High-performance n-Si/α-Fe2O3 core/shell nanowire array photoanode towards photoelectrochemical water splitting
High-performance n-Si/α-Fe2O3 core/shell nanowire array photoanode towards photoelectrochemical water splitting
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DOI：
10.1039/c3nr05429b
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发表时间：
2014-01-01
期刊：
影响因子：
6.7
通讯作者：
Shi, Wensheng
中科院分区：
文献类型：
--
作者：
Qi, Xiaopeng;She, Guangwei;Shi, Wensheng
许多窄带隙半导体不能满足水分解的能量要求，因此需要大的外部电压的帮助来完成水分解反应。通过化学腐蚀法制备的n-Si纳米线上Fe（NO3）3的热分解，制备了高性能的n-Si/α-Fe 2 O3核/壳纳米线阵列光阳极，在模拟AM 1.5G照射下，该光阳极的光电流起始电位为0.5V vs. RHE，在1.23V vs. RHE下的光电流为5.28mA cm（-2）。光电流起始电势代表基于n-Si或α-Fe 2 O3的光阳极中的最低电势之一，并且光电流比在α-Fe 2 O3上观察到的大多数光电流大得多。详细研究了α-Fe 2 O3壳层厚度对该光阳极光电化学性能的影响。结果发现，光电流和起始电位强烈依赖于α-Fe 2 O3壳层厚度。Mott-Schottky测量和能带计算表明，n-Si的能带边缘位置与α-Fe_2 O_3的厚度密切相关。具有优化厚度的α-Fe 2 O 3壳层有利于将n-Si的能带定位在相对高的能级，并最大化α-Fe 2 O 3中的电荷收集，从而实现低光电流起始电势和高光电流。
Many narrow band-gap semiconductors cannot fulfil the energetic requirements for water splitting, thus the assistance of large external voltages to complete the water decomposition reaction is required. Through thermal decomposition of Fe(NO3)(3) on n-Si nanowires prepared by the chemical etching method, we fabricated a high-performance n-Si/alpha-Fe2O3 core/shell nanowire array photoanode that exhibited a low photocurrent onset potential of 0.5 V vs. RHE and a high photocurrent of 5.28 mA cm(-2) at 1.23 V vs. RHE, under simulated AM 1.5G irradiation. The photocurrent onset potential represents one of the lowest in n-Si or alpha-Fe2O3 based photoanodes, and the photocurrent is much larger than most of those observed on alpha-Fe2O3. The impact of the thickness of the alpha-Fe2O3 shell on the photoelectrochemical performance of the present photoanode was investigated in detail. It was found that both the photocurrent and the onset potential depend strongly on the alpha-Fe2O3 shell thickness. Mott-Schottky measurements and energy band calculation reveal that the energy band edge positions of the n-Si are closely related to the thickness of the alpha-Fe2O3. The alpha-Fe2O3 shell with an optimized thickness is favorable for locating the energy bands of the n-Si at relatively high levels and maximizing the charge collection in alpha-Fe2O3, and thus achieving the low photocurrent onset potential and high photocurrent.