Preparation And Activity Study Of High Efficiency And Low-Platinum-Based Cathodic Electrocatalysts For Oxygen Reduction Reaction

In recent years,as a type of new clean and sustainable green energy system,hydrogen-oxygen fuel cells have recognized as the preferred power source for electric vehicles and fixed power stations because of its high energy density,zero pollution and easy device.To date,Pt-based catalysts are preferred to accelerate the oxygen reduction reaction rate in fuel cells.However,the commercialization of fuel cells has been heavily prevented by the high cost of the precious Pt-based catalysts.Therefore,in this thesis,in order to Reduce catalyst cost and improve the Pt utilization in fuel cell,we developed a series of low Pt-based electrocatalysts with high performance and excellent stability in Pt-based electrocatalysts.At the same time,combining with a series of physical characterizations,the main catalytic active sites in these catalysts were clarified,thereby revealing the reasons for the high oxygen reduction catalytic activity of this series of catalysts.The concrete results are as follows:（1）A carbon black-supported cost-effective,efficient,durable and low platinum electrocatalyst（PtN/C）with carbon black BP-2000 for the cathodic oxygen reduction reaction was synthesized for the first time.The catalyst greatly reduces the amount of precious metal Pt,and the platinum loading is 3.18 wt%.Under acidic conditions,the catalyst catalyzes the ORR process to be an efficient 4e^-process with excellent stability,and the utilization of Pt at 0.8 V(0.06 A/mg _Pt)is approximately 5.83 times the Pt utilization in commercial Pt/C(0.06 A/mg _Pt).（2）In order to further improve the Pt utilization in fuel cells,a carbon-supported highly dispersed PtNi nanocatalyst（PtNi/C）with low platinum content of 2.29 wt%was prepared simply based on galvanic replacement for a high-efficiency ORR process.Electrochemical test results show that the catalyst exhibits high performance under acidic conditions(E_1/2=0.841 V vs.RHE),and the mass activity of 0.57 A/mg _Pt（0.8 V）is 9.4 times that of commercial Pt/C,showing a reasonable electron transfer n（-3.99） and low H₂O₂ yield（-0.38%）with high stability.（3）To further enhance the catalytic activity of oxygen reduction electrocatalysts under acidic conditions,a low platinum-based oxygen reduction electrocatalyst（PtCu@Cu₂O）with nanoparticles highly dispersed on a carbon support was prepared by a simple displacement reaction with low platinum content of 3.22 wt%.Electrochemical test results show that catalyst exhibits excellent ORR activity(E_1/2=0.856 V vs.RHE),with the mass activity of 0.43 A/mg _Ptat 0.8 V,which is 7.17 times that of commercial Pt/C,and has high stability.