Fuel cells were once championed as viable alternatives to existing battery technology for energy storage. However, such hopes have not been realized due to poor assembly of the catalyst interface contributing to the meager performance of these devices. The research proposed here will use a new, integrated approach, combining the advantages of top down (microfabrication) with bottom up (electrostatic assembly) to obtain high-performance fuel cells. The work will integrate high-performance nanomaterials into a CMOS microfabricated fuel cell architecture, resulting in self-assembled nanomaterial/polyelectrolyte composites through water-based processing methods integrated into a silicon-based, microstructured fuel cell architecture.
Direct alcohol fuel cells (DAFCs) are of particular interest because of the high power density of renewable liquid fuels such as ethanol. The proposed fuel cell architecture will be achieved by etching microfluidic channels into a silicon-based substrate with integrated electrodes, heaters, and temperature sensors. The substrate will serve as a platform for the layering of the catalyst nanomaterials (e.g. decorated carbon nanotubes, polymers) on top of a monolithic, open face, fuel cell architecture. Exploration of the assembly methods as well as a comprehensive assessment of materials suitable for this approach would transform this field by creating next-generation power sources that can readily be integrated with electronic devices.
Intellectual Merit
The research is novel because it combines the advantages of top-down microfabrication with bottom-up electrostatic assembly to obtain unique fuel cell device structures. Furthermore, this research is potentially transformative because this new fabrication approach and its resulting device architectures have significant potential to make the breakthroughs needed to achieve high-performance alkaline fuel cells that convert ethanol, a renewable liquid fuel, directly to electricity for use in vehicles. Although the specific work will focus on alkaline direct ethanol fuel cells, the systems generated should prove to be applicable to hydrogen and bio-fuel cell systems.
The research plan incorporates top-down, bottom-up, and integrative approaches. First, in the top-down approach, an integrated monolithic microstructured fuel cell design will maximize bulk and surface micromachining processing capabilities originally developed for integrated circuits and MEMs devices. Design rules will be derived to capture operating conditions (e.g., flow rates and temperatures) and design parameters (e.g., channel length, electrode design, and active area) to maximize the performance of an individual microstructured fuel cell. Second, in the bottom-up approach, nanomaterials that exploit the advantage of superior electrocatalytic activity at both the anode and cathode will be employed, using carbon nanotubes decorated with transition metal catalysts. Third, in the integrative approach, the electrostatic layer-by-layer (LBL) assembly method will be used to generate ultrathin films (on top of the monolithic fuel cell) through the alteration of polycationic and anionic polymer/nanomaterial systems. This alteration will enable the nanoscale manipulation of thin film composition and the creation of molecular level blends that would be difficult to produce using conventional fuel cell assembly methods. Parameters (e.g. ionic strength and polyion composition) will be varied to generate a highly tuned membrane electrode assembly interface built directly on top of the integrated silicon based platform.
Broader Impact
In addition to the traditional interdisciplinary training of graduate and undergraduate students, web-based distance learning approaches will be used to reach a larger, broader audience of students from under-represented groups through a two-stage collaborative pipeline. The first stage is the development of electrochemistry modules for a Detroit High School chemistry class using YouTube, and the second is to have undergraduates at Armstrong Atlantic State University lead the design and development of a spray coat layer-by-layer deposition machine aimed to decrease the fabrication time of functional thin films used in the research. Other activities include development of modules for a course entitled Microelectrochemical Systems.
