Study Of Electrochemical Properties And Modified Photocatalytic Activity Of CuBi₂O₄

The CuBi₂O₄ spinel structure has many physical and chemical properties,and it has been extensively studied in photoelectrochemical properties.In this paper,CuBi₂O₄ is prepared by using the polyacrylamide gel method and the coprecipitation method.Our research is focused on the electrochemical performance of CuBi₂O₄ and the photocatalytic performance of Ag-CuBi₂O₄.The main research results are as follows:（1）Sphere-like CuBi₂O₄ particles were synthesized by a polyacrylamide gel method.The morphology of the prepared samples is observed like spheres that have anaverage particle size of²30 nm by SEM.The bandgap energy of the sample is measured to be 1.88 eV by UV-vis DRS.The electrochemical performance of CuBi₂O₄ particles was systematically investigated in 2 M KOH,6 M KOH,and 2 M KOH electrolytes at different temperatures.It is demonstrated that the temperature was one of the important influence factors on the electrochemical performance of CuBi₂O₄ particles,which exhibited relatively higher specific capacitance that is observed at 45°C,reaching 1458 F g^-1 at a current density of 2 A g^-1 in 2M KOH electrolyte.In addition,the sample has an increased capacitance in a higher-concentration electrolyte,but its charge–discharge cycling stability is decreased. Moreover,it is found that the sample exhibits relatively well electrochemical performance in KOH electrolyte compared with in NaOH electrolyte.（2）CuBi₂O₄ microstructures were prepared via coprecipitation route at assisted KH₂PO₄.The prepared samples were characterized by XRD,SEM,BET,XPS and UV-vis DRS.The result showed that the KH₂PO₄ paly an important role in prepared uniform CuBi₂O₄ microspheres hierarchically self-assembled by nanoparticles.The average diameter prepared microspheres takes on a kind of changing curve from 3.3μm to 1.4μm when the KH₂PO₄ concentration increases from 0.5 M to 1.4 M.But,when the concentration of KH₂PO₄ gets to 1.5 M,the average diameter of the prepared microspheres sudden adds to 2.3μm.At the same time,a minor amount of bamboo leaf-or pine needle-like structures,under the KH₂PO₄ concentrations of1.0–1.5 M,are observed in the prepared samples.By using the ultraviolet-visible diffuse reflectance spectroscopy,measuring the bandgap energy is 1.89 eV for the as-prepared samples.The electrochemical performance,using the cyclic voltammetry,galvanostatic charge–discharge measurements,and electrochemical impedance spectroscopy,is investigated in 2 M KOH electrolyte.The hierarchical microspheres that are prepared at the KH₂PO₄concentration of 1.4 M,have a relatively higher specific capacitance because of their smaller size.（3）CuBi₂O₄ particles（350–700 nm）,based on a method called hydrothermal route,were decorated by using Ag nanowires（30 nm in diameter and 0.8–1.5μm in length）.The as-prepared Ag-CuBi₂O₄ composite,with many implements such as XRD,TEM,XPS,UV-vis DRS,EIS,PL spectroscopy and photocurrent response,was systematically characterized.It is found that a separation efficiency of photogenerated electron-hole pairs is improved,because the electrons on CuBi₂O₄ particles can transform to Ag nanowires.The photocatalytic performance of the prepared samples is evaluated by degrading RhB and phenol in simulated-sunlight irradiation.There is a well photocatalytic activity for Ag-CuBi₂O₄ composite,which is 1.9 times higher than bare CuBi₂O_4.Based on a mechanism as the photoinduced charges are efficiently separated and thus more photocarriers participate in the photocatalytic reactions,the photocatalytic activity is increased in the composite.The reactive species,with the degrading effect added the ethanol,BQ and AO and to RhB and the formation of·OH radical,were detected.According to above experimental results,it is confirmed that·OH plays an important role in the reactive species to the dye degradation.The photocatalytic mechanism involved was discussed.