Analysis Of Photoelectrocatalytic Degradation Mechanism Of Methylene Blue And P-nitrophenol On The Modified Electrode

The control of environmental pollution has become a global important issue ofcommon concern.Photoelectrocatalytic and electrocatalytic study of organicpollutants is one of the forefront of hot spots in the environmental chemistry field.The in-depth study and understanding of the degradation mechanism and catalyticbehavior of organic pollutants is of great significance for the development of newmethods of pollution control.In this paper,the degradation mechanism and catalyticbehavior of methylene blue (MB) and p-nitrophenol (pNP) at modified electrode havebeen investigated.The detailed contents can be summarized as follows:1.The investigation of in situ photoelectrocatalytic degradation of the MB moleculesmerged into a nano-TiO₂ modified film by electrochemical techniques is proposed.The MB-Nafion-TiO₂ (MB/Nf/TiO₂) modified platinum electrode shows reversibleand faster electron-transfer efficiency in photoelectrocatalytic degradation reactions ofsurrounding compounds adsorbed on photocatalyst.Open-circuit potential (E_oc) of theMB/Nf/TiO₂ electrode shows that the MB molecules have an assured effect withtransferred photogenerated electrons on the Nf/TiO₂ interface under UV illumination.A linear regression equation is obtained by the cyclic voltammetry peak current of theresidual MB and the reaction time in the degradation process,in which MB undergoesdemethylation and C=N bond breaking.It is a promising approach for investigating insitu the photoelectrocatalytic degradation of pollution.2.A porous Nafion-TiO₂-polyaniline (Nf/TiO₂/PANI) composite film with a largeelectrode effective surface area was prepared on a platinum electrode by a simplemethod.The morphology and the interfacial properties of the composite film wereevaluated by scanning electron microscopy (SEM) and electrochemical impedancespectroscopy (EIS).The investigation of cyclic voltammetry (CV) confirmed that theNf/TiO₂/PANI film showed an excellent electrocatalytical response to the redox ofMB and was mechanically stable under hydrodynamic conditions.The resultsobtained reveal that the dimerization of MB in Nf/TiO₂/PANI film does not occurred and the introduction of the conducting polymer to electrocatalysts helps in increasingthe interfacial properties between the electrode and electrolyte.The composite filmwould be used as a promising support material in electrochemical orphotoelectrochemical applications.3.The photoelectrocatalytic degradation behavior of pNP was investigated by usinghydrodynamic differential pulse voltammetry (HDPV) technique.The method wasapplied on a nano-TiO₂ modified platinum rotating ring-disk electrode (RRDE) asversatile working electrode.The voltammetric response of the intermediate productwas recorded instantly at the rotating platinum-ring electrode under hydrodynamicconditions via compulsive transport during the photoelectrocatalytic degradationprocess of pNP.A distinct anodic peak at about 0.55 V is mainly attributed to theresult of the formation of electroactive intermediate product,namely hydroquinone(HQ),through the direct reaction between photo-generated powerful oxidant(hydroxyl radicals,·OH) andpNP.The present work has demonstrated that HDPV canbe effectively used to in situ monitor the formation of intermediate product atnano-TiO₂ modified RRDE,providing a promising approach to investigate in situ thephotoelectrocatalytic degradation mechanism of organic pollutants like toxicnitrophenols.4.A glassy carbon electrode modified with silver particles under polydopamine filmwas prepared successfully by means of electropolymerization and pulsedelectrodeposition.A detailed analysis of the scanning electron microscope imagesreveals that silver deposit,obtained under pulsed electrodeposition conditions,appears as homogeneously compact and the crystallites are well dispersed on thepolydopamine substrate than that observed on the unmodified glassy carbon surfaces.The resulting silver nanoparticle/polydopamine modified glassy carbon electrode(Ag/PDA/GC) was electrochemically characterized through the reduction ofpNP.Thepotential needed for the reduction of the compound on the Ag/PDA/GC electrode issignificantly less negative than that observed on the unmodified glassy carbonelectrode substrates.A linear equation is obtained between the cyclic voltammetrypeak current and the concentration of pNP.The Ag/PDA/GC would be used in the practical application for detecting toxic nitrophenols.