| Precious metal-based bimetallic nanocatalysts have attracted the interest of researchers due to their unique and efficient catalytic performance.How to realize their component optimization,structural design and performance improvement has become a hot topic of great significance in the application of precious metal-based nanocatalyst.In this thesis,Pt/Pd-based bimetallic nanocatalysts are selected as the research object;the purpose is to improve the efficiency of oxygen reduction reaction(ORR),H2O2 direct synthesis and formic acid oxidation reaction(FOR),and to explore the design and synthesis of catalysts and the interpretation of structure-activity relationship.(1)A polyamine(PAA)-assisted thermal decomposition method are developed to synthesize functionalized Pd-Pt bimetallic core/shell nanodendrites.Due to the ligand effect and geometric effect between Pd and Pt,the nanodendritic structure and the adsorbed polyamine molecule,Pd-Pt bimetallic nanocatalysts exhibit enhanced catalytic activity,stability and selectivity for ORR,providing a new idea for the design and synthesis of highly effective ORR electrocatalysts.(2)Sandwich-structured Au@PAA@Pd nanostructures are designed and synthesized successfully.The electronic structure of Pd shell with clean surface is greatly regulated by the amino group of PAA in the middle layer,which motivates Au@PAA@Pd nanostructures to exhibit ultra-high catalytic activity for FOR.An effective strategy for regulating the electronic structure of catalysts is revealed.(3)A series of Pd-Sn alloy bimetallic nanocatalysts with adjustable composition are synthesized and successfully applied to H2O2 direct synthesis.By controlling the composition and catalytic conditions,H2O2 degradation on the catalyst is completely inhibited,and high H2 selectivity and catalytic activity are achieved simultaneously.The improvement in catalytic performance is attributed to the oxidation of Pd,ensemble effects and interfacial synergistic effects,which provide multiple perspectives for the construction of structure-activity relationship.(4)The intermetallic Pd3Sn2 nanonetworks are synthesized and developed as electrocatalysts for FOR.On the one hand,the strong Pd-Sn interaction caused by the intermetallic structure inhibits the chemical decomposition of formic acid on Pd.On the other hand,the synergistic effect between Pd and Sn and the three-dimensional intermetallic structure improve FOR activity and stability of Pd active sites.Different structure-activity relationships of the same nanocatalyst for electrocatalysis and heterogeneous catalysis are well demonstrated.(5)A novel atomic diffusion synthesis method,from Pt-on-Au nanostructures to PtAu-on-Au nanostructures,is developed,that is,alloying of heterostructures.Due to the formation of the PtAu alloy,PtAu-on-Au nanostructures significantly enhance the direct oxidation pathway of FOR,providing new insights into the preparation of bimetallic alloy nanocatalysts.(6)PtAu alloy and Rh-doped PtAu alloy nanowires with adjustable composition are synthesized as FOR electrocatalysts.Based on component optimization,ensemble effects,and interfacial synergistic effects,the mass/intrinsic activities of Pt active sites are greatly improved,proving that PtAu alloy bimetallic nanocatalysts have more room for performance improvement in the field of FOR. |
