Preparation Of Nanoporous Copper And Tin Tellurium Alloy Catalyst And Electrocatalytic CO₂ Reduction Performance Research

Electrochemical conversion of carbon dioxide（CO₂）into fuels and chemicals with high commercial value by using renewable electric power is a potential method to reduce atmospheric CO₂emissions.In the electrocatalytic reduction of carbon dioxide,efficient and stable catalysts play a decisive role in achieving high selectivity,low overpotential and high current density of reduction products.However,the rational design and controllable preparation of catalysts with high catalytic activity,high selectivity and high catalytic stability are still facing great challenges.Among these carbon dioxide reduction products,formate and ethanol have attracted the attention of many researchers due to theirs ultra-high energy density and high economic value.Tin-based catalysts have been widely studied as their nontoxicity,low price and excellent catalytic performance for formate.However,there are still some problems about tin-based catalysts,such as low catalytic stability and narrow potential range with high selectivity,which make it difficult to meet the requirements of industrial application.Copper is considered to be the most potential catalyst for the reduction of carbon dioxide to ethanol due to its most appropriate binding energy of intermediate.However,it is hard to achieve the high selectivity of the reduction pathway for the directional formation of ethanol.Therefore,the efficient catalysts for the conversion of carbon dioxide to formate or ethanol need to be further explored.In order to solve the above problems,based on the principle of alloy phase diagram,we design and synthesize nanoporous tin tellurium intermetallic compound and vanadium oxide modified bicontinuous nanoporous copper materials by electrochemical/chemical selective phase etching method,which are applied to the electrocatalytic reduction of carbon dioxide to formate and ethanol respectively.By controlling the preparation parameters of the precursor,the composition and pore size of the nanoporous materials are directionally adjusted,leading to the improvement of electrocatalytic carbon dioxide reduction performance.In addition,the catalytic mechanism of the catalyst is revealed by various characterization methods and density functional theory calculation.The main research work is as follows:1.According to the principle of phase diagram,a novel nanoporous tin tellurium intermetallic compound（np-Sn Te）was prepared by a simple electrochemical dealloying method for the research of reducing carbon dioxide into formate.np-Sn Te catalyst showed the outstanding catalytic performance for formate.The Faraday efficiency of formate over a wide voltage range of-1.0 V to-1.3 V vs.RHE can be maintained at more than 90%,and the highest Faraday efficiency of formic acid can be achieved at 94%.While,the catalyst can maintain a stable and efficient catalytic reduction reaction for 80 hours.All results indicated that np-Sn Te catalyst showed much more excellent catalytic performance for formate than other tin based catalysts.Furthermore,the catalytic mechanism of np-Sn Te was verified by density functional theory calculation（DFT）and in-situ Raman spectroscopy characterization.In the catalytic process,the strong orbital interaction between Sn atoms and adjacent Te atoms is beneficial to improve the charge transfer efficiency between Sn atoms and O atoms,and promote the fracture of the bond between metal and oxygen.Thus,np-Sn Te has a lower energy barrier of*HCOO intermediate formation step and final desorption step,which could promote the reduction of carbon dioxide to formate.2.Vanadium oxide modified bicontinuous nano porous copper catalyst was designed and synthesized by chemical dealloying method.By controlling the preparation parameters（atomic ratio,rotating speed of copper roller）of precursor alloy strip,a series of vanadium oxide modified bicontinuous nano porous copper catalysts were prepared to explore the effect of precursor preparation parameters on the performance of CO₂reduction to ethanol.Among,np-Cu@VO₂-5%（Cu:V=19:1）could greatly improve the selectivity and current density of electrocatalytic ethanol production from carbon dioxide.It achieved a 30.1%Faraday efficiency for CO₂-to-ethanol production and an ethanol partial current density of-16 m A/cm²,corresponding to a 4-fold increase in activity compared to the bare np-Cu.It even delivers ethanol partial current density that exceeds-39 m A/cm²in a flow-cell reactor.Furthermore,the catalytic mechanism was studied by density functional theory calculation.Combined with the experimental results,it was concluded that the vanadium oxide modified copper surface was conducive to the dissociation of water and the adsorption of hydrogen on the copper surface,thus reducing the energy barrier of the two-step key reaction and promoting the formation of the key*HCCHOH intermediate on the copper surface in the ethanol production process.Thus,it promoted the selectivity of ethanol.In conclusion,the nanoporous tin tellurium intermetallic compound developed in this paper solves the problems of poor stability and narrow voltage range of high selectivity in formate industrialization,which provides a feasible idea for the design of efficient formate catalyst.Meanwhile,the study of vanadium oxide modified bicontinuous nanoporous copper materials confirmed that vanadium oxide modified metal copper surface plays a key role in improving the selectivity of ethanol,which provides a practical idea and direction for further design of catalyst and realization of ethanol industrial production.