Study On Regulated Preparation And Oxygen Reduction Performance Of Pt_xCo_y/C(N) Catalyst

PEMFC not only has high energy density and conversion efficiency,but also is environmentally friendly.However the use of precious metal platinum in the catalyst makes the cost of the fuel cell high,and secondly,the slow kinetic reaction（ORR）of the cathode requires higher use of Pt-based catalyst,so it is necessary to improve the performance of the catalyst or reduce the cost by controlling the composition,size,structure,morphology,sequence,and dispersion of the catalyst.Atomically ordered Pt-M intermetallic compounds are currently one of the most promising cathode electrocatalysts,but an economic and effective way to synthesize the intermetallic phase of highly dispersed metals remains a huge challenge.In this paper,a simple and economical aqueous synthesis method is introduced to prepare highly dispersible Pt-Co bimetallic alloy catalysts,and catalysts are characterized by TEM,XRD,and XPS.The electrochemical and single-cell performance of the catalyst were tested by RDE and fuel test system.（1）Preparation of surface N-modified Pt₃Co（N）catalyst:On the basis of urea liquid deposition method,Na₂CO₃（p H）adjustment was innovatively introduced to assist deposition,so that the two metal precursors were deposited uniform Ly and slowly on the carbon support,and the synthesis process was optimized by adjusting the urea ratio,reaction temperature and p H.Compared with Pt/C and Pt₃Co/C catalysts without N modification,Pt₃Co（N）has higher electrocatalytic activity,the formation of ordered phase and the introduction of N element improve the electron transfer efficiency and ORR performance,and the mass activity is twice that of commercial Pt/C(124A/g _Pt).Similarly,the performance of the catalyst on a single cell is also relatively improved,and it is found that the sample with ethanol as the main solvent has a higher voltage and peak power density due to the polarity and dielectric constant of the solvent in the experiment under the test conditions of the membrane electrode.（2）Preparation of ordered intermetallic Pt₃Co（N）catalyst:alloy catalysts with different Pt-Co ratios were prepared by an improved auxiliary liquid deposition method,and the dealloying process was optimized,and the experimental results showed that the catalyst had the highest performance and mass activity of 366 A/g _Ptat Pt:Co=1:1,which was three times that of Pt/C catalyst.The stability of the catalyst decreases with the increase of Co components,because the Co element disintegrates during the reaction process,and the migration of Co causes pollution to the membrane electrode.By adjusting the annealing temperature and time to improve the activity and stability of the catalyst,the catalyst prepared at the annealing temperature of800°C has the best comprehensive performance on the RDE,and has the highest performance on the membrane electrode,with a peak power density of1.501 W/cm²and a voltage of 0.652 V at a current density of 2 A/cm²,both higher than that of the Pt/C catalyst.