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The design of Pt-based cathode catalyst for the oxygen reduction reaction (ORR) is critical for fabricating high-performance polymer electrolyte membrane fuel cells. In this study, hollow PtNi alloy nanostructures (h-PtNi/C-X) deposited on a carbon black support are prepared using a facile synthesis method at various pH value (X). The degree of alloying of the hollow nanostructures is modulated with increasing pH. Among these h-PtNi/C catalysts, h-PtNi/C-11 exhibits superior ORR activity (five-fold mass activity and higher power density) and improved durability both in half and unit cells, compared to a commercial Pt/C catalyst. [Display omitted] • Hollow PtNi alloy nanostructures were formed by the Kirkendall effect. • With increasing pH, the degree of alloying were gradually increased. • h-PtNi/C-11 cathode catalyst exhibited the best ORR performance. • The enhanced performance is attributed to a hollow PtNi alloy nanostructure. • The enhanced performance can result from an electronic modification. [ABSTRACT FROM AUTHOR]

Doped carbon structures have been developed as non-precious metal catalysts for oxygen reduction reactions (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). Among doped carbon structures, Fe- and N-doped carbon (Fe/N/C) nanostructured catalysts have received attention due to their catalytic activity, comparable to that of Pt, avoiding the use of critical raw materials. However, obviously, its durability is not yet neither fully understood nor comparable to that of traditional catalysts. In this study, we synthesized mesoporous F-doped Fe/N/C, which is a tri-doped carbon nanostructure, as a cathode catalyst for ORR. Tri-doped carbon catalysts with different amounts (x) of F (Fx-Fe/N/C) were prepared using Fe-5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphine iron(III) chloride and NH 4 F as the Fe/N- and F- doping sources, respectively, and Santa Barbara amorphous-15 as the template. Fx-Fe/N/C with an optimal F content exhibited excellent electrocatalytic performance for ORRs i.e. a high half-wave potential of 809 mV in 0.1 M HClO 4 solution, a maximum power density of 280 mW cm−2, and a high stability for 4000 min at 0.5 V, owing to the high proportion of FeN x and pyridinic N as active sites, strong C–F bonds, and hydrophobic surfaces. We synthesized mesoporous F-doped Fe/N/C, which is a tri-doped carbon nanostructure, as a cathode catalyst for ORR. Fx-Fe/N/C with an optimal F content exhibited excellent electrocatalytic activity and durability for ORRs owing to the high proportion of FeNx and pyridinic N as active sites, strong C–F bonds, and hydrophobic surfaces. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A hybrid support was prepared by depositing Nb 2 O 5 nanoparticles on the carbon black(Nb 2 O 5 /C). • Pt nanoparticles were deposited on the Nb 2 O 5 /C support(Pt/Nb 2 O 5 /C). • Pt/Nb 2 O 5 /C with an optimal weight of Nb 2 O 5 exhibited an enhanced electrocatalytic performance. • The improved performance of Pt/Nb 2 O 5 /C may be attributed to the SMSI effect. In this study, in the polymer electrolyte membrane fuel cells, we report cathode catalysts (Pt/Nb 2 O 5 /C) for the oxygen reduction reaction (ORR). In Pt/Nb 2 O 5 /C, a hybrid support was prepared by depositing Nb 2 O 5 nanoparticles on the carbon black. Pt nanoparticles were deposited on Nb 2 O 5 decorated carbon black (Nb 2 O 5 /C) as the hybrid support as. The strong metal support interactions in Pt/Nb 2 O 5 /C, which was observed by X-ray photoelectron spectroscopy, prevented the degradation of the Pt nanoparticles and enhanced the stability of the carbon-based support. On the basis of our durability tests using half and single cells, Pt/Nb 2 O 5 /C prepared with an optimal weight of Nb 2 O 5 exhibited significantly lower reduction ratios, i.e., the improved durability of the catalyst. Hence, Pt/Nb 2 O 5 /C exhibited comparable activity and improved stability due to the SMSI effect compared to a commercial Pt/C. [ABSTRACT FROM AUTHOR]