Printed Honeycomb-Structured Reduced Graphene Oxide Film for Efficient and Continuous Evaporation-Driven Electricity Generation from Salt Solution

Water-evaporation-induced electricity generation provides an ideal strategy to solve growing energy demand and supply power for self-powered systems because of its advantages of a highly spontaneous process, continuous power generation, and low cost. However, the reported evaporation-induced generators are limited to working only in deionized (DI) water, leading to a low output power. Herein, we utilize a modified multiple ion mode to demonstrate that the streaming potential can be optimized in microchannels filled with salt solution and achieve an enhanced evaporation-induced output power in salt solution by a generator based on honeycomb-structured reduced graphene oxide (rGO) film with abundant interconnected microchannels. This generator enables an around 2-fold open-circuit voltage (V_oc) and a 3.3-fold power density of 0.91 μW cm^-2 in 0.6 M NaCl solution compared to that in DI water. Experiments evidence that the honeycomb structure with abundant interconnected microchannels plays a key role in achieving high and stable output power in salt solution because of its large specific surface area and excellent ion-exchange capacity. Notably, it can work at all times of day and night for more than 240 h in natural seawater, delivering a stable V_oc of ∼0.83 V with a power density of 0.79 μW cm^-2. This study expands a working solution for water-evaporation-induced electricity generation from DI water to natural seawater, advancing a great step toward practical applications.