Preparation of a low-cost electric compensation photothermal evaporator for all-weather-available and efficient evaporation

Solar-driven evaporation is an ideal technology for freshwater production. However, in the actual production and application process, due to the fluctuation of solar radiant intensity, the limitation of solar lighting time and the generation of dirt, the solar evaporator can only work for a limited time. To realize the all-weather-available efficient application of the evaporator, we mixed slag, metakaolin, graphite, and potassium silicate evenly, added a certain amount of foaming agent, and adjusted its pore size and shape to prepare a low-cost electric compensation evaporator that can be used for all-weather-available efficient evaporation. The geopolymer in the evaporator acts as a support with good hydrophilicity, and graphite exhibits good photothermal performance. At 1 sun, the evaporation rate of the three-dimensional graphite/geopolymer composite (3D-GR/Geo) evaporator reaches up to 3.23 kg/m2/h, and its evaporation efficiency is 186.46%. When the solar-driven evaporation is assisted by an external electric field, the evaporation rate of the 3D-GR/Geo evaporator reaches up to 16.3 kg/m2/h. In addition, after 72 h of alternating tests at 1 sun and an applied current of 2A, no salt accumulates on the top of 3D-GR/Geo, and its quality change curve remains stable, showing excellent stability. This is also consistent with the simulation results, indicating that 3D-GR/Geo can be used effectively over a long period.