Preparation Of Metal Composites And Their Electrocatalytic CO₂ Reduction Performance

With the development of industrialization,the emission of carbon dioxide（CO₂）caused by the massive combustion of fossil fuels is rising year by year,and the environmental problems caused by such emission are threatening our homeland,especially for a large developing country with a population of more than 1.4 billion,which needs to promote industrialization and to consider such emissions on the environment.In recent years,the rational and effective utilization of CO₂has gradually attracted people’s attention,if CO₂is converted into fuel or chemicals in a green economic way,it is of great significance to alleviate the energy and environmental problems caused by CO₂.As an applicable technology with great development potential,electrocatalytic CO₂reduction（e CO₂RR）can use renewable energy to convert CO₂into high value-added fuels and chemicals,which is an effective way to improve the level of new energy production and realize carbon recycling.There are many products of electrochemical reduction of CO₂,including formic acid（HCOOH）,carbon monoxide（CO）,methane（CH₄）,methanol（CH₃OH）,ethylene（C₂H₄）,ethanol（C₂H₅OH）,acetic acid（CH₃COOH）,propanol（C₃H₇OH）and other products.In the process of CO₂ electroreduction,due to the low reduction potential of the hydrogen evolution reaction of electrolyzed water,the selectivity of the catalyst for CO₂reduction products can often be reduced,which is also the main obstacle limiting its development.Therefore,people are also constantly designing and improving the performance of catalysts to achieve efficient catalysis of e CO₂RR,such as realizing the synergistic effect of multiple elements and improving the structure and morphology of catalysts.Therefore,the development of low-cost,high-activity and highly selective catalysts is the focus of CO₂electroreduction.The research direction of this paper is mainly to design and to prepare high-efficiency e CO₂RR catalytic materials to achieve effective CO₂conversion,mainly including the following two aspects:The bismuth carbonate（Bi₂O₂CO₃）catalyst synthesized at room temperature and pressure has high selectivity（FE～98%）in catalyzing the production of HCOOH from CO₂.Thanks to the unique nanoflower structure of Bi₂O₂CO₃,the catalyst has a large surface area,and the CO₂adsorption test shows that the catalyst has good CO₂chemical adsorption capacity.Therefore,the catalyst exhibited high current density and Faraday efficiency for HCOOH.By analyzing the phase results of the catalyst electrolysis,it was found that Bi₂O₂CO₃could exist stably in the form of Bi/Bi₂O₂CO₃.The stability test of the material shows that the catalyst can maintain a Faraday efficiency of more than 90%for the electroreduction of CO₂producing HCOOH for 30 h.Further,the material underwent a constant current electrolysis reaction of-500 m A cm^-2in a flow electrolytic cell,and the Faraday efficiency of HCOOH was～97%,and the yield was as high as 9054.25μmol h^-1cm^-2.Silver（Ag）is highly selective for CO,while copper（Cu）is an excellent catalyst for the synthesis of multi-carbon products.Based on their characteristics,we try to construct Ag@Cu₂O composite catalytic materials to use cuprous oxide（Cu₂O）to enable carbon-carbon coupling of Ag-stable key intermediates*CO,so that Ag@Cu₂O materials can achieve electroreduction of CO₂to produce C₂H₄.By adjusting the molar ratio of the two metals,Ag@Cu₂O-2 has fully optimized performance,and the Faraday efficiency for ethylene was up to 63.09%,and the highest yield was 588.7μmol cm^-2h^-1.