Photocatalytic Oxygen Evolution from Cobalt-Modified Nanocrystalline BiFeO3 Films Grown via Low-Pressure Chemical Vapor Deposition from β-Diketonate Precursors

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• 作者：Savio J. A. Moniz ; David Pugh ; Christopher S. Blackman ; Junwang Tang ; Claire J. Carmalt
• 刊名：Crystal Growth & Design
• 出版年：2016
• 出版时间：July 6, 2016
• 年：2016
• 卷：16
• 期：7
• 页码：3818-3825
• 全文大小：488K
• 年卷期：0
• ISSN：1528-7505

文摘

BiFeO₃ is an interesting multifunctional narrow band gap semiconductor that exhibits simultaneous multiferroic, photovoltaic, and photocatalytic behavior. Hence there is much interest in the growth of thin films of BiFeO₃ via chemical vapor deposition (CVD); however, the number of suitable bismuth precursors is severely limited. A series of homoleptic bismuth(III) β-diketonate complexes were synthesized via simple room temperature ligand-exchange reactions from [Bi(N(SiMe₃)₂)₃] and free diketonate ligands, which yielded the crystal structure of [Bi(acac)₃] as a 1-D polymer. We attempted to use these complexes for low pressure CVD (LPCVD) growth of BiFeO₃ films with [Fe(acac)₃]; however, all bismuth complexes exhibited poor volatilities and decomposition characteristics, and as a result film growth was unsuccessful. Subsequently, the volatile alkoxide [Bi(O^tBu)₃], with [Fe(acac)₃], was used to grow dense BiFeO₃ films via low pressure CVD. The BiFeO₃ films possessed multiferroic properties at room temperature and exhibited activity for visible light-driven water oxidation in the presence of a Ag⁺ electron scavenger, which improved significantly when modified with a cobalt surface cocatalyst. The increase in activity, probed by time-resolved photoluminescence spectroscopy, was attributed to improved charge carrier separation arising from the in-built internal electric field of BiFeO₃ in addition to the presence of an efficient cobalt oxygen evolution catalyst.