Ultrathin‐Polyaniline‐Coated Pt–Ni Alloy Nanooctahedra for the Electrochemical Methanol Oxidation Reaction

Abstract

Controlling the morphology and composition of nanocatalysts constructed from metals and conductive polymers has attracted attention owing to their great potential for the development of high‐efficiency catalysts for various catalytic applications. Herein, a facile synthetic approach for ultrathin‐polyaniline‐coated Pt–Ni nanooctahedra (Pt‐Ni@PANI hybrids) with controllable PANI shell thicknesses is presented. Pt–Ni nanooctahedra/C catalysts enclosed by PANI shells with thicknesses from 0.6 to 2.4 nm were obtained by fine control over the amount of aniline. The various Pt‐Ni@PANI hybrids exhibited electrocatalytic activity toward the methanol oxidation reaction that is highly dependent on the thickness of the PANI shell. Pt‐Ni@PANI hybrids with the thinnest PANI shells (0.6 nm) showed markedly improved electrocatalytic performance for the methanol oxidation reaction compared with Pt‐Ni@PANI hybrids with thicker PANI shells, Pt–Ni nanooctahedra/C, and commercial Pt/C due to synergistic benefits of ultrathin PANI shells and Pt–Ni alloy.

Catalyst overcoating engineering towards high-performance electrocatalysis

“…PANI with 5 nm thickness is able to embed Pt NPs on the surface of the carbon support. PANI-overcoated Pt nanocube assemblies, 66 hybrid Pd/PANI/Pd sandwich-structured nanotube arrays 67 and ultra-thin PANI-coated Pt-Ni nanooctahedra 68 have been synthesized by following a similar oxidative polymerization process. Electrochemical performance follows the change in PANI thickness; a thinner PANI layer (0.6 nm) is more beneficial for the markedly improved electrocatalytic activity towards methanol oxidation than a thicker layer.…”

Synthesis of Pd‐Pt Ultrathin Assembled Nanosheets as Highly Efficient Electrocatalysts for Ethanol Oxidation

“…Electrooxidation of ethanol in alkaline medium proceeds via the following i) reactive intermediate and ii) poisoning intermediate pathway. [32,33] i) reactive intermediate pathway: [3,20] It has been previously reported that the up-shift of d-band center of PdÀ Pt alloy surfaces compared with that of pristine Pd surface can promote the formation of OH ads with optimal binding strength [34] and thus enhancement of EOR activity can be achieved on PdÀ Pt alloy surface due to accelerated rate of (COCH 3 ) ads oxidation. To investigate the change in the electronic structure of the PdÀ Pt alloy UANs, X-ray photoelectron spectroscopy (XPS) spectra of valence band regions were obtained and corresponding d-band center positions relative to the Fermi level were calculated.…”

“…[15][16][17][18][19] Introducing the secondary metal component can modulate the electronic structure of Pt and thus weaken the affinity of poisoning species. [20] In particular, Pd is a promising candidate to form a strong coupling with Pt and synergistically enhance the catalytic properties due to the same face-centered cubic (fcc) structure with a highly similar lattice constant of nominal mismatch of 0.77%. [6,21,22] As an another approach to enhance the electrocatalytic performance, preparing nanocrystals (NCs) can offer an advantage for increasing high accessible active sites participating in the electrocatalytic reaction due to their large surface area to volume ratio as compared with bulk materials.…”

“…An effective strategy for improving the activity and stability of Pt is alloying it with other metals, such as Pd, Ir, Ru, Au, and Pb . Introducing the secondary metal component can modulate the electronic structure of Pt and thus weaken the affinity of poisoning species . In particular, Pd is a promising candidate to form a strong coupling with Pt and synergistically enhance the catalytic properties due to the same face‐centered cubic (fcc) structure with a highly similar lattice constant of nominal mismatch of 0.77% …”

“…For reactive intermediate pathway, electrooxidation of (COCH 3 ) ads intermediate on the metal surface by reacting with OH ads in the alkaline medium is the rate‐determining step . It has been previously reported that the up‐shift of d‐band center of Pd−Pt alloy surfaces compared with that of pristine Pd surface can promote the formation of OH ads with optimal binding strength and thus enhancement of EOR activity can be achieved on Pd−Pt alloy surface due to accelerated rate of (COCH 3 ) ads oxidation.…”