Photoelectrochemical Performance Of Titania Nanotube Arrays By Doping And Nanoparticle Modification

Among various photocatalysts,titanium dioxide is the most active materials due to its high chemical stability,resistance to corrosion,high photocatalytic activity,and is widely investigated on photodegration of colored pollutants and splitting water for hydrogen.Its large bandgap and high electron hole recombination limit the photocatalytic efficiency.In this article,titanium dioxide nanotube arrays were fabricated by anodization,the intrinsic properties of titanium dioxide have been improved by combining with semiconductor and self-doping.The obtained samples were analyzed by scanning electron microscope equipped with energy dispersive X-ray detector,X-ray photoelectron spectroscopy,Raman spectra and X-ray diffraction,etc.?1?Nano flower structure of molybdenum disulfide modified titanium dioxide was fabricated by hydrothermal process with sodium molybdate and thiourea.The results show that the charge transfer resistance of Mo S₂/TiO₂ is significantly reduced,forming a heterojunction reducing the electron and hole combination,the carrier density and photocurrent density significantly increased and the photoelectric performance improved.As the content of Mo S₂ is high,TiO₂ nanotube was blocked by Mo S₂,leading to weak light absorption ability and performance.?2?Selenide molybdenum modified titanium dioxide was synthesized by electrodeposition in the sodium dihydrogen phosphate electrolyte.The charge transfer resistance of Mo Se₂/TiO₂significantly reduced,resulting high carrier transfer.MoSe₂/TiO₂ formed a p-n heterojunction,effectively reduces the recombination of electrons and holes,it can achieve a maximum 5 orders of magnitude enhancement in carrier density.The photocurrent density of the Mo Se₂/TiO₂samples can increase 3 times than that of titanium dioxide with free bias voltage.Photoelectrochemical performance of the Mo Se₂/TiO₂ slightly increased after 300?heat treatment.Selenide molybdenum morphology formed serious agglomeration blocking titanium dioxide substrate after 330?treatment,resulting in lower performance.?3?Ag₃PO₄/TiO₂ prepared by dipping method,silver phosphate particle size was less than20 nm and evenly distributed;Ag₃PO₄/TiO₂ formed a heterojunction,can effectively reduce the recombination of photogenerated electrons and holes.Ag₃PO₄/TiO₂ has better photoelectrochemical properties by dipping four times,the carrier density is 6 times higher than pure TiO₂.Photocurrent density increased six times under no bias voltage,so silver phosphate modified TiO₂ nanotube arrays can significantly improve the photoelectrochemical performance.?4?An amorphous TiO₂ was heat treated at 200°C under atmospheric conditions,then Ti³⁺was accomplished by electrochemical reduction method in the sodium dihydrogen phosphate electrolyte.The morphology of TiO₂ has no significant changes after electrochemical reduction and nitrogen calcinations,forming Ti³⁺,N co-doped TiO₂.The formation of Ti³⁺and oxygen vacancies are produced simultaneously after electrochemical reduction,which leads to TiO₂lattice distortion,and reduces the photogenerated electron and hole combination and improves the photoelectrochemical performance.The photocurrent density of Ti³⁺,N co-doped TiO₂ is 7times large than pure TiO₂ under free bias voltage,and a lower charge transfer resistance.Also,carrier density and quasi Fermi level are increased,resulting band gap decrease of the doped TiO₂.Finally,we studied the electrochemical reduction time,electrolyte and pre-treatment temperature effect on the performance of Ti³⁺doping samples.