Preparation And Electrochemical Performance Of Expanded Graphite Composite Electrode Materials

In recent years,the global environmental situation has become increasingly serious,and environmental protection and pollutant treatment issues have aroused great attention.However,electrochemical technology plays an important role in environmental protection due to its unique advantages.Hydrogen energy as a kind of ideal,non-polluting and effective renewable energy,can help solve the environmental pollution problems caused by fossil fuel combustion.And hydrogen producing by electrochemical decomposition of water is a simple,ripe technology,but an appropriate and efficient electrocatalyst is critical to realize the engineering application of this technology for hydrogen evolution reaction?HER?.Molybdenum disulfide?MoS₂?has attracted much attention because of its low cost,high efficiency and simple preparation,but its poor electrical conductivity and less exposed active sites on the edges limit its engineering applications.Therefore,it is the focus of recent research that two drawbacks mentioned above should be overcome for making it an ideal material for HER.Thus,expanded graphite?EG?with excellent conductivity is used to improve the problem of poor conduction between layers of MoS₂ to improve its performance of HER.In this study,MoS₂/EGM composites were prepared via hydrothermal method and electrochemical performances of them were evaluated for pH-universal hydrogen evolution reaction.The results show that MoS₂/EGM-2 exhibits a small overpotential of 230 mV(j=10 mA·cm^-2),a low Tafel slope of 77 mV·dec^-1,a lower value of charge transfer resistance(R_ct,0.919?·cm²)and long-cycle stability of 12h benefiting from the participation of the EGM as a highly conductive substrate.In addition,MoS₂/EGM-2 has good activity of HER in neutral and alkaline electrolytes.Dyeing wastewater has become an important source of pollution in China's major waters due to its components are complex and difficult to degrade and most of the organics are carcinogenic of which.Electrochemical method for the degradation of dye wastewater has been widely used owing to it has the characteristics of low cost,high energy efficiency,thorough degradation and diverse uses.Compared to the research on the anode process,less attention is focused on the cathodic electrochemical degradation of organics because of H₂O₂ production being less and the side of HER inhibiting the reduction reaction of the cathode resulting in low current efficiency during the degradation of electrochemical cathode materials.In this work,a MnO₂/EGM electrode was prepared with EG which has low activity of HER and MnO₂ having reducing oxygen characteristics by electrodeposition method and used as a cathode material in the experiments of electrochemical degradation of Rhodamine B?RHB?.It's shown that RHB reached a maximum decolorization rate of 94.43%after 30 minutes of electrolysis,when the initial pH was 2,the current density was 40 m A·cm^-2,the electrolyte sodium sulfate concentration was 0.15 mol/L,the initial concentration of RHB was 8 mg/L,and the reaction system temperature was 25?.