Preparation Of Penta-High-Entropy Alloy Nanomaterials For Direct Ethylene Glycol Fuel Cells

In recent years,in order to solve the problems of environmental pollution and energy crisis,the development of new energy sources and the search for excellent energy conversion devices have become the focus of research.Direct ethylene glycol fuel cells（DEGFC）have been favored by researchers due to their excellent energy conversion efficiency,high current density and low polluting properties.Platinum-based catalysts are currently the most dominant catalysts used in fuel cell anodes,but factors such as the scarcity of precious metals and weak resistance to poisoning have severely limited the further application of fuel cells.In recent years,high-entropy alloys（HEA）have received a lot of attention from researchers because of their high thermal stability and excellent resistance to acid and alkali corrosion.These alloys are usually composed of five or more metallic elements.Due to its excellent intrinsic physical and chemical properties,it shows great potential in many fields.It has been shown that HEA electrocatalysts can be well applied to the electrocatalytic oxidation of methanol and ethanol,but not many applications in the field of catalytic oxidation of ethylene glycol.In this paper,HEA electrocatalysts with low precious metal dosage were prepared by a green approach to prepare low-cost and high catalytic activity DEGFC anode catalyst materials as a starting point.And the successfully prepared HEA electrocatalyst materials are applied to the electrocatalytic oxidation reaction of ethylene glycol.The research in this thesis is divided into the following three parts:in the first part,Pt Pd Au Ni Co/C HEA electrocatalysts formed by coupling ternary noble metal base with two non-precious metals were prepared by one-pot method;In the second part,five-element HEA materials coupled with two noble metals and three non-precious metals were prepared to reduce the proportion of noble metal atoms in HEA electrocatalysts and to investigate their catalytic;In the third part,only one noble metal was used to form the five-element HEA electrocatalyst,which further reduced the amount of noble metal and achieved the purpose of reducing the cost of catalyst use.In the third part,only one noble metal was used to form a five-membered HEA electrocatalyst to further reduce the amount of noble metal and to reduce the cost of the catalyst.The following are the details of the three parts of the study:Part I.Preparation of Pt Pd Au Ni Co/C catalysts and their application in DEGFCA five-element HEA electrocatalyst of Pt Pd Au Ni Co/C was prepared by a one-pot reduction method.The electrochemical test results showed that the starting potential of Pt Pd Au Ni Co/C for EGOR was low,0.55 V,which is 20 m V lower than the reference value of Pt/C（0.57 V）.In addition,its EGOR activity was 0.482 A mg^-1_{Pt Pd Au},which is 2.18 times higher than that of Pt/C(0.221 A mg_Pt^-1).At the end of the 3000 s chrono-current stability test,its residual current density was 0.091 A mg^-1_{Pt Pd Au};its peak current retention is 81.3%after500 cycles of stability test;and its ECSA value is～46.2 m²g^-1_{Pt Pd}.The final assembly of Pt Pd Au Ni Co/C as an anode catalyst into DEGFC was performed using Pt Pd Au Ni Co/C catalyst,the OCV（0.55 V）,maximum current density(0.093 A cm^-2)and maximum power density(8.38 m W cm^-2)of the cell were higher than those of commercial Pt/C(OCV（0.52 V）,maximum current density(0.080 A cm^-2)and maximum power density(8.38 m W cm^-2)and maximum power density(6.00 m W cm^-2).Part II Preparation of Pt Pd Ni Co Bi/C catalysts and their application in DEGFCIn the first part,ternary noble metal-based five-membered HEA electrocatalysts were successfully prepared and excellent ethylene glycol electrocatalytic oxidation performance was achieved.In order to further reduce the amount of noble metals,three noble metals were reduced to two,and Pt Pd Ni Co Bi/C HEA electrocatalyst was successfully prepared and applied to the catalytic oxidation reaction of ethylene glycol at 60℃using sodium borohydride to co-reduce two noble metals,platinum and palladium,and nickel-cobalt-bismuth precursor salt to investigate its catalytic performance.After the glycol oxidation test,a high current density of 0.782 A mg^-1_{Pt Pd} was obtained,which is 3.54 times higher than that of commercial Pt/C(0.221 A mg_Pt^-1);the electrochemical activity specific surface area（ECSA）value of 60.3 m²g^-1_{Pt Pd} was calculated by CO adsorption and desorption test,which is much higher than that of commercial Pt/C;after the timing current stability test and multi-turn The results were better than those of commercial Pt/C after the chrono-current stability test and the multi-turn stability test,and a power density of 3.39 m W cm^-2 was obtained after the assembly into the fuel cell reactor anode,indicating that the catalyst can be successfully applied in fuel cells.Part III Preparation of Pt Bi Ni Co Sn/C catalysts and their application in DEGFCBased on the studies in the previous two chapters,in order to further reduce the catalyst production cost,this section will continue to reduce the atomic percentage of noble metals in the HEA catalysts by using only a single Pt noble metal involved in the formation of HEA electrocatalysts.Pt Bi Ni Co Sn/C HEA electrocatalysts was successfully prepared at 180°C using precursor salts of Pt and bismuth-nickel-cobalt-tin by co-reduction with ethylene glycol.After the glycol oxidation test,a peak current density of 1.406 A mg_Pt^-1 was obtained,which is 6.36 times higher than the commercial Pt/C current density(0.221 A mg_Pt^-1).In addition,its onset potential at-0.47 V is also earlier than that of Pt/C,indicating a lower onset potential for alcohol oxidation on Pt Bi Ni Co Sn/C catalysts.A power density of 5.29 m W cm^-2 was obtained after assembling it to the cell set anode,which is close to the commercial Pt/C power density value of 6.00 m W cm^-2.