Enhanced Photocatalytic Production Of H₂O₂ Using Bi₂ MoO₆ Nanosheets With Surface Loading Regulation

Artificial photosynthesis,which uses sunlight to turn the Earth’s abundant resources into clean fuels,is a key technology for a sustainable future.As an emerging liquid clean fuel,hydrogen peroxide（H₂O₂）is widely used in chemical industry,environmental remediation,sustainable energy conversion/storage and other fields.Photocatalytic production of H₂O₂has attracted more and more attention from researchers,mainly through different photocatalysts.Bismuth molybdate（Bi₂Mo O₆）semiconductor nanomaterials are attractive two-dimensional photocatalytic materials with suitable valence band position and visible light response band gap（2.5 e V）,which has attracted wide attention from researchers.However,their poor photo charge separation effect limits the development of their catalytic properties.How to break through the problem of poor surface charge separation of Bi₂Mo O₆（BMO）,get a high efficiency and stable photocatalytic BMO catalyst for H₂O₂production,and expand its application in the field of photocatalysis has become a research hotspot.In this thesis,BMO was selected as the research target.Aiming at the performance problems existing in the photocatalysis of BMO semiconductor nanomaterials,BMO was modified by improving the material charge separation efficiency and the photocatalytic performance of H₂O₂ production was studied.The specific research is as follows:1.BMO nanosheets were prepared by a simple one-step hydrothermal method,and then three co-catalysts（Pd,Pt and Au）were introduced by photoreduction deposition to obtain three co-catalyst modified BMO nanosheets（M/BMO,M=Pd,Pt,Au）.The photocatalytic properties of different noble metal cocatalysts on the surface of BMO nanosheets for H₂O₂generation were studied.The catalytic activity of Pd/BMO(11.3μmol h^-1 g^-1)was 75 times that of BMO(0.15μmol h^-1 g^-1)and 1.2 times that of Pt/BMO(9.6μmol h^-1 g^-1).Electrochemical impedance test and transient photocurrent test results showed that due to the poor surface charge separation efficiency of bulk BMO catalyst,Pd noble metal assisted catalyst was loaded on the surface of BMO,which improved the charge separation efficiency of the material and inhibited the photogenerated electron-hole recombination.Therefore,M/BMO（M=Pd,Pt）can significantly improve the photocatalytic performance of H₂O₂ production.Mechanism studies show that·O₂^-is the most important intermediate in the photocatalytic generation of H₂O₂.Loading Pd on BMO nanosheets can effectively promote the generation of·O₂^-,thus improving the generation of H₂O₂.2.Bimetallic co-catalyst/catalyst composite system was constructed using BMO nanosheet as catalyst and Au-Pd as co-catalyst for photocatalytic production of H₂O₂.Au-Pd bimetallic cocatalyst was deposited on the surface of BMO by photoreduction deposition method to explore the effects of different proportions of Au-Pd bimetallic cocatalyst on the photocatalytic performance of H₂O₂ production in composite system.Through a series of characterization of catalyst materials and investigation of their photocatalytic production of H₂O₂.It is concluded that the interaction of Au-Pd bimetallic cocatalyst on the semiconductor surface expands the light absorption capacity,greatly promotes the separation and transmission of photogenerated charge,inhibits the charge recombination,and improves the catalytic performance of the composite system.The optimal ratio of Au-Pd bimetallic cocatalyst(Au_0.02-Pd_0.08/BMO)improves the catalytic performance to 123 times of the bulk BMO,and 2.05 times of the Pd/BMO system.This may be attributed to the effect of Au nanoparticles in bimetallic cocatalyst,indicating that bimetallic nanoparticles as cocatalyst show better catalytic performance through the synergistic interaction between the two metals than single metal nanoparticles as cocatalyst.