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

Abstract

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.

Salt Mitigation Strategies of Solar‐Driven Interfacial Desalination

“…In addition, various natural materials are increasingly used in SDID devices. Some of them use other materials with higher absorption to modify the biomass material to obtain a higher evaporation rate, [ 63,91 ] while others increase the light absorption by carbonizing the material to increase the evaporation rate. [ 92– 94 ] In conclusion, these operations are based on the hydrophilicity caused by the porous structure of the biomass material itself, it can quickly and massively complete the transportation of water and the backflow of salt ions to achieve salt mitigation strategies.…”

“…Such as PPy, it is also used to modify the evaporator to have high light‐to‐heat conversion performance. [ 72,91,97 ] In the meantime, metal nanoparticles exhibit strong light absorption and light‐to‐heat conversion capabilities due to their unique plasmon resonance effect. For example, Zhou et al.…”

Artificial Trees Inspired by Monstera for Highly Efficient Solar Steam Generation in Both Normal and Weak Light Environments

“…[ 12–15 ] The directional freezing method, porous foams, and plant materials are used to produce or provide large channels for water and steam transport. [ 16–21 ] Special structures, including the Janus structure, [ 22,23 ] interconnected structure, [ 24–26 ] and salt collection structure, [ 6,27,28 ] are designed to prevent salt from crystallizing, thus ensuring long‐term evaporation. Multilayer and hierarchical structures are designed to enhance the thermal and light management abilities of the evaporators.…”

Defect‐Induced Self‐Cleaning Solar Absorber with Full‐Spectrum Light Absorption for Efficient Dye Wastewater Purification

“…[ 2–5 ] In recent years, significant efforts have been made to develop solar absorbers and their structures with efficient photothermal conversion efficiency. [ 6,7 ] Many innovative materials with full‐spectrum light absorption, [ 8–10 ] periodic surface structures, [ 11,12 ] low heat conductivity, [ 13,14 ] water activation, [ 15–17 ] and salt‐rejecting performance [ 18–20 ] were proposed. In addition, hybrid systems based on solar‐driven water evaporation were also devised to solve energy and environmental issues jointly, such as solar steam sterilization, [ 21 ] water−hydrogen cogeneration, [ 22 ] water−electricity cogeneration, [ 23 ] and even water−electricity−hydrogen generation.…”