CeO 2/rGO/Pt sandwich nanostructure: RGO-enhanced electron transmission between metal oxide and metal nanoparticles for anodic methanol oxidation of direct methanol fuel cells
College of Chemistry and Materials Science, Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecular-Based Materials, Anhui Normal University, Wuhu, 241000, P. R. China. Nanoscale
(Impact Factor: 7.39).
08/2012; 4(18):5738-43. DOI: 10.1039/c2nr31765f
Pt-based nanocomposites have been of great research interest. In this paper, we design an efficient MO/rGO/Pt sandwich nanostructure as an anodic electrocatalyst for DMFCs with combination of the merits of rigid structure of metallic oxides (MOs) and excellent electronic conductivity of reduced oxidized graphene (rGO) as well as overcoming their shortcomings. In this case, the CeO(2)/rGO/Pt sandwich nanostructure is successfully fabricated through a facile hydrothermal approach in the presence of graphene oxide and CeO(2) nanoparticles. This structure has a unique building architecture where rGO wraps up the CeO(2) nanoparticles and Pt nanoparticles are homogeneously dispersed on the surface of rGO. This novel structure endows this material with great electrocatalytic performance in methanol oxidation: it reduces the overpotential of methanol oxidation significantly and its electrocatalytic activity and stability are much enhanced compared with Pt/rGO, CeO(2)/Pt and Pt/C catalysts. This work supplies a unique MO/rGO/Pt sandwich nanostructure as an efficient way to improve the electrocatalytic performance, which will surely shed some light on the exploration of some novel structures of electrocatalyst for DMFCs.
- "This strategy leads to the loss of conductivity and then fast degradation of the catalytic activity [20e22]. Therefore, it is very desirable to design and fabricate a new PteTiO 2 eC composite nanostructure that overcomes the shortcomings of TiO 2 and carbon  . Nowadays, graphene has drawn increasing attentions as the support of electrocatalysts owing to its high specific surface area and excellent electrical conductivity  . "
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ABSTRACT: Pt/TiO2-decorated reduced graphene oxide composite as catalyst for methanol electro-oxidation with three phase junction structure has been synthesized by UV-photoreduction (denoted as p-Pt/rGO@TiO2). The obtained p-Pt/rGO@TiO2 has been detailedly characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and chronoamperometry (CA). XRD and TEM characterizations indicate that photoreduction is favorable to anchoring Pt nanoparticles (NPs) (ca. 2.2 nm) at the interface between TiO2 and reduced graphene oxide (rGO), and forming the Pt, TiO2 and rGO three phase junction structure. P-Pt/rGO@TiO2 exhibits a higher activity for methanol electro-oxidation than m-Pt/rGO and m-Pt/rGO@TiO2 (prepared by microwave-assisted polyol process). Lifetime tests demonstrate that the electrochemical durability of p-Pt/rGO@TiO2 is improved by a factor of 2 or more as compared with m-Pt/rGO and m-Pt/rGO@TiO2. XPS characterizations of p-Pt/rGO@TiO2 reveal stronger interaction between Pt and support hybrid compared with m-Pt/rGO@TiO2, which facilitates poisoning species removal and prevents Pt nanoparticles from migrating/agglomerating on or detaching from carbon support. This provides a facile and promising strategy to improve both the activity and durability of electrocatalysts for DMFCs. Copyright
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ABSTRACT: Polypyrrole nanotubes (PPyNTs)/PtAu alloy nanoparticle (NP) hybrids were synthesized in gram-scale by using covalently attached imidazolium moieties as a linker. The approach involves the surface functionalization of PPyNTs with pendant imidazolium moieties (PPyNT-Im), anion-exchange with Pt and Au precursors, and followed by the reduction of metal ions to produce the PtAu alloy NPs on the surface of PPyNTs. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-angle annular dark-filed scanning transmission electron microscopy (HAADF-STEM), and elemental mapping showed that both Pt and Au were atomically distributed in the PtAu alloy NPs without phase segregation. The composition of the PtAu alloy NPs can be simply controlled by adjusting the feed ratio in the metal precursor solution. The electrocatalytic properties of prepared PPyNT-Im-PtxAuy (the suffixes x and y represent the relative molar ratio of Pt and Au in the feed, respectively) NP hybrids were determined by the composition of alloy NPs. The Pt-rich NP hybrids, PPyNT-Im-Pt8Au2, showed highly electrocatalytic activity and stability toward the methanol oxidation in both acidic and alkaline solutions, while the Au-rich NP hybrids, PPyNT-Im-Pt2Au8, showed an enhanced catalytic activity and durability upon oxygen reduction. The present study provided a simple and effective approach for the preparation of PtAu alloy catalysts with controllable composition for high performance fuel cells and electrochemical sensors.
Available from: Rongming Wang
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ABSTRACT: One-dimensional Co3O4 nanotubes were grown in alignment on the surface of micron-sized Co3O4 hexagonal-box via a mild template-free wet chemical method. The nanotubes are 250 nm in diameter with several micrometers in length. The growth mechanism and phase formation for the vertically grown nanotubes on the surface of the boxes have also been investigated. The intermediates of α-Co(OH)2 and β-Co(OH)2 towards the final products of Co3O4 are also characterized. The magnetization, M(T), measurements for the micro-boxes with nanotubes reveals that the Neel temperature is suppressed from the bulk value of 40 K down to 22 K, possibly due to finite size effect. The Curie–Weiss analysis on the paramagnetic behavior above the Neel temperature gives the average effective moment of 4.4 μB per formula unit, slightly higher than 4.14 μB of its bulk counterparts. The electrocatalytic experiments for the oxidation of methanol reveal that the final product exhibits better catalytic performance compared with the intermediate product due to its higher specific surface area.
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