Simultaneous solar-driven seawater desalination and spontaneous power generation using polyvalent crosslinked polypyrrole/alginate hydrogels

Sustainable green energy technologies have paid much attention to the development of a solar-driven seawater desalination technique due to its ecofriendly and efficient desalination performance. We propose a novel hybrid hydrogel consisting of conducting polymer of polypyrrole (PPy) and polyvalent cations crosslinked alginate (Alg) with strong repulsive force for simultaneous seawater desalination and electricity generation. The strong repulsive force of polyvalent cations crosslinked with Alg selectively rejects salt cations by inducing reverse salinity gradient against the rapid evaporation-induced salt accumulation on the upper surface of the solar evaporator. The proposed PPy–incorporated Alg (PPy/Alg) hydrogel exhibits an evaporation rate of 1.15 kg h−1 m−2 with a conversion efficiency of 54.12% under 1 sun solar irradiation. In addition, this hydrogel has an excellent crystalline antifouling property, and can be easily scaled-up with maintaining solar desalination performance. Depending on the compositions of PPy and Alg, the spontaneous electricity generation is largely affected by the balance between the decreased salinity gradient by the accumulation of salt cations and the increased salinity gradient by the strong repulsive force. The present results would pave a novel way for the development of sustainable electricity generation in combination with solar-driven seawater desalination by a facile methodology and energy-friendly process. •Al3+ or Zr4+ crosslinked alginate composites with polypyrrole were fabricated.•The composite efficiently desalinates seawater with solar irradiation.•The composite has crystalline antifouling property and is easily scaled up.•Electricity is spontaneously generated via salinity gradient and cation rejection.