What Limits the Performance of Ta3N5 for Solar Water Splitting?
What Limits the Performance of Ta3N5 for Solar Water Splitting?
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DOI：
10.1016/j.chempr.2016.09.006
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发表时间：
2016-10-13
期刊：
影响因子：
23.5
通讯作者：
Wang, Dunwei
中科院分区：
文献类型：
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作者：
He, Yumin;Thorne, James E.;Wang, Dunwei
氮化钽（Ta 3 N5）是一种很有前途的太阳能水分解光电极。虽然在Ta 3 N5上已经报道了接近理论极限的光电流，但其低的光电压和差的稳定性仍然是关键的挑战。在这项研究中，我们使用Ta 3 N5纳米管作为平台来了解这些问题的起源。通过光电化学和高分辨率电子显微镜测量的组合，我们发现，Ta 3 N5的自限制表面氧化导致了薄的非晶层（约。3 nm），这被证明是有效的钉扎表面费米能级，从而完全抑制了Ta 3 N5的光活性。X-射线芯级光谱表征不仅证实了氧化引起的表面组成变化，而且还揭示了费米能级向正方向移动高达0.5 V。这里报道的光活性降解机制很可能在其他太阳能-化学能转换系统中找到应用。
Tantalum nitride (Ta3N5) is a promising photoelectrode for solar water splitting. Although near-theoretical-limit photocurrent has already been reported on Ta3N5, its low photovoltage and poor stability remain critical challenges. In this study, we used Ta3N5 nanotubes as a platform to understand the origins of these issues. Through a combination of photoelectrochemical and high-resolution electron microscope measurements, we found that the self-limiting surface oxidation of Ta3N5 resulted in a thin amorphous layer (ca. 3 nm), which proved to be effective in pinning the surface Fermi levels and thus fully suppressed the photoactivity of Ta3N5. X-ray core-level spectroscopy characterization not only confirmed the surface composition change resulting from the oxidation but also revealed a Fermi-level shift toward the positive direction by up to 0.5 V. The photoactivity degradation mechanism reported here is likely to find applications in other solar-to-chemical energy-conversion systems.