Investigation of corrosion properties with Ni–P/TiNO coating on aluminum alloy bipolar plates in proton exchange membrane fuel cell

Aluminum alloy bipolar plates have unique application potential in proton exchange membrane fuel cell (PEMFC) due to the characteristics of lightweight and low cost. However, extreme susceptibility to corrosion in PEMFC operation condition limits the application. To promote the corrosion resistance of aluminum alloy bipolar plates, a Ni–P/TiNO coating was prepared by electroless plating and closed field unbalanced magnetron sputter ion plating (CFUMSIP) technology on the 6061 Al substrate. The research results show that Ni–P interlayer improves the deposition effect of TiNO outer layer and increase the content of TiN and TiO_xN_y phases. Compared to Ni–P and TiNO single-layer coatings, the Ni–P/TiNO coating samples exhibited the lowest current density value of (1.10 ± 0.02) × 10^?6 A·cm^?2 in simulated PEMFC cathode environment. Additionally, potential cyclic polarization measurements were carried out aiming to evaluate the durability of the aluminum alloy bipolar plate during the PEMFC start-up/shut-up process. The results illustrate that the Ni–P/TiNO coating samples exhibit excellent stability and corrosion resistance.     

具有高耐蚀性和导电性的掺Cr类金刚石非晶碳的化学式解析

Cr掺杂的类金刚石非晶碳具有良好的导电性和耐腐蚀性,这对于燃料电池金属双极板涂层改性特别重要。使用团簇加连接原子模型对其非晶结构进行了详细解析,在该模型中,良好的玻璃形成材料由覆盖特征性最近邻团簇加上几个下一壳层原子的结构单元来表述。根据文献,在Cr掺杂的类金刚石非晶碳中占优势的团簇是Cr中心和C壳层的[Cr-C4]四面体团簇,然后将该团簇与适当的连接原子匹配,以满足电子轨道饱和原理。由此推导出了两个最优组成式,即[Cr-C4]CrC3(22.2%Cr)和[Cr-C4]Cr3C2(40%Cr),它们显示出良好的非晶态结构稳定性。实验结果显示,所提出的这两组化学组成的涂层材料兼具低电阻率(低至10-4Ω·cm)和优异的耐腐蚀性(腐蚀电流密度~10^-2μA/cm^2)。在sp2键含量和渗流理论的框架内讨论了导电和耐蚀的协同行为。这项工作验证了团簇加连接原子模型在具有高耐腐蚀性和高导电性的涂层材料成分设计中的可行性。     

A novel flow field with controllable pressure gradient to enhance mass transport and water removal of PEM fuel cells

An easily machined novel flow field with controllable pressure gradient across adjacent channels was designed and a two dimensional, across-the-channel, two-phase model was developed to study the gas transport and water removal of the novel configuration. The effect of channel-rib width ratio, GDL thickness and pressure gradient on the profiles of oxygen concentration and water saturation within the GDL were investigated. Special attention was paid to the mechanisms of the promoted mass transport and water removal rates under a pressure gradient. The model was validated by experiments with various channel-rib ratios and GDL thicknesses at different operating pressure. The results revealed that, oxygen concentration was increased, and the water saturation was reduced under the rib with a pressure gradient generated across the adjacent channels. The optimal pressure gradient is between 0.1 to 0.2 atm for the studied channel geometry and configuration. The mechanisms of the improved cell performance were elucidated.     

Bipolar membrane electrodialysis for cleaner production of N-methylated glycine derivative amino acids

In this study, cleaner production of N-methylglycine (NMG), N,N-dimethylglycine (DMG), and N,N,N-trimethylglycine (TMG) with similar structures but different methylate groups was performed using bipolar membrane electrodialysis (BMED). The effects of the feed mass concentration and current density on the separation performance were intensively analysed in terms of the molecular size, molecular structure, ion concentration, and interaction between amino acids and membranes. The results indicated that the optimal recovery performance was achieved at a current density of 200 A/m² and feed mass concentration of 6%. Under the optimal conditions, the energy consumption and current efficiencies were 2.3 kWh/kg and 78% for NMG, 2.49 kWh/kg and 69.5% for DMG, and 3.52 kWh/kg and 39.6% for TMG, respectively. It was speculated a competition for water splitting occurs between the bipolar membranes and anion exchange membranes when BMED is used for the separation and purification of large-sized bioproducts.     

