Controllable Synthesis Of Bi-based Materials And Their Electrocatalytic Performance For Carbon Dioxide Rdeuction

Electrocatalytic reduction of carbon dioxide can reduce carbon dioxide concentration and produce some carbon-containing fuels and chemicals like CO,CH₄and HCOOH.It is an effective means to solve both environmental and energy problems.However,current carbon dioxide electrocatalysts have problems such as low reactivity,poor stability and selectivity.Therefore,how to construct a highly active electrocatalytic material is still a problem.High catalytic activity and single selectivity to the product can be achieved by designing and optimizing the electrocatalyst.The bismuth based material is a green,non-toxic,low-cost metal.It has been shown that it can effectively reduce carbon dioxide to formic acid or carbon monoxide.However,this material still has problems such as large overpotential,low activity and poor stability.Based on this,this thesis focuses on the design and optimization of bismuth based nanomaterials,and improves the performance of electrocatalysts through bimetallic composites and grain boundary engineering strategies.The main works are as follows:?1?BiOI nanosheets arrays were synthesized on carbon cloth by electrochemical deposition method,and reduced to Bi nanosheets array by cyclic voltammetry,and then a small amount of Cu nanowires were electrodeposited on the surface to form Bi nanosheets-Cu nanowires.The synthesized composites were tested for electrochemical reduction of carbon dioxide in a 0.5 M KHCO₃ electrolyte.The current density and the Faraday efficiency of formic acid production were better than that of the Bi nanosheets array without Cu and the Cu nanoparticle electrode.The results show that the bimetallic synergistic effect can effectively improve the activity and selectivity of bismuth based materials for electrocatalytic reduction of carbon dioxide to formic acid,and provide a new method for designing new electrocatalysts for efficient electrocatalytic reduction of carbon dioxide.?2?The bismuth oxide nanoflowers was synthesized by solvothermal method.Further,a Bi nanoparticles/Bi₂O₃ nanosheets electrocatalyst with rich grain boundaries was prepared by a controlled chemical reduction route.Electrocatalytic reduction of carbon dioxide performance test showed that Bi nanoparticles/Bi₂O₃nanosheets showed higher partial current density and higher Faraday efficiency of formic acid over a wide potential range,compared with Bi nanosheets/Bi₂O₃nanosheets obtained by electrochemical reduction of Bi₂O₃ nanosheets.In addition,they could achieve a partial current density of 24.4 mA cm^-2,obtain a FE of>90%over a broad potential range,and maintain more than 24h of durability,which was superior to other reported electrocatalysts with abundant GBs and comparable to other Bi-based electrocatalysts.The grain boundary engineering strategy provides a new idea for obtaining bismuth based electrocatalysts for efficient electrocatalytic reduction of carbon dioxide.