Studies On The Preparation And Application Of Photocatalytic Materials Based On Ag₃PO₄ Semiconductor

The future of the world will faced energy,water,environmental and other issues with the growing of social economy and population,the problem of water pollution has aroused widespread concern in society.Fortunately,the semiconductor Ag₃PO₄ photocatalytic material was reported for the first time in 2010.The forbidden band width of Ag₃PO₄ is 2.36 eV,which could absorb less than 520 nm of sunlight,and its degradation efficiency was much higher than the reported visible light semiconductor materials such as CdS,ZnO,WO3,BiOX and so on.However,it should also be noted that Ag₃PO₄ also faced some problems:?1?The photocatalytic performance of Ag₃PO₄ semiconductor photocatalytic materials was affected by its morphology,particle size and surface area greatly.?2?The reduction potential of H+ is more negative than that of Ag₃PO₄,resulting in Ag₃PO₄ was easily reduced into Ag element?Ag+ + e-? Ag?in the photocatalytic process,so the photocatalytic activity of Ag₃PO₄ semiconductor material was greatly reduced.?3?The solubility of Ag₃PO₄ in water is 10.2 g/L?20 ??and easier to dissolve in aqueous solution compared to AgX?X = Cl,Br,I?,thus the recycling in the practical application was limited.Based on the above problems,we have studied Ag₃PO₄ from the following three aspects in this paper:?1?The different morphologies of Ag₃PO₄ semiconductor were synthesized in the almost same condition.?2?N-GO/Ag₃PO₄ composite photocatalytic materials were prepared.?3?GO/Ag₃PO₄/AgBr heterostructure photocatalytic materials were prepared.The specific research contents were as follows.1.Concave dodecahedron Ag₃PO₄?CRD?and dodecahedral Ag₃PO₄?RD?were synthesized by a simple wet chemical method.Compared with Ag₃PO₄?RD?,Ag₃PO₄?CRD?was formed by concaving out four parallel hexahedrons at special junctions.However,it was found that the photocatalytic activity of Ag₃PO₄?CRD?decreased significantly,which was attributed to the concave nature-induced easier recombination of photo-generated holes and electrons and harderreaction with organic molecules with the space limitation and shadow effect.Except for other vital factors reported,this work indicated that the geometrical distribution of crystal facets also played the important role in photocatalytic property during the multielement determination.2.A series of N-GO/Ag₃PO₄ composites were prepared by simple two-step method.First of all,the N element was doped into graphene oxide?GO?in aqueous ammonia solution.Secondly,the N-GO/Ag₃PO₄ composite structure was synthesized by one-step precipitation.At last,it was found that the photocatalytic degradation of methyl orange?MO?for N-GO/Ag₃PO₄ composites was not only higher than that of Ag₃PO₄ significantly but also better than that of GO/Ag₃PO₄ composites.It could be deduced that the combination of N-GO and semiconductor have the potential to degraded organic dyes than GO.3.A series of GO/Ag₃PO₄/AgBr composites were prepared by one-step precipitation and in situ ion exchange?by changing the percentage ratio of GO and AgBr?for the photocatalytic degradation of rhodamine B?Rh B?and MO.The optimum parameters in degradation of RhB were in the range of 0.15-0.60 wt% for GO as well as 0.25-0.75 wt% for AgBr.Interestingly,RhB solution could be degraded completely within 12 min by modifying Ag₃PO₄ with 0.30 wt% of GO and 0.50 wt% of AgBr?GO2/Ag₃PO₄/AgBr2?,which the photodegradation rate constant?k = 0.315min-1?was 15 times of the pristine Ag₃PO₄?k = 0.021 min-1?.However,there were found to be in the range of 0.30-0.90 wt% for GO as well as 0.75-1.25 wt% for AgBr in degradation of MO respectively.MO solution could be degraded completely in nearly 18 min by modifying Ag₃PO₄ with 0.60 wt% of GO and 1.00 wt% of AgBr?GO3/Ag₃PO₄/AgBr4?,which the photodegradation rate constant?k = 0.178 min-1?was 4.56 times of the pristine Ag₃PO₄?k = 0.039 min-1?under visible-light irradiation.Besides,the heterostructure GO2/Ag₃PO₄/AgBr2 or GO3/Ag₃PO₄/AgBr4 presented excellent stability compared to pristine Ag₃PO₄ after three cycles.At last,it was found that the active species of h+ and.O2-played the major role in the whole photodegradation process through the species capture experiment.