Preparation Of Metal Oxide Catalyst And Its Application In Electroreduction Of Nitrate

Ammonia（NH₃）as a kind of important chemical and carbon-free energy carrier,has been widely used in the industrial and agricultural production and in daily life.The ammonia production mainly depends on Haber-Bosch process in the world,but it is a process that consumes huge amount of energy.Therefore,replacing industrial ammonia synthesis with an environmentally benign electrochemical nitrate reduction reaction has attracted much attention.The key of this reaction lies in the design and preparation of electrocatalyst.In this paper,a simple hydrothermal method was used to synthesize metal oxide catalysts.The Faraday efficiency and yield of nitrate reduction to ammonia were improved through the synergistic effect of two metal oxides and the introduction of oxygen vacancy.The main research contents and innovation points are as follows:（1）Preparation of CuO-CeO₂ catalyst and its application in electrocatalytic ammonia synthesis.CuO-CeO₂ composite oxide catalyst was synthesized by hydrothermal method and used in electrocatalytic nitrate reduction reaction,The morphology and composition of CuO-CeO₂ composite oxide catalyst were studied by different characterization methods.Potentiostatic electrolysis was carried out using the catalysts at 0.5 M K₂SO₄ electrolyte containing 1000ppm NO₃^-.The results showed that the catalytic performance of CuO-CeO₂composite oxide of proper compositions was obviously better than that of pure Cu O and CeO₂,indicating that there was a synergistic effect between Cu O and CeO₂.When the mass ratio of Cu/Ce was 0.8:1,the yield of NH₃was 63.5μg h^-1 mg^-1_cat and FE was 65.9%at the potential of-0.35 V vs reverse hydrogen electrode.Additionally,CuO-CeO₂ catalyst had good stability.（2）Preparation of NbO_x catalyst and its application in electrocatalytic reduction of nitrate.NbO_x catalyst with oxygen vacancy（OVs）was prepared by hydrothermal method and used in the electrocatalytic reduction reaction of NO₃^-.The experimental results showed that the concentration of reactants and p H of the electrolyte had obvious influence on the catalytic performance of the electrode.Electrolytic experiment data showed that in 0.5 M K₂SO₄electrolyte containing 1000 ppm NO₃^-,FE and yield of NH₃ over NbO_x were94.5%and 55.0μg h^-1 mg^-1_cat.The outstanding activity of NbO_x was mainly attributed to the nature of NbO_x and the presence of OVs,which affected the chemical state of Nb,improved the binding energy of key intermediates in the electrolysis process,reduced the reaction energy barrier,and promoted the electrochemical ammonia synthesis reaction process.