The Construction Of Bi₁₂TiO₂₀ Composite Electrode And Its Photoelectro-degradation Performance Of MB

Seriously polluting printing and dyeing production is an indispensable key link in the entire textile industry.The“China Dyestuff Industry Yearbook（2019）”shows that Chinese annual dye production volume ranks first in the world,reaching 900,000 tons,accounting for more than 70%of global output.Meanwhile,printing and dyeing wastewater has a complex composition,high chroma,and often contains"three causes"poisons,which is a difficult and painful point in the control of water environment pollution.Photoelectrocatalytic technology uses semiconductor photocatalysts as photoanodes,and utilizes tiny external bias voltage and solar energy to thoroughly treat low-concentration dye wastewater with technical advantages at low cost and high efficiency.So,it has great development prospects.The key to the photoelectrocatalytic degradation of methylene blue dye wastewater technology is the construction of a suitable photoanode with high efficiency and durability.In this study,Bi₁₂TiO₂₀（BTO）,which has a unique energy band structure with band gap is 2.5～2.8e V,is inexpensive,non-toxic,and can respond to visible light,so it was selected as the substrate catalyst.At the same time,BTO was combined with the new two-dimensional Ti₃C₂T_x material,the microstructure was adjusted,and the support research was carried out to construct an efficient and stable photoanode,in order to obtain an environmentally friendly photoanode that was expected to be practical.The main research results obtained include:（1）In order to effectively reduce the high recombination rate of photo-generated carriers of BTO,Ti₃C₂T_x/BTO/fluorine-doped tin oxide photoanodes were conveniently prepared with the aid of mechanical coating by gentle ultrasonic mixing.The anode material was tested by XRD,SEM,TEM,XPS,UV-vis DRS,PL,transient photocurrent and EIS.A platinum plate was used as the counter electrode and a bias voltage of 1V was applied to form a photoelectrochemical cell（PEC）to degrade MB under simulated sunlight.The experimental results showed that the photoelectocatalytic degradation rate of BTO-6 doubled that of BTO.A series of test characterization results showed that the reason for the increased degradation rate was that Ti₃C₂T_x and BTO can form a close contact interface;The difference in Fermi energy levels between the two caused the formation of Schottky heterojunctions between the interfaces,generating internal electric fields,the combination of the internal and external electric fields could effectively inhibit the recombination of photo-generated electrons and holes.And the hydrophilicity of Ti₃C₂T_x contributed to the adsorption of H₂O and the production of hydroxyl radicals,the main active species.In addition,a possible reaction mechanism was proposed based on the experimental and characterization results.This study showed that the internal electric field combined with the external electric field loaded with Ti₃C₂T_x could significantly enhance the catalytic performance of BTO,making innovative efforts for the modification of BTO,and at the same time providing a potential new type of photoelectrocatalytic composite catalyst for degradation of organic dye wastewater.（2）The TiO₂-NTs support substrate was prepared on the titanium plate by electrochemical anodization,and the BTO synthesized by the hydrothermal reaction was ultrasonically mixed with the optimized amount of Ti₃C₂T_x.The composite powder was mechanically coated on the surface of TiO₂-NTs to finally construct photoanodes.The photoanodes were characterized by XRD,SEM,XPS,UV-vis DRS,PL and transient photocurrent,and their photoelectrocatalytic degradation performance of methylene blue（MB）under simulated sunlight was studied.The results showed that the degradation rate of Ti₃C₂T_x/BTO/TiO₂-NTs reached 92.8%after 120 minutes,which was almost 3 times and 2 times that of TiO₂-NTs and BTO,respectively.There were two reasons for the significantly enhanced catalytic performance.One was the red shift of the absorption range from BTO and the high absorbance of Ti₃C₂T_x,and the other was the formation of an internal electric field and an external electric field between the composite materials promoted the separation of photogenerated electrons and holes.The photo-generated electrons retain their high reduction and oxidation reaction ability and produce·O₂^-,the main reactive species.