Structured and Nanoparticle Assembled Co-B Thin Films Prepared by Pulsed Laser Deposition: A Very Efficient Catalyst for Hydrogen Production

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• 作者：Nainesh Patel ; Rohan Fernandes ; Graziano Guella ; Ashwin Kale ; Antonio Miotello ; Barbara Patton ; Cristian Zanchetta
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：May 1, 2008
• 年：2008
• 卷：112
• 期：17
• 页码：6968 - 6976
• 全文大小：596K
• 年卷期：v.112,no.17(May 1, 2008)
• ISSN：1932-7455

文摘

Amorphous Co-B-based catalyst powder, produced by chemical reduction of cobalt salts, was used as thetarget material for Co-B thin film catalyst preparation through pulsed laser deposition (PLD). A comparativekinetic analysis of the sodium borohydride (NaBH₄) hydrolysis by using Co-B catalyst added to the hydridesolution as powder or as thin film was carried out. Both forms of catalyst (powder and film) were heat-treated at 623 K for 2 h under various atmospheric conditions (in vacuum or by using Ar, H₂, and O₂ gases)in order to study their effects on H₂ generation rate. Surface morphology of the catalyst was studied usingscanning electron microscopy (SEM) and atomic force microscopy (AFM), while compositional and bondformation analysis were carried out using X-photoelectron (XPS) and Fourier transform infrared spectroscopy(FT-IR), respectively. Structural characterization of catalysts was performed using the X-ray diffraction (XRD)technique. It was observed that nanoparticles produced during laser ablation process act as active centers inthe catalyst films, producing significantly higher rate (about 6 times) of H₂ generation than the correspondingCo-B powder. No significant changes were observed for Co-B powder treated in an inert atmosphere (vacuumand Ar) while it caused structural changes in Co-B films. Co₂B phase formation in films makes them moreefficient catalysts with 28% increase in rate of H₂ generation as compared to untreated film. Heat treatmentin an oxygen atmosphere causes complete inactivation of powder catalyst, while film still showed excellentcatalytic activity with just a longer induction time. The AFM and SEM analysis of the heat-treated films didnot show drastic change in surface morphology, indicating that changes in catalytic activity of the films werepossibly connected to structural modification and formation of boron oxide on the catalyst surface. We reportthat by using suitable thin film Co-B catalyst the maximum H₂ generation rate of about 5000 mL/(min g ofcatalyst) can be achieved. This can generate about 0.9 kW (0.7 V) for proton exchange membrane fuel cells(PEMFC), a critical requirement for portable devices.