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In the present work, CeO 2 nanocrystals with three well-defined morphologies including nanooctahedra, nanosphere and nanocube are synthesized and used as the promoter to Pt catalyst toward methanol electrooxidation reaction (MOR). The promotion effects of the CeO 2 nanocrystals are investigated through electrochemical techniques including cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). Results indicate that the promotion effects are closely related to the nanostructure of CeO 2 nanocrystals. Among the Pt-CeO 2 /C catalysts, Pt-CeO 2 /C- S catalyst with CeO 2 nanosphere as the promoter shows the highest catalytic performance for MOR, which arises from both physical interaction and electronic effects between CeO 2 and Pt. The loosened nanosphere structure with rough surface allows the Pt nanoparticles (NPs) to highly disperse onto the surface and thereby produce a strong physical interaction between Pt and CeO 2. In addition, the change in the valence state from Ce4+ to Ce3+ generates abundant oxygen vacancies (V O) into the crystal lattice, and the increased vacancies lead to surplus electrons which would transfer from CeO 2 to Pt. The increased electron density lowers the d-band center and thus improves the intrinsic activities (IA) of Pt. These data are used to discuss the role of physical interaction and electronic effects between the promoter and Pt and would be promising in designing the nanostructure of the Pt-based catalysts for DMFCs and other applications. • CeO 2 nanooctahedron, nanosphere and nanocube are prepared. • The CeO 2 nanocrystals are used as the promoter to Pt electrocatalyst for MOR. • Morphology effects of CeO 2 on the catalytic properties of Pt are investigated. • CeO 2 nanospheres show the highest promotion effects. [ABSTRACT FROM AUTHOR]

Abstract Three MnO 2 samples with different well-defined morphologies including nanoplates, nanorods and corallines are prepared through a simple chemical precipitation method and used as the promoter/support for Pt electrocatalysts (denoted as Pt/MnO 2 P , Pt/MnO 2 - R and Pt/MnO 2 C , respectively). The morphology effects of MnO 2 to the catalytic properties of Pt for methanol oxidation reaction (MOR) are intensively investigated. Results show that the catalytic properties of Pt are strongly dependent on the morphology of the promoter. Pt/MnO 2 - R with MnO 2 nanorods as the promoter shows the highest catalytic properties among the MnO 2 -promoted catalysts. The mass-specific activity and intrinsic activity of Pt in Pt/MnO 2 - R catalyst is 0.51 A mg−1 Pt and 11.54 A m−2 Pt , which is ca. 1.89 and 2.18 times that of commercial Pt/C catalysts (0.27 A mg−1 Pt and 5.29 A m−2 Pt), respectively. Change in the electronic structure of Pt is responsible for the enhancement in the catalytic properties of Pt/MnO 2 - R. Highlights • MnO 2 nanoplates, nanorods and corallines are used as the promoters to Pt for MOR. • Morphology effects of MnO 2 on the catalytic properties of Pt are investigated. • Pt/MnO 2 with MnO 2 nanorods as the promoter shows much higher catalytic properties. • Change in the electronic structure of Pt contributes to its enhanced activities. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (RGO) supported Pt m Au electrocatalysts with different atomic Pt/Au ratios ( m = 0.5–2.0) are prepared via co-reduction of H 2 PtCl 6 and HAuCl 4 . The catalysts are comprehensively characterized through TEM, XRD and XPS. The catalytic behaviors of the Pt m Au catalysts toward methanol oxidation reaction (MOR) in alkaline electrolyte are investigated via cyclic voltammetry (CV) and chronoamperometry (CA) techniques. Results show that methanol oxidation currents on the Pt m Au catalysts are higher than that on pure Pt catalyst, suggesting that the introduction of Au in Pt catalyst can significantly promote the catalytic properties of Pt. Among the Pt m Au catalysts, Pt 1.0 Au/RGO shows the highest mass-specific activity (MSA) and intrinsic activity (IA). The MSA and IA of Pt 1.0 Au/RGO is 0.72 A mg −1 Pt+Au and 105.4 A m −2 Pt , which are ca . 2.40 and 3.56 times those of Pt/RGO (0.30 A mg −1 Pt+Au and 29.6 A m −2 Pt ), respectively. CO stripping voltammograms and CV curves suggest that the improved electrocatalytic properties of the Pt m Au/RGO catalysts are especially attributed to the decreased CO formation rather than the facile removal of CO on the surface of Pt. The findings of this work have potential applications in understanding the mechanism of MOR and designing highly effective Pt-based anodic catalysts of direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: Composite metal oxides InxSnO2 are prepared with a simple hydrothermal process and used as functionalized support of Pt catalyst toward methanol electrooxidation reaction (MOR). The catalytic activity of Pt is strongly dependent on the composition of the support. Introduction of a small amount of In into SnO2 support exhibits much higher promoting effect to the Pt catalytic properties as compared with Pt/SnO2 and commercial Pt/C catalysts. The mass-specific activity (MSA) and intrinsic activity (IA) of Pt in Pt/In0.1SnO2 is 3.0 and 4.3 times that of Pt/C, respectively. Changes in Pt electronic structure arising from the interaction between Pt and the support are responsible for this improvement. Our findings clearly suggest that the composite metal oxides InxSnO2 can not only act as the catalyst support but also act as an effective promoter to Pt toward MOR, which would be promising in designing new catalysts that can replace the traditional catalytic nanostructure. [Copyright &y& Elsevier]

