Study on the performance of salinity gradient power generation of sodium alginate/tannic acid-trivalent iron ion cross-linked modified evaporator based on nickel foam

Solar energy, as a renewable and clean energy source, is utilized to obtain freshwater and power generation, serving as a sustainable solution to address water scarcity and power shortages. This study proposes a strategy for power generation based on salinity gradients and designs an inclined composite evaporator. The evaporator features a nickel foam substrate functionalized through cross-linking of sodium alginate (SA) and tannic acid (TA) with trivalent iron ions (Fe 3+ ), enabling efficient electricity generation and freshwater production, named as SA/TA-Fe@Ni. (“Fe” indicates trivalent iron ions (Fe 3+ ) crosslinking) The TA-Fe 3+ coordination complex formed in situ on the evaporator surface appears black and exhibits excellent broad-spectrum light absorption capability. The evaporator is designed with an inclined configuration, which can significantly enhance the water transport performance. The enhanced evaporation flux establishes a stable salinity gradient at the interface, which constitutes the core driving mechanism for salinity gradient power generation. The inclined SA/TA-Fe@Ni evaporator achieves an evaporation rate of 2.14 kg•m −2 •h −1 under standard sun irradiation (one sun). It simultaneously demonstrates excellent seawater desalination and wastewater purification, while generating an open-circuit voltage of 83.7 mV. The system demonstrates outstanding salt tolerance, stability, durability, and environmental adaptability, fully demonstrating the potential of practical applications.