Photocatalytic Production Of Hydrogen Peroxide Based On Carbon Nitride Materials And Its Application

Hydrogen peroxide（H₂O₂）is widely used in environmental remediation,organic synthesis and other fields because it only generates pollution-free water in the oxidation-reduction progress.At the same time,due to the existence of peroxide bonds in hydrogen peroxide,it can destroy the nucleic acid structure of bacteria and other microorganisms and inactivate them,so it has broad prospects in food and pharmaceutical industries.The traditional anthraquinone method and other industrial methods for preparing H₂O₂have disadvantages such as high energy consumption,large amount of organic solvents and complex processes.Photocatalytic technology is an efficient and environmentally friendly method for producing H₂O₂ in recent years.The use of semiconductor carbon nitride for photocatalytic hydrogen peroxide production has also become a research hotspot in recent years.However,carbon nitride has been limited for further development in the field of photocatalytic hydrogen peroxide production due to its poor ability to capture visible light and serious carrier recombination.Therefore,it is necessary to adopt ingenious strategies to modify carbon nitride to improve its photocatalytic performance.In this paper,a series of graphite phase carbon nitride-based photocatalytic materials were prepared by group modification from the molecular engineering project,and hydrogen peroxide production capacity was tested under visible light irradiation.The mechanism and influencing factors in the photocatalytic process were explored,and the practical application of the generated hydrogen peroxide for bacterial inactivation was carried out.The main work are as follows:（1）Firstly,the pyrimidine group was introduced into the carbon nitride framework by in-situ ketone-enol cyclization,and the introduction of pyrimidine enhanced the carrier separation ability.Subsequently,it was further calcined with zinc oxide particles to form a composite.Due to the transfer of carriers between carbon nitride and zinc oxide,electrons and holes were further separated,which greatly improved the efficiency of oxygen reducing reaction by electron.At the same time,the visible light absorption band edge of the material was widened to about 500 nm,corresbonding to the enhancement of the visible light capturing ability.The photocatalytic experiment showed that the yield of photocatalytic hydrogen peroxide reached 679.5μM h^-1,which is 5 times of the original carbon nitride system.In addition,a series of characteration experiments confirmed that the carrier recombination of the modified material was effectively suppressed.（2）The traditional molecular modification strategies of carbon nitride materials are relatively simple,and there are few ways to achieve the synergy effect between groups through double group modification.In this paper,the method of alkali metal doping was used to further modify the carbon nitride with pyrimidine group.After the treatment of alkali metal molten salt,not only potassium ion and sodium ion doping was realized,but also cyano group was introduced.The introduction of alkali metal ions enhanced the ability to capture photogenerated electrons and promoted the efficiency of oxygen reduction reaction（ORR）to generate H₂O₂.The doping of potassium and sodium ions also regulated the energy band position of the valence band,which proves that it is also feasible to generate H₂O₂ through water oxidation reaction（WOR）in thermodynamics.At the same time,due to the synergistic electron withdrawing effect of cyano and pyrimidine groups,the carriers on the carbon nitride framework were separated efficiently,and then hydrogen peroxide was produced efficiently.In this system,the photocatalytic hydrogen peroxide yield was as high as3320.8μM h^-1,which is 25 times of the original carbon nitride system,and the generation constant K_f of hydrogen peroxide obtained was as high as 50.01μM min^-1 by fitting,23 times than that of the original carbon nitride system.（3）Considering the shortcomings of traditional sterilization methods and the high cost of adding hydrogen peroxide for sterilization,the materials in system（2）were used to in situ generate hydrogen peroxide under visible light to inactivate E.coli.The experiment showed that the E.coli of6 orders of magnitude can be completely inactivated in only 50 minutes,and the sterilization efficiency was better than that of the original carbon nitride material and the extraneous hydrogen peroxide of the same concentration.Further investigation showed that in the process of sterilization,hydrogen peroxide produced in-situ can not only act on the barrier structure of the bacterial surface,rupture the cell wall and membrane,but also further decomposed into hydroxyl radicals,which played a key role in the efficient inactivation of bacteria.