| The rapid growth of the global population and booming industrialization have brought a huge amount of energy consumption and serious environmental problems.Among many different types of green energy sources,hydrogen is considered one of the most ideal candidates for the energy crisis because of its high combustion value,high efficiency and environmental friendliness.Traditional hydrogen production from electrolysis of water is not only costly,but also goes against the principle of not relying on fossil fuels and tends to cause pollution twice.Therefore,people are looking for better methods,of which photoelectrochemical(PEC)water splitting is one of them.The efficiency of the PEC water splitting performance is mainly limited by the structure of the semiconductors.Conventional inorganic semiconductors,such as Ti O2,Zn O and α-Fe2O3,are usually suffered from severe photogenerated electron-hole complexation,poor light collection capability,and mismatched band gaps.In the thesis,we designed several MOFs-based photoelectrochemical water splitting catalysts,which significantly improved the deficiencies of conventional semiconductors and enhanced the efficiency of the PEC hydrogen production.This thesis mainly prepared novel semiconductor catalysts from three strategies: Fabrication of MOFs-based heterojunctions,introduction of photosensitizer into MOFs-based semiconductors and decoration of MOFs-based co-catalysts on semiconductors.The detailed research contents are as follows:(1)By combining the MOFs-based Z-scheme catalysts with surface plasmon resonance(SPR)of gold nanoparticles(Au NPs),We constructed a novel cooperatively coupled catalyst(Ti O2/NH2-MIL-125/Au).Electron paramagnetic resonance(EPR)spectra and theoretical calculations showed that the charge transfer path followed a Z-scheme mechanism and the SPR effect of Au NPs,as a hot spot,significantly enhanced the electromagnetic(EM)field in the coupling region.This advantage in physical structure endowed Ti O2/NH2-MIL-125/Au with stronger redox ability and higher charge separation efficiency,and the photocurrent was 2.2 times higher than that of the original Ti O2 nanotube array.(2)Zn O@C was prepared by hydrothermal and in-situ derivation methods.Subsequently,Au nanorods were spin-coated on its surface to obtain a Zn O@C@Au composite photoanode.The Zn O@C@Au photoanodes showed plasmon-enhanced photocurrent density and IPCE values compared to the pristine Zn O nanorod arrays.The photoanode achieved a photocurrent density of up to 0.64 m A·cm-2 at 1.23 V vs.RHE,which is 14.8 times higher than that of the pristine Zn O nanorod array.At365 nm,the IPCE could reach up to 17%,which was 32.1 times higher than that of the pristine Zn O nanorod array.Mechanism investigation indicated that the carbon-doping could effectively improve the electron and hole separation efficiency,and the plasmonic effect of Au nanorods could broaden the light absorption,which finally improved the water oxidation ability from the interfacial dynamics aspect.(3)By using an impregnation method,a Co Ni-MOFs-based cocatalyst was in-situ anchored on a guest Ti-α-Fe2O3 photoanode.As a result,the Co Ni-MOFs could reduce the surface charge transfer resistance and provide more surface reactive sites,which significantly improved the photoelectrochemical water splitting efficiency.Typically,the photocurrent density of Co Ni-MOFs/Ti-α-Fe2O3 could reach up to 0.24 m A·cm-2(1.23 V vs.RHE),which was 1.6 times that of Ti-α-Fe2O3.This study offers a promising solution to tailor the growth and dispersion of high-quality dualcocatalysts and paves the way toward the commercial realization of watersplitting systems. |
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