Cost-Effective Hierarchical Catalysts for Promoting Hydrogen Release from Complex Hydrides

• Published in: ChemSusChem Vol. 8; no. 16; pp. 2713 - 2718
• Main Authors: Yang, Cheng-Hsien, Hsu, Chih-Ping, Lee, Sheng-Long, Wang, Kuan-Wen, Chang, Jeng-Kuei
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 24.08.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Aluminum Compounds - chemistry; Catalysis; Cost-Benefit Analysis; Graphite - chemistry; hierarchical catalysts; hydrides; Hydrogen - chemistry; Iron - chemistry; Lithium Compounds - chemistry; Metal Nanoparticles - chemistry; Microscopy, Electron, Transmission; nanotubes; Nanotubes, Carbon - chemistry; Nanotubes, Carbon - ultrastructure; Nickel - chemistry; supercritical fluid; X-Ray Diffraction; hydrides; nanotubes; hierarchical catalysts; x-ray diffraction; supercritical fluid
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201500413

Fe nanoparticles (∼10 nm), used to grow carbon nanotubes (CNTs), have an outstanding ability to catalyze the dehydrogenation of LiAlH4. The CNTs help connect Fe and LiAlH4 and create microchannels among the composite, thus promoting the release of hydrogen. Inspired by these results, a supercritical‐CO2‐fluid‐assisted deposition technique is employed to decorate the Fe/CNTs with highly dispersed nanosized Ni (∼2 nm in diameter) for better performance. With the incorporation of 10 wt % of this hierarchical catalyst (Ni/Fe/CNTs), the initial dehydrogenation temperature of LiAlH4 is decreased from ∼135 to ∼40 °C. At 100 °C, this catalyzed LiAlH4 takes only ∼0.1 h to release 4.5 wt % hydrogen, which is more than 100 times faster than the time needed with pristine LiAlH4. The dehydrogenation mechanism of the complex hydride is examined using in situ synchrotron X‐ray diffraction. No pressure, LiAlH4, just release H2: Highly effective Ni/Fe/carbon nanotubes (CNTs) hierarchical catalysts with low cost are constructed using a supercritical CO2‐assisted deposition technique. Using 10 wt % of this nanocatalyst, the initial dehydrogenation temperature of LiAlH4 is decreased from ∼135 °C to ∼40 °C. At 100 °C, the catalyzed LiAlH4 takes only ∼0.1 h to release 4.5 wt % hydrogen, which is more than 100 times faster than that required for pristine LiAlH4.