ABSTRACT
Pt-Based catalysts for the methanol oxidation reaction (MOR) are highly susceptible to poisoning due to the surface adsorption of reaction intermediates such as COads. Depositing Pt nanoparticles (NPs) on Ni(OH)2 to fabricate Pt-Ni(OH)2 interfaces is considered as a promising method to improve the stability of Pt-based catalysts because Ni(OH)2 could facilitate water dissociation in alkaline electrolytes to form OH adspecies and assist in the oxidative removal of COads on adjacent Pt sites. However, this supported structure rather limited Pt-Ni(OH)2 interfaces because only a small fraction of the Pt NP surface could come into contact with Ni(OH)2. Herein, this work has addressed a simple and efficient strategy to engineer novel-structure catalysts by tuning the properties of the interface of Pt-based NPs with high-index facets (HIFs). Pt1Ni1-Ni(OH)2 nanoparticles (NPs) were synthesized through Ni(OH)2 partially covering the HIFs of monodisperse Pt1Ni1 concave nanocubes (CNCs) in situ. Pt-Ni(OH)2 interfaces were characterized and over 40% of the Pt surface active sites fall within the periphery of Ni(OH)2. Thanks to the synergy of HIFs and abundant Pt-Ni(OH)2 interfaces, Pt1Ni1-Ni(OH)2 NPs exhibited remarkable catalytic performance towards the MOR in alkaline solution.
ABSTRACT
Metal-organic frameworks (MOFs), as precursors for synthesizing new carbon materials, hold promise for applications in the oxygen reduction reaction (ORR) as efficient non-precious metal catalysts. Here, a facile template-assisted strategy was adopted to fabricate a core-shell structure derived from MIL-101(Fe) and polyaniline. MIL-101(Fe) nanoparticles obtained by microwave-assisted synthesis were combined with PAni in different ratios and carbonized at 900 °C under flowing N2. An optimized core-shell Fe3O4/Fe3N@graphite carbon structure was successfully prepared and exhibited attractive ORR activity, with a half-wave potential of 0.916 V vs. RHE and an electron transfer number of 4.0 at 0.4 V vs. RHE. Furthermore, the catalyst displayed excellent stability in an alkaline solution. The superior ORR performance of the catalyst is mainly attributed to its stable core-shell structure, large specific surface area and high content of electrocatalytically active N species.
