Controlled Self‐Assembly and Photo‐Thermal Activation of Viologen‐Based 2D Semiconductors for Dual‐Function Energy Management in All‐Weather Applications

Abstract

Solar thermal technology offers a promising solution to water scarcity; however, the continuous operation of solar evaporators remains challenging due to sunlight's intermittent availability. Herein, an alternative strategy is proposed to achieve dual-functional energy management of photo-thermoactivated viologen T semiconductors for enhanced solar water evaporation, water-enabled electricity generation, and electrothermal evaporation. A sequential cyanide-bridged layer-directed intercalation approach is developed, where infinitely π-stacked, redox-active N-methyl bipyridinium cations with near-planar structures are sandwiched between cyanide-bridged Mn^II-Fe^III. The extended absorption range of 95% is achieved through radical-π interactions that occur within the continuously π-stacked N-methyl bipyridinium units upon thermal activation. The photo-thermoactivated Mn^II-Fe^III compounds anchored charcoal mask (Mn^II-Fe^III@CM) with a sided evaporation structure and controllable water transfer, offering a high evaporation rate of 2.39 kg m^-2 h^-1 under one sun (1 kW m^-2) illumination. As an energy nanogenerator, the output voltage and current of Mn^II-Fe^III@CM can reach up to ≈480 mV and ≈60 µA cm^-2 under ambient conditions. Furthermore, storage of electrical energy from Mn^II-Fe^III@CM using energy storage devices is expected to enable all-weather evaporation by electric heating due to unsustainable sunlight, providing a unique technology for seawater desalination and offshore work platform energy access.