The Construction Of Heterojunction Photocatalyst Based On G-C₃N₄,CdS & WO₃ And Study On H₂ Production Performance By Photolyzing Water

The serious energy crisis and environmental pollution motivate people to prepare H2 energy with pollution-free and high-clean,which is a potential feasible solution to replace traditional fossil energy Therefore,studies of this paper are mainly to constract composite nano-semiconductor materials based on CN and CdS,change its electron transport and improve the catalytic performance of H2 decomposed from water under visible light,meanwhile,explore the optical properties,electrical properties and reaction mechanism.This paper has mainly three research contents.1.The CN nanosheets were modified by bimetallic phosphide(CoMoP)nanoparticles by hydrothermal synthesis method and the composite photocatalyst CoMoP/CN showed promising photocatalytic activity in HER.The H2 production reached 646.4?mol after 5h under visible light irradiation,which is 66.7 times than that of pure CN.The characterization results of FTIR,XRD,SEM and TEM showed great crystal and unique functional groups.The results of UV-vis DR,transient fluorescence and electrochemical tests show that the composite has superior absorption capacity of visible light and electrical-chemical properties relative to single materials.The nanoparticle CoMoP attached to the CN surface provides a large number of active sites for the HER process,which greatly increases the separation efficiency of charges and holes,the transfer efficiency of photogenerated electrons as well,results in accelerating the rates of reduction reaction and H2 production rate in water Aiming at the efficient photocatalytic HER activity in EY sensitization system,a possible charge transport and HER mechanism were proposed.2.The Ni(OH)2 was successfully photodeposited on CdS@CN nanocomposites,and a special charge transport channel between CdS and CN was constructed to efficiently transfer photogenerated charges to the active sites Ni2+/Ni cluster,the separation of electron-hole pairs were significantly accelerated.The prepared composite catalyst CdS@CN/Ni(OH)2 greatly increased the HER rate,and the H2 production reached 1445.58?mol after 5h,which was 39.5 times and 149 times than that of CdS and CN respectively,and the measured AQE is 5.59%.The FESEM,TEM,XRD,XPS,UV-vis DR and BET characterization results show that the composite has a great crystal structure,the elements have specific valence state,stronger visible light absorption capacity and improved specific surface area Steady-state transient fluorescence spectroscopy and electrochemical characterization results show that CdS@CN/Ni(OH)2 has the highest photocurrent density,the lowest impedance and the longest lifetime of photogenerated electrons,which shows better photoelectrochemical performance.Simultaneously,the reaction mechanism of photocatalytic decomposition of water to H2 by composite semiconductor material under lactic acid as a sacrificial reagent was proposed.3.The Z-type heterojunction CdS@WO3 was successfully fabricated,and a unique photo-generated charge transport route was constructed to directly transfer the photo-generated charge on the CB of WO3 to the VB of CdS and recombine with the holes,thus effective suppressed the separation of photo-generated holes and electrons.With the sacrificial agent of lactic acid solution,the H2 production of the catalyst CdS@WO3/CoP is 736.89?mol after 5h under visible light,which was 20.2 and 24.5 times than pure CdS and WO3,respectively,and the corresponding AQE was 1.72%.The XRD,TEM and XPS characterization results show that the catalyst has high crystallinity,nanorod morphology and a specific valence distribution of the elements.The UV-vis DR,PL and electrochemical test results show that CdS@WO3/CoP has the highest absorption intensity for visible light,the highest intensity of photocurrent,and resultfully enhanced the separated of electron-holes.Its optical and electrical properties were better than single catalyst,and the energy band structure of the catalysts were calculated and analyzed in detail.The Z-type heterojunction CdS@WO3 with special energy band structure has more active sites after modified with CoP,which improves the transmission efficiency of photo-generated charges,promotes the photoreaction water reduction reaction then improves H2 production.Simultaneously,the charge transfer mechanism and HER mechanism based on Z-type heterojunction CdS@WO3 were explored and proposed.