An electric eel-inspired hydrogel salinity gradient electricity generator with long-term power generation capacity...

Salinity gradient energy has garnered considerable attention as a sustainable clean energy source. However, the existing salinity gradient electricity generators suffer from low output voltage and current, along with a short power generation duration, which are mainly attributed to uncontrolled and rapid ion diffusion. Herein, a salt gel with a crystalline structure was employed to fabricate an electric eel-inspired hydrogel salinity gradient electricity generator (ESGEG) with a bilayer hydrogel architecture. Driven by ion diffusion via the ion concentration gradient between the two hydrogel layers and coupled with galvanic effects, a single ESGEG device delivers an open-circuit voltage of 1.50 V and a short-circuit current of 5.72 mA at 20 °C. Notably, the sodium acetate trihydrate (SAT) crystals in the top-layer salt gel act as a "salt mine" analog, enabling continuous and slow ion release and diffusion. Consequently, the ESGEG maintains stable power generation for up to 28 days. Moreover, the power density of the ESGEG is temperature-tunable based on the crystallization and melting behavior of SAT in the salt gel layer. Furthermore, the ESGEG can serve as a self-sufficient power source to drive commercial LED bulbs and power mice. This work proposes a facile and novel strategy for the fabrication of long-lasting salinity gradient electricity generators, which provides a new design paradigm for high-durability power generation devices.