Study On The Preparation And Photoelectrochemical Performance Of Multi-Component Co Modified TiO₂ Nanotube Arrays

Titanium dioxide(TiO2)has been extensively studied in photoelectric conversion due to its excellent photoelectric conversion ability,excellent chemical stability and non-toxicity.Among various TiO2 nanostructure materials,TiO2 nanotube arrays(NTAs)prepared by electrochemical anodization are considered to be one of the most promising photoelectrode materials because of their highly ordered structure,large specific surface area,and unique electron transport structure.TiO2 NTAs is one of the various nanostructured materials of TiO2,so it is also limited by the inherent defects of TiO2.The band gap of TiO2 is wide and can only be excited under ultraviolet light,and ultraviolet light has a very small share in the solar spectrum(3-5%).Therefore,its photoelectrochemical performance will be affected by inherent defects,and it is often necessary to be modified in research and practical applications.Since its development,common and effective modification methods of TiO2 NTAs include self-doping(hydrogenation),transition metal ion doping,non-metal ion doping,precious metal deposition,and coupling with other semiconductors.Generally,different modification methods will improve the photoelectrochemical performance of TiO2 NTAs in different principle,the combination of various modification methods can produce a synergistic effect on the improvement of photoelectrochemical performance,which has increasingly become a new trend of TiO2 NTAs modification.This subject first studied the optimal sintering temperature of TiO2 NTAs,on this basis.using multi-component composite modification methods,through a simple operation method、respectively prepared hydrogenated and S-doped TiO2 NTAs(H-S-TiO2 NTAs),g-C3N4 composite H-S-Ti02 NTAs(g-C3N4/H-S-TiO2 NTAs)and WO3-xSx modified H-S-TiO2 NTAs(WO3-xSx/H-S-TiO2 NTAs).By testing the sample’s apparent morphology,microstructure,composition,optical properties,and photoelectrochemical performance,the optimal conditions for preparing the above composite materials were determined,and the enhancement mechanism of the sample’s photoelectrochemical performance was proposed.The research results show that the optimal sintering temperature of TiO2 NTAs is 550℃.Hydrogenation and S-doping can greatly improve the photoelectrochemical performance of TiO2 NTAs.Compared with the optimized TiO2 NTAs,the absorption range of the optimized H-S-TiO2 NTAs shows a clear red shift.The saturation photocurrent density and photoelectric conversion efficiency of the optimized H-S-TiO2 NTAs reached 1.97 mA/cm2 and 1.18%,which were 3.72 times and 4.92 times of the optimized TiO2 NTAs,respectively.In addition,the optimized H-S-TiO2 NTAs show the highest transient photocurrent density(1.08 mA/cm2),and have excellent photoelectric response characteristics,indicating that the transfer efficiently of photogenerated carriers was increased in the optimized H-S-TiO2 NTAs.The enhanced photoelectric performance of H-S-TiO2 NTAs can prove that hydrogenation and S-doping have a synergistic effect on improving the photoelectrochemical performance of TiO2 NTAs.H-S-TiO2 NTAs was used to obtain g-C3N4/H-S-TiO2 NTAs by dipping method,and the optimal number of dipping was 4.The photoelectric conversion efficiency of the optimized g-C3N4/H-S-TiO2 NTAs is up to 1.47%,which is about 5.44 times that of TiO2 NTAs.The optimized g-C3N4/H-S-TiO2 NTAs(1.64 mA/cm2)has a higher transient photocurrent density and better stability than the optimized TiO2 NTAs(0.29 mA/cm2).In addition,compared with other photoelectrodes,the optimized g-C3N4/H-S-TiO2 NTAs has a larger negative open circuit potential and the best photoelectric stability.This shows that hydrogenation,S-doping and g-C3N4 compound have a synergistic effect on the improvement of the photoelectrochemical properties of TiO2 NTAs.In order to simplify the operation process,another simpler method to realize the hydrogenation of TiO2 NTAs and S-doping modification treatment was determined,and on this basis,WO3-xSx/H-S-TiO2 NTAs was prepared for the first time.The photoelectrochemical performance test determines that the photoelectrochemical performance of WO3-xSx/H-S-TiO2 NTAs is the best when the concentration of Na2WO4·2H2O solution in the electrolyte is 20 mmol/L.Comparing the optimized TiO2 NTAs,H-S-TiO2 NTAs,WO3/TiO2 NTAs20 and WO3-xSx/H-S-TiO2 NTAs20,we can see that the light absorption edge of WO3-xSx/H-S-TiO2 NTAs20 shifts to higher wavelengths,showing stronger absorption of visible light.The saturation photocurrent density of WO3-xSx/H-S-TiO2 NTAs20 is 2.97 mA/cm2,which is about 5.60 times of the optimized TiO2 NTAs;the photoelectric conversion efficiency(1.76%)of WO3-xSx/H-S-TiO2 NTAs20 is about the optimized TiO2 7.33 times of NTAs;In addition,WO3-xSx/H-S-TiO2 NTAs20 shows good photoelectric response characteristics and photoelectrochemical stability,and the transient photocurrent density is as high as 1.66 mA/cm2,which is about 6.15 times of the optimized TiO2 NTAs.WO3-xSx/H-S-TiO2 NTAs20 has the best photoelectrochemical performance,which shows that hydrogenation,S-doping and WO3-xSx modification also have synergistic effect on the improvement of the photoelectrochemical performance of TiO2 NTAs.The research content of this topic is helpful for the development of high-performance photoelectrode materials.The photoelectrode materials prepared in this topic are also expected to be widely used in the field of photoelectric conversion.In addition,for other semiconductor materials,the multi-component composite modification method adopted in this subject can also be considered,and materials with good photoelectric properties also have good application prospects in the field of photocatalysis and photovoltaics.