Experimental Study On Catalytic Reduction Of No₃^-by Zinc-nickel Electrode

Since the contamination of groundwater nitrate nitrogen poses a serious threat to human health,it is particularly important to remove nitrate from groundwater.The electrochemical catalytic reduction of nitrate nitrogen wastewater has a small reactor size,is convenient for automatic control,does not require the addition of reducing agents and other reagents,and does not need to quote new chemical reagents,thereby reducing secondary pollution and the like,and has been accepted in recent years.Concerned that the development of cathode materials is the focus of research.Platinum group metals such as Pd and Pt have high electrochemical activity and strong corrosion resistance,It can effectively remove nitrate nitrogen from wastewater,but platinum group metals are more expensive and it is difficult to apply in practice.Non-precious metal electrode materials also do not very effectively remove nitrate nitrogen from groundwater.In this study,two kinds of new non-precious metal electrode materials Ti/ZnO electrode and Ti/ZnO-Ni electrode were prepared by brush pyrolysis using Ti plate as matrix.Scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy were used to describe the surface morphology,crystal structure,grain size and elemental valence of Ti/ZnO and Ti/ZnO-Ni electrodes.Electrochemical test electrodes were used to study two Electrocatalytic performance and corrosion resistance of the electrode to NO₃^-.The nitrate nitrogen reduction experiment was carried out to analyze the product selectivity of Ti/ZnO electrode and Ti/ZnO-Ni electrode.The conclusions obtained are as follows:?1?Ti/ZnO electrode with a molar concentration of 0.04 mol/L,0.1 mol/L,0.2mol/L and 0.4 mol/L was prepared by brushing pyrolysis.The SEM,XRD and XPS patterns of the respective Ti/ZnO electrodes illustrate the adhesion of the active coating zinc oxide to the electrode surface.Electrochemical testing of each Ti/ZnO electrode and experimental study on degradation of NO₃^-indicate that the presence of active coating zinc oxide not only can improve the electrocatalytic performance of the surface of the Ti/ZnO electrode,but also reduce the overpotential at the electrode reaction.The polarization reaction promotes the reduction reaction on the surface of the electrode;affects the selectivity of the reaction product;it can also improve the adsorption or reduction of NO₃^-on the surface of the electrode plate,thereby improving the removal rate of NO₃^-and also improving the removal rate.The reduction activity of NO₂^-can further promote the conversion of NO₂^-to NH₄⁺and N₂,and increase the selectivity coefficient of the plate to the ideal reaction product N₂,and the magnitude of these promotion changes with the change of the molar concentration of zinc.?2?Ti/ZnO-Ni electrode with a molar concentration of 0.2 mol/L and a molar ratio of Ni/Zn of 5 at%,10 at%,15 at%,and 20 at%was prepared by brushing pyrolysis.The SEM and XRD patterns of each Ti/ZnO-Ni electrode show that the Ti/ZnO-Ni electrode has a hexagonal crystal structure of ZnO crystal.The Ni element enters the ZnO lattice in the form of Ni²⁺,and the Ni element is solid-solubilized into ZnO.In the crystal lattice,the tability and corrosion resistance of the electrode are lowered.Electrochemical tests and NO₃^-degradation tests of various Ti/ZnO-Ni electrodes show that the electrocatalytic activity of Ti/ZnO-Ni electrodes is greatly reduced due to nickel doping;the overpotential of the electrode is also improved.Resulting in the Ti/ZnO-Ni cathode is more likely to undergo polarization reaction,which inhibits the reduction reaction on the surface of the electrode,affects the selection of NO₃^-reaction products,and inhibits the adsorption of NO₃^-by Ti/ZnO-Ni plates and reduces NO₃^-The removal rate,but also increases the reduction activity of NO₂^-,which is a function of the amount of nickel doping.Nickel doping can promote the conversion of NO₂^-to a large amount of NH₄⁺and a small amount of N₂.The reaction product NH₄⁺of each Ti/ZnO-Ni cathode can be used to prepare ammonium nitrogen fertilizer,which is then applied to agricultural production to increase crop yield.Compared with Ti/ZnO cathodes with a molar concentration of 0.2 mol/L,the corrosion potential of Ti/ZnO-Ni cathodes is usually lower than that of 0.2 mol/L Ti/ZnO cathodes,and the Ti/ZnO cathodes are less corroded than Ti cathodes.The potential,so that the corrosion potential of the Ti/ZnO-Ni cathode is also lower than that of the Ti cathode.so the active coating zinc oxide and the Ti/ZnO doped nickel element cannot enhance the corrosion resistance of the plate.