Self-assembled aerogel sheet electrodes of thermocells for low-grade heat harvest

Efficiently harvesting low-grade heat is crucial for sustainable energy management. Thermocells (TECs), inducing heat-to-electricity conversion via the thermogalvanic effect, have thus drawn tremendous attention in recent years. This study introduces a self-assembly approach for fabricating aerogel sheet electrodes (ASEs) tailored for TECs. The crafted ASEs retain a remarkable porous architecture with approximately 95% porosity, even with their slimmed-down thickness. Results reveal that the electrode composition has minimal influence on the thermopower of TECs. Notably, the porous ASE with tunned composition demonstrates an optimal effective surface area for the thermogalvanic effect, resulting in enhanced output current density. This balances the desirable traits of electrode compactness with abundant redox active sites, positioning it favorably against conventional bulky electrode designs. The TECs utilizing the optimized ASE achieve a peak output power of 22.10 µW cm −2 under a temperature difference of 30 K. Furthermore, a tubular TEC device is readily assembled and specially designed for harvesting heat energy from hot fluids. These findings underscore the potential of composite electrodes in the realm of low-grade heat harvest, paving the way for broader applications in sustainable energy solutions.