Efficient solar-driven interfacial evaporation and desalination by a low-cost and durable biochar/melamine foam

• The one-step preparation of PBC@MF offered both simplicity and cost-effectiveness. • The evaporation rate of PBC2@MF was 2.58 kg m −2 h −1 with energy conversion efficiency of 113 % under 1 sun. • The evaporation rate of PBC2@MF was 6.68 kg m −2 h −1 in 3.5 wt% brine under 1 sun and 2.5 m s −1 of convection. • During the 14-day outdoor desalination period, the evaporation accumulation surpassed 35 kg m −2 d −1 on sunny days. In recent years, solar-driven interfacial evaporation is a popular technology for water evaporation and seawater desalination, and the cost-effectiveness evaporator is important for the potential application. Here, we employed a straightforward one-step technique to synthesize the polydopamine bound commercial biochar on porous melamine foam (PBC@MF). After optimizing the preparation conditions, the price of 3 cm height of PBC2@MF was just 0.1508 $ and the cost-effectiveness was 54.74 g h −1 $ −1 . PBC2@MF exhibited superior light absorption capability with a rate of 96 % and a lower water evaporation enthalpy of 1844 J g −1 , and the heat harvest from the surroundings enabled the evaporation rate of 2.58 kg m −2 h −1 and energy conversion efficiency of 113 %. The evaporation rate increased to 6.80 kg m −2 h −1 in pure water with the convection of 2.5 m s −1 and maintained at 6.68 kg m −2 h −1 in 3.5 wt% brine. In the outdoor experiments, the evaporation rate reached 7.63 kg m −2 h −1 at 13:00 in the closed directional convection system. As for the 14 consecutive days outdoor evaporation for seawater, the accumulated evaporation amounts were above 35 kg m −2 d −1 on sunny days. The three-dimensional PBC2@MF, characterized by the simple preparation, high light absorption, super hydrophilicity, efficient desalination, high cost-effectiveness, and long-time stability offers a promising approach for the potential application of solar-driven interfacial evaporation technology.