Platinum and PtNi Nanoparticle-Supported Multiwalled Carbon Nanotube Electrocatalysts Prepared by One-Pot Pyrolytic Synthesis with an Ionic Liquid

Pt and PtNi alloy nanoparticle-supported multiwalled carbon nanotubes (Pt/MWCNTs and PtNi/MWCNTs) are prepared by a one-pot pyrolysis method with the N,N,N-trimethyl-Npropylammonium bis(trifluoromethanesulfonyl)amide ionic liquid (IL) containing platinum and nickel precursors, Pt(acac)(2), Ni[Tf2N](2), and Ni(acac)(2), with suspended MWCNTs. The composite materials can be prepared by simply heating the IL solution at 573 K. The resulting materials show favorable catalytic activity toward the oxygen reduction reaction and durability superior to those of typical commercially available electrocatalysts. The catalytic activity of the PtNi/MWCNTs depends on the Ni content of the PtNi alloy nanoparticles. One of the PtNi/MWCNTs shows 1.4 times higher mass activity than a typical commercial electrocatalyst. A plot of the mass activity as a function of the Ni content gives a mountain-shaped curve with a vertex at ca. 25 atomic percent Ni. This one-pot process can readily control the catalytic properties of the PtNi/MWCNTs by changing the molar fraction of Pt and Ni precursors.