Boosting solar vapor generation and desalination by low-cost reduced graphene oxide/cellulose aerogel and multiple energy utilization

Abstract

Solar interfacial vapor generation provides one of promising pathways for seawater desalination and wastewater treatment with minimized carbon footprint. There are still great challenges in architecting low-cost solar evaporators for rapid water transfer channels and high-throughput evaporation rate. Herein, an aerogel with reduced graphene oxide and cellulose nanofibers (rGC) was fabricated by one step self-assembly method. The rGC possessed excellent light absorption, superhydrophilic ability, and reduced energy requirement of water evaporation. The evaporation rate of rGC-3 (height of 3 cm) achieved 3.19 kg m−2 h−1 with the evaporation efficiency of 114.3% under 1 sun irradiation. The suspended vapor was timely diffused by directional convection, so as to minimize the stagnation of vapor in openly channels and continuously harvest additional environmental energy. The water evaporation behavior was improved to 9.40 kg m−2 h−1 under a convective flow of 2.5 m s−1, well beyond 200.3% of non-convective condition. Additionally, the three-dimensional rGC-3 consistently evaporated in 3.5 wt% brine and the evaporation rate kept at 8.61 - 9.39 kg m−2 h−1. In the outdoor solar water desalination, rGC-3 had excellent desalination behavior and evaporative performance in weak sunlight and relative low temperature. The realization of enhanced evaporation rate, overall seawater purification capability, and high cost-effectiveness of the nanofiber aerogel provide a new inspiration for designing high-throughput solar interfacial evaporator.