(35b) Testing of Electrode Durability for Extended Operation within An Alkaline Fuel Cell

Fuel cells hold promise as alternative power sources due to their ability to bypass Carnot efficiency limitations by directly converting chemical energy into electrical energy.  However, the high costs of catalysts and membranes, as well as component durability issues, have barred widespread implementation.  Alkaline fuel cells (AFCs) have gained increasing attention due to superior electrode kinetics in alkaline media, compared to acidic media, which enables the use of non-noble metal catalysts [1].  However, alkaline fuel cells are susceptible to flooding at the anode, which blocks gas diffusion and reduces catalyst utilization.  PTFE-bonded electrodes are standard in alkaline media, for both hydrophobicity to reduce flooding and stability; however, the sintering process required to produce these electrodes increases catalyst particle size, resulting in a decrease in catalytic activity [1].

Previously, we have developed a pH-flexible flowing electrolyte microfluidic fuel cell, which uses an external reference electrode to individually analyze cathode and anode performance.  This microfluidic configuration combines the versatility of a traditional three electrode cell with the conditions found in an operating fuel cell.  To date, typical analyses have consisted of short term experiments with a syringe pump supplying a liquid electrolyte.  Although this setup is valuable for short term experiments, long term experiments require a recirculating electrolyte, which is susceptible to dilution through water formation.  In addition, water buildup on the anode can cumulatively hinder the performance of the cell due to electrode flooding.  The effect of extended operation is not easily simulated using syringe pump experiments alone.

Here, we present long-term experimentation exploring the use of a hydrophobic additive in alkaline media.  The fuel cell is operated with a recirculating electrolyte, and full polarization curves are taken at regular intervals over the course of hours, revealing a full spectrum of insight into cell performance over time.  The use of the external reference electrode allows us to determine individual electrode performance over time, and the extent of degradation is quantified. 

[1] Brushett et al., Journal of the Electrochemical Society, 2009, 156, B565