Performance And Mechanism Research Of The Electrocatalytic Reduction Of P-Nitrophenol Based On A New Non-Precious Cathode

p-Nitrophenol?p-NP?as a common industrial raw material was widely used in industrial production and application.Owing to its anti-oxidation,refractory biodegradation and carcinogenic toxicity,United States Environmental Protection Agency had listed it as a priority pollutant.To date,some traditional treatment technologies can be used for the treatment of p-NP wastewater,but these technologies have certain defects,such as the consumption of chemical reagents in the Fenton reaction process,the low energy efficiency of the ozone oxidation process,and the difficulty of regeneration of the adsorbent in the physical adsorption process.As a new technology,the electrocatalytic reduction reaction can convert refractory phenolic contaminants into biodegradable substances,and hence,the development of non-precious metal material is the key to enhancing their industrial application potential.In view of this,a reduced TiO₂ cathode was developed(TiO_2-x/Ti electrode),which could remove p-NP and reduce the biodegradability of the pollutant by using the efficient catalytic reduction ability endowed by defects.In the process of preparing TiO_2-x/Ti electrode,controlling the crystal structure and reduction temperature of TiO₂ was conducive to regulating the electrochemical reduction activity of TiO_2-x/Ti electrode.Anatase TiO₂ is easier to prepare the electrode with high efficiency p-NP reduction activity at low temperature.In the p-NP solution with initial concentration of 0.1 m M,the apparent reduction rate constant of Ti electrode is only 0.0083 min^-1,and the apparent reduction rate of TiO₂/Ti electrode can reach 0.0196 min^-1.The reduction rate constant of TiO_2-x/Ti electrode can reach 0.0294 min^-1.At the same time,the electrochemical active area?5.2 cm²?of TiO_2-x/Ti electrode is higher than that of TiO₂/Ti electrode?2.9 cm²?.In addition,on the basis of defect etching,TiO₂ Electrode with defects on high energy?001?crystal surface was prepared by facet control(001-TiO_2-x/Ti electrode),which can further improving the catalytic reduction activity of TiO₂.The electrochemical active area of 001-TiO_2-x/Ti electrode reached 30 cm²,which was much higher than that of TiO_2-x/Ti electrode without facet control.The results show that the reduction of p-NP on 001-TiO_2-x/Ti electrode was more favorable under acidic condition.The reason is that the decrease of buffer p H,the more favorable combination of electron and H⁺,and the transformation to atomic hydrogen through Volmer mechanism.At the same time,the strong electrostatic repulsion between p-NP and cathode in alkaline condition leads to the lower removal efficiency of p-NP than that in acidic condition.With the increase of cathode applied potential,the removal rate of p-NP increased,and the increase of potential enhanced the direct reduction ability,while more atomic hydrogen was produced to enhance the indirect reduction ability.For the 001-TiO_2-x/Ti electrode,even in the high concentration of p-NP atmosphere,the removal rate is still high?> 80%?,which shows that the 001-TiO_2-x/Ti electrode with facet control has higher industrial application potential.In addition,based on the CV test and the tert-butanol capture experiment,it was found that the removal of p-NP on the 001-TiO_2-x / Ti electrode mainly relies on the indirect reaction path.Finally,we found that the electrode life can be effectively prolonged by the process of exchanging anode and cathode.In summary,the electrochemical activity of TiO₂ catalytic materials was optimized step by step by defect etching and facet control,and an electrochemical system was constructed to treat phenol containing wastewater with electrochemical reduction process as the main body.Through direct reduction and indirect reduction,the transformation of p-NP from oxidation-resistant to biodegradation to biodegradation was realized.The results show that the modified TiO₂ electrode can effectively treat the high concentration phenol wastewater and reduce the toxicity of phenol.The stability of the electrode is effectively improved by inverting the electrode,which provides a reference value for industrial application.