Preparation Of CoNi Nanoparticles Supported On Ionic Liquid Functionalized Graphene Cathodic Catalyst And Study On Degradation Of PPCPs

Pharmaceuticals and personal care products(PPCPs),as emerging contaminants,have been frequently detected in aqueous environment in recent years.Most of PPCPs poses a serious harmful to the ecosystem and human beings,which have aroused more and more concerns.Electrochemical technology has advantages of simple operation,green environment protection and easy control.It shows a good application prospect in water treatment.Electrode material is the core of electrocatalysis technology,which plays a decisive role in the degradation rate of pollutants and electrode stability.However,the heterogeneous distribution or agglomeration of nanoparticles on the electrode surface will directly affect the catalytic performance of the catalytic electrode.Thus,based on the excellent properites of graphene and ionic liquid,metal nanoparticles were chemically reduced and loaded on the surface of ionic liquid functionalized graphene to overcome the poor dispersion of nanoparticles,and a catalytic cathode with both oxygen reduction and hydrodehalogenation properties was obtained to detoxication and degradation of PPCPs.The mechanism of electrocatalytic performance is systematically discussed.In order to evaluate electrocatalytic performance of cathodic catalysts,the structure and properties are characterized by characterization analysis and electrochemical performance tests,the optimum content of ionic liquid and metal loading were selected.The synthesis mechanism of the as-prepared catalysts was discussed.The results show that metal nanoparticels size of catalyst is smaller and electrocatalytic performance is higher than other catalysts when mass ratio of ionic liquid to graphite oxide(GO)is 2:1,the metal loading of Co/IL-rGO and Ni/IL-rGO is 5%,and the bimetallic loading of CoNi/IL-rGO is 2.5%,and the metal crystallites of the three catalysts were 3.64,3.66 and 3.60 nm,respectively.The metal nanoparticles of Co/IL-rGO,Ni/IL-rGO and Co Ni/IL-rGO catalysts were dispersed uniformly on the surface of the support.The oxygen reduction current values were 0.07,0.06 and 0.51 mA.Moreover,the catalytic activity of CoNi/IL-rGO cathodic catalyst is higher than that of Co/IL-rGO and Ni/IL-rGO cathodic catalysts,which is due to the synergistic effect of Co and Ni bimetals.The catalytic performance of Co/IL-rGO,Ni/IL-rGO,CoNi/IL-rGO,and CoNi/rGO cathodic catalysts for oxygen reduction and hydrodechlorination were compared.The results showed that CoNi/IL-rGO exhibited higher oxygen reduction activity in the four catalytic electrodes.The initial potential and peak potential were-0.15 V and-0.28 V,respectively.And the peak current intensity was-0.51 mA which were 6.3,7.8 and 6.1 times of Co/IL-rGO,Ni/IL-rGO and CoNi/rGO,respectively.The oxygen reduction process generates H2O2 by two electron transfer,and the yield was above 80%.The hydrodechlorination of chlorophene by CoNi/IL-rGO was also higher than that of the other three kinds of catalytic electrodes.The hydrodechlorination function difference of Co and Ni on CoNi/IL-rGO cathodic catalyst promotes the hydrodechlorination of chlorophene.The internal resistance of CoNi/IL-rGO cathodic catalyst is 7.5 ? and it shows a slower decay rate,indicating that CoNi/IL-rGO has higher conductivity and stability.The modified CoNi/IL-rGO catalytic cathode was used as cathode to study the electrocatalytic reduction and oxidation of chlorophene.The kinetics of the electrochemical degradation of chlorophene was studied and the optimum technological conditions were optimized.CoNi/IL-rGO and CoNi/rGO catalytic systems were compared in terms of degradation rate,salinity,dechlorination rate and concentration of active species.Degradation mechanism and toxicity evaluation of chlorophene were discussed.The results showed that the optimum conditions were:current density 68 mA/cm2,electrolyte concentration 0.05 mol/L,pH 5.5 and initial concentration 20 mg/L.The catalytic performance of CoNi/IL-rGO is better than that of CoNi/rGO catalytic cathode without ionic liquids,because the addition of ionic liquids enlarges the surface area of graphene,reduces the size of crystallites and enhances the catalytic active surface area.Six aromatic products and five carboxylic acids were detected.The degradation pathways of chlorophene by CoNi/IL-rGO catalytic cathode was proposed.The toxicity of chlorophene in cathodic compartment and anodic compartment were detoxified after 120 minutes.To further prove the high activity of CoNi/IL-rGO catalytic cathode,the degradation of 4-bromophenol by CoNi/IL-rGO and PdFe/rGO doped with noble metals was compared.The removal rate,salinity and bromine removal rate of 4-bromophenol by CoNi/IL-rGO catalytic cathode were 98.6%,94.2%,and 99.1%,respectively,which were higher than that by PdFe/rGO cathode.The results show that CoNi/IL-rGO can be a good substitute for PdFe/rGO catalytic cathode doped with precious metals for the oxidation degradation of 4-bromophenol,reducing the cost of electrode and expanding the application range of catalytic cathode.The intermediate products in the degradation process of 4-bromphenol were determined and the degradation pathway was deduced.Kinetic analysis showed that the decomposition rate of aromatic products was faster during the degradation of 4-bromophenol,which was the key reaction step.The high catalytic activity of CoNi/IL-rGO catalytic cathode prevents the accumulation of benzoquinone and hydroquinone in solution,reduces the toxicity of cathodic compartment and achieves the purpose of detoxification.