Ultralight Biomass Porous Foam with Aligned Hierarchical Channels as Salt-Resistant Solar Steam Generators

The creation of solar steam generators with both high energy conversion efficiency and desired salt resistant performance is essential for practical desalination. Herein, we report for the first time the fabrication of polypyrrole-coated biomass porous foam as efficient solar steam generators. The as-prepared foams possess a low thermal conductivity of 0.022 W M-1 K-1 for alkali-treated corn straw (CSA) and 0.027 W M-1 K-1 for both microwave and alkali-treated corn straw (CSMA). Based on their high light absorption (95-100%), superhydrophilic wettability, excellent thermal insulation, and unique aligned channels, the foams show excellent energy conversion efficiency of 89.74, 91.08, and 91.54% for the polypyrrole-coated CSA (P-CSA) and 96.8, 97.05, and 98.32% for the polypyrrole coated CSMA (P-CSMA) at light intensities of 1, 2, and 3 kW m(-2), respectively. Importantly, thanks to their aligned hierarchical channels, our generators show extraordinary salt-resistant performance, e.g:, the energy conversion efficiencies of P-CSA and P-CSMA were measured to be 62.30 and 94.7% in 20 wt % NaCl at 1 kW m(-2) irradiation, respectively. Furthermore, no obvious salt accumulation was observed after 30 d of continuous operation at real sunlight irradiation, implying an outstanding long-term stability for practical solar steam generation.