Regulation Of Interfacial Photocarrier Transport And Photocatalytic Hydrogen Evolution Of Phosphate-based Photocatalytic Materials

The problem of non-renewable energy consumption and pollution greatly affects our environment and climate.In the future,environmentally friendly renewable energy is considered as the most promising clean energy to replace traditional fossil fuels.Among them,hydrogen energy is considered as an ideal renewable energy to deal with energy crisis because of its high combustion efficiency and pollution-free combustion products.Photocatalytic hydrogen evolution technology as the most ideal method has been paid more and more attention.However,the photocarriers of the photocatalysts are easy to recombine,which limits the photocatalytic hydrogen evolution rate.The hydrogen evolution performance of the photocatalyst was improved by regulating the transport path of photocarriers of the phosphate-based photocatalyst.（1）The composite photocatalyst RP/BP/Co-MOF with Z-Scheme heterojunction structure was successfully prepared by solvothermal method.The metal-organic framework Co-MOF acted as an electron transfer medium and accelerated the electron transfer rate between red phosphorus and black phosphorus.The composite material showed a high rate of hydrogen evolution in the dye sensitization system.The photocatalytic activity of RP/BP/MOF reached 63.25 mmol·g^-1at 5 h.A series of characterization of the RP/BP/MOF composite photocatalyst shows that the RP/BP Z-Scheme heterojunction can effectively inhibit the recombination of photocarriers and promote the rate of charge separation.（2）Furthermore,a composite photocatalyst for the purification of RP and a novel nickel-cobalt layered dihydroxide（Ni Co-LDH）was prepared,and the hydrogen evolution activity of composite photocatalyst RPNC-70%reached 32.80 mmol·g^-1at 5 h.Further studies showed that when the purified RP was in contact with Ni Co-LDH,electrons were transferred from Ni Co-LDH to the pure RP,resulting in a built-in electric field at the interface between the two photocatalysts.The photoexcited electrons migrate from the conduction band in the pure RP to the valence band in the Ni Co-LDH,forming a typical S-Scheme heterojunction and effectively inhibiting the recombination efficiency of photogenerated charges.（3）Nickel cobalt transition metal phosphide（NiCoP）was prepared by solvothermal method using pure RP as phosphorus source.Mn_0.2Cd_0.8s nanorods were modified to form a complex photocatalyst for efficient hydrogen evolution.The hydrogen evolution rate of Mn_0.2Cd_0.8S/NiCoP catalyst reached 78.60 mmol·g^-1at 5 h.Further studies show that NiCoP is an effective cocatalyst because it can effectively increase the active site of the composite photocatalyst,thus improving the visible light absorption capacity and photocarrier transfer rate.（4）Furthermore,three metal phosphorus compounds（NiCoP Ni₂P and Co₂P）were synthesized by solvothermal method.After that,three transition metal phosphating compounds（TMPs）were loaded on Zn_0.5Cd_0.5S respectively in the form of physical agitation to form binary nanocomposites（ZnCdS/TMPs）.Among them,ZCS/NCP-5%has the highest hydrogen evolution rate,and its 5 h hydrogen production activity reaches 6.4mmol·g^-1.By comparing the results of hydrogen production test,the bimetallic phosphating NiCoP nanoparticles not only provide more active sites for Zn_0.5Cd_0.5S,but also promote the charge transfer rate of the composite photocatalyst,thus effectively improving the performance of photocatalytic hydrogen evolution.