Large-scale production of spent coffee ground-based photothermal materials for high-efficiency solar-driven interfacial evaporation

Solar-driven interfacial evaporation is an emerging technology with promising solutions towards water scarcity. Nevertheless, many challenges remain in realizing its implementation including inefficient utilization of thermal energy and difficult to scale production. Herein, we develop a simple, low-cost and scale-producible photothermal material for high-efficiency solar-driven interfacial evaporation, prepared by functionalizing the delignified spent coffee ground (D-SCG) with polypyrrole (PPy) via in-situ growth of PPy nanoparticles. The PPy modified D-SCG (PPy@D-SCG) performed high evaporation rate of 1.54 kg m-2h−1 and solar-thermal energy conversion efficiency of 89.1 % under 1 sun illumination. Furthermore, we designed a 3D solar evaporator fabricated by utilizing the 3D printing technique, which took the thermoplastic composite filaments combining PPy@D-SCG and polylactic acid (PLA) as raw materials. The 3D solar evaporator demonstrated higher water evaporation rate of 1.81 kg m-2h−1 and photothermal conversion efficiency of 92.7 % than the previous reports data of natural materials-base solar evaporator, with the potential applications in the purification of wastewater containing organic dyes and heavy metal ions. It is anticipated that the developed SCG employ as cost-effective scalable 3D photothermal materials for point-of-use water purification in real-world scenarios.