All‐In‐One Carbon Foam Evaporators for Efficient Co‐Generation of Freshwater and Electricity

Abstract Combining interfacial solar steam evaporation with power generation to produce freshwater and electricity is an effective approach to alleviating freshwater scarcity and energy crises. However, constructing low‐cost, efficient integrated evaporator‐generator devices remains challenging, and the synergistic mechanism underlying evaporation‐power co‐generation is not yet well understood. Herein, low‐cost carbon foam‐based bifunctional evaporators that effectively achieve freshwater and electricity co‐generation are designed. Carbon foam is obtained from waste polyester using a ball‐milling‐assisted carbonization strategy. The bifunctional evaporator demonstrates excellent water transport, outstanding sunlight absorption, and low evaporation enthalpy. It achieves an ultra‐high evaporation rate of 3.03 kg m −2 h −1 with a conversion efficiency of 99.4%. Additionally, it exhibits continuous high voltage (0.33 V) and current output (14.4 µA), surpassing the performance of state‐of‐the‐art carbon materials‐based evaporators/generators. The outcome of molecular dynamics simulations demonstrates that the stronger interaction of surface functional groups in carbon foam with Na + than Cl − results in the formation of flow potential, when exposed to sunlight, further insights into the synergistic mechanism of power generation. This study expands a new path for sustainable electricity and freshwater co‐production by collecting natural energy using single, low‐cost, carbon foam‐based functional evaporator devices.