Ultrathin\nAtomic\nLayer Deposited Al₂O₃ Overcoat Stabilizes Al₂O₃‑Pt/Ni-Foam\nHydrogenation Catalysts

Abstract

Galvanic\nexchange seeds the growth of Pt nanostructures\non the\nNi foam monolith. Subsequent atomic layer deposition of ultrathin\nAl₂O₃ followed by annealing under air affords\nsupported Pt catalysts with ultralow loading (0.020 ppm). In addition\nto the expected enhancement of the stability of the Pt particles on\nthe surface, the ∼2 nm Al₂O₃ overcoat\nappears to also play a crucial role in the overall structural integrity\nof the NiO_<i>x</i> nanoplates that grow on the\nNi foam surface as a result of the preparative route. The resulting\nmaterial is physically robust toward repeated handling and showcases\nretention of catalytic activity over 10 standard catalyst recycling\ntrials, standing in marked contrast to the uncoated samples. Catalyst\nactivity was tested via the hydrogenation of various functionalized\nstyrenes at low temperatures and low hydrogen pressure in ethanol\nas a solvent, with a TOF as high as 9.5 × 10⁶ h^–1 for unfunctionalized styrene. Notably, the catalysts\nshow excellent tolerance toward F, Cl, and Br substituents and no\nhydrogenation of the aromatic ring.