L的甲醇溶液实现了最大的放电功率13.9mW/cm^2,并能在60mA下稳定放电长达20h.这取决于电池运行过程中电极内部的甲醇传质和甲醇透过的共同作用.     

直接甲醇燃料电池甲醇传质过程分析及浓度控制策略

甲醇溶液浓度对于直接甲醇燃料电池(DMFC)的性能具有重要影响。 本文旨在建立一种能在电源系统中有效控制甲醇浓度的策略。 通过构建电池内甲醇物料守恒和热守恒方程,确定了基于电量和温度这两个参数的甲醇浓度控制策略。 通过测试温度-浓度关系验证了控制策略的可行性。 结果表明,采用该策略,DMFC电源系统稳定运行超过420 min;合适的甲醇浓度范围为0.70~0.87 mol/L。 该策略完成了甲醇浓度控制的目标,并将在电源系统中发挥重要作用。     

直接甲醇燃料电池的甲醇浓度控制方法

直接甲醇燃料电池(DMFC)直接以甲醇为阳极燃料,具有系统结构简单、体积能量密度高、燃料补充方便等特点,非常适合用于小型移动电源。甲醇浓度对DMFC性能和燃料利用效率的影响非常大,甲醇浓度高低直接决定DMFC输出性能的好坏,控制好DMFC中的甲醇浓度,对其寿命长短起着至关重要的作用。本文将目前已有的甲醇浓度控制方法分为有甲醇浓度传感器和无甲醇浓度传感器两大类,评述了这些浓度控制方法的研究现状和优缺点,并展望了甲醇浓度控制方法的趋势。     

Au/Pt纳米柱阵列电极的制备及光电催化氧化甲醇性能

利用纳米压印、 电沉积和气相沉积方法构筑了有序均一的Au及Au/Pt纳米柱阵列电极. 通过反射光谱观测到580和660 nm附近的特征吸收谱峰, 并基于有限元电磁场(FEM)理论模拟, 确定其表面等离激元共振(SPR)性质分别对应于纳米柱柱顶的电偶极模式(584 nm)、 电四极模式(638 nm)以及表面等离激元极化子(666 nm). 制备的等离激元纳米柱电极用于甲醇光电催化氧化反应时, SPR效应能显著地增强甲醇的电催化氧化电流. 当表面负载2 nm的金属Pt时, 光电催化氧化甲醇活性最高, 光照使氧化电流增加, 同时甲醇的氧化峰电位随光强的增加逐渐负移, 证明SPR弛豫产生的热空穴参与到光电协同甲醇氧化中. 在恒电流甲醇氧化实验中, 光照使表面氧化反应时间延长6倍, 减小了CO的毒化, 证明SPR对于电极表面产生一定的清洁作用.     

纳米钯催化剂对甲醇的电催化氧化

采用水热法,以甲醛作还原剂还原Pd2+-EDTA络合物,制得钛基纳米钯颗粒电极(nanoPd/Ti).扫描电子显微镜(SEM)显示,纳米钯颗粒直径约为60 nm,形成三维立体网状结构.在碱性溶液中,循环伏安及交流阻抗测试分别表明:nanoPd/Ti电极对甲醇氧化有极高的阳极电流、较低的起始氧化电位和较强的抗CO毒化能力.在nanoPd/Ti电极上甲醇电氧化反应的阻抗值较低,增加甲醇浓度,电极阻抗更低.电极对甲醇氧化具有极好的电催化活性.     

FeTSPc对Pt电极对氧还原的电催化性能和耐甲醇性能的影响

为了解决直接甲醇燃料电池(DMFC)中“甲醇渗透”的问题, 用大环化合物四磺酸基酞菁铁(FeTSPc)对光滑铂(Pt)电极进行修饰, 发现FeTSPc修饰的Pt电极(Pt-FeTSPc)和Pt电极对氧还原的电催化活性相近, 而Pt-FeTSPc电极对甲醇氧化的电催化活性比Pt电极下降30.9%, 表明Pt-FeTSPc电极有较好的耐甲醇能力.     

