Bacterial cellulose-based dual chemical reaction coupled hydrogel thermocells for efficient heat harvesting

Reasonable and efficient utilization of low-grade thermal energy in nature is the choice for sustainable energy development. We demonstrate a bacterial cellulose (BC) hydrogel thermocell (TEC) based on BC electrolyte combined with carbon fiber paper and copper composite electrode sheets. The large specific surface area of carbon fiber paper provides a large number of active sites for thermoelectric ions, which drives the redox reaction inside the electrolyte and stimulates the chemical reaction between the electrolyte and the electrode. The combination of the two chemical reactions significantly improves the thermoelectric performance of the thermocell. The thermopower of the BC-TEC reaches 5.9 mV·K^-1 at a temperature difference of 50 K. The TEC consisting of 6-units in series produces an open-circuit voltage of about 2 V and a peak power of 535 μW. The TEC shows new potential and prospects in ambient thermoelectric energy conversion by rationally designing the power generation principle.