A Multifunctional tannic acid–Fe3+–graphene oxide loaded alginate photothermal network: an interfacial water evaporator, a disinfector and a power generator

Abstract

The development of efficient photothermal materials with multifunctional capabilities is considered an effective approach for utilizing abundant free solar energy and exploring new concepts for prospective sustainable energy and environmental applications. A facile stepwise synthesis strategy for a tannic acid–Fe³⁺–graphene oxide impregnated alginate photothermal network (TA–Fe³⁺–GO–ALG) was developed through sonication assisted loading of tannic acid and Fe³⁺ into graphene oxide layers followed by impregnation of the whole assembly into an alginate polymeric network. The portable device fabrication involves simply coupling the developed TA–Fe³⁺–GO–ALG with a specially shaped water floater material. The TA–Fe³⁺–GO–ALG photothermal material exhibited remarkable proficiency of light to heat transformation of 87% under 0.5 sun solar illumination. The rate of water evaporation under favourable circumstances attained a maximum of 1.8 kg m² h⁻¹, indicating great feasibility for its implementation as a solar water purifier. The TA–Fe³⁺–GO–ALG photothermal material displayed excellent stability, recyclability, no photo leaching under different aquatic environments and could effectively produce potable water from real seawater and other simulated wastewater. A maximum increase of 70 °C in water temperature under 2 sun irradiation was achieved for sea water. Moreover, the developed TA–Fe³⁺–GO–ALG material also showed exceptional antibacterial efficacy towards E. coli, eradicating nearly 100% of bacteria when exposed to 0.5 solar irradiation. Spot assays as well as viability counts indicated the superior antimicrobial properties. The excellent photo-thermal conversion efficiency integrated with the Bi₂Te₃ based commercial thermoelectric module exhibited a good photo-thermoelectric effect. Its significant generation of Seebeck voltage has opened up avenues for its application towards solar-to-electricity conversion. Our effort delivers novel insights into the rational strategy of benchmark TA–Fe³⁺–GO–ALG based floatable photothermal devices with interfacial water evaporation, antimicrobial properties for sustainable water treatment and power generation through the photo-thermoelectric effect.