Abstract
Large scale syntheses of uniform metal nanoparticles with hollow porous structure have attracted much attention owning to their high surface area, abundant active sites and relatively efficient catalytic activity. Herein, we report a general method to synthesize hollow porous Pd nanospheres (Pd HPNSs) by templating sacrificial SiO2 nanoparticles with the assistance of polyallylamine hydrochloride (PAH) through layer-by-layer self-assembly. The chemically inert PAH is acting as an efficient stabilizer and complex agent to control the synthesis of Pd HPNSs, probably accounting for its long aliphatic alkyl chains, excellent coordination capability and good hydrophilic property. The physicochemical properties of Pd HPNSs are thoroughly characterized by various techniques, such as transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The growth mechanism of Pd HPNSs is studied based on the analysis of diverse experimental observations. The as-prepared Pd HPNSs exhibit clearly enhanced electrocatalytic activity and durability for the formic oxidation reaction (FAOR) in acid medium compared with commercial Pd black.
Highlights
Palladium (Pd) plays an important role in a variety of chemical reactions [1,2,3,4], such as serving as an efficient electrocatalyst towards formic acid oxidation reaction (FAOR) in direct formic acid fuel cells (DFAFCs) [5,6,7]
The as-prepared Pd HPNSs exhibit observably enhanced electrocatalytic activity and durability for FAOR compared with commercial Pd black [18,19,20,21]
SiO2 template, PdCl42− can be uniformly adsorbed owning to electrostatic attraction, and be in-situ reduced by NaBH4, mostly taking place on the surface of the SiO2
Summary
Palladium (Pd) plays an important role in a variety of chemical reactions [1,2,3,4], such as serving as an efficient electrocatalyst towards formic acid oxidation reaction (FAOR) in direct formic acid fuel cells (DFAFCs) [5,6,7]. The morphology of Pd nanocrystals powerfully influences their electrocatalytic activity and stability because of structural effects. (2) Such hollow porous nanostructures supply abundant active sites owning to ample edges and corners, and improve the mass transfer promoting the electrocatalytic activity obviously [15]. Positively charged colloidal modified silica serve as a sacrificial template to synthesize the hollow porous Pd nanospheres (Pd HPNSs). The outermost PAH functions as polyelectrolyte to strongly adsorb negatively charged precursors and reductants, and serves as a stabilizer and complex agent to effectively avoid the aggregation of the Pd nanoparticle owning to its long aliphatic alkyl chain and excellent hydrophilic property. After removing the SiO2 sacrificial template, the morphology of the outermost Pd nanospheres is maintained to obtain the hollow porous nanostructure. The as-prepared Pd HPNSs exhibit observably enhanced electrocatalytic activity and durability for FAOR compared with commercial Pd black [18,19,20,21]
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