Electrochemical fabrication of Hydrangea macrophylla flower-like Pt hierarchical nanostructures and their properties for methanol electrooxidation

Abstract

The electrochemical preparation of non-carbon supported catalysts is a favourable way for fuel cells to keep catalysts from agglomerating during the electrocatalytic process and provide the catalyst layer with higher mechanical stability than the established drop-coating deposition of a mixture of catalysts and carbon powder. Herein, one-step current-directed approach is proposed to fabricate 3-dimensional (3D) Pt hierarchical nanostructures (3DPHNs) without any capping agents. The resulting 3DPHNs were composed of Hydrangea macrophylla flower-like Pt microspheres, and each microsphere consisted of several nano-petals. The size, the number density and the exposed facets of Pt microspheres in 3DPHNs can be adjusted by changing the current density of Pt deposition. High-resolution transmission electron microscopy (HRTEM) revealed that Pt nano-petals obtained at deposition current densities higher or lower than 3.5 mA cm⁻² contained Pt{200} and Pt{111} facets. However, Pt nano-petals obtained at 3.5 mA cm⁻² were single crystals with {111} orientation that showed better specific catalytic activity and stability to methanol electrooxidation compared to commercial Pt/C catalyst due to its resistance to catalyst agglomeration and the exposure of specific facets and the specific nanostructure.