Recent developments in passive direct methanol fuel cells

Abstract

Direct methanol fuel cells (DMFCs) are in the Energy Agenda due to their market potential to replace the conventional batteries in portable applications, either for recreational, professional, military and medical purposes, since they enable the direct conversion of the chemical energy stored in a fuel, methanol, to electrical energy with water and carbon dioxide as final products. Moreover, DMFCs offer higher energy densities than batteries, longer runtime, instant recharging, use a liquid fuel, operate at room temperature and can rely on a passive flow of reactants, allowing to operate the cell without any additional power consumption. Therefore, in the last years, the passive DMFCs systems, where the fuel and the oxidant are feed in a passive mode, have been studied and some progress towards its commercialization has already been achieved. However, the current systems still have higher costs, lower durability and power outputs due to the slow electrochemical reactions, water and methanol crossover and an inefficient products removal from the anode (gaseous carbon dioxide) and cathode sides (liquid water), which may hinder the fuel and the oxidant supply to the reaction zone. This chapter discusses the key work done in order to improve the passive DMFC performance based on the challenges of this technology. The main goal is to provide a review on the most recent developments in passive DMFCs and on the recent work concerning the optimization of the operating and design conditions and on empirical and fundamental modelling. This chapter starts by a brief introduction recalling the passive DMFCs technology followed by a description of the fundamentals of these systems. Then an intensive review on the recent experimental and modelling works performed with these cells is presented. Towards the introduction of passive DMFCs in the market, studies regarding its lifetime and durability, as well as a cost benefit analysis where this technology is compared with the traditional ones is also presented.