Preparation Of A Novel Ternary Composite Of TiO₂/UiO-66-NH₂/graphene Oxide With Enhanced Photocatalytic Activities

As a kind of low-cost,non-toxic and relatively active photocatalyst,TiO2 has been widely used for photocatalytic degradation of organic pollutants and hydrogen production by photocatalytic water splitting in wastewater treatment and clean energy.However,the photocatalytic performance of TiO2 is limited by the defects such as fast recombination of photogenerated electron-hole pairs and narrow spectral response range.Therefore,TiO2,as an excellent photocatalyst,still has great potential not been shown.Composite of TiO2 with other materials to form heterostructures is a common method at present to improve the photocatalytic performance of TiO2.In this paper,a novel photocatalyst for TiO2-based ternary composite was designed and prepared by introducing metal-organic frameworks(MOFs)and graphene oxide(GO),and then its photocatalytic property and reaction mechanism were studied.The main research content of this paper is as following:Firstly,TiO2 was compounded with Zr-based MOFs UiO-66 and UiO-66-NH2,and GO respectively to prepare corresponding binary composites TiO2/UiO-66,TiO2/UiO-66-NH2 and TiO2/GO.On this basis,the TiO2-based ternary composites with different component ratios were synthesized,namely,TiO2/UiO-66-NH2/GO.It can be seen from the characterization results of XRD,TEM,UV-Vis DRS and PL that there are good contacts between different components of the TiO2-based composites,and ternary composites TiO2/UiO-66-NH2/GO exhibit stronger light absorption in the range of 450-800 nm and lower recombination rate of photogenerated electron-hole pairs.When the molar ratio of Ti to Zr is 19:1,TiO2/UiO-66-NH2/GO has the strongest visible light absorption ability,also can effectively inhibit the recombination of photogenerated electron-hole pairs of TiO2.The tests of photocatalytic degradation of organic dye RhB and photocatalytic hydrogen evolution were carried out to examine the photocatalytic properties of the prepared ternary composites,binary composites and single component.The order of photocatalytic activities for materials involved is TiO2/UiO-66-NH2/GO>Ti02/Ui0-66-NH2>TiO2/UiO-66>TiO2/GO>TiO2>UiO-66-NH2>UiO-66.When the molar ratio of Ti to Zr is 19:1,TiO2/UiO-66-NH2/GO exhibits the best photocatalytic performance of which the dye degradation rate is over 97%in a period of 45 min dye removing tests,and the hydrogen production rate could reach 27.0 mmol/(g·h)within 2 hours of visible light.The tests of photocatalytic stability were carried out on the TiO2/UiO-66-NH2/GO with the molar ratio of Ti to Zr of 19:1.In the cyclic test of photocatalytic degradation,the dye degradation rate of TiO2/UiO-66-NH2/GO in the fifth cycle was still over 90%.In addition,the total hydrogen release of TiO2/UiO-66-NH2/GO could reach 254 mmol/g in the 12-h photocatalytic hydrogen production test.The crystal structure of TiO2/UiO-66-NH2/GO remained intact after testing.It can be concluded that TiO2/UiO-66-NH2/GO exhibits excellent photocatalytic stability.