Design And Preparation Of Bi-based Catalysts And Study On Electrocatalytic CO₂ Reduction Performance

With the rapid development of industry and the improvement of human living standards,the concentration of CO₂ on the earth continues to rise,causing a serious energy crisis and severe global warming.Reducing CO₂ to formate products through electrocatalysis or photoelectric catalysis technology can effectively reduce the concentration of CO₂ in the atmosphere.,which is considered to be an ideal way to alleviate the energy crisis.However,the electrocatalytic（EC）or Photoelectrocatalytic（PEC）CO₂ reduction reaction（CO₂RR）generally has problems such as slow kinetics and competition accompanied by hydrogen evolution reaction（HER）.For CO₂RR,the adsorption strength of the catalyst to CO₂ and reaction intermediates is the key to affect the catalytic activity and product selectivity.Therefore,the design and preparation of highly active catalysts is imminent.In this thesis,a kind of non-toxic and low-cost Bi-based catalysts was for CO₂RR via interface control and crystal surface engineering,which showed enhanced adsorption and activation ability of the catalyst for CO₂ as well as the adsorption strength of formic acid intermediates,thereby achieving efficient selectivity for formate.Futhermore,the relationship between the structure and properties of the material was analyzed by using various characterization methods.The main contents are listed as follows:（1）Preparation of high crystal oriented Bi based photocathode and study on its solar assisted electrocatalytic performance for CO₂ reductionIn order to achieve efficient conversion of CO₂ to formate,a seried of Bi-based photocatalysts were prepared through a strategy of crystal surface regulation.Using p-Si as carrier,a x-Bi/p-Si（x-EB,x=0,1,2）catalyst was prepared via an electrodeposition process with the assistence of disodium ethylenediaminetetraacetic acid（EDTA-2Na）salt,therein,the metal Bi exposed a specific crystal plane（003）.The experimental results showed that Bi（003）crystal plane could enhance the adsorption strength of CO₂ and promoted the activation of CO₂.In addition,the Schottky junction formed in between Si and Bi species could effectively promote the separation of photogenerated carriers,thereby enhancing the catalytic reduction activity of CO₂.The prepared 1-EB exhibits high formate selectivity（80%）and good catalytic stability over a wide potential range.（2）Multicore-shell structure Bi@NC Preparation of Composite Catalysts and Study on the Performance of Electrocatalytic CO₂ ReductionIn order to improve the selectivity of metal Bi for formate within wide electric potentials,a core-sell structure Bi@NC catalyst was developed.Specifically,Dopamine（PDA）was polymerized and grown on the surface of Bi nanoparticles,and then calcined in H₂/Ar atmosphere to form a nitrogen doped carbon（NC）coated Bi composite catalyst.The porous NC shell has a high specific surface area,which not only enhances the adsorption capacity of CO₂,but also effectively regulates the electronic structure of Bi.Thereby enhancing the adsorption and activation of CO₂ molecules by the catalyst and accelerating the reaction kinetics.The optimal catalys 600-Bi@NC was obtained under calcination at 600℃,which showed a formate Faraday efficiency of nearly 90%in a wide potential range of-1.0 V to-1.7 V（vs RHE）.More importantly,both the current intensity and Faraday efficiency of the formate remained basically unchanged within the reaction time of 7 hours,suggesting good stability.