Ultrahigh solar vapor evaporation rate of super-hydrophilic aerogel by introducing environmental energy and convective flow

Abstract

The renewable solar energy provides one of promising pathways of interfacial vapor evaporation for freshwater resources with minimized carbon footprint. The high-throughput evaporation rate needs to be further achieved for the demand of practical application. Herein, a three-dimensional hybrid aerogel (rGP) with reduced graphene oxide (rGO) and polyvinyl alcohol phosphate ester (PVAP) was fabricated by hydrothermal method. The rGP aerogel had broadband light absorption ability and interconnected pore structure. This evaporator achieved fully hydrated state within 5 s due to the superabsorbent PVAP. The existence of intermediate water in rGP reduced the energy requirement for evaporation. The 3D aerogel also harvested additional energy from surroundings caused by evaporation cooling effect. Therefore, the rGP with height of 3 cm (rGP-3) achieved a higher evaporation rate of 4.89 kg m-2h−1 with the energy efficiency of 124.8% under 1 sun irradiation. The vapor diffusion could be assisted by convective flow and minimized the stagnation of vapor in the pores. Then the evaporation rate of rGP-3 increased to 16.22 kg m-2h−1 under the convective flow of 2.5 m s−1. Additionally, the 3D rGP can be consistently evaporated for 8 h in 3.5 wt% brine and no salt deposition occurred. More importantly, the evaporated fresh water from actual seawater was up to 156.30 kg m−2 in 8 h under outdoor sunlight and directional convective flow, which implied the remarkable potential in practical application. This rGP evaporation platform with 3D pore structure, high light absorption, efficient water activation, rapid water transport, extra heat collection, and effective vapor diffusion provides a new inspiration for designing high-throughput evaporators of superhigh evaporation rate and a large-scale application in desalination under convective flow.