Preparation Of G-C₃N₄ Matrix Composite And Study On The Properties Of Photothermal Synergistic Catalysis

With the rapid development of science and technology in industry and agriculture,the earth environment that human beings rely on is facing more and more threats.The wide application of volatile organic compounds?VOCs?in daily life is the main source of pollutants in the atmosphere,which not only causes pollution to the ecological environment,but also seriously endangers human health.Therefore,it is urgent to study and develop new high-efficiency VOCs purification materials,new principles and new technologies.In the field of catalytic materials technology,photocatalysis technology and thermal catalysis technology are the two most mainstream technologies.However,thermal catalysis technology and photocatalysis technology have their own advantages and disadvantages in the field of catalysis.Compared with photocatalysis technology,thermal catalysis technology often has higher catalytic efficiency,but requires more energy consumption.Photocatalytic technology is environmentally friendly and energy saving,but the catalytic rate is often slow and the efficiency is limited.Therefore,it is hoped that the advantages of photocatalytic technology and thermal catalytic technology can be combined to prepare a catalyst with photothermal synergistic effect.In addition,at present,most studies on degradation of gaseous organic pollutants are carried out in a closed environment,while in real life,most of the pollutants are mobile.Therefore,this paper studies the degradation of mobile gaseous organic pollutants through a self-made experimental device to simulate the polluted environment in real life.This article selects the graphite carbon nitride?g-C₃N₄?as photocatalyst,selected do not have light catalysis of transition metal oxides?manganese base?with rare earth elements with the photocatalysis(cerium oxide as the hot catalyst prepared by one step high temperature firing of the two has the catalytic action of field composite catalyst?MnO_x/g-C₃N₄ composite catalyst and CeO₂/g-C₃N₄ composite catalyst?,succeeded in photocatalytic technology and thermal catalytic technology coupled together.Compared with the pure MnO_x catalyst prepared under the same conditions,the thermal catalytic efficiency of MnO_x/g-C₃N₄ composite catalyst was greatly enhanced.Not only that,MnO_x/g-C₃N₄ composite catalyst enters a concerted catalysis,compared with the single thermal catalysis,low-temperature catalytic efficiency enhanced obviously,the best active temperature range moved 30?low temperature zone,high temperature active interval extension,solar-thermal synergy effect is obvious.CeO₂/g-C₃N₄ compound compared with thermal catalytic light of catalyst,temperature 35?,reduces the low-temperature?100?-140??light of the catalytic rate for thermal catalytic rate four times,the best activity moved 70?temperature range to the low temperature area,Photothermal synergy effect is obvious.MnO_x/g-C₃N₄ composite catalyst as an example,its synergistic catalytic mechanism of field is:thermal catalytic comply with Mars-Van Krevelen mechanism of MnO_x is thermal catalytic center,and oxygen adsorption center,the whole process of reaction heat in the process of catalytic cycle is divided into two processes,reduction process for high state MnO_x?MnO₂?Mn₂O₃?react with IPA to produce acetone water and low state of MnO_x?MnO?,oxidation process for low state MnO_x?MnO?and surface adsorption oxygen reaction to generate high state MnO_x?MnO₂?Mn₂O₃?.During the oxidation reaction on the metal oxide catalyst,the oxygen in the gas phase is adsorbed on the surface of the catalyst,interacts with the surface ions and continuously obtains electrons,which change from the electron-loving O₂^-to the nucleophilic lattice oxygen O^2-.In the whole process,the adsorbed oxygen and the lattice oxygen can be converted reversible to form the thermal catalytic cycle.When MnO_x and g-C₃N₄ form heterogeneous junction,MnO in MnOx matches g-C₃N₄energy level,and photoexcitation of g-C₃N₄ produces photogenic electron hole pairs,which are bound by MnO_x lattice oxygen and participate in the oxidation of IPA to form more oxygen vacancies.However,photogenic electrons are transferred to the surface of MnO to form reactive oxygen species?ros?with surface-adsorbed oxygen.The co-oxidation of ros and ros with low-valent MnO accelerates the generation of high-valent MnO_x?MnO₂?Mn₂O₃?.In addition,the formation of heterojunction,light hole was MnO_x lattice oxygen,reduces the light carrier recombination composite,and with the increase of temperature,oxygen ionic conductivity increases,the rise of temperature accelerates the migration rate of oxygen ions,such photoproduction holes and electrons separation efficiency also increases,produce more light raw holes and electrons,involved in the catalytic process,and further enhance the catalytic efficiency.