Research On Controllable Preparation And Electrochemical Denitrification Performance Of Cu-Fe Nanoalloys

Industrial nitrogen emissions have caused serious nitrogen pollution to the earth’s water resources.The development of efficient and stable nitrogen removal technology is of great value to realize the global nitrogen cycle rebalancing.At present,electrocatalytic denitrification technology has attracted extensive attention in academia and industry.However,the reaction process involves multi-electron and multi-proton coupling reaction,with redundant steps and slow kinetics.Therefore,the development of high-performance catalysts is very important to improve the efficiency of electrochemical denitrification.At present,the research on Cu-Fe nanoalloy catalysts has attracted extensive attention.Metal copper has a highly occupied and unclosed d-orbital,and the energy of d-orbital is similar to that of nitrate LUMOπ*orbital,which can improve the electrochemical reduction activity of nitrate by exchanging electrons;The introduction of iron can effectively adjust the center position of the d-band of the catalyst and promote the adsorption of nitrate on the catalyst surface.In addition,the strong adsorption of Fe on H is helpful to promote the selective hydrogenation of reaction intermediate（NO_x）to NH₃.Based on the above thinking,this paper realizes the controllable preparation of Cu-Fe nanoalloy from bottom to top by reactive mechanical milling,and deeply explores the structure-activity relationship between alloy component content and denitrification performance.The specific contents are as follows:（1）By changing the element ratio of Cu/Fe catalyst to adjust the d-band center and hydrogenation performance of the catalyst,through a series of electrochemical performance tests,Cu₃Fe was finally confirmed to be the most suitable Cu-Fe catalyst for this process.Through the electrocatalytic process of100 ppm nitrate nitrogen electrolyte for 6 hours,the results show that Cu₃Fe reduces 82.7%nitrate and generates 70.3%ammonia nitrogen at the voltage of-0.7 V（vs.RHE）,realizing high nitrate reduction efficiency and better ammonia nitrogen selectivity under low energy consumption.In terms of Faraday efficiency,Cu₃Fe also achieved an efficiency of 74.2%,indicating that its hydrogen evolution side reaction is controlled at a low level.However,the stability is not as good as expected.Fe²⁺is unstable in aqueous solution and is easy to be oxidized to Fe³⁺.Therefore,after multiple electroreduction of nitrate,the nitrate reduction efficiency of the catalyst decreased slightly,which can be attributed to the reduction of electron density on Cu⁰.（2）In order to improve the stability of the electrode in aqueous solution,a simple pyrolysis carbon coated surface treatment was carried out on Cu₃Fe to reduce the oxidation of Fe²⁺on the surface during electrolysis.The results show that when the C/Cu ratio is 15 and the pyrolysis temperature is 700℃,the performance of Cu₃Fe/CN is the best,which can achieve 61.6%ammonium selectivity and 57.0%mass ratio catalytic activity.Cu₃Fe/CN showed excellent stability and nitrate degradation performance in the long-term electrolytic nitrate cycle experiment.Cu₃Fe/CN showed 96%initial current density retention rate in the chronoamperometry test,which was better than 88%initial current density retention rate of Cu₃Fe electrode,and the specific mass activity was higher than that of Cu₃Fe nano catalyst after cycles,Therefore,the carbon coating generated by pyrolysis can effectively enhance the cyclic stability of the electrode.