Enhancing the photothermal performance of polydopamine with sludge-based carbon dots and constructing a solar evaporation system with catalytic performance

Polydopamine (PDA), as a widely studied photothermal material, has been extensively applied in solar-driven evaporation systems. However, problems such as the low photothermal conversion efficiency of pure polydopamine have hindered its large-scale application. Meanwhile, the global scientific community is paying increasing attention to sludge, a large amount of solid waste. This work presents a novel sludge-upgrading strategy to enhance PDA's photothermal performance for constructing high-efficiency solar evaporation systems. A CDs@PDA@SA hydrogel was synthesized through the polymerization of dopamine hydrochloride and sodium alginate with a dialyzed solution derived from co-hydrothermal carbonization of sewage sludge and corn cob. Under 1 kW m−2 solar irradiation, the composite achieved an evaporation rate of 2.15 kg m−2 h−1. On this basis, a cup-internal light condensing system was constructed through cheap and readily available reflector materials. Under one sun, the evaporation rate reached 3.92 kg m−2 h−1. Meanwhile, the reactor could degrade volatile organic pollutants under the condition of adding PMS. Taking 10 mg/L phenol solution as an example, the purification rate of condensed water obtained by evaporation in the reactor is 49.6 %. This study promotes efficient and environmentally friendly solar interface evaporation technology through the synergistic effect of waste resource utilization and solar evaporation systems.