Preparation of mechanically robust Fe3O4/porous carbon/diatomite composite monolith for solar steam generation.

Mechanically robust Fe3O4/porous carbon/diatomite composite monolith was prepared from waste corrugated cardboard box and diatomite via slurrying in FeCl3 solution, dewatering, molding, and carbonization at 600 °C. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (SEM), N2-adsorption/desorption, Raman spectroscopy, and ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy. The water wettability, photothermal conversion property, and solar steam generation performance of the products were also evaluated. Results showed that the presence of FeCl3 led to the formation of more pores and magnetic Fe3O4 crystallites, while diatomite provided good hydrophilicity for the composite. The product exhibited light absorption above 65% within the wavelength ranging from 200 to1974 nm, and its surface temperature eventually increased by 30 °C under 0.25 sun irradiation due to photothermal effect. Moreover, solar steam yield under 0.25 sun irradiation for 3600 s was improved by 67% with the presence of the monolithic composite because of the occurrence of interfacial solar steam generation and heat transfer from the composite acted as a heat island.