Construction Of TiO₂ Nanowire Secondary Structure And PEC Performance Test

In order to alleviate the environmental pollution and energy shortage caused by the burning of fossil fuels,the development of new renewable clean energy has been valued by various countries around the world.As an emerging energy carrier,hydrogen energy has been favored by researchers for its many advantages.At present,photoelectrochemical?PEC?water splitting hydrogen production technology has been widely studied.Therefore,it is essential to develop efficient,inexpensive and readily available semiconductor materials for PEC water decomposition.This paper aims at enhancing the performance of TiO₂ nanowires as the main line,using cheap easy transition metals oxide,phosphide,polyoxometelates and schiff base ligand to modify TiO₂,respectively,CoO-Co₃O₄/TiO₂ nanowire arrays?NAs?,Ni₃?PO₄?₂/TiO₂NAs,cobalt substituted polyoxometallate Na₂Co₄[Co₄(PMo₉O₃₄)₂]·14H₂O?Co-POMs?/TiO₂NAs and salicylaldehyde o-toluidine?ST?/TiO2 NAs secondary structure were constructed as photoanode materials.Through a variety of characterizations,their elements composition,morphology and structure were studied.At the same time,PEC performance was tested using an electrochemical workstation equipped with a three-electrode system under AM 1.5G simulated sunlight.The main reaearch contents are as follows:?1?First,TiO₂ NAs were grown on conductive glass?FTO?by a hydrothermal method.Secondly,CoO-Co3O4 was loaded onto TiO2 NAs by impregnation and then calcination.The characterization results showed that the TiO₂ NAs grown on the FTO were densely packed and secondary deposition occurs.The PEC test was performed in a 1 M KOH electrolyte solution.The research results showed that the loading of CoO-Co₃O₄ can reduce the charge transfer resistance of TiO₂ itself and improved the charge separation efficiency.At the applied voltage 1.23 V vs.RHE,the photocurrent density of CoO-Co₃O₄/TiO₂ NAs was 0.23 mA cm^-2and had good stability for more than 13 hours.?2?Similarly,TiO₂ NAs were first grown on FTO by hydrothermal method.Then,Ni3?PO4?2 was introduced into TiO2 NAs by dipping and then heating at high temperature.By the XRD,SEM,EDS,TEM,XPS characterization results showed closely spaced TiO₂ NAs and Ni3?PO4?2 was successfully deposited onto TiO2 NAs.After PEC test in 1 M KOH electrolyte solution,it was found that Ni₃?PO₄?₂ can enhance the light absorption ability of TiO₂ itself,reduce the charge transfer resistance and accelerate the surface reaction kinetics,thus Ni₃?PO₄?₂/TiO₂ NAs photoelectrode material having excellent PEC performance.When the applied potential is 1.4 V vs.RHE,its current density reaches 0.25 mA cm^-2,and its stability is longer than 11.5 hours.?3?TiO₂ NAs were grown on FTO by hydrothermal method.Secondly,Co-POMs can be grown directly and efficiently on TiO₂ NAs by using the synthesis strategy of ultrasonic and heating under reflux.The characterization results showed that the growth of TiO₂ NAs was relatively loose and Co-POMs had been successfully introduced into TiO₂ NAs.At the same time,the element combinations and structures of Co-POMs were confirmed by ICP,TG,FT-IR,EDS and XPS.The PEC test was performed in a 0.5 M Na₂SO₄ electrolyte solution.The results showed that Co-POMs had excellent light capture capability,which was introduced into TiO2 NAs to further enhance its light response characteristics,and the charge transfer resistance was also reduced,which significantly improved the PEC performance.Under the same applied voltage of 1.23 V vs.RHE,the photocurrent density is 1.2 times that of the blank TiO₂ NAs,and the PEC water oxidation reaction can be continued for more than14 hours.?4?TiO₂ NAs were first grown on FTO using the previous hydrothermal method.Then,the immersion ultrasonic method was used to directly load ST ligand on TiO2 NAs.Elementary analysis was used to characterize the structure of ST.Similarly,a PEC test was performed in a 0.5 M Na2SO4 electrolyte solution.The results showed that ST can significantly enhance the PEC activity of TiO₂ itself.The photoelectrode material obtained at1.43 V vs.RHE reached a maximum photocurrent density of 0.49 mA cm^-2,which is 1.2 times that of TiO₂ NAs,and the stability can reach more than 13 hours.The main reason was that the supported ST reduced the charge transfer resistance and effectively suppressed the recombination of electron-hole pairs,while enhancing their light-trapping ability.