Preparation Of Copper-Bismuth Bimetallic Catalysts And Research Of Their Catalysis In Carbon Dioxide Reduction Reaction

With the development of industry,the consumption of fossil fuels such as coal,oil and natural gas has risen sharply.Excessive use of fossil energy leads to the emission of excess greenhouse gases（CO₂）,which have caused various climate changes and bringing endless environmental crises.How to reduce the continuous rise of CO₂content in the atmosphere is an urgent problem to be solved.The method of electrocatalytic reduction to convert CO₂ into products with high added value is considered as a promising solution.At present,copper-based materials have unique advantages in the CO₂ reduction reaction in aqueous solution which have numerous reaction paths and complex catalytic mechanism.It is generally accepted that CO is regarded as a key intermediate in the process of reducing CO₂ to multi-carbon products,two CO molecule undergo a C-C coupling reaction when they are close enough to the surface of the catalyst.However,the solubility of CO is low in aqueous solution,and the adsorption capacity of copper-based catalyst is also inferior.In contrast,formates are more easily dissolved in aqueous solutions as liquid products.The electrode is more likely to absorb formates from the aqueous solution and thus increase the reaction rate.Therefore,we need to explore whether there exists a formic acid pathway to prepare multi-carbon products which is of great significance for improving copper-based catalysts.In this paper,a series of different kinds of high-efficiency electrocatalysts were synthesized by modifying the copper-based catalyst for the electrocatalytic reduction of CO₂,which can reduce CO₂ to a variety of high value-added chemicals with high selectivity.The main research contents are as follows:（1）Bi metal was electrodeposited on Cu foam substrate and used for electrocatalytic reduction of CO₂ to prepare alcohols.By scanning electron microscopy,EDS,and XRD.The morphology and structure of the Cu@Bi electrode were analyzed.The results showed that Bi was successfully loaded on the Cu foam substrate.Bismuth block structure is evenly distributed on the surface of Cu foam,and the shape is roughly in the shape of a ball flower,and the edges and corners are clearly visible.After electrolytic catalysis,the morphology of Bi blocks on the catalyst surface undergoes changes and reorganization,resulting in rough surface structure,more dispersed distribution of Bi elements,and more complex binding with Cu elements.Through XPS analysis,it can be observed that the valence states of Bi and Cu elements have changed before and after catalytic action.The catalytic reduction of Cu²⁺content is due to the continuous reduction of Cu²⁺in CO₂ electrolysis,while Bi element is reduced to Bi⁰during CO₂ electrolysis.Comparing different Cu@Bi electrode,it was found that the ratio and composition of bimetallics have a significant impact on the activity of the catalyst and the selectivity of alcohol compounds.Prepared by electrodeposition for 90seconds.The Cu@Bi electrode exhibits superior catalytic selectivity and activity for the electrochemical reduction of CO₂ to alcohols.At an electrolysis voltage of-0.80 V vs RHE,the reaction current density is-27.56 m A cm^-2,and the maximum Faraday efficiency of alcohols can reach 43.7%.The remarkable performance of this electrode is attributed to the expanded active surface area and rich Active site,rapid charge transfer,and the appropriate metal oxide/metal interface to stabilize the^*CO₂^-intermediate.（2）A CuBi₂O₄ catalyst was synthesized by hydrothermal method as a cathode for electrocatalytic reduction of CO₂ to alcohols.The morphology and structure of the catalyst electrode were analyzed using scanning electron microscopy and EDS.The results showed that the catalyst was spherical in shape with small particle sizes,and was formed by the aggregation of finer nanostructures.By analyzing the crystal surface of the catalyst through transmission electron microscopy,it was found that the catalyst has grain boundaries.Through XRD analysis,the catalyst has crystal planes of CuBi₂O₄and CuO,and is a CuBi₂O₄/CuO catalyst composed of CuBi₂O₄ and CuO.Through XPS analysis,it can be observed that the valence peak positions of Bi and Cu elements have changed before and after catalytic action.The position of the valence state peak of Bi element increases,while the position of the valence state peak of Cu element decreases.From the analysis of Cu LMM spectrum combined with XPS valence state spectrum,the valence state of Cu in CuBi₂O₄/CuO catalyst is+1.The current density of the catalyst is-62.72 m A cm^-2 at a voltage of-0.90 V vs RHE,and the Faraday efficiency of CO₂ reduction to alcohol compounds is about 50%.The significant performance of this electrode is attributed to the synergistic effect of copper bismuth bimetallic material,which enhances the selectivity of CO₂ for the conversion of alcohol compounds.