Preparation And Properties Of Biochar-based Photothermal Conversion And Photocatalytic Materials

At present,energy shortage and environmental pollution have become two major global problems,and looking for green,clean and renewable energy has become the main way to solve the two problems.In recent years,solar energy as a kind of inexhaustible clean energy has received more and more attention.In the current research,the use of solar energy is mainly concentrated on the following aspects:solar photothermal conversion,solar photoelectric conversion and solar photochemical conversion,but no matter what form of conversion,the first problem is the capture of solar energy.On the one hand,natural plants themselves contain a lot of pigment can effectively absorb light;On the other hand,the porous structure inside the plant can effectively trap light,and the combination of the two makes the plant itself have efficient light absorption effect.Biochar materials not only retain the light trapping structure of natural materials,but also the biochar materials obtained through carbonization basically appear black,so it presents broadband light absorption,so it can be used as an ideal solar energy conversion material.In this study,starting from the utilization of solar energy,biochar as the research object,solar photothermal conversion and photocatalytic degradation of organic matter as the research content,the preparation of biochar based functional materials,and their performance was tested.First,inspired by the anisotropic surface of lotus leaves,we prepared biochar based bionic layered hybrid photothermal conversion materials.First,we chose the hydrophilic cotton cloth as the substrate,and selected the biocar powder as the light absorbing material to be supersonic loaded on the cotton cloth.Then,Nafion was used as hydrophobic modification on one side to obtain the bionic layered hybrid photothermal conversion material with Janus structure.Finally,the wavy bionic hybrid photothermal conversion material（w-cotton cloth-NCC）was obtained by folding for water purification.The biochar powder’s irregular structure and macroscopic folding structure make it have a high light absorption rate more than 95%.In addition,the water evaporation efficiency of the photothermal conversion material prepared by us can reach 1.88 kg m^-2 h^-1 and show long-term cycling stability,it also shows excellent performance in seawater evaporation and the evaporation efficiency is 1.52 kg m^-2 h^-1.The biochar based bionic layered hybrid photothermal conversion material prepared by us also shows good effects in wastewater containing organic pollutants and bacteria.The removal rate of rhodamine B is up to 98.3%and the removal rate of bacteria is more than 99.9%.Therefore,w-cotton cloth-NCC shows better solar interfacial evaporation performance by improving water transfer,enhancing light absorption and reducing heat loss.Secondly,inspired by the porous structure of plant leaves can effectively trap light,the biochar-based Au/ZnO multilevel structure photocatalyst was prepared by carbonized spinach which preserved the structure of plant leaves.We choose spinach leaves with a typical hierarchical structure as raw materials,obtain a biochar substrate by high-temperature carbonization,and then grow ZnO nanorods and Au nanoparticles on carbonized spinach to obtain carbonized spinach@Au/ZnO（CS@Au/ZnO）three element hybrid photocatalyst.The approximation of the biochar framework can enhance light absorption and further accelerate the transfer of photogenerated electrons.Modification of ZnO and Au can broaden the light response range,reduce the probability of electron-hole recombination and improve the catalytic efficiency.We measured that its degradation of rhodamine B（Rh B）and ciprofloxacin（CIP）were 97.3%and 61.0%,respectively,and the current density was 63.6μA/cm²,and the H₂production efficiency was 2.384 mmol g^-1h^-1.Therefore,the biochar-based Au/ZnO multi-level structure photocatalytic material prepared by us has shown good application prospects in the field of photocatalytic degradation of organic pollutants and photocatalytic H₂ production.Finally,inspired by the effective adsorption and light trapping effects of the porous structure of the sponges,a biomass aerogel with reduced graphene oxide（r GO）partially modified loofah（HLS@r GO-3）was prepared.The hydrophilicity of the loofah sponges guarantees effective water transmission during the photothermal conversion process,and the hydrophobic r GO aerogel not only guarantees high light absorption characteristics,but its hydrophobic characteristics also enable the material to have good applications in the field of seawater desalination.We measured that the pure water evaporation rate of the biomass aerogel was 1.77 kg m^-2 h^-1,and the seawater evaporation rate was 1.53 kg m^-2 h^-1.In addition,we also tested the photothermal degradation of organic pollutants and photothermal sterilization performance of the binary hybrid photothermal conversion material.The efficiency of photothermal degradation of organic pollutants and photothermal sterilization can reach more than99%.Therefore,our reduced graphene oxide aerogel partially modified loofah binary hybrid light-to-heat conversion material shows excellent application prospects in the field of sewage purification.