Photovoltammetric Behavior Analysis Of Several Electroactive Compounds On Nanocomposites

In this thesis,CdS QDs and BiOI nanosheets were synthesized,and then incorporated with reduced graphene oxide?RGO?to obtained CdS-RGO and BiOI-RGO nanocomposites,respectively.These CdS-RGO and BiOI-RGO nanocomposites with highly photoelectrocatalytic activity employing to modify GCE obtained CdS-RGO/GCE and BiOI-RGO/GCE.These PEC sensors were applied for the study the photovoltammetric behavior of electroactive compounds.The main contents include the following two parts:1.Water-soluble CdS QDs were prepared by a hydrothermal method.The photoactive electrode was coated with a hybrid film of CdS quantum dots?QDs?and low content of RGO.Photovoltammetric behaviors of irreversible,quasi-reversible and reversible electrochemical systems represented by 2,4-dichlorophenol?DCP?,hydroquinone?HQ?and K₃[Fe?CN?₆],respectively,were investigated on a CdS-graphene hybrid film electrode.The cyclic voltammetric?CV?curves of HQ and K₃[Fe?CN?₆]showing a pair of redox peaks became sigmoidal in shape under visible light irradiation.In contrast,the CV curve shape of DCP showing an oxidation peak was not changed under photoirradiation,although the oxidation peak current was enhanced by the photoelectrocatalysis.Furthermore,it was demonstrated that the photovoltammetric curve shapes were not changed by pH and intensity of light source,but were tunable with scan rate and concentration of reactants on HQ and K₃[Fe?CN?₆]of the electrochemical reactions.The calibration sensitivity was 0.369 A/M for photovoltammetry,higher than 0.213 A/M for conventional CV,showing the advantage of the former for detection of DCP.And CdS-RGO/GCE has good reproducibility and stability.2.In the study,BiOI nanosheets were synthesized by a chemical bath method at low temperature.The BiOI-RGO composites were prepared by directly mixing BiOI and graphene suspensions under ultrasonic agitating.The obtained BiOI-RGO composites were applied for development of BiOI-RGO/GCE.The morphology of BiOI and BiOI-RGO were analyzed by scanning electron microscopic?SEM?and the transmission electron microscopic?TEM?.A pair of well-defined redox peaks appears at the CV responses of CAP in the dark and the redox peaks are ascribed to the quasi-reversible reaction of CAP in the absence of proton.The photovoltammetric behavior of CAP on p-type BiOI doped with graphene?BiOI-RGO?was investigated.Under visible light irradiation,the voltammetric reduction peak of CAP on BiOI-RGO increased to a limiting current platform.As a result,the cathodic photovoltammogram became sigmoidal in shape.Nevertheless,the shape of photovoltammetric curve of CAP could be tuned by the content of graphene which influences the electron transfer ability of BiOI-RGO composite.Moreover,the scan rate and the concentration of CAP could also regulate the shape of photovoltammogram of CAP on BiOI-RGO,because they affect the electron transfer and mass transfer,respectively.