Effects Of Physical Properties Of Bi-based Oxides Catalysts Towards Electrochemical Reduction Of CO₂

Limited by the present immatural development of new energy,the requirement of energy consumption in human society is still mainly dependent on fossil fuels such as petroleum,coal and natural gas.As we all know,the accumulation of carbon dioxide,resulted by the utilization of large quantities of fossil fuels,has largely contributed to the growing greenhouse effect.Therefore,the conversion and utilization of carbon dioxide has become an increasingly important issue.Since electricity is renewable and its sources are widespread,converting carbon dioxide into high-value chemicals with the help of electricity provides a promising new way to solve the carbon dioxide problem.Briefly,using renewable electricity generated by wind,light,water,etc.,or surplus nuclear power as an energy source,and coupling the electrolyzed water reaction and obtaining hydrogen from the water,can achieve carbon dioxide to carbon monoxide and carbon under relatively mild reaction conditions.The conversion of high-value chemicals,such as hydrogen compounds and methanol,and liquid fuels also enables the storage of electric energy that is difficult to use at the same time.Based on this idea,the development of highly efficient catalysts that can effectively reduce the overpotential of reaction and significantly increase the conversion efficiency of carbon dioxide has become a very important issue in the electroreduction of carbon dioxide.At this stage,there have been many reports describing different types of heterogeneous catalysts,roughly divided into metal catalysts,oxide catalysts,transition metal sulfur/selenide catalysts,CN-structured catalysts,and monoatomic catalysts,among which oxide catalysts are Wide-ranging,inexpensive and readily available features have received extensive attention.At the same time,in terms of designing a highly efficient catalyst,in addition to considering its source,it is necessary to further understand the relationship between catalyst structure and performance in order to design and produce targeted,highly efficient,and stable electrochemical catalysts to improve energy conversion efficiency..Therefore,many researches are devoted to understanding the influence factors and control methods of the electroreduction performance of carbon dioxide.By summarizing previous studies,we have found that physical properties are closely related to the performance of carbon dioxide electroreduction.The physical properties of materials are numerous.In this paper,Bi-based oxide catalysts were used as the control targets to study the relationship between the physical properties and properties of Bi-based oxide catalysts in the electro-catalytic reduction of liquid-phase CO₂,and it is expected to provide effective catalyst design.Strategy.This thesis is divided into four chapters.The contents of each chapter are as follows:In the first chapter,we briefly introduced the background,the development needs of the CO₂ electro-reduction reaction,the development of the current catalysts,and the research status of Bi-based catalysts.In the second chapter,we construct different states of charge order in the BaBiO₃ system by doping,and use this as a model to study the effect of charge order on the electroreduction of CO₂.Combining structural characterization,catalytic data,and density functional theory calculations,we reveal the intrinsic causes of the intrinsic activity of the charge-ordered BBO that is significantly stronger than that of the LBBO and the charge-disordered KBBO of the charge-ordered partially weakened:BBO This feature of charge ordering makes the Bi-O bond formed between Bi in the crystal lattice and O in CO₂ be dissociated,resulting in the addition of H on O,which leads to the non-uniform effect of O on the crystal lattice.At the same time,the O-C-O bond angle in CO₂ is increased,which is beneficial to the addition of H in the next step C,and reduces the formic acid-shaped barrier.By extension,the asymmetric structure in the system may become the main reason that restricts the catalytic effect of carbon dioxide electroreduction.In the third chapter,we use the hydrothermal method,we prepared BiO₂-x nanosheets using sodium citrate monohydrate and sodium hydroxide as raw materials,and obtained single-layer BiO₂-x nanosheets by stripping.The data show that single-layer BiO₂-x nanosheets exhibit excellent current density and faradaic efficiency for electrocatalytic reduction of CO₂ under the same reducing conditions,and can remain stable over a continuous 10-hour test.By comparing the three kinds of catalysts,we found that the gap gradually decreases with the change of the dimension and thickness of the material.This property enhances the electron transport capability of the catalyst,thereby increasing the CO₂ adsorption and stabilization ability of the catalyst.The reaction barrier is reduced and more excellent catalytic activity is exhibited.In the fourth chapter,we summarized the work of this thesis briefly,and prospected the application prospect of Bi-based oxide catalyst in the electrocatalytic reduction of CO₂.