Preparation Of Palladium-based Alloy Nanomaterials And Their Aplication In Electrochemical Reduction Of Carbon Dioxide

Since the industrial revolution,the socio-economic level has been continuously improved and the population has grown,which cause the problems of energy and environmental becoming increasingly prominent.It is imminent to explore efficient and renewable clean energy to substitute for traditional fossil fuels.In recent years,electrochemical carbon dioxide reduction technology has received widespread attention.The technology cannot only reduce human dependence on fossil fuels,but also reduce the concentration of carbon dioxide in the atmosphere by converting CO2 into high-value fuels.In order to achieve the efficient conversion of CO2,it is indispensable to seek high performance electrocatalysts.In the electrochemical CO2 reduction system some great progresses have been obtained,however,there still exists a series of challenges,such as large overpotential,poor stability and low Faraday efficiency.Therefore,the design and the development of new electrochemical CO2 reduction catalysts have vital scientific significance and potential application value.Based on the previous research work,although Pd-based catalysts show excellent activity in the application of electrochemical CO2 reduction to formate,they still face such problems as high cost and poor stability at a relatively negative reduction potential.Therefore,the purpose of this paper is to develop bimetallic strategies to design and synthesize highly active and stable palladium-based nanomaterials for electrocatalytic carbon dioxide reduction.We adopted the method of wet chemical synthesis and hydrothermal synthesis,and the chemical composition and morphology of alloy nanomaterials could be effectively controlled by optimizing the selection of surfactant.A variety of characterization techniques are used to explore the crystalline structure,electronic structure and phase composition of nanomaterials.The electrocatalytic performance of the catalysts was studied systematically,for preliminarily explaining the structure-activity relationship between the nanomaterial structure and the catalytic performance.The main research contents and results of this paper are as follows:1.In the first work,in order to seek the high efficiency electrocatalyst for CO2 reduction,we used a simple wet-chemical one-pot method to prepare three-dimensional structured bimetallic palladium silver nanospheres(PdAg NSs)with uniform size and uniform appearance.The catalyst showed excellent electrocatalytic CO2 reduction performance because of abundant active sites and strong tolerance to CO.Compared with pure Pd nanoparticle catalyst,it has better catalytic activity and stability:In the range of reduction potential,the Faraday efficiency of producing formic acid can reach more than 90%;under the relatively negative reduction potential(-0.27 V vs RHE),the current density hardly attenuates after a long time of constant voltage test of 10000s.PdAg NSs catalyst also has obvious advantages in activity and stability by comparing with other pd-based catalytic materials,2.In the second work,in order to further improve the activity and stability of bimetallic Pd-Ag materials in electrocatalytic CO2 reduction,we prepared one-dimensional PdAg nanowires catalyst(PdAg NWs)by changing the surfactant and other reaction parameters based on the first work.The activity and stability of electrocatalytic CO2 reduction were further improved under the synergistic effect of structural effect and electronic effect.The results showed that the selectivity of ele ctrochemical CO2 reduction to formate could reach 100%under low overpotential for Pd4Ag1 NWs catalyst.In the constant voltage test under negative reduction potential(-0.25 V vs RHE),the catalyst still has good current stability after a long time test of 30000s.3.In the third work,we focused on the controlled preparation of PdPb alloy and PtPb alloy.PdPb alloy nanoparticles with uniform structure were prepared by hydrothermal method under the action of cetyl trimethylammonium chloride(CTAC)as surfactant.The preliminary synthesis of PtPb alloy nanorods and PtPb alloy nanowires was successfully achieved by regulating the important parameters of metal precursors and reaction solvents.These results of the study lay the material foundation for the subsequent catalytic application.