*Article* **Fabrication of Size- and Shape-Controlled Platinum Cones by Ion-Track Etching and Electrodeposition Techniques for Electrocatalytic Applications**

**Yuma Sato <sup>1</sup> , Hiroshi Koshikawa <sup>2</sup> , Shunya Yamamoto <sup>2</sup> , Masaki Sugimoto <sup>2</sup> , Shin-ichi Sawada <sup>2</sup> and Tetsuya Yamaki 1,2,\***


**Abstract:** The micro/nanocone structures of noble metals play a critical role as heterogeneous electrocatalysts that provide excellent activity. We successfully fabricated platinum cones by electrodeposition using non-penetrated porous membranes as templates. This method involved the preparation of template membranes by the swift-heavy-ion irradiation of commercially available polycarbonate films and subsequent chemical etching in an aqueous NaOH solution. The surface diameter, depth, aspect ratio and cone angle of the resulting conical pores were controlled in the ranges of approximately 70–1500 nm, 0.7–11 µm, 4–12 and 5–13◦ , respectively, by varying the etching conditions, which finally produced size- and shape-controlled platinum cones with nanotips. In order to demonstrate the electrocatalytic activity, electrochemical measurements were performed for the ethanol oxidation reaction. The oxidation activity was found to be up to 3.2 times higher for the platinum cone arrays than for the platinum plate. Ion-track etching combined with electrodeposition has the potential to be an effective method for the fabrication of micro/nanocones with high electrocatalytic performance.

**Keywords:** ion-track etching; electrodeposition; micro/nano-sized metal cones; template synthesis; electrocatalyst
