Autonomous Voltage Oscillations in a Direct Methanol Fuel Cell
Autonomous Voltage Oscillations in a Direct Methanol Fuel Cell
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DOI：
10.1016/j.electacta.2016.07.050
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发表时间：
2016-09
影响因子：
6.6
通讯作者：
J. Nogueira;I. Arias;R. Hanke‐Rauschenbach;T. Vidaković-Koch;H. Varela;K. Sundmacher
中科院分区：
文献类型：
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作者：
J. Nogueira;I. Arias;R. Hanke‐Rauschenbach;T. Vidaković-Koch;H. Varela;K. Sundmacher
质子交换膜燃料电池在阳极供给H2/CO混合物具有比供给纯氢的燃料电池低得多的性能。然而，当在自主振荡机制中操作时，由于自清洁机制，整体电压损耗降低。另一种分子是甲醇，也被广泛用作燃料电池的原料，对动力学不稳定性敏感。据我们所知，目前还没有关于直接甲醇燃料电池（DMFC）中自发电压振荡的报道。这项工作的目的是探讨这种不稳定性是否也发生在DMFC系统。最初，进行具有气体扩散电极的半电池实验。然后，直接甲醇燃料电池在电流控制下运行，并通过电化学阻抗谱研究。半电池的测量表明，振荡的诱导期取决于传质条件，其中在停滞电极的诱导时间比在强制对流的情况下短。DMFC也表现出一定的阈值电流以上的自主电压振荡。电化学阻抗谱得到的结果给出了证据的负微分电阻在燃料电池中，迄今为止没有在文献中描述，这可能与恒电流甲醇电氧化过程中的振荡的外观。这些结果打开的可能性，以评估在振荡操作条件下的含碳燃料供给的低温燃料电池的性能。
Proton exchange membrane fuel cells fed with H2/CO mixtures at the anode have a considerably lower performance than fuel cells fed with pure hydrogen. However, when operated in an autonomous oscillatory regime, the overall voltage loss decreases due to a self-cleaning mechanism. Another molecule, also widely used as feed in the fuel cell and susceptible to kinetic instabilities, is methanol. To the best of our knowledge, there are no reports on autonomous voltage oscillations in the direct methanol fuel cell (DMFC). The purpose of this work was to explore if such instabilities also occur in the DMFC system. Initially, half-cell experiments with a gas diffusion electrode were performed. Then, a DMFC was operated under current control and studied by means of electrochemical impedance spectroscopy. The half-cell measurements revealed that the induction period for oscillations depends on the mass transfer conditions, where on stagnant electrode the induction time was shorter than in the case of forced convection. The DMFC showed also autonomous voltage oscillations above a certain threshold current. The results obtained by electrochemical impedance spectroscopy give evidence of a negative differential resistance in the fuel cell, hitherto not described in the literature, which can be related to the appearance of oscillations during galvanostatic methanol electro-oxidation. These results open the possibility to evaluate the performance of low-temperature fuel cells fed with carbon-containing fuels under oscillatory operating conditions.