Preparation Of Fe And Cu-Based Catalytic Materials And Applications In Electrochemical Reduction Reactions

With the continuous industrial development of modern society,the energy and environment crisis brought by human production and life is becoming increasingly serious,especially the excessive use of fossil fuels and the excessive emission of nitrate pollutants,which pose a serious threat to human health and ecological environment.In this situation,hydrogen fuel cell technology and efficient and clean nitrate pollutant treatment technology emerge at the historic moment.Hydrogen fuel cell,as a new energy technology with the most potential and the most likely to achieve large-scale application,is gradually favored by the majority of researchers.And electrocatalytic treatment of nitrate pollutants is also becoming a research hotspot in the environmental field due to its advantages of mild conditions and high reaction efficiency.The two parts of the work in this paper focus on oxygen reduction reaction（ORR）in hydrogen fuel cells and electrocatalytic nitrate reduction（NO₃RR）synthesis of ammonia.High ORR performance and electrocatalytic reduction of nitrate to synthesis of ammonia performance are achieved by Fe and Cu-based transition metal catalysts,respectively.At first,Fe-C_xN_y non-noble metal electrocatalytic oxygen reduction catalysts（Fe-C₃N₄,Fe-C₃N₅ and Fe-C_aN_b）were synthesized by using different carbon nitride materials（C₃N₄,C₃N₅ and C_aN_b）as support and iron phthalide as Fe source under high temperature.The catalyst was characterized by XRD,TEM,BET,XPS,FT-IR and Raman,and then the electrocatalytic ORR performance and stability of the catalyst in alkaline electrolyte were studied.The results showed that Fe-C_xN_y catalyst with high surface area,layered structure and a large number of folds was successfully synthesized by high-temperature pyrolysis.The limiting current and half-wave potential of Fe-C₃N₅ catalyst under alkaline conditions were 7.0 m A cm^-2 and 0.91 V vs.RHE,respectively.Fe-C₃N₅ catalyst has high stability in the 4-electron ORR process.In the second part,Cu-N/C non-noble metal catalysts（Cu-N/C（1:400）,Cu-N/C（1:200）,Cu-N/C（1:100）,Cu-N/C（1:80）,Cu-N/C（1:10）,and Cu-N/C（1:5））with different proportions of Cu-acetone as Cu source and melamine as the precursor of N-doped C carrier were synthesized under high temperature conditions.The catalyst was characterized by XRD,SEM,EDS,TEM and XPS,and the Cu load in the catalyst was measured.Then the electrocatalytic electrocatalytic reduction of nitrate to synthesis of ammonia performance and stability of the catalyst in alkaline electrolyte（0.1M KOH and 0.1M KNO₃）were studied.Finally,the source of N element in ammonia was analyzed by nuclear magnetic resonance.The results show that Cu is successfully loaded on N-doped C carrier through high temperature pyrolysis,and Cu-N/C（1:10）The catalyst has the highest ammonia production rate(0.6378 mmol h^-1mg_cat^-1)and Faraday efficiency（83.96%）at-0.9 V vs.RHE potential,and can still achieve high electrocatalytic reduction of nitrate to synthesis of ammonia performance after several tests.Finally,¹H NMR spectra confirmed that the ammonia produced in the electrolytic process was from electrocatalytic nitrate reduction.In this paper,the transition metals Fe and Cu are used as research objects to prepare Fe-C_xN_y catalyst which can be used in oxygen reduction reaction of hydrogen fuel cells and Cu-N/C catalyst which can electrocatalytic nitrate reduction synthesis of ammonia.The ORR properties and stability of Fe-C_xN_y catalyst and electrocatalytic reduction of nitrate to synthesis of ammonia properties and stability of Cu-N/C catalyst were studied.Although Fe-based transition metal catalysts and Cu-based catalysts have certain catalytic performance in electrocatalytic ORR and electrocatalytic reduction of nitrate to synthesis of ammonia applications,there is still a long way to go before realizing the actual industrial application of Fe-C_xN_y and Cu-N/C catalysts,so further research is needed.Thus,energy and environment problems brought by industrialization can be solved at an early date and sustainable development can be realized.