ZnWO4/WO3 Composite for Improving Photoelectrochemical Water Oxidation

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• 作者：Kevin C. Leonard ; Ki Min Nam ; Heung Chan Lee ; Soon Hyung Kang ; Hyun S. Park ; Allen J. Bard
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：August 8, 2013
• 年：2013
• 卷：117
• 期：31
• 页码：15901-15910
• 全文大小：618K
• 年卷期：v.117,no.31(August 8, 2013)
• ISSN：1932-7455

文摘

A rapid screening technique utilizing a modified scanning electrochemical microscope has been used to screen photocatalysts and determine how metal doping affects its photoelectrochemical (PEC) properties. We now extend this rapid screening to the examination of photocatalyst (semiconductor/semiconductor) composites: by examining a variety of ZnWO₄/WO₃ composites, a 9% Zn/W ratio produced an increased photocurrent over pristine WO₃ with both UV and visible irradiation on a spot array electrode. With bulk films of various thickness formed by a drop-casting technique of mixed precursors and a one-step annealing process, the 9 atomic % ZnWO₄/WO₃ resulted in a 2.5-fold increase in the photocurrent compared to pristine WO₃ for both sulfite and water oxidation at +0.7 V vs Ag/AgCl. Thickness optimization of the bulk-film electrodes showed that the optimum oxide thickness was 1 渭m for both the WO₃ and ZnWO₄/WO₃ electrodes. X-ray diffraction showed the composite nature of the WO₃ and ZnWO₄ mixtures. The UV/vis absorbance and PEC action spectra demonstrated that WO₃ has a smaller band gap than ZnWO₄, while Mott鈥揝chottky analysis determined that ZnWO₄ has a more negative flat-band potential than WO₃. A composite band diagram was created, showing the possibility of greater electron/hole separation in the composite material. Investigations on layered structures showed that the higher photocurrent was only observed when the ZnWO₄/WO₃ composite was formed in a single annealing step.