Study On Bio-inspired Multi-scale Structure Design Of Carbon-based Solar-thermal Materials In Interfacial Evaporation System

Facing the increasingly serious global water scarcity and energy crisis,interfacial solar evaporation system is becoming an important research frontier due to its zero-energy consumption.However,compared to traditional desalination technologies,because of narrow solar spectrum absorption and low solar-thermal conversion efficiency of the solar-thermal materials,a low fresh water production rate of the system confines its further industrial application.Therefore,the key issue on lifting the water yield for system is the solar-thermal conversion property of solar-thermal materials,and multiscale structure design to the materials is an important solution.Surprisingly,many living creatures are adept to absorbing solar energy through their natural multiscale structure obtained from millions-of-years evolution.Inspired by the biomass in nature,in this thesis,with an interdisciplinary research strategy including engineering thermophysics and biological and bio-inspired engineering,we mainly focus on constructing bioinspired structures for the carbon-based solar-thermal materials as well as the energy conversion and mass transport in the device.1)Bio-inspired tree’s needles structure designed carbon-based solar-thermal materials:since the portability and low cost of solar thermal material are still challenges for its further practical implementation;besides,the fundamental understanding of thermal management on the effect of efficiency remains unclear.Herein,we demonstrate a novel bionic strategy to construct a solar thermal material of needles structure designed hierarchical carbon framework decorated by Fe₃O₄ nanoparticles as artificial chloroplast（Fe₃O₄@CA/CF）.Under 1 Sun irradiation(1 k W m^-2),the as-prepared bio-inspired absorber shows broad spectrum absorption（～99%）and outstanding water evaporation rate(1.316 kg m^-2 h^-1)with～91.0%efficiency,which is six times as that of water without absorber.Significantly,a marvelous volumetric water evaporation rate(up to 658 kg m^-3 h^-1)has been obtained,indicating its portable and cost-effective superiorities.Besides,for the first time,we quantitatively reveal a strong correlation between evaporation efficiency and porosity of 1D water path in isolation configuration through numerical simulation;the optimum range of porosity for evaporation is also identified.Combining low-cost materials,broad spectrum absorption,high solar thermal conversion efficiency and excellent portability,the as-prepared material is likely to be a promising absorber for solar interfacial evaporation system.2)Bio-inspired fractal structure designed carbon-based solar-thermal materials:since 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 rarely 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^-1with 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.