硫化氫毒化現象對質子交換膜燃料電池性能影響之暫態分析

Abstract

本文旨在發展質子交換模燃料電池在陽極觸媒層受到燃料氣體中不純物質硫化氫毒化之數學模型，及探討其內部氫氣、硫化氫之濃度、白金表面覆蓋率、電流密度分佈的暫態行為。在陽極觸媒層內，由於硫化氫會與白金形成穩定的鍵結，造成氫氣的使用率下降。研究中主要是尋找各個參數範圍和影響，以及建立起模擬硫化氫毒化現象的反應項。此數學模型主要是考慮氫氣與硫化氫因吸附、脫附、電化學氧化行為以及新假設的硫化氫搶奪已吸附氫氣之白金表面項，造成在白金表面覆蓋率的改變，進而影響到電池的性能。 研究結果顯示，由結果圖形趨勢確定硫化氫毒化模式中必須考慮本文所假設的硫化氫搶奪已吸附氫氣之白金表面項和硫覆蓋率變化對硫化氫吸附反應速率常數的影響。用本文所建立之數學模型來預測，當通入的硫化氫濃度達5ppm時，電池達穩態時間僅800分鐘左右；硫化氫濃度為0.2ppm時，電池達穩態時間約21天；硫化氫濃度降到0.05ppm時，電池達穩態時間達81天；硫化氫濃度僅剩0.01ppm時，電池達穩態時間將有一年的可能性。在硫化氫濃度為0.2ppm時，通入純氫性能可回復，但效果不盡理想。

A new mathematical model was established to simulate the hydrogen sulfide poisoning effects on the performance of the proton exchange membrane fuel cell. The hydrogen sulfide poisons the anode reaction through preferential adsorbing to the platinum surface and the blocking of active sites of hydrogen. The discussions were focused on finding the range and effects of existing parameters, and on establishing new terms simulating hydrogen sulfide effect. The mechanism was described in terms of adsorption, desorption, electro-oxidation, and terms of hydrogen sulfide on capturing platinum surface from adsorbed hydrogen, by which the performance of PEMFC is affected. The results showed that it was necessary in the hydrogen sulfide poisoning model to evaluate the effect of hydrogen sulfide on capturing platinum surface, and also the effect of sulfide coverage on the parameter of hydrogen sulfide adsorption. The PEMFC duration was obtained for variable hydrogen sulfide concentration by employing this model. The cell duration was 800 minutes for 5ppm of hydrogen sulfide, 21 days for 0.2ppm, and 81 days for 0.05ppm. For 0.01ppm, the duration could be probably extended to about 1 year.