| Ammonia has an important role in industrial and agricultural fertilizer production.Conventional industrial ammonia synthesis requires huge energy consumption and requires high temperature and high pressure reaction conditions with low safety margins.Photocatalytic nitrogen fixation reaction conditions are mild and inexpensive,so the research on photocatalytic nitrogen fixation has become a hot spot.The layered structure of BiOBr makes it promising for photocatalytic nitrogen fixation,although the shortcomings of BiOBr such as low solar light utilization,low quantum efficiency and low photogenerated electron reduction capacity limit its application,so this paper uses a solvothermal method to prepare BiOBr and enhance its photocatalytic performance by ozone modification and elemental doping.The main elements are as follows.(1)Bi(NO3)3·5H2O and KBr were used as raw materials to prepare BiOBr,and the resulting BiOBr was fed into ozone,and the strong oxidizing and corrosive properties of O3 treated BiOBr,and a series of modified catalysts were obtained with ozone feeding flow rate and ozone reaction time as the only variables,respectively,and then photocatalytic nitrogen fixation experiments were carried out on the modified catalysts before and after respectively,and the catalysts were thus The catalysts were then adjusted to determine the amount of catalyst and trapping agent,and the type of trapping agent.The catalysts with excellent nitrogen fixation performance were characterized and the differences between the ozone-modified catalysts and the original BiOBr catalysts were analyzed.The study showed that the ozone-treated catalysts showed oxygen vacancies,and that too long an ozone modification time or too high an ozone flow rate inhibited the improvement of the nitrogen fixation effect of the catalysts,with the catalysts modified with an ozone flow rate of 3 L/min for 2 h having the best effect;the specific surface area of the modified catalysts was greatly increased due to the ozone etching,and was 1.7 times higher than that of the unmodified BiOBr;and the nitrogen fixation effect was best when ethylene glycol was used as the capture agent compared to 1,3-The best nitrogen fixation was achieved when ethylene glycol was used as the trapping agent compared to the three trapping agents of 1,3-butanediol,ethanol and isopropanol.(2)Modification of BiOBr by P-element doping.The catalysts were prepared by using Bi(NO3)3·5H2O and KBr as raw materials,sodium hypophosphite(NaH2PO2)as the P source,adjusting the molar ratio of Bi to P,using a solvothermal method,and the catalyst with the best nitrogen fixation effect was derived from nitrogen fixation experiments and characterized and tested.The P doping of the catalysts has also increased the transient photocurrent intensity of the catalysts,which means that the P doping can generate more electron-hole pairs in the catalysts;the P doping has increased the nitrogen fixation performance of the catalysts by 4.7 times higher.(3)Modification of BiOBr with S elemental doping.Using thiourea(CH4N2S)as the S source,the ratio of Bi to S was adjusted and the catalysts were prepared using a solvothermal method.The catalysts with the best nitrogen fixation effect were derived from nitrogen fixation experiments and characterized for testing.It is shown that the XPS characterization data plotted that S element is successfully doped into the catalyst,and some of the S element replaces the oxygen element in BiOBr,forming a Bi-S bond,while S may also bind some of the oxygen,forming oxygen vacancies in the catalyst.S doping also greatly increases the specific surface area of the catalyst material,which is more than twice as large as the original,providing better N2 adsorption capacity,more reaction sites and better nitrogen fixation efficiency than the original BiOBr,which is about 4.6 times more effective.Figure[37]Table[5]Reference[130]... |
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