Combined Charge Carrier Transport and Photoelectrochemical Characterization of BiVO4 Single Crystals: Intrinsic Behavior of a Complex Metal Oxide

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• 作者：Alexander J. E. Rettie ; Heung Chan Lee ; Luke G. Marshall ; Jung-Fu Lin ; Cigdem Capan ; Jeffrey Lindemuth ; John S. McCloy ; Jianshi Zhou ; Allen J. Bard ; C. Buddie Mullins
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：July 31, 2013
• 年：2013
• 卷：135
• 期：30
• 页码：11389-11396
• 全文大小：444K
• 年卷期：v.135,no.30(July 31, 2013)
• ISSN：1520-5126

文摘

Bismuth vanadate (BiVO₄) is a promising photoelectrode material for the oxidation of water, but fundamental studies of this material are lacking. To address this, we report electrical and photoelectrochemical (PEC) properties of BiVO₄ single crystals (undoped, 0.6% Mo, and 0.3% W:BiVO₄) grown using the floating zone technique. We demonstrate that a small polaron hopping conduction mechanism dominates from 250 to 400 K, undergoing a transition to a variable-range hopping mechanism at lower temperatures. An anisotropy ratio of 3 was observed along the c axis, attributed to the layered structure of BiVO₄. Measurements of the ac field Hall effect yielded an electron mobility of 0.2 cm² V^鈥? s^鈥? for Mo and W:BiVO₄ at 300 K. By application of the G盲rtner model, a hole diffusion length of 100 nm was estimated. As a result of low carrier mobility, attempts to measure the dc Hall effect were unsuccessful. Analyses of the Raman spectra showed that Mo and W substituted for V and acted as donor impurities. Mott鈥揝chottky analysis of electrodes with the (001) face exposed yielded a flat band potential of 0.03鈥?.08 V versus the reversible H₂ electrode, while incident photon conversion efficiency tests showed that the dark coloration of the doped single crystals did not result in additional photocurrent. Comparison of these intrinsic properties to those of other metal oxides for PEC applications gives valuable insight into this material as a photoanode.