| Semiconductor photolysis of aquatic hydrogen technology has gradually become an effective approach to produce clean energy,thus it can effectively alleviate the energy shortage issue.During the process of photolysing water,the half-reaction of oxygen evolution involving the four-electron transfer step is more difficult to trigger,which makes the development of highly active,stable and low-cost photoanode catalysts a hot research area.Compared to traditional binary metal oxides such as WO3,the ternary metal oxide CuWO4 has received widespread attention due to its narrow band gap,good stability,and theoretical STH conversion efficiency over 10%.However,according to the current reported results,the performance of CuWO4 is still far from the theoretical one,whose reasons have also never been clearly identified.Referring to the problems mentioned above,CuWO4 films were prepared viaself-assembled spray pyrolysis device in this essay.Based on the principle that the performance varies with optical contacts changing during photoelectrochemical tests,we studied the characteristics of photogenerated electron-hole transfer of the CuWO4 photicatalyst and clarify the specific limitations of its performance caused by the transfer of charge carriers with the assistance of other microstructure,electrochemical,and photoelectrochemical testing methods.Further research was carried out by doping CuWO4 with Mo and in situ form n-n junctions with WO3.The obtained research results have been listed as follows:1.The CuWO4 film was successfully prepared using self-assembly spray pyrolysis equipment.The experimental results show that the sample of thin CuWO4 film with the best crystallinity,the purest and the smoothest surface can be obtained when the tungsten source is ammonium metatungstate and the substrate temperature is 400?.By studying the light absorption and photoelectrochemical properties of CuWO4 samples with different tungsten sources,different substrate temperatures,and different film thicknesses,the carrier transport as the entry point was used to study the reasons for the limited performance of CuWO4.It was found that the optimal thickness was 2.16?m through testing numerous samples with various thickness,and the photocurrent can be up to 41 ?A/cm2(1.23 V vs.RHE).By analyzing the differences of photoelectrochemical properties between various samples caused by the change of photo-contacts,it can be considered that the weak transfer ability of photogenerated electrons in CuWO4 films is the main factor to limit the performance of CuWO4.2.CuWO4 samples uniformly doped by Mo were successfully synthesized via the self-assembled spray pyrolysis equipment.By studying the characteristics of photo-generated electron transfer resistance,interfacial migration resistance,intrinsic carrier concentration,and photo-generated hole-electron transport characteristics of samples with different Mo-doped amounts,the disadvantages of limited electron transport of the sample and the photoelectrochemistry are maximized performance.When the thickness of all the sample is about 2.1?m it was found that the dominant surface of the photo-contact performance of the sample to gradually shift from back to front while the content of Mo increases.Besides,it reached saturation when the doping content of Mo was up to 40%and the performance reaches a maximum of 0.32 mA/cm2?23 V vs.RHE),which is 7.6 times than that of the pure CuWO4.The results show that the introduction of Mo reduces the resistance of electron transfer in the CuWO4 film and the migration resistance at the interface between the film and the solution,which can effectively solve the problem of electron confinement in the CuWO4 film.In addition,combined with the increase of the intrinsic carrier concentration and the absorbance,a number of factors have combined to greatly improve the performance of the sample.3.CUWO4/WO3 composites with precise controllable ratio of two phases and film thickness have also been successfully prepared by the self-assembly spray pyrolysis equipment.By studying the changes in sample morphology,structure,film thickness,and performance,the heterojunction content and the optimal film thickness in the sample were optimized.Subsequently the hole transfer distance,electron transport characteristics were studied to realize photogeneration electron-hole transfer.It was found that the performance can be up to the highest of 0.66 mA/cm2(1.23 V vs.RHE)when the sample is dominated by the light contact and the ratio of CUWO4/WO3 is 1,as well as the thickness is increased to be 3.99 ?m,which is 15 times than that of pure CuWO4.The above results prove that the composite sample faciliate the transfer of holes,which is consistent with the band theory.Experiments combined with EIS test show that the rapid transfer of holes accelerates the transfer of electrons,which can effectively solve the problem of limited electron transfer of samples with pure CuWO4 phase.And the combination of the improvement of the light absorption of the sample has greatly improved the photoelectric performance of the sample. |
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