Abstract: Alloyed Pt m Ag nanostructures (m being the atomic Pt/Ag ratio, m =0.03–1.0) supported on carbon black were prepared and comprehensively characterized by ultraviolet–visible spectroscopy, X-ray diffraction, and transmission electron microscopy techniques. Cyclic voltammetry (CV) and chronoamperometry studies of methanol electro-oxidation reaction (MOR) in alkaline electrolyte indicated that the catalytic activity and CO tolerance of Pt were improved remarkably by the co-presence of Ag. A volcano relationship between the activity and m was found for the Pt m Ag/C catalysts, and both the highest mass-specific activity and the highest intrinsic activity of Pt were reached at m =0.5. Interestingly, we also found that the catalytic activity of the Pt m Ag/C catalysts strongly depended on the high-potential limit of CV. When the Pt m Ag/C catalysts were cycled up to 0.5V (vs. saturated calomel electrode), which induced a significant redox process of Ag, they showed ca. 50 times higher catalytic activity than those not subjected to the Ag redox process (up to 0.1V). Our study clearly demonstrated that the Ag oxide played a crucial role in promoting the catalytic role of Pt for MOR in alkaline electrolyte. [Copyright &y& Elsevier]

Abstract: Dealloyed PtAg/C nanostructures, prepared by selective electrochemical etching of Ag in 0.5M H2SO4 from a series of alloyed Pt m Ag/C samples with atomic Pt/Ag ratio m =0.1, 0.5, 1.0 and 1.5, were employed as cathode electrocatalysts for oxygen reduction reaction (ORR) in 0.5M KOH. Compared with their as-prepared counterpart alloy catalysts, the dealloyed catalysts showed higher half-wave potentials (E 1/2) and significantly higher Pt mass-specific activity (MSA) data. The intrinsic activity (IA) of Pt increased more or less after the dealloying treatment but was strongly dependent on the composition (m) of the alloyed sample. The Pt IA numbers were comparable for the dealloyed catalysts derived from Pt m Ag/C of m =0.5, 1.0 and 1.5, which were nearly twice that for E-TEK Pt/C catalyst and 3 times that for the dealloyed catalyst derived from Pt0.1Ag/C. [ABSTRACT FROM AUTHOR]

The promoting effect of metal oxides to Pt catalysts toward methanol oxidation reaction (MOR) has attracted widespread attention in recent years. In this communication, we report the promoting effect of MoO 3 to Pt catalyst by rationally designing and tuning the nanostructure of the catalysts. MoO 3 nanorods are firstly synthesized through hydrothermal method and used as the substrate for the deposition of polyaniline (PANI) layer. The PANI-MoO 3 composite nanostructures are then used as the support for Pt catalyst. Depending on the preparation method of Pt nanoparticles, the nanostructure can be PANI nanotube supported Pt (Pt/PANI) through etching MoO 3 nanorods with NaBH 4 and PANI-MoO 3 composite nanorods supported Pt (Pt/PANI-MoO 3 ). The catalytic properties of the two catalysts toward MOR are investigated. Results show that the current of methanol oxidation on Pt/PANI-MoO 3 catalyst is comparable to that on Pt/PANI, while the peak potential of MOR on the former is lowered by 180 mV as compared with the latter, suggesting a much higher catalytic activity of Pt/PANI-MoO 3 . The presence of MoO 3 may be responsible for the improvement of the catalytic properties through the co-synergistic effects of PANI and MoO 3 . [ABSTRACT FROM AUTHOR]

Composite oxides (MoO 3 ) m SnO 2 ( m being the atomic Mo/Sn ratio) are prepared and employed as the promoter to Pt toward methanol electrooxidation reaction (MOR) in alkaline electrolyte. The Pt electrocatalysts supported on (MoO 3 ) m SnO 2 /C are comprehensively characterized by TEM, XRD, XPS and electrochemical techniques. Electrochemical measurements for MOR indicate that molybdenum-doped SnO 2 show much higher promotion effect to the catalytic performances of Pt than the undoped SnO 2 . The activities of Pt in Pt–(MoO 3 ) m SnO 2 /C catalysts are also much higher than those in commercial Pt/C catalyst. Among the series of Pt–(MoO 3 ) m SnO 2 /C catalysts, Pt–(MoO 3 ) 0.2 SnO 2 /C shows the highest catalytic performances. The mass-specific activity (MSA) and intrinsic activity (IA) of Pt in Pt–(MoO 3 ) 0.2 SnO 2 /C is ca . 3.0 and 3.5 times higher than those of Pt/C catalyst, respectively. The high content of Pt(II and IV) in the catalysts and the changes in Pt electronic structure are responsible for this improvement. These data suggest that the composite metal oxides (MoO 3 ) m SnO 2 are effective promoter to Pt toward MOR, which would be promising in designing new catalysts for high-performance alkaline direct methanol fuel cells and other technologies. [ABSTRACT FROM AUTHOR]