Increasing fuel cell run time by preventing precipitation of reactants or products in direct sodium borohydride fuel cell

摘要

This work aims to maximize usable run time of direct sodium borohydride / hydrogen peroxide (NaBH4 / H2O2 ) proton exchange membrane fuel cell, given a fixed volume of fuel solution . In the fuel cell being developed here at the University of Illinois, there is a need to manage water flow so as to avoid reaching solubility limits of reactants as well as products, which dominate the fuel cell run time. The model for solubility is built on solubility product and common ion effect theory. Hence, the model not only considers the decrease of water in the solution but also considers the effect on solubility limit of both reactant and product due to dynamic formation of NaBO2, utilization of NaBH4 and presence of NaOH; which is used to stabilize the NaBH4 solution to keep it from producing H2 gas. A voltage current model has also being incorporated to enhance our model by studying variation in voltage and current with time and reflecting back the values for realistic run time calculation for constant power usage. Our model predicts an improvement in fuel cell run time with optimum water addition. This would require additional water management schemes as discussed in the work.