Spent coffee ground-based interfacial solar steam generation

In this work, for the first time, spent coffee grounds (SCGs) were utilized for photothermal conversion. SCG-coated filter paper was obtained by a facile vacuum filtration method, then a floatable interfacial solar steam generation (ISSG) device was fabricated by wrapping expandable polyethylene (EPE) foam with the SCG-coated filter paper. The photothermal property and solar-driven evaporation performance of the ISSG device were investigated. Experimental results showed that there were graphitic π electrons in SCG and it exhibited light adsorption above 50% within the wavelength of 200–720 nm. The surface temperature of the ISSG device can finally achieve 63.2 °C under 0.25 sun irradiation, and the solar steam yield was enhanced by 0.56 times with the assistance of the floating ISSG device on bulk water surface. This study can provide a feasible technical support for the effective utilization of SCG and water treatment via low-cost ISSG process.