K₄Nb₆O₁₇-derived photocatalysts for hydrogen evolution from water: Nanoscrolls versus nanosheets

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• 作者：Michael C. Sarahan ; Elizabeth C. Carroll ; Mark Allen ; Delmar S. Larsen ; Nigel D. Browning ; Frank E. Osterloh
• 关键词：Nanosheets ; Nanoscrolls ; Exfoliation ; Photocatalysis ; Water splitting ; Hydrogen
• 刊名：Journal of Solid State Chemistry
• 出版年：2008
• 出版时间：July 2008
• 年：2008
• 卷：181
• 期：7
• 页码：1678-1683
• 全文大小：943 K

文摘

The layered hexaniobate K₄Nb₆O₁₇ is known as a photocatalyst for methanol dehydrogenation and hydrogen evolution from water under ultraviolet (UV) light. Here we show that the activity is retained in propylammonium- (PA) or tetrabutylammonium- (TBA) stabilized H₂K₂Nb₆O₁₇ nanosheets and TBA-stabilized H₄Nb₆O₁₇ nanoscrolls that can be obtained by exfoliation of K₄Nb₆O₁₇ followed by cation exchange. The catalytic activity of the exfoliated systems is comparable to K₄Nb₆O₁₇, with scrolls being most active in water, and PA sheets giving enhanced H₂ rates due to sacrificial electron donor action of PA. Femtosecond absorption spectra for TBA scrolls and PA sheets exhibit broad features between 450 and 700 nm due to trapped holes and electrons. Electron–hole recombination follows approximately second-order kinetics, with rates of decay similar for sheets and scrolls. In addition, catalysts were characterized with UV/vis and fluorescence spectroscopy and transmission electron microscopy.