Bio-Inspired 3D Substrates for Efficient Interfacial Solar Steam Generation: FeNi Nanoparticles-Coated Wood Sponge and Pine Cone for Sustainable Desalination

Interfacial solar steam generation (ISSG) is an emerging technology for sustainable water production, harnessing solar energy to desalinate seawater and treat wastewater. However, the development of efficient, cost-effective photothermal materials for these systems remains a challenge. This study investigates the use of FeNi nanoparticles (NPs) coated on bio-inspired substrates—wood sponge (WS) and pine cone (PC)—for ISSG. These substrates, enhanced for their high porosity and hydrophilicity, facilitate water transport via capillary action, whereas the FeNi NPs improve light absorption and photothermal conversion. Results show that both PC/FeNi and WS/FeNi demonstrate high evaporation efficiencies, with PC/FeNi outperforming WS/FeNi in terms of evaporation flux and stability across multiple cycles. The PC-based device achieved a solar evaporation flux of 1.73 kg m² h⁻¹ and an efficiency of 97.59% under 1 sun illumination, showing promise for large-scale desalination. Furthermore, both photoabsorbers effectively reduced ion concentrations in seawater, meeting WHO drinking water standards. This study highlights the potential of bio-inspired, 3D structured substrates like PC for efficient and sustainable ISSG applications.