| The people’s living standards get to improve and the demand for medical and public health services is greatly increasing,with the development of the social economy.The large amount of medical wastewater produced contains antibiotic residues and pathogenic bacteria that will cause serious ecological environment pollution and threats to human health if the pre-discharge treatment is improper.Solar-driven photocatalytic technology is considered as an ideal water treatment method for degrading organic pollutants and kill pathogenic bacteria,where the development of high-efficiency photocatalysts is the key.Bismuth oxyhalide,a promising twodimensional photocatalyst,is regarded as an ideal catalyst for photocatalytic degradation and antibacterial,due to its stable chemical properties,low toxicity,a rich source of raw materials,and no secondary pollution.The built-in electric field of bismuth oxyhalide in the layered structure facilitates the separation of photogenerated electron and hole pairs to participate in the catalytic reaction.Nevertheless,there are still some problems that restrain its photocatalytic performance,such as the wide bandgap,the easy recombination of photo-generated electronhole pairs,and easy stacking between the two-dimensional interfaces of materials to inhibit catalytic activity.In our work,bismuth oxychloride(Bi OCl)and bismuth oxybromide(Bi OBr)in the bismuth oxyhalide family are the main research objects to construct two-dimensional heterojunction(Bi OCl@G and Bi OBr@G)with graphene(G)to further enhance the photocatalytic performance.The main contents of this paper are as follows:(1)Bismuth oxyhalide was successfully formed in-situ on the two-dimensional surface of graphene through the hydrothermal method by using mannitol and polyvinylpyrrolidone as template agents,beneficial to expand light absorption and surface area for the catalytic reaction.The two-dimensional bismuth oxyhalide/graphene heterojunction has a significantly reduced band gap,better carrier separation,and transport performance,compared with pure bismuth oxyhalide.The photocatalytic degradation and antibacterial experiments were carried out under simulated sunlight.The degradation rate constants of tetracycline and rhodamine B by Bi OCl@G(2.5)were 38.33% and 104.78% higher than that by Bi OCl,respectively,and the degradation rate constants of tetracycline by Bi OBr@G(2.5)was 54.78% higher than that by Bi OBr.The antibacterial rates of S.aureus and E.coli by Bi OCl@G(2.5)reached 99.36% and98.90%,and the antibacterial rates of S.aureus and E.coli by Bi OBr@G(2.5)reached 99.41%and 99.23%,respectively.The co-culture experiment of mouse bone mesenchymal stem cells shows that the two-dimensional bismuth oxyhalide/graphene heterojunction is good cell compatibility.(2)It is found that the graphene two-dimensional heterojunction interface changes the ground-state electron density of bismuth oxyhalide and improves their carrier separation behavior,through energy band structure and carrier performance analysis.Simulated sunlight,λ≤420 nm or λ≥420 nm are used as the light source to carry out photocatalytic degradation and antibacterial experiments,that reveals the contribution of graphene photothermal effect to the photocatalytic reaction based on the experimental results of thermal imaging analyzer,total active oxygen fluorescence,and electron spin resonance.Graphene absorbs broad-band photon energy to facilitate the rapid diffusion of surface electrons,and transfers energy to phonons,resulting in violent vibration of the crystal lattice with significant thermal effects,at the same time.The rising temperature of the reaction system and the Increased production of active oxygen significantly enhance photocatalytic activity.In summary,the two-dimensional heterojunction scheme of graphene and bismuth oxyhalide is used to achieve high-efficiency photocatalytic degradation and antibacterial performance,which is expected to be used in medical wastewater treatment and photocatalytic antibacterial treatment. |
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