Fabrication of thick AAO template via stepwise voltage reduction hard anodization for long nanowire arrays

As an important type of one-dimensional material, nanowire arrays hold great application potential in fields such as sensors. Template-assisted electrodeposition is the core technology for their large-scale preparation. Anodic aluminum oxide (AAO) templates have become commonly used templates in this method due to their high stability and low cost. However, AAO templates prepared by traditional methods have a low growth rate, making it difficult to fabricate long nanowire arrays. In this study, a stepwise voltage reduction-assisted hard anodization method was adopted to prepare thick AAO templates. We successfully prepared AAO templates with a thickness of more than 120 μm after 3 h of anodization. Post-treatment of the samples was carried out at different voltage reduction rates, and the effects of voltage reduction rate on the template’s morphology and electrochemical performance were compared. The results show that the AAO template treated at a voltage reduction rate of 1 V/min exhibits relatively optimal pore uniformity, with an average pore diameter of 165.25 nm. This treatment reduces the AC impedance from 1.881 × 10¹³ Ω to 8.334 × 10⁶ Ω and lowers the polarization to 0.52 V. Additionally, complete peeling of the AAO template was achieved via reverse electrolysis, and long cobalt nanowire arrays with a length exceeding 80 μm were deposited. This work provides a simple method for preparing long nanowire arrays with a thick AAO template, which is of great significance to promote the practical application of nanowire arrays.