High-Performance Janus Solar Evaporator for Water Purification with Broad Spectrum Absorption and Ultralow Heat Loss

Interfacial solar vapor generation offers a promising zero-CO2-consuming energy conversion technology for the production of renewable clean water. The key for boosting solar vapor efficiency relies on the rational design of materials composition and structure at the micro/nanoscale to improve light utilization. Here, we demonstrate a Janus evaporator based on a hydrophilic carbon-black-decorated copper oxide (C@CuO) membrane as the light-absorbing layer and an opposite hydrophobic polymer nanofibers as the thermal insulation layer, which enables efficient energy utilization and vapor generation through a synergistic light absorption and thermal confinement strategy. In addition, the hydrated C@CuO surface reduces vaporization enthalpy that accelerates the efficient evaporation of water. A high evaporation rate of 1.88 kg m–2 h–1 is achieved by the Janus evaporator under 1 sun irradiation. This high photothermal conversion rate and ultralow heat loss synergistic engineering offers a bright future for high-efficiency solar water purification applications.