Rare Earth Compound Composite Semiconductor Catalyst:Design And Synthesis Of Novel Non-precious Metal Photocatalysts And Study On Dye Sensitized Photocatalytic Hydrogen Production System

The energy crisis has been a huge challenge for population growth and industrialization.Therefore,there is an urgent need for sustainable clean energy.Therefore,the use of solar energy to generate hydrogen by photocatalytic water decomposition is one of the most promising methods.The semiconductor photocatalyst has low electron and hole separation efficiency,resulting in poor photocatalytic activity.Rare earth compounds as co-catalysts can provide active sites and effectively increase the separation efficiency of photogenerated electron-holes,thereby increasing photocatalytic activity.1.The Ce/CoWO₄ composite catalyst prepared by microwave method has good photocatalytic hydrogen production performance.Under visible light（≥420nm）,the optimal hydrogen production of 10%Ce/CoWO₄ photocatalyst is 200.89μmol,which is three times that of CoWO_4.It is known from Electrochemistry and PL that CeO₂can not only rapidly capture electrons excited by CoWO₄ to absorb photons to improve charge separation efficiency,but also promote H⁺reduction to H₂.Compared with CoWO₄,Ce/CoWO₄ has a larger specific surface area and can adsorb more dyes,thereby increasing photocatalytic activity.2.Sm₂MoO₆/Ni（OH）₂ photocatalyst was successfully prepared by impregnation method.With blush as a sensitizer and triethanolamine as a sacrificial agent,it is used for efficient photocatalytic hydrogen production.When Sm₂MoO₆ loaded on the surface of Ni（OH）₂,the photocatalytic activity(2407.48μmol·g^-1·h^-1)was 2.6 times that of Ni（OH）₂(925.36μmol·g^-1·h^-1).14.2 times Sm₂MoO₆(169.36μmol·g^-1·h^-1).From a series of characterizations,Sm₂MoO₆ is an effective cocatalyst to improve the separation of photogenerated charges and the efficiency of electron transfer.A large specific surface area is a major requirement for a high efficiency catalyst,and the catalyst is sufficiently contacted with a sensitizer and a sacrificial agent to enhance photocatalytic activity.3.The two-dimensional nanosheet Sm₂MoO₆ was loaded onto a three-dimensional bulk NiS to form a durian-like 2D/3D heterojunction photocatalyst,and its photocatalytic activity was studied.The photocatalytic activity of the optimal composite catalyst was 8.3 times that of NiS and 186.7 times that of Sm₂MoO₆.The increase in photocatalytic activity is due to:on the one hand,the two-dimensional nanosheet loaded onto the three-dimensional structure effectively prevents stacking problems due to high surface energy and interlayer van der Waals attraction.The specific surface area of the catalyst is enlarged to provide more active sites which promote contact of the catalyst with the sensitizer and the sacrificial agent.On the other hand,Sm₂MoO₆,as a rare earth promoter,can reduce the activation energy required for the surface reaction and can improve the electron-hole separation ability.4.Co₂P is hydrothermally synthesized from red phosphorus and cobalt nitrate to increase the photocatalytic activity of MoS₂.When Co₂P loaded onto the surface of MoS₂,the photocatalytic activity(9.15mmolg^-1h^-1)was three times that of MoS₂(3.14mmolg^-1h^-1),which was twice that of Co₂P(4.60mmolg^-1h^-1).Fluorescence and electrochemistry show that the composite photocatalyst improves the efficiency of photo-generated charge separation.It is known from BET that the composite catalyst has a larger specific surface area and can provide more active sites.