Microstructured Cathode for Self-Regulated Oxygen Generation and Consumption

UCLA researchers have developed a cathode that generates oxygen, consumes the oxygen as needed, and stops the oxygen generation when it is not consumed, all in a self-regulated fashion.

Despite anticipated promise in high energy densities and efficiency, fuel cells have failed to reach practical applications for portable electronics primarily due to the inability to miniaturize the ancillary parts (e.g., pumps, valves, etc.) needed to operate the fuel cell and package them into a small space without eating up the volume for fuel. Removing all ancillary parts would allow a simpler design for fabrication, a more mechanically robust device, and a system with a higher energy and power density. Recent inventions have produced centimeter-sized fuel cells by removing ancillary parts, but these designs require access to ambient air and thus prevent the feasibility for stacking of the fuel cells for higher power output. In need of active oxygen supply within the fuel cell stacks, presented technology has been devised.

Researchers from the UCLA mechanical and aerospace engineering department have designed and fabricated a microstructured cathode capable of generating oxygen bubbles, consuming the oxygen bubbles as needed, and stopping the oxygen generation when it is not consumed all in a self-regulated fashion. The microstructure of the device is designed such that an electrolytic oxidant comes in contact with an electrocatalyst to generate oxygen bubbles via a reduction reaction. The cathode does not need pressurized gas tank, moving pumps or ambient air to introduce the oxygen and they can therefore be compactly stacked for higher power output. The system operates in a manner free of gravitational forces and thus may be used in non-stationary applications. The monolithic, self-regulating cathode is simple and mechanically robust, and would ideally be coupled with the recently developed monolithic anode (by the authors) that self-pumps the fuel.

Devices that generate and consume oxygen in a self-regulated manner have been fabricated and tested in electrochemical and visual experiments. Future work will focus on optimizing parameters such as hydrogen peroxide concentration, volume of stored hydrogen peroxide, and cathodic micropocket dimensions. Other future work will strive to implement the cathode into existing self-pumping fuel cells to realize a "true miniature fuel cell" that does not lack oxidant and self-regulates in both anode and cathode.