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In this study, hierarchical NiCo2S4 nanostructures have been successfully prepared on Ni foam support using a simple and economical two-step hydrothermal process. The hierarchical NiCo2S4 nanostructure comprises rod-like NiCo2S4 cores enveloped by a thin nanoribbon shell. When the NiCo2S4/Ni foam was employed as an electrode for methanol electrooxidation directly, a current density of 194 mA mg−1 was achieved at 0.60 V. The prepared NiCo2S4/Ni foam demonstrates high electrocatalytic activity and durability in alkaline environments for the methanol oxidation reaction. After 1000 cyclic voltammetry cycles in the alkaline electrolyte, the current density of the hierarchical NiCo2S4 decreased to 72.2% of its initial value, with the loss of catalytic activity during the cycling test attributed to their surface oxidation. These findings suggest the NiCo2S4 sample as a non-noble metal electrocatalyst holds great potential for direct methanol fuel cells. [ABSTRACT FROM AUTHOR]

Due to their unique open structural features, cubic nanoframes have a large specific surface area, which greatly increases their atomic utilization in catalytic reactions. In this study, PtPdCu cubic nanoframes were prepared via a one-pot wet-chemical process. Time-dependent experiments show that the formation of PtPdCu cubic nanoframes experienced a solid to hollow process, and the etching is performed by Br−/O2. As an electrocatalyst for the methanol oxidation reaction, the PtPdCu cubic nanoframes present 2.57 times higher mass activity than commercial Pt/C catalyst. Moreover, the as-prepared PtPdCu cubic nanoframes exhibit superior durability for electrocatalysis. This study provides a facile method for the preparation of cubic nanoframe-structured Pt-alloy electrocatalysts, and demonstrates that the rational design of electrocatalysts with specific morphology and composition can optimize their electrocatalytic performances. [ABSTRACT FROM AUTHOR]

In this work, Ni foam supported hierarchical NiCo 2 O 4 nanomaterials are successfully prepared through a hydrothermal process and subsequent calcination process, then the hierarchical NiCo 2 O 4 is converted to hierarchical NiCo 2 S 4 through a hydrothermal anion exchange process. The hierarchical nanomaterials are constructed by a nanorod core and nanoribbons shell. The morphology evolution mechanism of the hierarchical NiCo 2 O 4 is studied by exploratory experiments, the results show that the morphology evolution from nanorod to hierarchical nanostructure undergo a solid–solid process, and the calcination temperature is crucial for the formation of the hierarchical nanostructure. The hierarchical NiCo 2 O 4 and NiCo 2 S 4 nanomaterials are both used as electrocatalysts for methanol oxidation reaction in alkaline electrolyte, and the electrocatalytic activity of the NiCo 2 S 4 is higher than that of the NiCo 2 O 4. Cycling test shows the good stability of the NiCo 2 S 4 , and the slight loss of activity during cycling is caused by the surface oxidation of NiCo 2 S 4 in alkaline electrolyte. This work indicate that the hierarchical NiCo 2 S 4 is a promising non-noble metal electrocatalyst for direct methanol fuel cells. [Display omitted] • Hierarchical NiCo 2 O 4 and NiCo 2 S 4 nanostructures are grown on Ni foam. • The morphology evolution of the hierarchical nanostructure is researched. • The NiCo 2 S 4 shows a better electrocatalytic activity than that of the NiCo 2 O 4. • The surface oxidation of NiCo 2 S 4 causes the loss of activity during cycling test. [ABSTRACT FROM AUTHOR]

In this work, ZnCo 2 O 4 nanomaterial with a hierarchical three-dimensional (3D) architecture is directly grown on Ni foam by a convenient solvothermal process and subsequent calcination treatment. The ZnCo 2 O 4 hierarchical 3D architecture is constructed from coating a layer of ZnCo 2 O 4 nanowires on ZnCo 2 O 4 nanosheets. The growth mechanism of the ZnCo 2 O 4 hierarchical 3D architecture is studied by control experiments. The as-prepared ZnCo 2 O 4 /Ni foam is applied as a binder-free electrode for the electrooxidation of methanol in KOH electrolyte. The electrocatalytic performances of the ZnCo 2 O 4 electrodes prepared with different solvothermal reaction duration are studied, and the ZnCo 2 O 4 electrode prepared with solvothermal reaction duration of 18 h shows the highest activity. The high electrocatalytic activity and excellent stability of the ZnCo 2 O 4 relate to its hierarchical 3D architecture, porous nature, reversible redox characteristics and stability in alkaline electrolyte. Image 1 • ZnCo 2 O 4 with a hierarchical 3D architecture is prepared. • The growth mechanism of the hierarchical 3D architecture is studied. • The ZnCo 2 O 4 displays excellent electrocatalytic performances. • The ZnCo 2 O 4 electrocatalyst is inexpensive and durable. [ABSTRACT FROM AUTHOR]

Previous reports show that the {1 1 1} crystal facets of Pt-based nanocrystal catalysts are highly active for the electrooxidation of methanol. In this work, platinum–silver (Pt–Ag) alloy octahedral nanocrystals with exposed {1 1 1} facets are successfully synthesized through a one-pot, wet-chemical route. The growth mechanism of octahedral nanocrystals can be attributed to the stabilization of {1 1 1} facets by PVP. The electrocatalytic performances of the Pt–Ag octahedral nanocrystals with different Pt/Ag ratio and commercial Pt/C are studied. The results show that the electrocatalytic performances of the Pt–Ag octahedral nanocrystals are much better than that of the commercial Pt/C catalyst, and the Pt–Ag octahedral nanocrystals with a Pt/Ag ratio of 2:1 show the best electrocatalytic performances among the Pt–Ag octahedral nanocrystals. The Pt–Ag octahedral nanocrystals might be a promising candidate as anode catalyst for DMFCs. [ABSTRACT FROM AUTHOR]

In this paper, gold–platinum (Au–Pt) bimetallic nanotubes with different Au/Pt ratio are successfully synthesized through a simple wet-chemical reduction route in which tellurium (Te) nanowires serve as both sacrificial template and reducing agent. The hollow nanostructure of Au–Pt nanotubes is formed due to Kirkendall effect. The as-prepared Au–Pt nanotubes can be applied as catalyst for methanol oxidation reaction, and the results indicate that the Au–Pt nanotubes with an Au/Pt ratio of 1:1 show the best electrochemical catalytic performances. Furthermore, the catalytic activity of the Au–Pt nanotubes is also better than Pt nanotubes and commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesis method is simple and economical. • The gelidium-shaped NiCo 2 O 4 is a bifunctional electrocatalyst for both MOR and ORR. • The unique gelidium shape gives the NiCo 2 O 4 electrocatalyst abundant active sites. Gelidium-shaped NiCo 2 O 4 nanomaterial is synthesized via a two-step process including hydrothermal synthesis and calcination. The NiCo 2 O 4 nanomaterial has a unique hierarchical nanostructure which is constructed by a nanorod backbone and many tiny nanoneedles on the nanorod. The electrocatalytic performances of the NiCo 2 O 4 nanomaterial for both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) are tested. As for MOR, the NiCo 2 O 4 nanomaterial delivers a high current density of 139 mA·mg−1 at 0.60 V (vs Ag/AgCl). As for ORR, the electrocatalytic activities of the NiCo 2 O 4 nanomaterial are comparable to those of commercial Pt/C. The results reveal that the NiCo 2 O 4 nanomaterial is a promising bifunctional electrocatalyst for DMFCs. [ABSTRACT FROM AUTHOR]