Electrocatalytic Reduction Of Carbon Dioxide With Cu-based Materials

The increasing consumption of fossil fuels has aggravated the emission of the carbon dioxide,causing a series of global environmental problems such as global warming and glacial melting.Currently,the conversion of CO₂ into high value-added energy and chemicals using electrocatalytic,photocatalytic,thermocatalytic and biocatalytic technologies is considered to be promising to achieve a carbon-neutral cycle.Electrocatalytic CO₂ reduction is a highly promising technology for CO₂conversion,due to its simple reaction device,mild reaction conditions,and the use of green electricity as the driving force.Due to the highly symmetrical linear molecular structure possessed by carbon dioxide molecules,which makes it extremely stable,the selection of suitable catalysts to reduce the carbon dioxide reduction energy barrier is the core of electrocatalytic carbon dioxide reduction.The electrocatalytic CO₂ reduction process usually involves the transfer of multiple electrons and protons,and the reduction potential of the products are approach.and the reaction intermediates are intertwined,therefore,how to design the catalyst structure to improve the Faraday efficiency,selectivity and yield of the specified products has become a hot research problem.Because the non-precious metal copper is widely available and inexpensive,it is widely used in electrocatalytic carbon dioxide reduction.Recent studies have shown that copper-based materials are among the few catalysts capable of converting CO₂ to polycarbonate products due to its moderate anchoring and coupling ability to*CO intermediates.However,they are still facing problems such as poor product selection.Based on this,this paper takes copper-based materials as the research object to investigate the coordination microenvironment and heterogeneous structure on the regulation of product species and selectivity of electrocatalytic reduction of carbon dioxide.This paper includes the following three main research components:1.Two copper-based metal-organic frameworks（Cubipy I and Cubipy Cl）with N-Cu-X（X stands for I,Cl）coordination environment were constructed based on 4,4’-bipyridine and copper halide salts.Electrocatalytic CO₂ reduction activity studies showed that products of liquid-phase（methanol and ethanol）were the main products of this series of structures.Compared with Cubipy Cl,Cubipy I has a more excellent selectivity for methanol,with a high Faraday efficiency of 47.6%at-0.8 V vs.RHE,and methanol as the only liquid-phase product,achieving effective modulation of the liquid-phase product.Meanwhile,Cubipy I showed good stability and its structure remained unchanged after the reaction,and the catalytic activity was basically unchanged after 10 h of continuous reaction.This study provides new insights into the regulation of the active site ligand microenvironment to enhance the selectivity of CO₂reduction products.2.A Cu（Ⅱ）-MOF with O-Cu-N coordination mode was synthesized by using1,2,4-triazole,isophthalic acid,and transition metal Cu²⁺.Electrocatalytic reduction of carbon dioxide was investigated and found that the main products were CO and C₂H₄.The faraday efficiency of C₂H₄ is 19%at-1.2 V vs.RHE,accounting for more than 50%of the total carbon product.The O-Cu-N coordination form in Cu-MOF has an important contribution to the selective generation of ethylene.The work provides some ideas to study the ligand microenvironment on the generation of ethylene products by electrocatalytic CO₂ reduction.3.CuO/C-TiO₂ composites with stable heterogeneous structures were prepared by high temperature heating using CuCl₂ and titanium isopropoxide.Electrochemical tests showed that FE_CO of Cu/C-TiO₂ reached up to 32.2%at-1.03 V vs.RHE,which is 5 times higher than that FE_CO of C-TiO₂ under the same conditions.Meanwhile,its current density remains unchanged for 8 hours of continuous reaction,indicating that the material has good stability.The impedance tests show that CuO/C-TiO₂ has superior electrical conductivity compared to C-TiO₂,facilitating electron transfer during the CO₂ reduction reaction This also indicates that the introduction of heterostructure can effectively enhance the electron transfer ability of the catalyst in the electrocatalytic CO₂ reduction process,and improve its catalytic performance.