Preparation Of NiCu Electrode And Its Electro-oxidative Nitrogen Removal Performance Based On Optimization Of Surface/interface Modulation Strategy

As an important part of the global nitrogen cycle balance,ammonia-nitrogen is also one of the main forms of nitrogen pollutants in water bodies.Once discharged in excess,it can easily cause serious environmental problems such as eutrophication and black odor of water bodies.For the efficient treatment of ammonia-nitrogen wastewater,the economical and environmentally friendly direct electrochemical oxidation technology is expected to be researched and applied.Recently,cheap and readily available NiCu electrodes have shown great catalytic potential in the field of ammoxidation(AOR)due to the good electronic coordination effect between bimetals.However,it has been faced with many problems,such as anode AOR kinetic hysteresis resulting from the shortcomings of high overpotential,insufficient exposure of active sites,and low selectivity of products.In this work,the design of NiCu electrodes is further optimized by surface/interface regulation strategies,such as doping modification,heterostructure construction,defect engineering and atomic level engineering.It is to improve the internal electronic structure and deeply regulate the formation and exposure of active sites,thereby promoting the rapid initiation of AOR at lower potentials.The morphological structure and phase composition,electrochemical performance and electro-oxidative nitrogen removal treatment utility of each catalytic electrode are examined.Providing proven methods and concepts for the rational design and development of stable and efficient catalytic electrodes,as well as advancing the application of direct electrochemical oxidation technology in the field of ammonia-nitrogen wastewater treatment.The main research contents are as follows:(1)A stable and efficient Ni1Cu3-S-T/CP catalytic electrode was synthesized through hydrothermal synthesis and alkaline electrochemical tuning strategy for AOR.The dynamic migration of sulfur ions deepens surface reconfiguration level to promote the full formation and exposure of active species,which effectively reduces the reaction energy barrier.With the help of theoretical models and calculations,the function mechanism of Cu of NiCu-based catalytic electrodes in the catalytic AOR process is proposed and verified,which can regulate the d band center and state density of electrode materials to optimize its endogenous electronic structure.The experimental results showed that the Ni1Cu3-S-T/CP catalytic electrode exhibits excellent AOR activity with a high current density of 150 mA/cm2;After 5 hours of operation,the removal efficiency of NH4+-N reached 96.23%,and it showed strong cycling stability.It not only provides an example for the controllable synthesis of excellent NiCu-based catalytic electrodes,but also facilitates the efficient removal of ammonia-nitrogen in wastewater.(2)With the help of electrochemical deposition and alkaline electrochemical tuning strategy,Co and S co-doping successfully constructed a three-dimensional(3D)nanoflower-like structure Ni1Cu1Co0.5-S-T/CP catalytic electrode.The special 3D heterojunction structure furnishes a large number of ion transport channels,which lays a good foundation for the acceleration of AOR kinetics.Co further enhances the inter-metal electron coordination effect,reducing the onset potential of AOR.The experimental results displayed that the Ni1Cu1Co0.5-S-T/CP catalytic electrode has excellent AOR activity,then realized the efficient degradation of NH4+-N in wastewater,namely the removal efficiency up to 98.07%accompanied by 81.21%high N2 selectivity.This has certain guiding significance for the construction of heterojunction catalytic electrodes,which is convenient for giving impetus to the green and efficient treatment of ammonia-nitrogen wastewater.(3)NiCu3-N-C DAC anchored in nitrogen-doped carbon was synthesized by simple solid-phase pyrolysis method,where an NiCu diatomic site structure was innovatively designed.By means of HAADF-STEM and XAFS analysis methods,the existence of adjacent diatomic sites was confirmed and local coordination environment of Ni-N4/Cu-N4 groups was revealed.The results show that after 6 hours of operation in the electrocatalytic system constructed by NiCu3-N-C DAC,NH4+-N removal efficiency reached 99.52%,N2 selectivity reached 99.58%,FE was 86.60%,and stability could be maintained for at least 36 h.Meanwhile,the variations in the degradation mechanism of NH4+-N between the catalyst and the nanoscale catalyst are briefly described.In conclusion,NiCu3-N-C DACs with specific diatomic site structures can achieve efficient degradation of NH4+-N,realizing resource utilization and harmlessness of product.This not only has certain guiding significance for the rational design of multi-synergistic single-atom catalysts,but also promotes the green and efficient treatment of ammonia-nitrogen wastewater,helping the implementation of the“dual carbon”policy.