A Benchmark Quantum Yield for Water Photoreduction on Amorphous Carbon Nitride
A Benchmark Quantum Yield for Water Photoreduction on Amorphous Carbon Nitride
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DOI：
10.1002/adfm.201702384
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发表时间：
2017-10-19
影响因子：
19
通讯作者：
Qiao, Shi-Zhang
中科院分区：
文献类型：
--
作者：
Rahman, Mohammad Z.;Tapping, Patrick C.;Qiao, Shi-Zhang
无定形氮化碳（a- cn）是一种开发较少但很有前途的制氢光催化剂。尽管可见光吸收（EVLA）得到了扩展，但水光还原的低量子效率（QE）是一个长期存在的问题。这意味着EVLA不能成比例地转化为大量光生电子的收集。最大限度地减少光吸收和电荷收集之间的不匹配仍然是一个科学挑战。这里报告了一种类似海绵的a- cn分层结构，解决了这种明显的不匹配。结合实验和时域有限差分模拟，证明了a-CN海绵能够诱导全内光反射散射，从而促进局域电荷载流子的产生。扩散反射率和瞬态荧光衰减研究结果与模拟结果一致，海绵状a- cn的光捕获增强了40%，电子寿命比块状材料长约23倍。该结果是在10vol %三乙醇胺和1wt % Pt助催化剂的反应体系中，以6.1%的QE在420 nm处产氢203.5 μ mol h（-1）的新基准。增强的水光还原是由于a- cn海绵内部存在可调节的光物理和电化学属性。
Amorphous carbon nitride (a-CN) is a less-explored but promising photocatalyst for hydrogen production. Despite an extended visible light absorption (EVLA) its low quantum efficiency (QE) for water photoreduction is a long standing problem. This implies that EVLA is not proportionally translated into collection of large amounts of photogenerated electrons. Minimizing the mismatch between light-absorption and charge-collection remains a scientific challenge. Here a sponge-like hierarchical structure of a-CN that addresses this apparent mismatch is reported. Combined experimental and finite difference time domain simulations demonstrate the ability of the a-CN sponge to induce scattering for total internal light reflection that promotes localized charge carrier generation. Diffused reflectance and transient fluorescence decay studies show good agreement with simulations with a 40% enhanced light-trapping and an approximate to 23 times longer electron lifetime in spongy a-CN compared with that of the bulk material. The result is a new high benchmark for hydrogen production of 203.5 mu mol h(-1) with a QE of 6.1% at 420 nm in a reaction system of 10 vol% triethanolamine and 1 wt% Pt cocatalyst. The enhanced water photoreduction is a result of amenable photophysical and electrochemical attributes existing within the a-CN sponge.