Salt-resistant hierarchically porous wood sponge coated with graphene flake/polyaniline nanocomposite for interfacial solar steam production and wastewater treatment

This research presents an innovative approach for developing a flexible wood sponge (WS) with a hierarchically porous structure. This unique structure is achieved through a sequential process involving balsa wood delignification, freeze-drying, and subsequent coating with graphene flake (GF)/polyaniline (PANI) nanocomposite. The resulting GF/PANI nanocomposite significantly reduces electron transfer resistivity, thereby enhancing heat generation for water evaporation. This results in self-cleaning photoabsorber, benefiting from GF’s salt-rejecting properties, PANI’s ionic network, and the WS’s porous structure. The photoabsorber demonstrates improved mechanical strength, reduced thermal conductivity, and a single water route design atop a drilled insulator foam, effectively minimizing heat loss during solar desalination. Under 1 sun (1 sun = 1 kW m⁻²) illumination, the photoabsorber achieves an impressive evaporation flux of 1.49 kg m⁻²h⁻¹ and a high solar to thermal efficiency of 95.51 %. Importantly, continuous 10-cycle testing under 1 sun illumination reveals no salt deposition on the surface. Furthermore, the photoabsorber demonstrates promising applications in wastewater treatment, effectively purifying dye-contaminated seawater and desalinating both acidic and alkaline seawater. The investigation into the GF/PANI nanocomposite’s effect on steam generation, conducted through electrochemical impedance spectroscopy in a 0.5 M Na₂SO₄ electrolyte, reveals enhanced interfacial charge transfer, surpassing both PANI and GF due to reduced electrochemical resistance. Evaluation of desalinated seawater and purified wastewater demonstrates a significant decrease in major cation concentrations, meeting WHO and EPA drinking water standards. These findings underscore the potential of the GF/PANI nanocomposite in superior steam generation applications.