![]() Therefore, extensive research efforts have been devoted towards the development of Pd-based nanomaterials for oxygen reduction at the cathode of direct liquid fuel cells 8, 12, 13, 14. Specifically, for direct methanol fuel cell (DMFC), the Pd-based ORR electrocatalysts could be hardly affected by methanol crossover compared with Pt catalysts 12. Fortunately, current studies have found that the relatively inexpensive Pd-based nanomaterials have great potential to substitute for Pt as the cathodic catalysts of direct liquid fuel cells 6, 8, 11. However, the high cost of precious Pt metal and its instability as ORR electrocatalysts at cathode enormously limit the commercialization of direct liquid fuel cells 9, 10. Currently platinum (Pt)-based nanomaterials are the most effective electrocatalysts to facilitate ORR in direct liquid fuel cells 6, 7, 8. relatively small environmental footprint, compact system design, high energy conversion efficiency and higher volumetric energy densities 1, 2, 3, 4, 5. Oxygen reduction reaction (ORR) is the key catalytic reaction occurred at the cathode electrode of direct liquid (methanol, ethanol, or formic acid) fuel cells, which have garnered sustained research interest due to their desirable features as energy suppliers for mobile and portable power devices, e.g. In comparison with the core-shell nanoparticles upon directly depositing Pd shell on the Au seeds and commercial Pd/C catalysts, the core-shell nanoparticles via their core-shell templates display superior activity and durability in catalyzing oxygen reduction reaction, mainly due to the larger lattice tensile effect in Pd shell induced by the Au core and Ag removal. Subsequently, the Ag component is removed from the alloy shell using saturated NaCl solution to form core-shell nanoparticles with an Au core and a Pd shell. Then, the pure Ag shells are converted into the shells made of Ag/Pd alloy by galvanic replacement reaction between the Ag shells and Pd 2+ precursors. This strategy begins with the preparation of core-shell nanoparticles in an organic solvent. Herein, we demonstrate the synthesis of core-shell nanoparticles from their core-shell parents. Core-shell nanoparticles often exhibit improved catalytic properties due to the lattice strain created in these core-shell particles.
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