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Open Access Publications from the University of California

Stackable Miniature Fuel Cells with On-Demand Fuel and Oxygen Supply

  • Author(s): Hur, Janet
  • Advisor(s): Kim, Chang-Jin "CJ"
  • et al.

This dissertation summarizes our progress towards miniature fuel cells that could replace and outperform small batteries to meet various power demands. With increasing need of power being critical for portable electronics, the demand for better batteries continues to grow. Lithium-ion batteries dominate the market at the moment, but the current capacities on the order of 200 Wh/kg are approaching their inherent limits. Many researchers have being pursuing alternative power sources, forming a rapidly growing field in engineering and science. For applications too small for batteries (below 1 cm and even 1 mm), currently no proper power source is available, despite over a decade of significant efforts by many in power micro electromechanical systems (power MEMS).

Encouraged by the advantages of their macro counterparts, micro fuel cells have received attention as a potentially powerful, efficient, and clean power source for miniature applications, resulting in extensive research in micro fuel cells and even commercial introduction of some small fuel cells. However, they are not yet powerful enough to consider someday replacing batteries for a wide range of portable applications. While the promise of fuel cells is in their high theoretical energy density, unfortunately the promise is lost in current portable fuel cells because of their complex system that includes ancillary components such as mechanical pump, reformer, pressurized oxygen source, and gas separator.

This dissertation summarizes our attempt to realize a full (i.e., complete, standalone) fuel cell with small footprint, extending the spirit of self-pumped fuel that eliminated ancillary components in the active fuel circulation system to self-controlled oxygen generation for a packaged oxidant supply. We first eliminate fuel pump, gas separator, membrane electrode assembly (MEA) and even pressurized oxygen tank to make anodic chamber simple and self-regulating. As the next step towards realizing a full fuel cell stackable as batteries, we develop a self-regulating oxygen generation system that supplies oxygen within the fuel cell, i.e., not relying on the ambient air. For our final goal, we integrate the self-pumped fuel supply and the self-regulated oxygen supply into one device to prove the concept of a full fuel cell suitable for a stacked configuration.

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