Studies Of Effects Of Element Doping And Surface Modification Of?-Fe₂O₃ Photoanode On Photoelectrochemical Water Splitting

With the development of modern society,the demand for energy is increasing.At present,we mainly rely on fossil energy,of which the reserves are very limited while resulting in serious greenhouse.In order to achieve sustainable development,we must explore and develop alternative energies to replace traditional fossil ones.Up to date,the widely recognized alternative energy sources are solar energy,wind energy,nuclear energy,etc.Among them,solar energy owns various advantages like abundant reserves,wide distribution,low cost,easy access and so on,which has attracted more and more attentions of related researchers.Photoelectrochemical?PEC?water splitting is an effective way to harvest solar energy and further storing it in the form of hydrogen.Hydrogen can not only be used as clean energy to meet our needs,but also as an important raw material for various chemical industries such as fertilizer production,petroleum refining and so on.However,reserves of hydrogen in nature is very low,and it is very difficult to obtain directly from nature because of its very small density.It is often obtained by decomposition and reforming of fossil fuels and electrochemical water splitting.Nevertheless,it can be produced by PEC water splitting.Semiconductor materials have been considered to be feasible in the field of photocatalysis in recent years.The preparation of a highly efficient PEC water splitting semiconductor material is a current research hotspot.In a PEC water splitting system,it is essential to fabricate a high performance photoanode.A series of transition metal oxides,such as titanium dioxide,zinc oxide,and iron oxide,have been investigated as PEC anodes.However,the wide band gap semiconductors such as titanium dioxide and zinc oxide are doomed to meet the requirements of photoconversion efficiency of PEC water splitting.More researchers have narrowed their search targets to semiconductor materials with more suitable band gaps.Hematite?alpha-Fe₂O₃?have been paid more and more attentions because of its suitable band gap,stable chemical performance,abundant reserves,environmental protection and pollution-free use process.However,as a photoanode,alpha-Fe₂O₃ itself also has serious shortcomings,such as poor conductivity and sluggish water oxidation kinetics.Therefore,in this work experiments were designed and carried out to fabricate alpha-Fe₂O₃ photoanode with higher PEC water splitting efficiency.1.Studies of the mechanism of performance enhancement of Ti-doped?-Fe₂O₃photoanode photoelectrolytic waterDoping is a type of method commonly used to improve the performance of photoelectrolyzed water of?-Fe₂O₃ photoanodes.Among the many doping elements,Ti is a common class of dopants.In the published literature,the Ti-doped?-Fe₂O₃ photoanode exhibits excellent water oxidation properties,which are often considered to be significantly improved in electrical conductivity and reduce charge recombination during charge to the electrode surface.However,few have further studied the effects of electrode surface area changes and charge transfer properties.Based on the above discussion,after introducing Ti element into the?-Fe₂O₃ precursor solution,a Ti:Fe₂O₃ photoanode was prepared based on the chemical bath deposition method,and photoelectrochemical test was carried out.It was found that the photoelectrolytic water ability was obvious.Upgrade.Further,after performing electric double layer capacitance analysis and intensity modulation current spectrum?IMPS?analysis,the results show that the surface area of the?-Fe₂O₃ photoanode will increase significantly,and the surface state is more suitable for charge transfer.Both of these will be more suitable for water oxidation reactions in higher water oxidation performance properties.2.Co–B modified hematite photoanode for higher PEC water splitting performanceIn addition to doping,surface modification is also a common means of improving the performance of?-Fe₂O₃ photoanode photoelectrolytic water.Recently,there have been many reports on various types of transition metal boride-modified?-Fe₂O₃ photoanodes,which have attracted more and more researchers'interest.This transition metal boride always causes a great increase in its water oxidizing ability after being deposited on the?-Fe₂O₃ photoanode,but the specific mechanism has not been reported in detail.Based on this,we successfully prepared Co-B modified?-Fe₂O₃ photoanode by simple immersion method,and tested its physical and electrochemical properties.Results Surface Co-B can significantly improve the water oxidation performance of?-Fe₂O₃ photoanode.After further research,it was found that Co-B modification can not only improve the charge separation efficiency of?-Fe₂O₃ photoanode,but also improve the surface water oxidation performance.Under the combined effect of both,the Co-B modified?-Fe₂O₃ photoanode will exhibit greatly improved photoelectrolytic water performance.