Galvanic Deposition of Pt Nanoparticles on Black TiO<sub>2</sub> Nanotubes for Hydrogen Evolving Cathodes
Aikaterini Touni, Xin Liu, Xiaolan Kang, P.A. Carvalho, Spyros Diplas, Kevin G. Both, S. Sotiropoulos, Athanasios Chatzitakis
Abstract
Abstract A galvanic deposition method for the in‐situ formation of Pt nanoparticles (NPs) on top and inner surfaces of high‐aspect‐ratio black TiO 2 ‐nanotube electrodes (bTNTs) for true utilization of their total surface area has been developed. Density functional theory calculations indicated that the deposition of Pt NPs was favored on bTNTs with a preferred [004] orientation and a deposition mechanism occurring via oxygen vacancies, where electrons were localized. High‐resolution transmission electron microscopy images revealed a graded deposition of Pt NPs with an average diameter of around 2.5 nm along the complete nanotube axis (length/pore diameter of 130 : 1). Hydrogen evolution reaction (HER) studies in acidic electrolytes showed comparable results to bulk Pt (per geometric area) and Pt/C commercial catalysts (per mg of Pt). The presented novel HER cathodes of minimal engineering and low noble metal loadings (μg cm −2 range) achieved low Tafel slopes (30–34 mV dec −1 ) and high stability in acidic conditions. This study provides important insights for the in‐situ formation and deposition of NPs in high‐aspect‐ratio structures for energy applications.