多電極質子交換膜型純水電解產氫器之設計製造研究

Abstract

本研究旨在設計並改良質子交換膜型純水電解器，藉以得到氫氣，以供燃料電池使用。首先決定流道的型式以及材料，流道型式以計算流體力學軟體-FLUENT，進行分析，進而了解流場性質，以格點式流場做為最終設計。在材料的選用上，根據電化學電位以及電解環境，選擇抗腐蝕與抗氧化的鈦材作為流道板材料。整體實驗以改善單電極的性能開始，經由改變觸媒漿料的配方、質子交換膜種類、電極板夾持型式以及陽極觸媒使用量等變因，希冀能掌握單電極電解器的各項控制變因，以作為提升多電極電解器性能的依據。文中針對各種變因所造成的性能差異，以電壓效率、法拉第效率以及能源轉換效率作為性能比較的指標，深入討論之。 為了獲得足夠的產氫量，組裝多電極電解器是必然的趨勢。多電極電解器有其設計重點，特別是在流道的配置、氣體密封效果以及穩定的單電極性能等方面，須審慎設計。本研究初步的製作出三個膜電極組所堆疊的多電極電解器，從分別測定的膜電極組端電壓來看，每片膜電極組的性能相類似，而在氫氣的產生方面，純度經由氣相層析儀的測定，可知氫氣純度達99.84%；產氫量方面，以法拉第效率作為依據，也高達98%以上，因此可知多電極電解器之氣密效果良好，流場排出氣體的效果順暢。 本實驗所設計的電解器最佳性能為：  單電極：200mA/cm2@2V，電壓效率74%，產氫量76ml/min，法拉第效率98.55%，能源轉換效率73.16%  多電極：200mA/cm2@6.91V，電壓效率64.25%，產氫量228ml/min，法拉第效率98.83%，能源轉換效率63.47%

In this study, the main point is to develop and improve the efficiency of a SPE-type water electrolyzer. The design process starts with choosing the type of flow field and the material of electrode. First, verify the flow field by CFD software-FLUENT the grid type flow field forms a uniform flow field; Second, according to electrochemistry, a non-corrosive electrode has to be used in the electrolysis process. Titanium is a good electrode material that can stand in acid enviroment and anti-oxidation. So, the titanium plate with grid type flow field has been chosen. In the single-cell test, this study discuss the performance of the electrolyzer with different thickness of the proton exchange membrane, different nafion loading in the catalyst layer, different locking type of titanium plate and different catalyst loading on anode. The performance will be verified by voltage efficiency, Faraday efficiency and energy conversion efficiency. The multi-cell electrolyzer is designed on the basis of single-cell electrolyzer. A three-cell electrolyzer is built. Each cell’s performance has been shown by its IV-Curve. The product (hydrogen gas) has the purity 99.84%, which is tested by gas chromatograph(GC) and the Faraday efficiency is up to 98%. From the result of high purity and high Faraday efficiency of product gas, good sealing and unhindered flow field can be confirmed. The optimum performance of the electrolyzer in this study is:  Single cell: 200mA/cm2@2V, voltage efficiency 74%, hydrogen production rate 76ml/min, Faraday efficiency 98.55%, energy conversion efficiency 73.16%  Three-cell stack: 200mA/cm2@6.91V, voltage efficiency 64.25%, hydrogen production rate 228ml/min, Faraday efficiency 98.83%, energy conversion efficiency 63.47%