基于可再生阴极的高燃料浓度微流体燃料电池内多过程耦合传输特性研究

A microfluidic fuel cell is a new type of the micro fuel cell which exploits the co-laminar flow nature of multistream in a microchannel to segregate the fuel and oxidant and therefore eliminates the proton exchange membrane adopted in the traditional fuel cell. It is regarded as one of the promising micro power sources for portable applications. The Fe2+/Fe3+ redox couple is adopted as an oxidant with some advantages such as high electrochemical activity, regeneration under the oxygen condition and no need of catalysts for cathode reaction. And a microfluidic fuel cell is constructed with high fuel concentrations and the reproducible cathode to solve the problem associated with the severe cathode depolarization caused by fuel crossover. In this project, the experimental and theory methods are adopted to explore the relations between the mass transfer and the performance of the microfluidic fuel cell, respectively. By experimental researches, the influences of the mass transfer on the performance of this fuel cell and the conversion characteristics of cathode regeneration under the coupled several processes are studied. The processes in this fuel cell mainly include the electrochemical reactions, cathode regeneration, and a complex process of the multi-component transport involving the flow and transfer of the reactants, oxygen transfer from the air to the micro holes in the hydrophobic carbon paper and to cathode electrolyte, and proton transfer and so on. Based on the experimental results, the whole model of the multi-component transfer under the coupled processes in the microfluidic fuel cell is set up and solved by the numerical solution. In this model, the relevant transfer processes are the gas-liquid flow and multi-component (proton, oxygen, redox couple and so on) transport. By combined the experimental research and theoretical analysis, the interactions among the mass transfer, electrochemical reactions, cathode regeneration and the power generation of the microfluidic fuel cell are revealed, which provide a sound theoretical basis for the research and development of microfluidic fuel cells.

微流体燃料电池是一种利用微通道内多股流体呈平行层流特性而自然分隔燃料和氧化剂的新型燃料电池，是便携式电子设备最具潜力的电源之一。本项目采用电化学活性高、氧气条件下即可再生、阴极反应无需催化剂的Fe2+/Fe3+氧化还原对作为氧化剂，构建阴极可再生、阳极可采用高浓度燃料的微流体燃料电池，以解决燃料渗透引起阴极电位降低的问题。实验研究该电池含电化学反应、阴极再生反应、氧气由气相通过憎水碳纸微孔到电解液相的传输、质子传递等多过程耦合下物质传输对电池产电和阴极再生转化特性的影响。在此基础上，建立能够完整描述电池内阳极两相流动与传输、阴极多组分传输、氧气传输和质子传递等多过程耦合下多组分物质传输的理论模型，并进行数值求解。将实验研究与理论分析相结合，揭示不同阴极和阳极操作条件下电池内物质传输、电化学反应、阴极再生过程与电池产电特性之间的相互作用关系，为高性能微流体燃料电池的研究与开发奠定理论基础。

微流体燃料电池是利用两股流体在微通道内呈层流流动的特性，无需质子交换膜即可将氧化剂和燃料自然隔开，是便携式电源的研究热点之一。本项目主要Fe2+/Fe3+氧化还原对为氧化剂，针对阳极可采用高燃料浓度、阴极反应无需催化剂且可再生的微流体燃料电池开展研究工作。通过系统的实验研究，获得了以Fe2+/Fe3+氧化还原对为氧化剂的微流体燃料电池性能影响规律：首先构建以碳纸作为电极材料、含Fe3+溶液为氧化剂的微流体燃料电池，考察了不同铁盐在碳纸上的电化学行为，也研究了不同铁盐为氧化剂的微流体燃料电池性能。此外，考察了反应物流量、氧化剂浓度、阴极支持电解液浓度等参数对微流体燃料电池性能的影响，并获得了这些参数下的最佳电池性能；再次，针对碳纸电极本身的亲水性较差、表面官能团较少，采用热酸处理方法活化碳纸电极，以提高微流体燃料电池的性能。采用 FTIR、XPS、SEM 等技术手段表征处理过电极的物理化学性质，采用CV和EIS等手段表征处理过电极的电化学性质，考察了处理过电极作为阴极时的微流体燃料电池性能，获得了碳纸电极的物理和电化学性质对微流体燃料电池性能影响的规律。本项目的实施为微流体燃料电池技术的应用和发展奠定了一定的实验基础，具有重要的研究意义。