Research On Electrocatalytic Properties Of Iron Based And Copper Based Perovskite Materials For Nitrate Reduction To Ammonia

In response to the national requirements for environmental protection and energy structure upgrading,the use of electrocatalytic technology to reduce nitrate nitrogen in wastewater and synthesize usable ammonia is a promising development direction for the environmental protection and energy industry.The key to restricting the development of this technology lies in the design of electrocatalysts.Perovskite materials are expected to play a significant role in the above-mentioned technology due to their wide range of electrocatalytic activities,as well as their safety and affordability.However,their performance indicators such as ammonia yield,Faradaic efficiency,and ammonia selectivity are difficult to meet the requirements of industrial applications at present.Aiming at the above issues,the main research content and results of this article are as follows:The modification of iron-based perovskite,La Fe O₃,using A-site defect doping and B-site transition metal doping improved the activity of the material in the electroreduction of nitrate to ammonia.The introduction of A-site defects led to the production of a large number of oxygen vacancies in the catalyst,promoting the adsorption and conversion of NO₃^-and reaction intermediates.La_0.9Fe O_3-δreached the ammonia yield of 1024.8μg h^-1cm^-2and the Faradaic efficiency of 78.1%.B-site Cu doping led to electron accumulation around Cu⁺/Cu²⁺in the catalyst lattice,becoming new active sites,optimizing the energy of reaction intermediates,and reducing the energy barrier of potential-determine-step.La Fe_0.9Cu_0.1O_3-δreached the ammonia yield of 1005.0μg h^-1cm^-2and the Faradaic efficiency of 71.9%.In order to further enhance the catalytic activity of Cu doped La Fe O₃,hydrothermal method was used to regulate the crystal plane and morphology,and Cu doped La Fe O₃with a dominant crystal plane of（1 2 1）and a surface rich in pits and cross-sections was synthesized.The doping of Cu elements in the（1 2 1）plane formed new active sites,optimizing the energy of the reaction intermediates.At the same time,the large number of pits and cross-sectional areas on the catalyst surface increased the specific surface area of the catalyst.The synergistic effect of the two enhanced the activity of Cu doped La Fe O₃for electrocatalytic reduction of nitrate to ammonia,reaching the highest Faradaic efficiency of 93.0%at a low overpotential of-0.7 V（vs.RHE）and the highest ammonia yield of 1231.6μg h^-1cm^-2at-0.9 V（vs.RHE）.Perovskite-like Bi₂Cu O₄was employed as an electrocatalyst to synthesize ammonia by electroreduction of nitrate,and it was then combined with Cu O to form a Bi₂Cu O₄/Cu O composite catalyst.The combination of two heterogeneous materials in a composite catalyst formed a heterogeneous interface,which regulated the electronic structure of active sites,promoted the adsorption and conversion of reactants and reaction intermediates on the catalyst surface,inhibited the formation of adverse byproducts,and thereby enhanced the catalytic activity of the material,surpassing the two single component catalysts.The composite catalyst achieved the highest Faradaic efficiency of 94.1%at a low overpotential of-0.7 V（vs.RHE）and the ammonia yield of 1842.7μg h^-1cm^-2at-0.9 V（vs.RHE）.