Electrochemical Kinetic Energy Harvesting Mediated by Ion Solvation Switching in Two-Immiscible Liquid Electrolyte

Abstract

The potential of kinetic energy harvesting is highly promising; however, current existing methods, such as those based on friction and deformation, necessitate high-frequency kinetic energy and demand materials with exceptional durability. We report a new two-phase immiscible liquid electrolyte system comprising identical Prussian blue analogue electrodes for the electrochemical kinetic energy harvesting accommodating low-frequency kinetic input. This system demonstrates the electrochemical conversion of translational kinetic energy, associated with the displacement of electrodes across different electrolyte phases, into electrical energy. The system generated 6.4 μW cm-2 of peak electrical power, accompanied by 96 mV of peak voltage and 183 μA cm-2 of peak current density when connected to a load resistor of 300 Ω. The load is several thousand times smaller than those typically employed in conventional methods. Moreover, the proposed method supplied a continuous current flow of approximately 5 μA cm-2 at the frequency of 0.005 Hz for 23 cycles without performance decay. The disparity in solvation Gibbs free energy from the two-phase electrolyte, arising from the removal and subsequent re-establishment of solvation shells surrounding solvated cations, acts as the driving for both voltage and electron flow within the system. Furthermore, we successfully demonstrated the operational functionality of our system in a microfluidic harvester. By harnessing the conversion of kinetic energy to propel the electrolyte through the microfluidic channel, our system achieved a peak power density of 200 nW cm-2. We believe that the microfluidic harvester possesses the potential to provide power supply solutions for various applications, including environmental monitoring sensors and Internet-of-Thing (IoT) devices.