Cobalt-Doped Pd@Pt Core–Shell Nanoparticles: A Correlative Study of Electronic Structure and Catalytic Activity in ORR

Abstract

Platinum (Pt) is a critical catalytic component used in polymer electrolyte membrane fuel cells. However, its low abundance, limited supply, and increasing demand have limited the commercial applications of this metal. One of the most recent ways to meet these demands is to utilize Pt-based bimetallic nanoparticles. Using the Pt metal as the shell material of the catalyst not only increases the surface area but also creates an interfacial interaction between the core metal and platinum, which results in enhanced catalytic activity. Recently, octahedral Pd@Pt nanoparticles with controllable Pt shells have been shown to exhibit greatly enhanced activity and durability compared to commercial Pt/C. In this study, Pd@Pt nanoparticles will be surface doped with cobalt to further boost their durability and activity. Characterizing the synthesized catalyst with X-ray absorption fine structure at the Pt L3-edge and cobalt K-edges, together with performance tests, has revealed information about the effect of the dopants on the catalytic activity of catalysts. The results of the local and electronic structures of the catalysts are correlated with electrocatalytic activity to optimize performance. Cobalt has been found to be simultaneously efficient in enhancing catalytic activity, increasing long-term durability, and reducing the platinum content in the catalysts.

Pt-1,1′-Bi(2-Naphthol) Nanostructures for Electrochemical H2 Evolution in Alkaline Media

“…The lower h Ts value suggests that the Pt NPs may gain the excited electrons more effectively from the π* state of BINOL nanoflakes, transferring to the unfilled 5d states of Pt . Consequently, the intensity of the white line at the Pt L 3 -edge for the Pt-BINOL nanoflakes exhibits a slight decrease compared to that of the Pt-BINOL nanospheres …”

“…Meanwhile, the white-line intensity of the Pt-BINOL nanoflakes is lower than that of the Pt-BINOL nanospheres. It infers that the Pt NPs likely have a stronger electronic effect with BINOL nanoflakes than with BINOL nanospheres, by which more electrons possibly move from BINOL molecules to fill the empty 5d holes in the Pt conduction band . Hence, there are fewer unoccupied holes for electron transfers under X-ray excitation.…”

“…It infers that the Pt NPs likely have a stronger electronic effect with BINOL nanoflakes than with BINOL nanospheres, by which more electrons possibly move from BINOL molecules to fill the empty 5d holes in the Pt conduction band. 41 Hence, there are fewer unoccupied holes for electron transfers under X-ray excitation. To determine the unfilled d-band holes in the Pt-BINOL nanocomposites, we conducted measurements and calculations, whose details are recorded in the Experimental Section (see the Supporting Information).…”

“…30 Consequently, the intensity of the white line at the Pt L 3 -edge for the Pt-BINOL nanoflakes exhibits a slight decrease compared to that of the Pt-BINOL nanospheres. 41 EXAFS spectra were subjected to Fourier transform (FT) analysis to investigate the local structure of the Pt-BINOL nanocomposites in detail. Figure 3b presents the k 3 χ(k)weighted Fourier transform EXAFS spectra at the Pt L 3 -edge for the Pt-BINOL nanosphere, Pt-BINOL nanoflake, and Pt foil, with the fitting results shown as red dashed lines.…”