Bioinspired Fractal Design of Waste Biomass‐Derived Solar–Thermal Materials for Highly Efficient Solar Evaporation

Abstract

Solar evaporation is considered a promising technology to address the issue of fresh water scarcity. Although many efforts have been directed towards increasing the solar-thermal conversion efficiency, there remain challenges to develop efficient and cost-effective solar-thermal materials from readily available raw materials. Furthermore, further structural modification of the original biomass structure, particularly at multiple length scales, are seldom reported, which may further improve the solar-thermal performance of these material systems. Herein, a novel low-cost system is developed based on a common bio-waste, pomelo peels (PPs), through a bioinspired fractal structural design strategy, fractal carbonized pomelo peels (FCPP). This FCPP system shows an extremely high solar spectrum absorption of ≈98%, and marvelous evaporation rate of 1.95 kg m −2 h −1 with a solar-thermal efficiency of 92.4%. In addition, the mechanisms of the evaporation enhancement by fractal structural design are identified by numerical and experimental methods. Moreover, using FCPP in solar desalination shows great superiority in terms of cost and its potential in sewage treatment is also studied. The present work is an insightful attempt on providing a novel proposal to develop bio-waste-derived solar-thermal materials and construct biomimetic structures for efficient solar evaporation and applications.

Biomimetic Ultra‐Black Sponge Derived from Loofah and Co‐MOF for Long‐Term Solar‐Powered Vapor Generation and Desalination

“…The efficiency calculated according to the energy loss analysis and the efficiency calculated according to the efficiency calculation formula (Experimental Section) can be considered as matching within the error range. The water evaporation rate and photothermal conversion efficiency of BUBS are higher than those of most recently reported photothermal materials, including plasmonic materials, [ 26,57 ] semiconductors, [ 27,28,58–60 ] carbon materials, [ 36,40,61–64 ] polymers, [ 65,66 ] and MXene [ 49,52 ] (Figure 4f and Table S1, Supporting Information).…”

“…Solar‐powered vapor generation and desalination, which is an economical strategy that mainly utilizes solar energy and ultra‐black materials with efficient light absorption and photothermal conversion properties in solar band, is used to powerfully accelerate the evaporation of water and collect water and thereby solve the crises of drinking water shortage and water pollutions. [ 18–21 ] In the last few years, some evaporators based on different photothermal materials such as metal nanoparticles, [ 22–26 ] semiconductors, [ 27–30 ] polymers, [ 31–35 ] carbon materials, [ 36–48 ] and MXene [ 49–52 ] have been reported. However, most evaporators with high water evaporation rates and photothermal conversion efficiencies have some limitations in practical application scenarios, such as the use of expensive metals (Au and Ag) to enhance light absorption and photothermal conversion, strict and complex preparation processes to achieve microstructural control, and poor durability when used for solar‐powered desalination.…”

Confinement Capillarity of Thin Coating for Boosting Solar‐Driven Water Evaporation

“…[ 7,9 ] The first is to develop photothermal materials with a high spectral absorption across the entire solar spectrum, including metallic materials, [ 10–16 ] semiconductors, [ 17–20 ] polymer, [ 21–26 ] and carbonaceous materials. [ 27–35 ] The second is to design 3D evaporator to maximize the use of heat or increase the surface area. [ 36–47 ] Although progress has been made in the two strategies, there are still some inherent obstacles to be resolved for further improvements in evaporation rate and efficiency.…”

An Easy‐to‐Fabricate 2.5D Evaporator for Efficient Solar Desalination

“…[4][5][6] There are several design factors that have been considered to significantly raise the effectiveness of 2D evaporator designs, including using photothermal materials with broadband optical absorption, [7,8] minimizing heat loss to the water sink and ambient environment, [9] and implementing an efficient water transport path. [10,11] More recently, a flood of 3D evaporator designs have exhibited evaporation performance far exceeding the theoretical limit regarding to 2D structure designs, because 3D structures allow for a reduction of diffuse reflection and heat loss, [12][13][14] a large expansion of the evaporation surface area, [15][16][17] and utilization of side areas which obtain energy from the ambient surroundings. [18] Currently most 3D evaporators focus on recovering heat lost by the solar absorber surface.…”