Effects of Nafion^®Dehydration in PEM Fuel Cells

Performance Improvement by Temperature Control of an Open‐Cathode PEM Fuel Cell System

“…Hence, there is a tradeoff between increasing temperature and water content in order to optimize ionic conductivity. However, as shown in experiments of [9] and [10], the change in the ohmic losses due to temperature is only responsible for a relatively small part of the voltage increase/decay, shown in chapter 2. The major part is related to changes in the activation polarization losses.…”

“…For instance, a positive temperature step of 2 ºC, as depicted in Figure 2, results in a theoretical stack voltage gain of 86 mV only due to the increase of i 0 by 17%. However, the capability of improving performance by increasing temperature is limited due to drying of the cathode catalyst layer by elevated temperatures and the related loss of active sites [9], as shown in the experiment. Moreover, the dynamic of the temperature related drying effect on fuel cell voltage is very slow and strongly dependent on the operating conditions.…”

Experimental analysis of a degraded open-cathode PEM fuel cell stack

“…This indicates a reduction in the number of available active sites in the catalyst layer. That this is not a reversible degradation, due to a possible lack of humidification in the catalyst layer, is shown by the change in the phase diagram of cell 2 in Figure 6(b), which indicates a change in the dielectric properties of the double layer capacity [2].…”

“…The oxygen concentration oscillates continuously in saw tooth shape about +/-0.05% around a set point of 20.8%. The voltage peaks represent activation of catalyst sites due to higher water content in the cathode catalyst layer, as described in [2], since these spikes cannot be observed at dry conditions. This phenomenon is only present in cell 2, which indicates the advanced catalyst degradation of this cell.…”

Evaluation of polymer electrolyte membrane fuel cells by electrochemical impedance spectroscopy under different operation conditions and corrosion

“…Yuan et al [1] reported EIS has already become a primary tool in PEMFC research. EIS method is also used effectively for analyses of the amount of catalysts [2][3][4][5], nafion content [3,[6][7][8], membrane thickness [9,10], GDL structure [11][12][13][14][15][16][17][18][19], proton conductivity [20][21][22][23][24][25][26], humidification condition [3,9,[27][28][29][30] and stack [24,[31][32][33][34][35][36]. For example, Paganin et al [2] and Song et al [3] suggested that charge transfer resistance is much smaller with increasing amount of catalysts.…”