Passive Fuel Delivery in Direct Methanol Fuel Cell by Surface Tension Driving Effect

Abstract

Nowadays, there is tremendous interest in direct methanol fuel cells (DMFCs) as a potential replacement to current lithium-ion battery for portable electronics due to their high power density, efficient and environment friendly operation. However, conventional fuel supply methods either with diluted methanol stored or driven by an attached active pump degrade their power density or efficiency dramatically. The active components also represent a considerable parasitic system loss adding complexity while consuming a significant part of power output which getting more severe in micro-scale DMFCs. In this paper, a passive fuel supply component with surface tension driving effect was designed and assembled in a laboratory-made DMFC prototype. The unidirectional methanol-to-water flow through Teflon PTFE membrane was achieved smoothly in its capillaries depending on their different surface tension. The prototype was demonstrated to last a largely extended operating time and exhibit higher fuel efficiency with pure methanol storage and passive fuel delivery compare to conventional DMFCs. The fluctuant output performance during its operation revealed that precise surface tension and geometry modification on further micro DMFC design is necessary. An improved model was then developed to facilitate instruction on such modification to achieve high cell performance. The passive surface tension driving fuel delivery effect demonstrated here is believed more applicable for the micro scale DMFC development.