Sm3+对甲醇电化学氧化反应的助催化作用

分别以相同面积的光滑Pt电极和吸附了Sm3+的铂电极作为工作电极,在酸性介质中采用循环伏安法对甲醇氧化进行测定.结果表明,吸附了Sm3+的Pt电极上产生了更大的氧化电流,表明Sm3+的加入对甲醇的电催化氧化起到了促进作用.这一研究结果在直接甲醇燃料电池(DMFC)阳极催化剂研制方面具有较大的应用潜力.     

直接甲醇燃料电池用磺化聚醚醚酮膜初探

应用电化学方法研究了SPEEK膜的甲醇渗透性能.SPEEK膜具有比Nafion115膜低的甲醇渗透.以其作质子交换膜电解质组装的直接甲醇燃料电池(DMFCs)开路电压高于Nafion115膜组装的DMFC开路电压,但电池的放电性能尚待改进.本研究可为SPEEK应用于直接甲醇燃料电池提供一定的依据.     

四磺酸基酞菁钴对于光滑Pt电极上氧还原过程的影响

将大环化合物四磺酸基酞菁钴(CoTSPc)加入到电解液中, 研究了其对Pt阴极催化氧还原以及耐甲醇性能的影响. 实验结果发现, 这种影响与加入到溶液中的CoTSPc的浓度有关, 当溶液中加入CoTSPc的浓度为0.09 mmol•L^－1时, Pt电极催化氧还原的电流基本不变, 而有效抑制了甲醇在阴极的氧化, 使甲醇氧化的峰电流值下降79.7%.     

光电催化氧化甲醇电极

直接甲醇燃料电池 (DMFC)可直接利用甲醇 ,无须中间转化装置 ,具有系统结构简单、体积能量密度高、燃料补充方便等优点 .从提高电流密度和稳定催化剂本征活性这两方面来看 ,DMFC需要解决的关键问题是使甲醇直接氧化的阳极材料 .近年来有关此类阳极材料的制备与催化性能的研究报道日益增多 [1,2 ] ,但都是单纯地从光催化或电催化的角度出发 .本文提出一种利用 Ti O2 为光催化剂 ,Pt- Ru为电催化剂 ,试图将光催化与电催化反应发生于一体 ,使甲醇能得到联合的催化氧化作用 ;同时为了能进一步增加Ti O2 的光催化氧化能力 ,改变 Ti O2 - n…     

MEA with double-layered catalyst cathode to mitigate methanol crossover in DMFC

Methanol permeation is one of the key problems for direct methanol fuel cell (DMFC) applications. It is necessary to change the structure of the cathode of membrane electrode assembly (MEA). Therefore, a novel MEA with double-layered catalyst cathode was prepared in this paper. The double-layered catalyst consists of PtRu black as inner catalyst layer and Pt black as outer catalyst layer. The inner catalyst layer is prepared for oxidation of the methanol permeated from anode. The results indicate that this double-layered catalyst reduced the effects of methanol crossover and assimilated mixed potential losses. The performance of MEA with double-layered catalyst cathode was 52.2 mW cm⁻², which was a remarkable improvement compared with the performance of MEA with traditional cathode. The key factor responsible for the improved performance is the optimization of the electrode structure.     

操作条件对DMFC阴极电化学阻抗谱参数的影响

通过降低阴极催化剂载量强化了阴极氧还原反应的电化学极化, 测量了不同操作条件下直接甲醇燃料电池(DMFC)的极化曲线和交流阻抗谱,并提出了改进的等效电路模型LR(CR)(QR(LR))用以分析温度、空气流量和甲醇流量对DMFC阴极电化学反应和传质极化过程的影响. 研究结果表明, 提高工作温度会导致更多的甲醇渗透到阴极, 加大阴极氧气还原反应的电荷转移电阻; 只有采用大的空气流量,才会有效地防止水淹, 加大氧气向催化剂层的传质, 促进阴极反应的进行; 适当提高甲醇的流量可以促进阳极和阴极电化学反应的进行, 但是过高的甲醇流速可能会降低电极表面的温度, 加剧甲醇的渗透.     

