Abstract
High-performance PtNi alloy nanoparticle-supported multiwalled carbon nanotube composite (PtNi/MWCNT) electrocatalysts can be prepared via one-pot preparation for oxygen reduction reaction. This route of preparation utilizes the pyrolytic decomposition of metal precursors, such as Pt(acac)2 with Ni precursors, nickel bis(trifluoromethanesulfonyl)amide (Ni[Tf2N]2) or nickel acetylacetonate (Ni(acac)2), in an ionic liquid (IL), N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)amide ([N1,1,1,3][Tf2N]). Currently, there is insufficient information concerning the effect of difference in preparation conditions on the formation mechanism and catalytic activity of PtNi/MWCNT. In this article, a staircase heating process was used to investigate the PtNi alloy nanoparticle formation mechanism and catalytic activity of the resulting PtNi/MWCNT. We found that the alloy formation process, composition, and crystal structure, which directly affect the electrocatalytic activity, strongly depended on the Ni precursor species and heating process. The catalytic performance of certain PtNi/MWCNTs collected during the staircase heating process was better than that of PtNi/MWCNTs produced via the conventional heating process.
Highlights
Pt alloy nanoparticles have been actively investigated as a promising catalytic material in the polymer membrane electrolyte fuel cell (PEMFC) system because such nanoparticles can reduce the Pt consumption and enhance the electrocatalytic performance in the oxygen reduction reaction (ORR).[1−5] Improvement of the catalytic performance is attained by adjusting the alloy composition, i.e., lattice parameters and electronic structures, of the Pt alloy nanoparticles.[6−9] it is not easy to vary the composition of the alloy while maintaining a desired particle size
It is consisted of a Pt sputtering process onto an ionic liquid (IL)[23] and an agitation process of the Pt-sputtered IL with the carbon support at 573 K or less.[24−26] Based on that, we proposed a simple and massproducible one-pot pyrolysis method with an ionic liquid (IL one-pot process) for preparing Pt metal and PtNi alloy nanoparticle-supported multiwalled carbon nanotube composite (Pt/MWCNT and PtNi/MWCNT) electrocatalysts for ORR.[27]
The formation mechanism of the PtNi/MWCNTs prepared via an IL one-pot process was examined using the staircase heating process with two different Ni metal precursors, Ni[Tf2N]2 and Ni(acac)[2]
Summary
Pt alloy nanoparticles have been actively investigated as a promising catalytic material in the polymer membrane electrolyte fuel cell (PEMFC) system because such nanoparticles can reduce the Pt consumption and enhance the electrocatalytic performance in the oxygen reduction reaction (ORR).[1−5] Improvement of the catalytic performance is attained by adjusting the alloy composition, i.e., lattice parameters and electronic structures, of the Pt alloy nanoparticles.[6−9] it is not easy to vary the composition of the alloy while maintaining a desired particle size To date, such Pt alloy nanoparticles have been prepared via commonly used methods, such as electrochemical deposition[10−13] and colloidal synthesis,[14−17] wherein the latter is often preferred as it is a controllable synthesis procedure.[18] In most cases, the synthesis is carried out through the following steps: (i) seed growth, (ii) deposition of the second metal on the seed, and (iii) supporting of the prepared nanoparticles onto the carbon materials. Such a process is time-consuming, complicated, and unsuitable for a large-scale industrial process
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