Hierarchically Nanostructured Janus Membranes Toward Sustainable and Efficient Solar‐to‐Thermal Management

Abstract Solar‐enabled thermal management is emerging as a promising candidate to exploit green, low‐cost and efficient heat‐related applications, which has drawn extensive intensity for the development of solar‐to‐thermal materials with high‐performance and desirable functionality. However, there still remain considerable challenges, such as the sharp temperature fluctuations under water‐related environment, high cost, complex fabrication approaches and limited energy efficiency. Here, superhydrophobic and photothermal nanostructured Janus membranes composed of hierarchical candle soot and transparent polydimethylsiloxane is proposed in a simple, low‐cost, and effective way. The achieved membranes can readily adapt to curved surfaces and enable efficient solar‐to‐thermal capability of ≈68 °C under 1 sun and good water‐repellant property of ≈159.7. Therefore, it can still maintain stable temperature without remarkable temperature decline when exposed to the high‐moisture environment. Also, the asymmetric structure can further endow the membrane with declined heat dissipation for high‐performance thermal management. Moreover, it can further function as a self‐supported agricultural film to continuously heat the soils with stable temperature for efficient bean growth, demonstrating significant potential in the new generation of urban agriculture.