Preparation Of Titanium-based And Carbon Nitride-based Catalysts For Photosynthesis Of Hydrogenperoxide

Hydrogen peroxide(H2O2)is an important chemical,widely used in various fields.At the same time,H2O2 can also be used as a fuel cell,the final product only water and oxygen,is clean energy.Light driven synthesis of H2O2 is the use of light irradiation of semiconductor materials to stimulate its electron hole separation,on the surface of the catalyst,the photoinduced electron reduction of oxygen molecules to generate H2O2.It is a great challenge to design high performance catalysts to improve H2O2 production and control product selectivity.This paper focuses on the research of the synthesis of H2O2 catalyst.The main results are as follows:Titanium matrix mixed metal hydroxide(LDHs)was used as precursor,and was converted to mixed metal oxide(MMO)by calcination precursor,which was used as catalyst for the synthesis of H2O2.MMO found in Zinc Oxide(ZnO)crystal phase in the synthesis of H2O2 under acidic conditions will gradually dissolution.The structure of high-resolution transmission electron microscopy(TEM)was observed:Before the dissolution,the ZnO crystal phase was in contact with titanium dioxide(TiO2)After the disappearance of the ZnO crystal phase,the TiO2 crystal phase is exposed to contact with the ZnTiO3 phase to form TiO2-ZnTiO3 heterostructures.MMO(c=77.4 μmol/L)and TiO2-ZnTiO3(c=79.7 μmol/L)are shown to be better than the commercial P25(c=60.4 μmol/L)better performance of H2O2 synthesis.Analysis of the simulation results:the formation rate constants of H2O2 in the Ti02-ZnTi03(Kf=3.5810.852 μM/min)is P25(Kf=0.8520.852μM/min)4.20 times,is ZnTi-MMO(Kf=0.9820.852 μM/min)3.65 times;and the corresponding decomposition rate constants of H2O2 in the TiO2-ZnTiO3(Kd =0.0472 min-1)is P25(Kd =0.0374 min-1)1.26 times,is ZnTi-MMO(Kd=0.0119 min-1)3.97 times.When TiO2-ZnTiO3 is used as photocatalyst,the formation rate of H2O2 is faster,but the competitive reaction is faster.Carbon nitride(C3N4)is a kind of semiconductor material,the band gap width(2.81 eV)is less than TiO2(3.20 eV),can absorb visible light,has been used in the synthesis of H2O2.How to control the surface properties of C3N4 and improve the yield and selectivity of H2O2 is the key to the development of high performance catalysts.A simple precursor modification method was developed to control the carbon modified state of C3N4,and the Carbon-modified C3N4 catalyst was obtained.The study found that the change of carbon precursor concentration,can control the Carbon-modified C3N4 flat band potential,flat band potential shift to two electron reduction of molecular oxygen to generate H2O2,this is because of inhibition of the reduction of protons hydrogen to molecular hydrogen reaction.When the carbon precursor concentration was 0.006M,the yield of H2O2 was the highest,which was about 2.5 times of that of C3N4(582.3 μmol/L).The results show that the appropriate carbon modified contributes to the positive shift of the flat band potential,and then enhances the performance of H2O2.