It
is highly attractive but challenging to develop transition-metal electrocatalysts
for direct hydrazine fuel cells (DHzFCs). In this work, a nickel crystalline
core@nickel phosphide amorphous shell heterostructured electrocatalyst
supported by active carbon (Ni@NiP/C) is developed. Ni@NiP/C with
a P/Ni molar ratio of 3:100, Ni@NiP3.0/C, exhibits outstanding
catalytic activity for the hydrazine oxidation reaction (HzOR) in
alkaline solution, achieving a much better catalytic activity (2675.1
A gNi
–1@0.25 V vs RHE) and high stability,
as compared to Ni nanoparticles supported on carbon (Ni/C) and Pt/C
catalysts. The results indicate that formation of the NiP amorphous
shell effectively inhibits the passivation of the Ni core active sites
and enhances the adsorption of hydrazine on Ni by improving the adsorption
energy, leading to high electrochemical activity and stability of
the Ni@NiP3.0/C catalysts for HzOR. The density functional
theory calculation confirms the structural and electrocatalytic effect
of the core–shell heterostructure on the stability and activity
of Ni active sites for HzOR. The unique crystalline core/amorphous
shell-structured Ni@NiP/C demonstrates promising potential as an effective
electrocatalyst for DHzFCs.
Ni–P/C NPs were prepared through a two-step liquid phase reduction method, which exhibited a significant enhancement for the electro-catalytic activity towards the carbohydrazide oxidation reaction compared with Ni/C NPs.
Carbon-supported Pt-Ru alloys with a Pt/Ru ratio of 1:1 were prepared by NaBH 4 reduction at room temperature. X-ray diffraction (XRD) measurements indicate that the as-prepared Pt-Ru nanoparticles had a face-centered cubic (fcc) structure. X-ray photoelectron spectroscopy (XPS) analyses demonstrate that alloying with Ru can decrease the 4f electron density of Pt, which results in a positive binding energy shift of 0.2 eV for the Pt 4f peaks. The catalytic properties of the synthesized Pt-Ru alloy catalysts were compared with those of commercial Pt/C catalysts by linear sweep voltammetry (LSV). The results show that the mass activity of the oxygen reduction reaction (ORR) is enhanced by 2.3 times as much mass activity of Pt relative to the commercial Pt/C catalyst. Single-chambered microbial fuel cell tests also confirm that the Pt-Ru alloys as cathode catalysts have better performance than that of commercial Pt/C catalysts.
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