Modification Of Copper-based Materials And Their Electrocatalytic Nitrate Reduction Performance In Electrochemical And Microbial Synergistic Electrocatalysi

With the progress of human civilization and increased human activity,more and more industrial wastewater and domestic sewage are discharged,which could greatly damage the ecological balance of the earth.Especially,groundwater contaminated with nitrate can endanger human health in a direct or indirect way.A series of removal methods for nitrate pollution are proposed.Among them,the electrochemical reduction strategy has the advantages of energy saving,environmental friendliness and controllable products.Ammonia（NH₃）,as an important chemical raw material,has been widely applied in many fields,such as agriculture,industry and medicine.Therefore,the electrochemical nitrate reduction to ammonia（NRA）strategy has attracted considerable attention.Nevertheless,the complex 8e^-process from nitrate to ammonia and competitive hydrogen evolution reaction（HER）make NRA a low selectivity of ammonia and low Faraday efficiency.Therefore,a series of copper based electrocatalysts were proposed to improve the ammonia selectivity and Faraday efficiency of NRA.Microbial fuel cells（MFC）,as microbial electrochemical systems（MESs）,can degrade organic matter while converting chemical energy into electrical energy.Nitrate can act as an electron acceptor for MFC,allowing it to be used for denitrification and power generation.In the experiment,MFC can provide the electrical energy required by NRA.Therefore,we combined the NRA process with MFC to establish a new MES combined process for nitrate removal.This paper adopts the method of doping and alloys of copper catalysts were modified to improve its electrical efficiency of catalytic nitrate reduction for ammonia selective and Faraday,respectively.At the same time,the cathode and anode prepared on carbon cloth by the above method were combined with MFC system to form MESs,and the nitrate reduction and electricity generation performance in the system were investigated.The main research content of this paper are as follows:1.Ce doped Cu electrode material was prepared by electrodeposition method,and its performance of nitrate electrochemical reduction and microbial electrochemical reduction were investigated.The SEM showed that Cu₁₀Ce₁₀electrode presented a unique point structure.The prepared electrode was analyzed by TEM,HRTEM,XRD and XPS techniques.The results showed that Cu₁₀Ce₁₀electrode could tune electronic structure of Cu by generating Cu/Cu₂O interfacial structure as active phase,which reduces the overpotential of nitrate reduction and improves the NH₃selectivity of Cu electrodes.At-0.23 V vs.RHE,Cu₁₀Ce₁₀electrode demonstrated the best performance of NRA,with ammonia yield of 0.99mmol h^-1cm^-2,Faraday efficiency of 98.43%and NH₃selectivity of 79.33%,which were obviously better than other electrodes In MESs,the performance of Cu₁₀Ce₁₀@CC electrode as an anode needs to be improved.2.Cu-Ni-Pd alloy electrode was prepared by electrodeposition and substitution reaction,and the performance of nitrate electrochemical reduction and microbial electrochemical reduction were investigated.The successful substitution of Pd made the electrodes exhibited spherical structure.TEM,HRTEM,XRD and XPS analysis showed that Pd existed in the form of Pd（111）and Pd（100）on Cu₁₀Ni₁₀/Pd₁electrode.At-0.23 V vs.RHE,Cu₁₀Ni₁₀/Pd₁electrode showed the best performance of NRA,with an ammonia yield of 1.53 mmol h^-1cm^-2,Faraday efficiency of 91.63%and ammonia selectivity of 81.71%,which are better than other electrodes.This reflects that noble metal Pd significantly improves the NRA performance of electrode.In the MESs,Ni_20/Pd₁@CC electrode shows the best performance.The maximum power density of the Ni₂₀/Pd₁@CC MES was 209.3 m W m^-2,and the nitrate conversion rate was 45.31%,both of which were about twice that of the control group.