In Situ EC-NMR Spectroscopy In Studies Of Conducting Films

Electrochemistry and NMR spectroscopy(EC-NMR)can present an investigate mechanism of redox and kinetics at the molecular level.Recently,more and more researchers pay attention to this technology.However,because of the electrolytic cell or electrode is placed in the NMR detection area,the eddy current effects of electrodes and electrolytic currents affect the magnetic field,which disturbs the homogeneity and sensitivity of the magnetic field,cause the problems such as the loss of signal-to-noise ratio and line broadening.Furthermore,excessive unstable intermediate and product give rise to the spectrum peaks overlapping.To resolve these issues,we have proposed the in situ EC-NMR device which is capable of quantitatively monitoring the generation of products and evaluating reaction rate.We have utilized in situ EC-NMR to study the electro-oxidation of hydroquinone and dopamine,the real-time and high resolution information of the hydroquinone and dopamine oxidation under different conditions can be acquired by in situ EC-NMR.The main research results are shown as follows:1.In this work,an Indium tin oxide glass or a polyaniline/ITO has been used as working electrodes.A platinum wire as the counter electrode,and a thin silver wire as a quasi-reference electrode.Only the part of WE was located in the range of RF coils in the NMR probe.The main advantage of the ITO or PAn/ITO is lesser impactg to the RF,magnetic field,and line broadening.The real-time and high resolution information of the oxidation under different conditions can be acquired by in situ EC-NMR.The proposed in situ EC-NMR is capable of quantitatively monitoring the dynamic distribution of the reagent and products and the kinetic information of chemical reaction.2.In this paper,We adopt the typical REDOX system(Hydroquinone/Benzoquinone)to verify the spectroelectrochemical devices and detection methodology,it can be concluded that in situ EC-NMR provides a powerful tool to probe products distribution and reaction rate,which could be useful to investigate electro-catalytic mechanism and evaluate the electro-catalytic capacity.We developed a direct way for the study of hydroquinone oxidation through in situ electrochemistry-combined nuclear magnetic resonance(EC-NMR).Electro-polymerization-induced nano-polyaniline film was utilized as the catalyst in the process of electrochemical oxidation of hydroquinone.To study the influence of both protic and aprotic media in the electrocatalytic process,we mixed water and dimethylsulfoxide to mimic possible real-life electrochemical environments.The proposed in situ EC-NMR is capable of quantitatively monitoring the generation of products under varied solvent composition and pH values.A positive effect to electro-catalysis capacity is observed when the concentration of DMSO or water is increased from the volume equivalent point,implying that there should be a competition between protic and aprotic media,which can be characterized by EC-NMR technique.3.We utilize the EC-NMR technique to study the electro-oxidation of dopamine in the presence of Au/PAn/ITO film.It is found that Au/PAn/ITO electrode displays higher electrocatalysis activity,The dopamine oxidation by Au/polyaniline under varied pH has been systematically investigated.We have deduced different reaction mechanism of DA at two different pH values.The results indicated that the in situ EC-NMR is capable of quantitatively monitoring the generation of products and evaluating reaction rate.4.Due to its high conductivity,good redox reversibility,and environmental stability,polyaniline(PAn)is one of the most promising conductive polymers.Nanostructured photoelectrochemical solar cells were prepared by combining a Sb2S3-sensitized photoactive electrode,polyaniline nanobelts,and an Ag counter electrode to form a layered structure.Here Sb2S3 acts as an absorbing semiconductor,and polyaniline acts as both a hole conductor and light absorber(a hole conducting dye).Via optimizing the bath deposition duration of 3h,the cell shows a high photovoltaic performance with 7.05 mA·cm2 short-circuit current density,0.695 V-open-circuit voltage,0.457 fill factor,and 2.24%power conversion efficiency.Lay the foundation for the research of solar cells by NMR spectroelectrochemistry.