Emulsions that Store Oxygen for Fast ORR Kinetics and Multifunctional Robotic and Mobility Systems

Abstract

Many processes such as catalysis, energy transport, and carbon capture rely on the transport or storage of gases in liquid phases, but the low solubility of gases in liquids limit the rate and efficiency of these processes. Human circulatory systems store large concentrations of oxygen and provide it continuously and simultaneously to trillions of cells without the need for each cell to access the surrounding environment. Inspired by biological circulatory systems, we envision future robotic systems with multifunctional, fully integrated, air-rechargeable energy delivery and storage. This paper presents a high-pH aqueous air catholyte emulsion (ACE) with high oxygen solubility so that metal-air batteries can derive energy entirely from dissolved oxygen. With only 20% silicone oil by volume, ACEs can store twice as much dissolved oxygen (15 mg/L) as pure KOH samples, remain stable for several months, and show superior oxygen reduction reaction kinetics compared to KOH. Zinc-air flow cells with fully submerged electrodes can achieve 4.6 mW/cm2 at 5.6 mA/cm2. A multifunctional actuator flow cell configuration employs an ACE as both a hydraulic actuator and energy storage fluid, demonstrating the feasibility of ACEs as multifunctional, flexible power sources for soft robotic systems.

Keywords: Multifunctional Energy Storage, Catholyte, Air Cathode, Flow Battery, Zinc Air Battery, Soft Actuators