Department of Chemical Engineering and Division of Advanced Nuclear Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang, 790-784, South Korea.
ChemSusChem. 2012 Oct;5(10):1926-34. doi: 10.1002/cssc.201200254. Epub 2012 Aug 27.
The visible-light-induced water oxidation ability of metal-ion-doped BiVO(4) was investigated and of 12 metal ion dopants tested, only W and Mo dramatically enhanced the water photo-oxidation activity of bare BiVO(4); Mo had the highest improvement by a factor of about six. Thus, BiVO(4) and W- or Mo-doped (2 atom %) BiVO(4) photoanodes about 1 μm thick were fabricated onto transparent conducting substrate by a metal-organic decomposition/spin-coating method. Under simulated one sun (air mass 1.5G, 100 mW cm(-2)) and at 1.23 V versus a reversible hydrogen electrode, the highest photocurrent density (J(PH)) of about 2.38 mA cm(-2) was achieved for Mo doping followed by W doping (J(PH) ≈ 1.98 mA cm(-2)), whereas undoped BiVO(4) gave a J(PH) value of about 0.42 mA cm(-2). The photoelectrochemical water oxidation activity of W- and Mo-doped BiVO(4) photoanodes corresponded to the incident photon to current conversion efficiency of about 35 and 40 % respectively. Electrochemical impedance spectroscopy and Mott-Schottky analysis indicated a positive flat band shift of about 30 mV, a carrier concentration 1.6-2 times higher, and a charge-transfer resistance reduced by 3-4-fold for W- or Mo-doped BiVO(4) relative to undoped BiVO(4). Electronic structure calculations revealed that both W and Mo were shallow donors and Mo doping generated superior conductivity to W doping. The photo-oxidation activity of water on BiVO(4) photoanodes (undoped<W doped<Mo doped) was in accordance with the results from electrochemical impedance spectroscopy, Mott-Schottky analysis, and theoretical electronic structural calculations. Thus, Mo or W doping enhanced the photocatalytic and photoelectrochemical water oxidation activity of monoclinic BiVO(4) by drastically reducing its charge-transfer resistance and thereby minimizing photoexcited electron-hole pair recombination.
研究了金属离子掺杂的 BiVO(4) 的可见光诱导水氧化能力，在测试的 12 种金属离子掺杂剂中，只有 W 和 Mo 显著提高了裸 BiVO(4) 的水光氧化活性；Mo 的提高幅度最大，约为 6 倍。因此，通过金属有机分解/旋涂法在透明导电基底上制备了约 1μm 厚的 BiVO(4) 和 W 或 Mo 掺杂（2 原子%）的 BiVO(4) 光阳极。在模拟的一个太阳（空气质量 1.5G，100mWcm(-2)) 和相对于可逆氢电极 1.23V 下，Mo 掺杂的最高光电流密度（J(PH)）约为 2.38mAcm(-2)，其次是 W 掺杂（J(PH)≈1.98mAcm(-2)），而未掺杂的 BiVO(4) 的 J(PH)值约为 0.42mAcm(-2)。W 和 Mo 掺杂的 BiVO(4) 光阳极的光电化学水氧化活性对应于约 35%和 40%的入射光子到电流转换效率。电化学阻抗谱和 Mott-Schottky 分析表明，相对于未掺杂的 BiVO(4)，W 或 Mo 掺杂的 BiVO(4)的平带位移约为 30mV，载流子浓度提高了 1.6-2 倍，电荷转移电阻降低了 3-4 倍。电子结构计算表明，W 和 Mo 都是浅施主，Mo 掺杂比 W 掺杂产生更好的导电性。BiVO(4)光阳极上水的光氧化活性（未掺杂<W 掺杂<Mo 掺杂）与电化学阻抗谱、Mott-Schottky 分析和理论电子结构计算的结果一致。因此，Mo 或 W 掺杂通过极大地降低电荷转移电阻从而最小化光激发电子-空穴对复合，增强了单斜 BiVO(4)的光催化和光电化学水氧化活性。