Investigations of flow field designs in direct methanol fuel cell

An experimental and simulation research had been performed to investigate the performance as well as the flow distribution in the cathode flow field in the case of direct methanol fuel cells (DMFCs). The gas was well distributed in serpentine flow field, whereas stagnation of the gas was observed in parallel flow field. These would contribute to the cell performance greatly due to mass transfer effect when the cells start operating. In addition, the durability test of DMFC was drastically affected in parallel flow field due to poor ability to drain flooded water produced electrochemically at cathode and crossover from anode. In addition, pressure drops of different flow fields were also investigated to evaluate their contribution and feasibility as an economic application for DMFC. DMFC with serpentine flow field featuring higher pressure difference resulted in a larger parasitic energy demand. However, the optimal flow field designs are needed to balance the performance and pressure loss to achieve a uniform fluid distribution and simultaneously minimize energy demand for mass transport. Consequently, flow field with grid pattern appears to be the optimal design for the DMFC cathode.     

自呼吸直接甲醇燃料电池膜电极的优化(英文)

针对空气自呼吸式直接甲醇燃料电池甲醇易渗透和阴极易水淹的特点,通过对催化层催化剂载量、阴极微孔层、阳极微孔层和膜等因素进行调控,对膜电极结构和性能的进行了优化.结果表明,使用高载量催化剂能有效降低甲醇渗透,但载量过高会引起传质阻力.当阳极微孔层PTFE含量为30%(bymass)时,可以有效促进CO2的均一析出,从而降低甲醇浓度梯度,减小甲醇透过.综合考虑甲醇渗透和阴极自返水,经优化后所得MEA在室温时自呼吸工作条件下,比功率密度达到33mW·cm-2,最优甲醇工作浓度为4mol·L-1.     

Effect of sorbed methanol, current, and temperature on multicomponent transport in nafion-based direct methanol fuel cells

The CO2 in the cathode exhaust of a liquid feed direct methanol fuel cell (DMFC) has two sources: methanol diffuses through the membrane electrode assembly (MEA) to the cathode where it is catalytically oxidized to CO2; additionally, a portion of the CO2 produced at the anode diffuses through the MEA to the cathode. The potential-dependent CO2 exhaust from the cathode was monitored by online electrochemical mass spectrometry (ECMS) with air and with H2 at the cathode. The precise determination of the crossover rates of methanol and CO2, enabled by the subtractive normalization of the methanol/air to the methanol/H2 ECMS data, shows that methanol decreases the membrane viscosity and thus increases the diffusion coefficients of sorbed membrane components. The crossover of CO2 initially increases linearly with the Faradaic oxidation of methanol, reaches a temperature-dependent maximum, and then decreases. The membrane viscosity progressively increases as methanol is electrochemically depleted from the anode/electrolyte interface. The crossover maximum occurs when the current dependence of the diffusion coefficients and membrane CO2 solubility dominate over the Faradaic production of CO2. The plasticizing effect of methanol is corroborated by measurements of the rotational diffusion of TEMPONE (2,2,6,6-tetramethyl-4-piperidone N-oxide) spin probe by electron spin resonance spectroscopy. A linear inverse relationship between the methanol crossover rate and current density confirms the absence of methanol electro-osmotic drag at concentrations relevant to operating DMFCs. The purely diffusive transport of methanol is explained in terms of current proton solvation and methanol-water incomplete mixing theories.     