多孔金属流场双极板研究进展

多孔金属是一种兼具结构与功能的材料,得益于其低密度、高孔隙率、可控渗透性的优点,在许多领域都有广泛应用。本文综述了多孔金属在质子交换膜燃料电池(proton exchange membrane fuel cell,PEMFC)双极板流场中的研究进展,相较于传统流道流场,高开孔率(>70%)的多孔金属具有相互连通的三维立体结构,可以增加气体分布均匀性、并加强气体传质、增强电子和热的传导及水的排出,从而对电池性能有较大提升。同时探讨多孔金属参数、流场结构设计、服役参数目和多孔材料本身对多孔金属流场在PEMFC应用中的影响。目前阻碍多孔金属在PEMFC应用的最大问题是腐蚀,且多孔金属内部结构复杂对涂层制备工艺提出更大挑战,因此如何有效解决多孔金属在PEMFC两极环境中的腐蚀问题,对推进多孔金属在燃料电池领域中的应用意义重大。     

高熵合金CrNbTiVZr的微观组织及其在模拟PEMFC环境中腐蚀行为研究

采用真空电弧熔炼和热处理制备了CrNbTiVZr高熵合金,利用XRD、SEM/EDS、动电位与恒电位极化曲线测试及XPS表面分析等方法,研究了高熵合金铸态及退火后的微观组织特征以及合金在模拟PEMFC环境中的电化学腐蚀行为及其钝化膜组成。结果表明,CrNbTiVZr高熵合金的铸态和退火组织均由富集Ti、Nb元素的无序BCC相和富集Cr、V、Zr元素的Laves相组成。铸态和退火合金在模拟PEMFC阴极环境中腐蚀电流密度Icorr均比304SS不锈钢下降一个数量级,具有较好的耐蚀性和稳定性,但在阳极环境中其耐蚀性与304SS相当,其中铸态合金的稳定性较差。合金在阴极环境良好的耐蚀性主要与其表面形成由Cr2O3、Nb2O5、V2O3、Ti2O3及ZrO2组成的致密钝化膜关系密切。     

光催化双极膜的制备及应用

以聚乙烯醇（PVA）和羧甲基纤维素钠（CMC）混合制成阳膜层材料,以聚乙烯醇和壳聚糖（CS）混合制成阴膜层材料。分别用氯化铬、戊二醛对阳膜、阴膜进行交联改性,并在阴阳膜层间加入具有光催化活性的纳米二氧化钛,得mCMC/TiO2/mCS双极膜。该双极膜在紫外光照射下,具有高的水解离效率,优良的亲水性能,双极膜阻抗小,工作电压低,并将该膜应用于合成乙醛酸和丁二酸体系中。     

TA2钛板掺杂钒离子渗碳层的耐腐蚀性能

为提高钛基双极板的耐腐蚀性能和导电性,在TA2纯钛的表面进行双辉离子渗碳,另外为降低渗碳温度,在渗碳过程中掺杂钒。使用扫描电镜和能谱分析、X射线衍射对改性层的组织结构、化学成分、物相组成进行研究,并测得改性层的界面接触电阻率、耐腐蚀性能。结果表明,在优化的制备工艺参数下,在TA2表面生成结构致密的TiC改性层、钒掺杂渗碳改性层。当压实力为140 N/cm²时,730℃下制备的钒掺杂渗碳改性层、850℃下制备的TiC改性层、TA2基体的界面接触电阻率分别是1.17、3.66、14.71 mΩ/cm²。在模拟双极板的工作环境中,测得730℃下制备的钒掺杂渗碳改性层、850℃下制备的TiC改性层的自腐蚀电流密度分别是5.238、7.563μA/cm²,均比TA2基体的腐蚀电流密度低1个数量级。在离子渗碳的过程中掺杂钒可以有效降低渗碳的工艺温度,并且提高TA2基体的导电性和耐腐蚀性能。     

Surface technology should improve PEM fuel cell performance

Leading industrial nations are investing in hydrogen technology as energy storage solution with fuel cells as the main converter to electric energy. Improvements in the performance of the key components: electrode catalyst, bipolar plates and polymer electrolyte membrane are needed to reduce costs for mass-market introduction. Consequently, surface technology has an essential role in meeting the goals.     

Development and Electrochemical Testing of Novel Bipolar Nickel Metal Hydride Batteries

With the enhancement of consciousness of envi-ronmental protection and the increasing exhaustion ofoil resources,study on electric vehicles(EV)or hy-brid electric vehicles(HEV)are being actively con-ductedin the countries worldwide[1-3].Ni/MHbat-tery is p…