Preparation And Electrocatalytic Performance Of Rare Earth Modified PtRu Catalyst For Hydrooxidation

As an anode catalyst,PtRu shows excellent activity in fuel cells and has attracted much attention due to its strong resistance to CO poisoning and high stability.In view of this,this paper designed and successfully synthesized PtRu nanocrystalline and rare earth modified PtRu catalyst.Combined with electrochemical performance test and single cell performance evaluation,the catalytic activity of the prepared catalyst HOR was explored,confirming that the introduction of rare earth atoms can significantly improve the hydrogen oxidation performance of platinum-ruthenium catalyst.It provides a new idea for the development of efficient PtRu based electrocatalyst.The density of states and the free energy of hydrogen adsorption on different crystal surfaces of the catalysts with the best performance were studied by density functional theory.The specific research contents are as follows:1.PtRu nanocrystals were prepared at 120-160℃by solvothermal synthesis with DMF as the solvent under the action of hydrogen and sodium borohydride dual reducing agent.The obtained catalyst and carbon black were mixed evenly and then heat treated to obtain PtRu/C,which was used for electrocatalytic hydrogen oxidation reaction under alkaline conditions.The influence of Pt/Ru ratio on the performance of the catalysts was investigated by introducing small molecular gases such as H₂ and CO to control the atmosphere during the synthesis process.TEM results showed that PtRu catalyst has uniform particle size,regular morphology and good dispersion.The elemental valence and structure of the catalyst were characterized by XRD,XPS and HRTEM.The current density of platinum-ruthenium catalyst is 2.28 mA/cm²,which is superior to that of commercial platinum-carbon（1.98 mA/cm²）,when the potential of the platinum-ruthenium catalyst is 50 mV（vs.RHE）in 0.1M KOH solution.2.In order to further improve the activity and stability of HOR catalyst,trace rare earth metals were introduced to modify the platinum-ruthenium catalyst.In terms of morphology,the size of PtRu nanoparticles doped with rare earth elements is concentrated at 2-5 nm,and they are uniformly dispersed.The valence states of the elements were characterized by XRD and XPS,and the dispersion of the elements on the surface of the carrier was characterized by EDS and AC-TEM.The platinum-ruthenium catalysts doped with erbium,europium and cerium（20%metal load）showed good hydrogen oxidation activity.When the potential is 50 mV（vs.RHE）,the current densities are 2.28 mA/cm²,2.34 mA/cm²,and 2.36 mA/cm²,respectively.The mass activity of Er is 0.112 mA/μg _PtRu,which is 9.8%higher than that of platinum-ruthenium nanoparticles without rare earth doping(0.102 mA/μg _PtRu),and the material has good stability.According to DFT calculation,Pt₂Ru₁-Er₂O₃（1 1 1）has a gibbs free energy change value closer to zero,indicating that the introduction of rare earth Erbium atom will greatly improve the performance of HOR.The adsorption energy of H atom on Pt₂Ru₁-Er₂O₃ is lower than that on Pt₂Ru₁ on both（1 0 0）and（1 1 0）crystal planes.Therefore,it can be said that the introduction of rare earth oxides can effectively adjust the structure and properties of the catalyst surface,so that the catalyst has a very appropriate△G_H,which is conducive to the progress of HOR reaction.Differential charge density and state density calculations show that erbium oxide clusters tend to transfer charge to Pt（1 1 1）,and this strong interfacial charge interaction makes Ptsites on Er-O-Pt（1 1 1）more negatively charged than surface Ptsites on pure Pt（1 1 1）.There are obvious electronic hybridization between O-2p and Pt-5d orbitals in-5～0 e V,which proves that there is strong interfacial interaction between Erbium oxide clusters and Pt（1 1 1）.As a result,the d-band center of Pton Er-O-Pt（1 1 1）interface increases,and the adsorption capacity of Ptsurface to HOR intermediate is enhanced,which is conducive to enhancing the adsorption of the surface to the intermediate,and theoretically can improve the activity of HOR.These results indicate that the modification of Er-O-Ptbond can greatly affect the chemisorption behavior of Pt.The MEA was prepared by selecting the platinum-ruthenium catalysts with better performance and modification of rare earth Er and Ce,and the metal load was increased to 50%and assembled into a single battery for testing to investigate the practical value of the catalyst.When the catalyst load is 0.1 mg/cm²,the peak power density of Pt₂Ru₁,Pt₂Ru₁-Ce₂O₃/C and Pt₂Ru₁-Ce₂O₃/C are 1.62 W/cm²,1.71 W/cm² and1.69 W/cm²,respectively.Obviously superior to platinum-ruthenium catalyst without rare earth.When the catalyst load is 0.05 mg/cm²,the peak power density of Pt₂Ru₁/C,Pt₂Ru₁-Er₂O₃/C and Pt₂Ru₁-Ce₂O₃/C are 1.69 W/cm²,1.78W/cm² and 1.73 W/cm²,respectively.Obviously introducing rare earth elements Er and Ce can effectively improve the peak power density of single cell.In addition,the peak power densities of the three catalysts at 0.05 mg/cm²are all higher than those at 0.1 mg/cm²,which provides the possibility for the development of low platinum devices.