Mordenite-incorporated PVA–PSSA membranes as electrolytes for DMFCs

Composite membranes with mordenite (MOR) incorporated in poly vinyl alcohol (PVA)–polystyrene sulfonic acid (PSSA) blend tailored with varying degree of sulfonation are reported. Such a membrane comprises a dispersed phase of mordenite and a continuous phase of the polymer that help tuning the flow of methanol and water across it. The membranes on prolonged testing in a direct methanol fuel cell (DMFC) exhibit mitigated methanol cross-over from anode to the cathode. The membranes have been tested for their sorption behaviour, ion-exchange capacity, electrochemical selectivity and mechanical strength as also characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. Water release kinetics has been measured by magnetic resonance imaging (NMR imaging) and is found to be in agreement with the sorption data. Similarly, methanol release kinetics studied by volume-localized NMR spectroscopy (point resolved spectroscopy, PRESS) clearly demonstrates that the dispersion of mordenite in PVA–PSSA retards the methanol release kinetics considerably. A peak power-density of 74 mW/cm² is achieved for the DMFC using a PVA–PSSA membrane electrolyte with 50% degree of sulfonation and 10 wt.% dispersed mordenite phase. A methanol cross-over current as low as 7.5 mA/cm² with 2 M methanol feed at the DMFC anode is observed while using the optimized composite membrane as electrolyte in the DMFC, which is about 60% and 46% lower than Nafion-117 and PVA–PSSA membranes, respectively, when tested under identical conditions.     

聚偏氟乙烯-Nafion共混膜的制备及阻醇质子导电性能研究

直接甲醇燃料电池 (Ｄｉｒｅｃｔｍｅｔｈａｎｏｌｆｕｅｌｃｅｌｌ,ＭＤＦＣ)以高效、清洁和燃料储运方便等优点成为一类极具发展潜力的新型动力源 .但目前ＤＭＦＣ中普通使用的全氟磺酸膜 (如ＮａｆｉｏｎＴＭ 系列膜 )阻醇性能太差 ,导致大量甲醇从阳极穿过膜直接透到阴极 ,造成燃料的浪费和电池整体性能的下降 .据文献报道 ,即使甲醇浓度低到 1ｍｏｌ Ｌ ,也有近40 %的醇透过膜 .缺乏高性能的阻醇质子导电聚合物电解质膜是制约ＤＭＦＣ发展的瓶颈之一 .已有一些研究人员致力于新型膜材料的开发 ,如有人研制了聚苯并咪唑膜[1] 及各种掺杂…     

A novel MEA architecture for improving the performance of a DMFC

Direct methanol fuel cell (DMFC) consisting of a double-catalytic layered membrane electrode assembly (MEA) provide higher performance than that with the traditional MEA. This novel structured MEA includes a hydrophilic inner catalyst layer and a traditional electrode with an outer catalyst layer, which was made using both catalyst coated membrane (CCM) and gas diffusion electrode (GDE) methods. The inner catalyst was PtRu black on anode and Pt black on cathode. The outer catalyst was carbon supported Pt–Ru/Pt on anode and cathode, respectively. Thus in the double-catalytic layered electrodes three gradients were formed: catalyst concentration gradient, hydrophilicity gradient and porosity gradient, resulting in good mass transfer, proton and electron conducting and low methanol crossover. The peak density of DMFC with such MEA was 19 mW cm⁻², operated at 2 M CH₃OH, 2 atm oxygen at room temperature, which was much higher than DMFC with traditional MEA.     

Effects of polymer electrolyte membrane's property on fuel cell performances

Platinum and/or metal‐oxide nanocrystals (d = 1 ‐ 2 nm) were highly dispersed in membranes such as a Nation® commercially available (denoted as Pt‐PEM or Pt‐oxide‐PEM) attempting to self‐humidify the PEMs and/or to suppress the short‐circuit reaction by a catalytic oxidation of the crossover hydrogen or methanol with oxygen on the Pt catalyst. High and stable performances under the suppressed crossover and lowered internal resistance are demonstrated at the H₂/O₂ fuel cells applied Pt‐PEM or Pt‐oxide‐PEM without any external humidification. An appreciable increase of the cathode potential due to the reduced methanol crossover was clearly demonstrated at a direct methanol fuel cell (DMFC) with Pt‐PEM. It also becomes clear that the development of new PEMs with lowered permeability against methanol is essential for DMFCs.     

杂多酸修饰的电极对于甲醇电氧化的促进作用

采用杂多酸修饰光滑铂电极,研究其对甲醇电催化氧化的作用,发现与未修饰光滑铂电极相比,分别经磷钨酸和硅钨酸修饰的电极上甲醇电催化氧化速率明显增加.