Directional‐Thermal‐Conductive Phase Change Composites Enabling Efficient and Durable Water‐Electricity Co‐Generation Beyond Daytime

Abstract Solar‐driven water‐electricity co‐generation (WEC) emerges as a viable solution to address global freshwater and energy scarcity. Phase change materials (PCMs)‐based WEC systems have been proposed to solve intermittent solar radiation issues. Nevertheless, WEC performances decline significantly leading to limited operating durations in dark. The study proposes a new concept of directional‐thermal‐conductive PCMs to address above challenges. By precisely regulating hydrophilicity/hydrophobicity distribution of Cu substrates, the structural disorder of boron nitride‐based PCMs is effectively tuned to achieve directional thermal transport. These directional‐thermal‐conductive PCMs exhibit a high phase transition enthalpy of 250.4 J g −1 and a large thermal‐conductivity anisotropy index of 3.24, which improves heat exchange between PCMs and photothermal/thermoelectric, and minimizes transverse heat dissipation simultaneously. Consequently, the directional‐thermal‐conductive PCMs‐based WEC achieves evaporation rates of 2.51 kg m −2 h −1 with power outputs of 1759.7 mW m −2 at 1 sun, among the best performance reported in the state‐of‐the‐art studies. More impressively, its evaporation rate still reaches 0.93 kg m −2 h −1 with a superior power output of 411.0 mW m −2 and a prolonged operation time of 90 minutes in nighttime, significantly surpassing previously‐reported devices with nondirectional‐thermal‐conductive designs. Finally, an omniphobic PVDF membrane is demonstrated that can improve the anti‐fouling performance of WEC systems for prolonged lifespan.