Synthesis Of Metal Oxide-supported Copper-based Catalysts And Their Performances For Electrochemical Reduction Of CO₂

The rapid development and massive consumption of fossil fuels have led to a corresponding sharp rise in CO₂emissions in the atmosphere with the advancement of industrialization,which has triggered a dual crisis of energy utilization and environmental protection.Powered by renewable clean energy,and converting CO₂into non-polluting,high value-added chemicals by electrochemical methods is an important measure to reduce CO₂concentration and achieve global carbon balance.In recent years,a series of high-efficiency catalysts have been designed to reduce the competition between the higher activation energy and kinetically preferential hydrogen evolution reaction in the electrochemical CO₂reduction reaction（CO₂RR）.Especially,Cu-based catalysts with unique properties that can catalyze the reduction of CO₂to hydrocarbon and alcohol products have attracted much attention,but such catalysts still suffer from high overpotentials and poor product selectivity.Therefore,Three kinds of Cu-based composites were reverse engineered and synthesized based on the generated products,and catalytic performances of their CO₂RR were studied in this paper.The effects of the composition and structure of Ce O₂nanorods/Cu O nanosheets,the loading amount and structure of Cu on Zn O nanosheets,and the loading amount of Cu₃P on Zn O on the performances and products of CO₂RR have been studied,in order to accumulate data for the synthesis of practical Cu based catalysts.The specific research contents are as follows:First,the Ce O₂nanorods were synthesized by hydrothermal reaction and used as oxides support.By adjusting the Cu O content,a series of x-Cu O/Ce O₂composites were obtained by hydrothermal reaction,and the catalytic performances of CO₂were studied.The CO₂RR product distributions of composites were experimentally verified to be dependent on the Cu O nanosheets loading amounts.In 5-Cu O/Ce O₂,the small fragments of Cu O were uniformly dispersed on Ce O₂,and a CH₄product with a current density of 8.7 m A cm^-2and a Faradaic efficiency（FE）of 37.8%was obtained.In 60-Cu O/Ce O₂,Ce O₂nanorods were dispersed in large-sized Cu O nanosheets,a C₂H₄product with a current density of 11.8 m A cm^-2and a FE of 44.8%was obtained.CO₂/CO-TPD and in situ FT-IR showed that the strong metal-support interaction of Cu O and Ce O₂in the composite affected the adsorption performance of the intermediate*CO with the increase of Cu O content.Therefore,different adsorption types of*CO and key reaction intermediates*CHO and*OCCO would be formed,making*CO proceed toward the hydrogenation and dimerization coupling,respectively.In addition,OH^-adsorption tests and Cu underpotential deposition also demonstrated that the exposed crystal planes of Cu during the reaction process were favorable for the formation of major reduction products.Second,the porous Zn O nanosheets were prepared by hydrothermal reaction and used as support,then Cu was deposited on the surface of Zn O by wet impregnation,and Cu/Zn O composites were obtained by high temperature thermal reduction.Cu particles of different sizes were obtained on the Zn O surface by adjusting the deposition amount of Cu,and the CO₂electrocatalysis results showed that the syngas（H₂:CO）ratio can selectively fluctuate in the range of 0.1～3.7 over the entire test potentials.Among them,Zn O obtained a current density of 6 m A cm^-2and FE was close to 82%CO at-1.08 V.While the 20-Cu/Zn O,25-Cu/Zn O,30-Cu/Zn O composites achieved current densities of 28 m A cm^-2,32 m A cm^-2,38 m A cm^-2and syngas（H₂:CO）ratios of 0.6,1.0 and 2.0,respectively.Based on existing research,it is known that the binding energy of Cu and Zn for COOH*is similar,but the adsorption energy of Cu to*H is stronger than Zn.Therefore,the generation of H₂is promoted with the increase of Cu loading,which will have a significant impact on the choice of syngas ratio.Third,Cu deposition on the Zn O surface by wet dipping method,then the Cu₃P/Zn O composites were obtained by high-temperature phosphating treatment.By changing the content of Cu in the precursor,the effects of a series of Cu₃P/Zn O composites on the catalytic performances of CO₂RR were investigated.The experimental results showed that the Cu₃P loading changed the electrochemically active area and charge transfer rate of the composites.Importantly,the P doping changed the adsorption properties of Cu to the intermediates COOH*and*H,so that different ratios of Cu₃P/Zn O realized the FE of syngas with a specific ratio in a wide potential range,which is beneficial to the re-upgrading process of products directly through the Fischer-Tropsch reaction.