Surface Modification Of Hematite-based Photoanode And Photoelectrochemical Water Splitting

As the global population continues to increase,excessive reliance on fossil fuels exacerbates the energy crisis and global climate volatility.How to protect the natural environment of the earth while developing the economy has become an urgent problem to be solved in today's society.Therefore,seeking clean and renewable energy is imminent.Rich solar energy resources and efficient use of solar energy resources are considered to be an effective way to solve the fossil energy crisis.Photoelectrochemical water splitting technology is the use of semiconductor photoelectrodes to directly convert solar energy into hydrogen energy,which can effectively solve energy demand and reduce environmental pollution,and hydrogen is also one of the most promising clean energy sources in the future.The design and preparation of high-efficiency and stable semiconductor photoelectrode materials is the key to achieving high-performance photoelectrochemical water splitting.Hematite materials are promising semiconductor photoelectrode materials because of their suitable forbidden band width,high chemical stability,non-toxicity and abundant reserves on the earth.However,its charge transfer and separation ability is poor,the hole diffusion length is short,and the water oxidation kinetics are slow.These shortcomings limit the photoelectrochemical water splitting properties of the hematite photoanode.In this paper,we constructed an ideal hematite-based photoanode model,which illustrates the electron transfer and photogenerated electron-hole pairs in the catalyst by means of density functional theory(DFT)and X-ray photoelectron spectroscopy(XPS).The effect of separation transport on photoelectrocatalytic performance.The research content of this thesis mainly includes the following aspects:1?An ideal interface model combining a hematite nanoplate-based photoanode with Au nanoparticles(NPs)is proposed for elucidating the specific role of Au NPs in photoelectrochemical performances.The theoretical and experimental results reveal that Au/Fe2O3 nanoplates can lead to an enhanced localized electric field at the metal-semiconductor interface upon the formation of surface plasmon resonance and hot electrons,which can be injected into the conduction band of the semiconductor,thus improving the efficiency of the generation and separation of electron-hole pairs.As expected,the Au/Fe2O3 nanoplate-based photoelectrode possessed a higher carrier density and a photocurrent of 1.7 mA/cm2 and 3.8 mA/cm2 at 1.23 V and 1.5 V vs.RHE,which are nearly 5 times and 30 times larger than that of the Au/Fe2O3 nanocrystals and pristine Fe2O3 nanoplate-based photoelectrodes,respectively.2?In order to improve the performance of the photoelectrochemical water splitting of the hematite-based photoelectrode,we constructed an ideal model,which is a synergistic effect between the Au substrate and the NiO cocatalyst to improve the efficiency of decomposing water by PEC.The improved performance can be attributed to the innovative electrode design that promotes the generation and separation of photogenerated electron-hole pairs under solar illumination and reduces recombination losses,and provides a good electrode/electrolyte interface to promote water oxidation.The experimental results show that the photocurrent densities of the NiO/?-Fe2O3/Au photoanodes at 1.23 V and 1.6 V vs.RHE reach 2.60 mA/cm2 and 6.7 mA/cm2,respectively,compared to the light of the ?-Fe2O3/Au photoanode.The current density is 2.7 times and 2.6 times higher.This ideal model can promote the efficiency of photoelectric water splitting,thus providing new opportunities for improving photoelectrochemical water splitting.