Fabrication And Photocatalytic Performance Of Ag₂O-based Semiconductor Composites

Solar energy is an important renewable energy source to solve the energy and environmental crisis,it plays a crucial role in the increasingly serious environmental and energy problems.How to use semiconductor photocatalyst for solar energy conversion and environmental governance has caused widespread concern.However,the photocatalytic quantum efficiency of the semiconductor photocatalyst are still low at present.Therefore,it is urgent to find nove semiconductor photocatalysts and raise the conversion efficiency from solar energy to chemical energy and photocatalytic efficiency.At present,the silver oxide have attracted more and more attention because of its high utilization factor of sunlight.However,the photoexcited electron-holes of silver oxide could be easily recombined,which limited its practical application.Constructing of hybrid photocatalytic systems is a very effective method to improve the mobility efficiency of photo-induced electron-hole pairs.Ag₂O/NaTaO3 、AgCl/Ag₂O/NaTaO3 and Ag/AgCl/Ag2 O photocatalysts were successfully prepared by wet chemical method.The recombination of photo-generated electron-hole pairs of silver oxide were remarkably suppressed,thus the photocatalytic efficiency was improved.The results are as follows:（1）An efficient visible-light-driven p-n Ag₂O/NaTaO3 heterojunction was successfully prepared by chemical precipitation method at room temperature.The recombination of silver oxide photoelectron-hole pairs was suppressed by the interfacial electron transfer between p-n heterojunction.The crystalstructure and morphology of the prepared samples were discussed in detail by XRD、SEM and TEM.The result indicted that the heterojunction posed higher photocatalytic activities for degrading rhodamine B（RhB）compared to the pure Ag2 O.Based on the trapping experimental and the position of semiconductor band gap,the possible mechanism for the photodegradation process was also proposed.（2）A three-component AgCl/Ag₂O/NaTaO3 photocatalyst was prepared by a simple synthesis process.The addition of AgCl not only introduced Cl radicals as a new active species,but also increased the electron transfer pathway of Ag2 O.The three component AgCl/Ag₂O/NaTaO3 p-n heterojunction photocatalysts have higherphotocatalytic activity for degrading Rhodamine B（RhB）under visible light irradiation.（3）A new Ag/AgCl/Ag₂O heterostructure was synthesized via in-situ growth strategy for the first time.The mobility efficiency of photo-generated carries were improved by the local plasma resonance effect of Ag nanoparticles and the synergistic effect of heterojunction.The prepared samples showed higher photocatalytic activity and stability for photocatalytic degradation of Ciprofloxacin（CIP）aqueous solution under visible light.The optimum photocatalytic efficiency of 50% Ag/AgCl/Ag2 O heterostructures for the degradation of CIP was about 2.9 and 3.73 times higher than that of individual Ag2 O and Ag/AgCl,respectively.A possible mechanism toward the photocatalysis of the Ag/AgCl/Ag2 O heterostructures has been studied,and a plasmonic Z-scheme mechanism was proposed on the basis of the active species trapping experiments.