Leveraging Hydrophilic Hierarchical Channels to Regulate Excessive Water for High-Efficiency Solar Steam Yield

Abstract

Both the solar absorptance and water content in solar-driven interface evaporation (SDIE) devices are of equal importance for efficient solar steam yield and freshwater production, but water content regulation has garnered relatively less attention, as it is more challenging to balance the water supply rate and the evaporation rate inside SDIE devices. Herein, an SDIE device is designed by coating natural luffa with polypyrrole, which could effectively regulate the water content during the solar steam yield by its unique hydrophilic hierarchical channels to transform excessive water from the bulk state into the film state on the porous skeleton. The hierarchical channels revealed by cryoelectron microscopy experiments not only reduce the loss of heat in unevaporated water but also offer abundant escape channels for solar steam, thus enabling the proposed SDIE device to achieve an evaporation rate of 2.38 kg m–2 h–1 under 1 sun illumination. This work reveals the key role of hierarchical channels for water regulation in the high-efficiency solar steam yield and triggers further application of natural biomaterials with unique structures in the field of solar interfacial evaporation.

Highly Effective Multifunctional Solar Evaporator with Scaffolding Structured Carbonized Wood and Biohydrogel

“…Solar evaporators have attracted much attention as an efficient technology for desalination and power generation. 1,2 A solar evaporator absorbs solar energy to generate heat at the water−air interface and converts water into steam to obtain clean water and energy. 3,4 The evaporation performance relies on the framework structure of evaporators, which usually have the following characteristics: 5,6 first, appropriate materials and structure are necessary for high solar energy absorption and photothermal conversion efficiency.…”

“…Water and energy shortages are the two major challenges in some developing countries. Solar evaporators have attracted much attention as an efficient technology for desalination and power generation. , A solar evaporator absorbs solar energy to generate heat at the water–air interface and converts water into steam to obtain clean water and energy. , The evaporation performance relies on the framework structure of evaporators, which usually have the following characteristics: , first, appropriate materials and structure are necessary for high solar energy absorption and photothermal conversion efficiency. , Second, the evaporator structure needs to be efficient for water transportation and robust to avoid channel clogging by salt crystallization . Third, the contact interface between the structure and water needs to be meticulously designed to achieve a high efficiency and versatility, which includes reducing vaporization enthalpy, regulating surface energy and temperature distribution, and realizing hydrovoltaic power generation. − …”

Recent advances in structural regulation and optimization of high-performance solar-driven interfacial evaporation systems

“…107 Polypyrrole (PPy) is the most commonly used photothermal organic polymer, and it is usually decorated on some substrate following in situ polymerization of pyrrole. [108][109][110] For example, the microwave-and alkali-treated corn straw coated with PPy had an evaporation efficiency of 96.8% under one sun. 111 In addition, polyaniline, [112][113][114] polydopamine (PDA) 17 and poly(3,4--ethylenedioxythiophene) 115 have also been used in SIE applications.…”

Sustainable Self-Cleaning Evaporators for Highly Efficient Solar Desalination Using a Highly Elastic Sponge-like Hydrogel

“…According to current research advances in salt rejection strategies for interfacial solar evaporators, , the construction of salt exchange pathways with bimodal pore channels or bimodal vertical microchannels to facilitate salt redissolution into the bulk water has shown to be an effective strategy in preventing salt accumulation in various interfacial solar evaporators. Examples include drilled wood/biomass − and porous foam/sponge materials. − However, highly interconnected 3D bimodal porous structures have been shown to enhance salt solution exchange while introducing more water, resulting in more heat loss. − Therefore, constructing hydrogels with a bimodal pore structure while minimizing heat loss is the key issue that needs to be addressed. In addition, to meet the requirements of practical applications, hydrogel-based solar evaporators must have good toughness and elastic compressibility properties, as well as low-cost raw materials and simple preparation processes.…”