A hierarchically porous reduced graphene oxide-based hydrogel for enhanced solar-driven wastewater treatment via...

Integrated photothermal evaporation-photocatalytic systems are promising for solar-driven water purification. However, due to inefficient carrier migration pathways and energy competition between photothermal conversion and photocatalytic oxidation-reduction reactions, the overall utilization efficiency of solar energy is severely weakened. Herein, a one-step hydrothermal method is developed to in-situ fabricate a reduced graphene oxide (rGO)/CoS/TiO₂ (RTC) hydrogel, which enables the synchronous reduction of graphene oxide to rGO, oxidation of MXene into TiO₂, and formation of CoS, thereby constructing an integrated heterostructure. More critically, the interfacial band alignment and the resultant built-in electric field between TiO₂ and CoS rationally modulate the charge transfer pathway, driving the directional migration and spatial separation of photogenerated electrons and holes. The charge transfer pathway promotes the recombination of low-redox-potential carriers for photothermal conversion and retains the separation of high redox carriers for surface redox reactions, thereby enabling an optimized allocation of solar energy for concurrent photothermal conversion and photocatalytic reactions. As a result, the RTC hydrogel achieves a high-water evaporation rate of 2.88 kg m^-2 h^-1 with an energy conversion efficiency of 94.4% under 1 sun illumination, while simultaneously removing over 95% of different dye pollutants. This work provides a novel strategy for addressing the energy-pathway mismatch in photothermal-photocatalytic integrated systems.