| With the rapid development of society and economy,the energy crisis and environmental pollution problems have become more and more serious,thus limiting the development of sustainable society.At present,semiconductor photocatalytic technology is getting more and more attention and research by researchers,because it can use inexhaustible solar energy to convert into chemical energy to eliminate pollutants and generate new energy to solve energy shortage and environmental pollution problems.In addition,the most researched semiconductor in photocatalysis technology is TiO2,but studies have shown that it is limited by the practical use of TiO2 semiconductor solar energy.Therefore,it is imperative to seek new and efficient and cost-effective visible light photocatalysts for environmental restoration.Graphite-phase carbon nitride(g-C3N4)semiconductors have become widely used and studied as photocatalytic semiconductors due to their low cost,non-toxicity,chemical stability and absorption of visible light.However,due to the small specific surface area of g-C3N4,poor conductivity and low utilization of solar energy,the recombination rate of photogenerated electron-hole pairs is high,which limits its photocatalytic activity.Therefore,in view of some shortcomings of single-component semiconductors,the composite modification and morphology control of g-C3N4 semiconductors are used to improve the efficiency of photo-carrier migration and separation.The main research contents of this paper are as follows:(1)The novel catalyst of g-C3N4-SnS2-rGO(CN-S-G)was prepared by thermal polycondensation and solvothermal combination for visible light catalytic degradation of rhodamine B and photocatalytic reduction of Cr(?),and the prepared catalyst was characterized.The results show that SnS2 exhibits a nanoflower structure,and the g-C3N4 nanosheet adheres to the surface of the SnS2 nanoflower and is simultaneously dispersed and reduced on the surface of the graphene sheet.The CN-S-G catalyst has a larger specific surface area and pore d.iameter than pure g-C3N4,so that the catalyst can absorb more photon energy and have more active sites to enhance the photocatalytic activity of the catalyst.In addition,the CN-S-G catalyst has stronger visible light absorption capacity,lower and higher photogenerated electron-hole separation efficiency than pure g-C3N4.Therefore,the CN-S-G composite catalyst achieved the highest photodegradation rate of 100%in 150 minutes,and exhibited the highest activity of 93%reduction in 5 hours in the visible light catalytic reduction of chromium.In addition,the stability and mechanism of CN-SG catalysts were studied.The results show that the catalyst has high stability.The active factors affecting photocatalytic degradation of RhB are mainly ·OH and h+,and the photocatalytic activity of Cr(?)is reduced.The factor is mainly e-and the reduction product is Cr(?).(2)A novel TiO2-g-C3N4-rGO(T-CNS-G)composite photocatalyst was prepared by two-step hydrothermal method.The photocatalytic activity of the prepared catalyst for photocatalytic degradation of rhodamine B and photocatalytic reduction of Cr(?)was studied.And the prepared catalyst was characterized.The results show that g-C3N4 has a 3D spherical structure,TiO2 nanoparticles are attached to g-C3N4 spheres,and both are dispersed on the surface of the reduced graphene sheets.The g-C3N4 sphere is beneficial to the dispersion of TiO2 nanoparticles.After the introduction of TiO2 and rGO,the specific surface area of the T-CNS-G catalyst is significantly higher than that of pure g-C3N4.The UV-vis/DRS results show that T-CNS-G has excellent visible light absorption properties,which is also a key factor for improving the visible light photocatalytic activity of the catalyst.PL characterization and photocurrent response tests showed that the recombination rate of photogenerated electron-hole pairs of T-CNS-G catalyst was significantly lower than that of pure g-C3N4.Therefore,the T-CNS-G composite catalyst achieved the highest photoreduction rate of 97%in 4 hours in photocatalytic reduction of chromium,it showed degradation of 93%in 5 hours in visible light catalytic degradation of RhB.In addition,the results of masking experiments show that the main active factors for photocatalytic degradation of RhB are ·OH and h+,while the active factor affecting photocatalytic reduction of hexavalent chromium is e-. |
PDF Full Text Request