Constructing Nano-TiO₂ Three-Dimensional Electrode System For Photoelectrocatalytic Degradation Of Phenol

Phenolic water pollution is one of the difficulties in wastewater treatment,which has caused great harm to human health and ecological environment.Photoelectrocatalysis technology has combined the advantages of photocatalysis and electrocatalysis together,thus showing good degradation performance for phenol.TiO₂ has attracted much attention due to its advantages of low cost,corrosion resistance,and high catalytic activity as photoelectrocatalyst.In this paper,phenol serves as degradation target pollutant,and an efficient,safe,stable and low energy consumption nano-TiO₂ three-dimensional electrode photoelectrocatalysis system is successfully built.The main content of this paper is as follows:（1）Four kinds of TiO₂ photoanodes,including titanium foam,titanium mesh,carbon felt and foamed nickel,were prepared by anodizing method,sol-gel method and coating method,respectively.The material properties（analyzed by XRD,SEM,EDS,XPS,UV-Vis DRS）and photoelectro-chemical properties（analyzed by i-t,LSV,EIS）of the four anodes were compared,and the effects of different pore sizes on the titanium-based TiO₂ photoanode were investigated.The results show that the photoelectrochemical performance of the titanium-based TiO₂ photoanode is better than that of the non-titanium-based TiO₂ photoanode.Under the potential of+1.5 Vνs.Ag/Ag Cl,TiO₂ photoanode with different substrates shows different photocurrent density as follows:TiO₂/Ti160μm(3.34 m A·cm^-2)>TiO₂/Ti_100mesh(3.29m A·cm^-2)>TiO₂/carbon felt(0.10 m A·cm^-2)>TiO₂/nickel foam(0.05 m A·cm^-2).When the pore size of foamed titanium increasing,the photocurrent of it shows an increasing trend as well.The photocurrent of the titanium mesh increased with the increasing of the aperture first,and then showed a trend of decreasing.（2）Construct two-electrode systems and carry out research on photoelectrocatalysis degradation of phenol.In the prepared systems,TiO₂/Ti160μm and TiO₂/Ti_100mesh serve as photoanodes,and carbon felt,nickel foam,platinum sheets,and titanium mesh serve as cathodes.The electrochemical test results show that the TiO₂/Ti_100mesh-carbon felt system has the fastest reaction rate and the best photoelectrocatalysis degradation performance.In the test,the initial condition of phenol,the voltage and p H are 10 mg/L,2.0 V and 7,respectively.The TiO₂/Ti_100mesh-carbon felt system can almost completely remove the phenol within 105 min,and the rate constant of the degradation reaction is 0.0252 min^-1.The photoelectric synergy was verified according to the reaction rate constant（photoelectrocatalysis was 17.1 times and12.5 times that of photocatalysis and electrocatalysis,respectively）,and it was confirmed by radical scavenging experiments that hydroxyl radicals contributed the most（60%）during the reaction.The effects of different factors on the degradation of phenol were analyzed,and it was concluded that the lower the initial concentration,the higher the voltage between electrodes,and the lower the p H value of the solution,the faster the photocatalytic degradation rate of phenol.In addition,the TiO₂/Ti_100mesh-carbon felt system has good stability,and the degradation efficiency of 90%can still be maintained after 4 cycles.（3）CQDs（Carbon Quantum Dots）were synthesized by high temperature carbonization and hydrothermal method using vinegar residue as carbon source.TiO₂/Ti_100mesh was doped and modified by CQDs by hydrothermal method.The material characterization tests（XRD,SEM,EDS,XPS,UV-Vis DRS,PL）,photoelectrochemical tests（i-t,LSV,EIS）and phenol degradation studies were carried out on CQDs/TiO₂/Ti_100mesh.The results showed that CQDs/TiO₂/Ti_100mesh exhibited higher photocurrent density(4.07 m A cm^-2),smaller charge transfer resistance and faster phenol degradation rate compared with TiO₂/Ti_100mesh.