Structure Modulation Of Copper-Based Catalyst For Electrocatalytic Reduction Of Carbon Dioxide

The excessive consumption of fossil fuels with limited reserves on the earth,and the greenhouse effect caused by excessive emission of carbon dioxide make the energy and environmental crisis become two major challenges facing the world today.It is urgent to find an effective means to balance the environment and energy,while controlling carbon dioxide emission and effectively capturing and transforming carbon dioxide will become the supplement and balance means for the current sustainable development of human beings.Converting carbon dioxide into usable fuels or chemicals is considered an effective way to reduce carbon dioxide concentrations.The electrochemical reduction of CO₂ powered by solar wind and other renewable energy is high-profile due to its mild reaction conditions,the diversiform product selectivity,which is committed to improve the energy storage,reduce the carbon dioxide concentrations and relieve the energy crisis.As a non-noble metal with abundant reserves on the earth,copper is one of the most important electrocatalysts for the efficient conversion of carbon dioxide to hydrocarbons and alcohols reported at present.As a non-noble metal with deep reductivity,copper has a strong comprehensive utilization potential of carbon dioxide through direct conversion of carbon dioxide into different value-added products.However,the strong reducing ability also leads to the complexity of the product,low selectivity and instability of the catalyst.In order to solve these problems,this paper designed a P-Cu catalyst with stable Cu^δ+electronic structure,a Cu-Sb catalyst with tunable interface adsorption structure,and a Cu₂O catalyst with regular cubic microcrystalline structure to improve the selectivity and stability of copper catalyst.The main research content of this paper includes the following three parts:（ⅰ）P-Cu catalysts with stable Cu^δ+electronic structure were used for efficient electrocatalytic reduction of carbon dioxide.The electron donor/acceptor relationship was created in the P-Cu catalyst prepared by non-metallic doping,which was rich in Cu^δ+active sites.Under the effect of electron delocalization,Cu surface was induced to produce Cu^δ+sites with catalytic activity.Compared with the pristine Cu,the catalytic activity and selectivity of P-Cu catalyst were greatly improved.The Faradaic efficiency of C2 products is up to 44.9%,expecially for ethylene with a FE of 30.7%at-1.6 V.Meanwhile,the current density of P-Cu catalyst is up to 57.2 m A cm^-2,which is much higher than that of pristine copper.In addition,the advantageous Cu^δ+electronic structure in the process of electrocatalytic reduction of carbon dioxide can maintain excellent stability for the long time.The experimental results and density functional theory calculations show that the near Cu atom surface electron transfer can be induced by the introduction of P.Meanwhile,the Cu^δ+site can enhance the adsorption of carbon intermediates,and promote carbon carbon coupling,further enhancing the ethylene production.This study shows that the electronic structure engineering control technology has important application value in the design of multistage chemical conversion catalyst.（ⅱ）Cu-Sb catalysts with tunable interfacial adsorption structure were used for efficient electrocatalytic reduction of carbon dioxide.By means of theoretical prediction,Cu/Cu₂O-Sb catalyst with excellent performance of electrocatalytic reduction of carbon dioxide（significant CO₂ activation and hydrogen evolution inhibition）was selected.The Cu/Cu₂O-Sb catalyst was synthesized by low temperature co-reduction.The synthesized catalyst has strong inhibition of hydrogen evolution and can maintain high selectivity to CO at low over-potential.It was found that the typical Cu/Cu₂O-Sb-5 catalyst can achieve the Faradaic efficiency up to～95%at-0.9 V,while maintaining the CO partial current density of 6.3 m A cm^-2.In the process of electrocatalytic reduction for up to18 h,the activity of the catalyst is basically unchanged and has excellent stability.Density functional theory studies and experimental results further show that the excellent catalytic performance is attributed to the Cu/Cu₂O-Sb catalyst with the pre-adsorption of*CO intermediates.The pre-adsorption of*CO intermediates can promote the continued desorption of*CO and inhibit the subsequent C-C coupling,so as to achieve the production of highly selective CO in CO₂RR.（ⅲ）Cu₂O catalyst with regular cubic microcrystalline structure was used for efficient electrocatalytic reduction of carbon dioxide.The complex Cu₂O@Cu catalyst and simplex Cu₂O catalyst were synthesized by the reaction under different atmosphere of Ar and Air.The results show that the Cu₂O catalyst with regular cubic microcrystalline structure has a larger electrocatalytic active area,provides more catalytic active sites,and can efficiently electrocatalytic reduction of carbon dioxide to high value ethylene products.The Faradaic efficiency of ethylene in Air-Cu₂O is up to 40%（the Faradaic efficiency of hydrocarbon products is about 55%）at-1.6 V.At the same time,the partial current density of 12.4 m A cm^-2 can be maintained in CO₂RR.The selectivity and current density of ethylene do not decay in the process of 11,000 s electrocatalysis,showing excellent catalytic stability.Our study provides a reference for the selection of microcrystalline catalysts in electrocatalytic carbon dioxide reduction.