Janus Co@C/NCNT photothermal membrane with multiple optical absorption for highly efficient solar water evaporation and wastewater purification

Solar-driven interfacial water evaporation has emerged as a promising approach for green and sustainable production of clean water to alleviate freshwater shortage, especially in remote and arid regions. However, limited photothermal conversion efficiency and poor water transport remain challenges to achieve highly efficient solar water evaporation. In this study, we propose a facile strategy to construct a novel Janus photothermal membrane by combining highly hydrophobic nitrogen-doped carbon nanotubes encapsulating cobalt nanoparticles ([email protected]/NCNT) with a hydrophilic nylon membrane, which enables simultaneous realization of asymmetric surface wettability and multiple optical absorption pathways. The as-fabricated Janus [email protected]/NCNT evaporator achieves a high solar water evaporation rate of 1.55 kg m−2 h−1 and an evaporation efficiency of 89.7% under one sun irradiation, which are well maintained after 10 cycles. Meanwhile, the Janus evaporator can be used for practical purification of various simulated wastewater, such as dyeing sewage and heavy metal wastewater, with high rejection efficiency and long-term stability. This Janus evaporator design provides an efficient, low-cost solar water evaporation system for potential water purification.