Galactomannan/graphene oxide/Fe3O4 hydrogel evaporator for solar water evaporation for synergistic photothermal power generation

With the increasing scarcity of freshwater resources and electricity, solar water evaporation and photothermal power generation are effective ways to solve energy shortages by utilizing renewable sunlight. However, current solar evaporators have low mechanical strength and evaporation rate. In this study, an interpenetrating network hydrogel evaporator with high mechanical strength, high water evaporation rate and photoelectric conversion performance was developed using galactomannan (GG), polyacrylamide (PAM), graphene oxide (GO) and Fe3O4 nanoparticles (Fe3O4 NPs). Among them, PAM forms a three-dimensional cross-linking network structure with crosslinking agents, while the cis hydroxyl groups on the mannose branch chain in GG form a borate ester bond cross-linking network, enhancing the mechanical properties of the system; The GO and Fe3O4 NPs uniformly dispersed in the evaporator can provide significant photothermal conversion efficiency for water evaporation. Under 1 sun irradiation, the water evaporation rate reaches up to 2.3 kg m−2 h−1 and conversion efficiency is 90.7 %. In addition, the combination of the hydrogel and the thermoelectric device module achieves thermoelectric conversion with a power density of 0.46 Wm−2. Excluding losses in practical applications, the combined equipment could in the future heat the collected water to the required temperature to cope with extreme environments.