A Superhydrophobic Self-Cleaning Flexible Hydrogel for Solar Thermoelectric Power Generation

Solar energy is one of the most promising energy sources, and its effective use has been continuously attracting widespread attention. Here, a solar-power thermoelectric system with self-cleaning capability was introduced based on a hydrogel. The hydrogel is formed through the polymerization of acrylic acid and acrylamide, resulting in the formation of compact ion channels within its structure. The mixed solvent of dimethyl sulfoxide and ethylene glycol plays a crucial role in this process by generating a significant number of hydrogen bonds, which enables the hydrogel to retain water and possess exceptional strength. Based on the coupling effect of the aforementioned two characteristics, the hydrogel exhibits a stable and remarkable electrochemical reaction facilitated by the synergistic action of NaCl and Fe(CN)63–/4–. By leveraging the unique reaction mechanism within the hydrogel, we achieved significant improvements in multiple aspects of the system, including high Seebeck coefficient (2.1 mV K–1), excellent thermoelectric figure of merit (9.84 × 10–3), good electrical conductivity (1.6 S m–1), and low thermal conductivity (0.251 W m–1 K–1). Furthermore, the integration of superhydrophobicity using fluoridated carbon nanotubes endows the system with photothermal and self-cleaning capability simultaneously. Particularly, the power density can reach 3.3 mW m–2, which could lit the LED easily. Thus, this self-cleaning thermoelectric system represents a promising option for solar-energy-dependent outdoor solar energy utilization.