Thermocells Driven by Phase Transition of Hydrogel Nanoparticles

Area of Science:

• Materials Science
• Electrochemistry
• Energy Conversion

Background:

• Thermoelectric conversion is vital for the Internet of Things (IoT) and a carbon-free society.
• Low-temperature heat sources are abundant but challenging to utilize efficiently.
• Thermocells offer a low-cost, flexible approach to thermoelectric conversion, but require efficiency improvements.

Purpose of the Study:

• To develop highly efficient thermoelectric conversion using hydrogel nanoparticles.
• To explore the potential of hydrogel volume phase transitions for energy harvesting.
• To create a sustainable, non-toxic, and inexpensive energy source.

Main Methods:

• Utilizing entropically driven volume phase transition (VPT) of poly(N-isopropylacrylamide) nanoparticles.
• Generating pH gradients via VPT around physiological temperatures.
• Employing proton-coupled electron transfer (PCET) reactions of quinhydrone on electrodes.

Main Results:

• Achieved pH gradients of up to 0.049 and -0.053 pH K⁻¹.
• Obtained high Seebeck coefficients (S) of -6.7 and +6.1 mV K⁻¹.
• Demonstrated efficient thermoelectric conversion driven by hydrogel phase transitions.

Conclusions:

• Hydrogel nanoparticle VPT can drive efficient thermoelectric conversion.
• These thermocells provide a flexible, non-toxic, and inexpensive method for harvesting carbon-free energy.
• Potential applications include charging devices using solar, body, or waste heat.