| The large consumption of fossil fuels such as petroleum and natural gas has caused many problems,such as the rise of the earth's temperature,the aggravation of environmental pollution and the loss of energy.The problems of energy and the problems brought about have attracted more and more attention.Low carbon economy is rapidly becoming the focus of global concern and research because of its low energy consumption and low pollution.Hydrogen,as an energy carrier,has attracted more and more attention due to its high efficiency and cleanliness.It is regarded as the best fuel to replace fossil fuels.Therefore,the development and utilization of hydrogen energy is a bright way to achieve sustainable economy.With the rapid development of science and technology,the technology of hydrogen production without pollution and low cost is being replaced by energy maximization 1972,Fujishima and Honda first discovered that the n-type semiconductor TiO2 single crystal photoelectrode can decompose the phenomenon of aquatic hydrogen,which makes it possible to use solar energy and photocatalytic semiconductor material to generate hydrogen.Amony many semiconductor materials,there are few semiconductors that conform to the band gap of decomposition water and highly efficient,stable and sustainable semiconductor.P semiconductors in photocatalytic semiconductor materials can be directly used p-type to produce hydrogen and have high conversion efficiency.At present,the development of n-type semiconductor materials is lagging behind,mainly because the semiconductor materials with suitable band gaps are less,and the two-photon system needed to form a highly efficient catalytic system must have a suitable n type semiconductorAs an ideal n-type semiconductor with a band gap of(2.0eV-2.2eV)the ?-Fe2O3 has high solar energy conversion efficiency(16%)economically,unpolluted and condultion,which has attracted more and more attentions of researchers.However,the position of the band edge of ?-Fe2O3 is higher than the reduction potential of water,so to achieve the water splitting bias must be added.The iron oxide for research of iron saturation current is not very high and the onset potential is relatively poor,it is bad to the practical application.At present,the bottleneck of the modification of iron oxide is mainly due to the following aspects,which are bulk composite,surface composite,and the existence of large surface back reactionIn this paper,reducing the surface back reaction increase the conversion efficiency of hematite photoanode solar energy to hydrogen,the alumina modified the surface of iron oxide to achieve the high photoelectric.We improved the iron oxide saturated photocurrent by ion doping,annealing,surface modification and supporting catalyst.The main research contents of this paper are as follows:The photoelectrode was grown on FTO by hydrothermal method,the conductivity was enhanced by Ti4+ ion doping.The preparation of photoelectrode on the FTO is the common practice way of electrode material.It is simple,low cost and easy to obtain the nanorod array film by hydrothermal method.By adjusting the ratio of ferric chloride and urea in the preparation process,the preparation of iron oxide nanorods with different aspect ratio.In general,the larger the aspect ratio is helpful to the separation of charge and reduce the charge transfer distance,but the nanorods can not be too long,longer nanorods will be bad to the longitudinal charge transfer,the length of hematite is between 600nm-700nm.In this paper,Ti3+ ions were doped(TiCl3 was added into the precursor)into hematite,then Ti4+ ions were produced by high temperature annealing.The effect of alumina on hematite was mainly inhibited by the surface reaction,the paper found that the effect of alumina on the surface of hematite is inhibition of the back reaction rather than alumina as a passivation layer passiving surface states.At present,the high temperature annealing and ions doping of iron oxide were used to solve the bulk recombination and reduced the surface recombination by supporting the passivation layer such as alumina and germanium oxide.However,the inhibition of surface back reaction is also one of the important factors that limiting the saturation photocurrent.Therefore,we found that loading alumina on the surface of iron oxide has a good effect on inhibiting the surface back reaction by changing the loading process and sintering temperature.After loading the alumina,we found that the saturation photocurrent of hematite was increased six times as well as before,but the onset potential did not shift negatively.On the contrary there was a positive shift in past paper,it was attributed to the fact that the alumina did not passivate the surface state. |
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