Metal-free dual-phase full organic carbon nanotubes/g-C3N4 heteroarchitectures for photocatalytic hydrogen production
Metal-free dual-phase full organic carbon nanotubes/g-C3N4 heteroarchitectures for photocatalytic hydrogen production
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DOI：
10.1016/j.nanoen.2018.05.070
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发表时间：
2018-08-01
期刊：
影响因子：
17.6
通讯作者：
Fornasiero, Paolo
中科院分区：
文献类型：
--
作者：
Christoforidis, Konstantinos C.;Syrgiannis, Zois;Fornasiero, Paolo
利用太阳能从水中产生氢气已经成为一种很有前途的可持续能源生产方法。近年来，基于七嗪基团的聚合物--石墨化碳氮化物(g-C3N4，CN)被广泛应用于光催化析氢。CN的电荷分离效率较低被认为是主要缺点。在这里，我们研究了CN与不同类型的碳纳米管的偶联对碳纳米管的电荷转移性质和光催化放氢的影响。利用不同壁数的碳纳米管(单碳纳米管、双碳纳米管和多壁碳纳米管)制备了全有机碳纳米管复合光催化剂。光活性受碳纳米管含量的影响很大，但更重要的是受碳纳米管的性质影响。单壁碳纳米管功能化的碳纳米管复合材料活性最高，在太阳光和纯可见光照射下的氢气释放比相应的多壁碳纳米管和多壁碳纳米管高2-5倍。光活性主要受电子性质的改善所控制，电子性质与光生电荷的丰度和稳定性有关，电子顺磁共振光谱证明这一点。瞬时吸收光谱证实了反应电子从碳纳米管向碳纳米管的转移。碳纳米管起到了电子受体的作用，改善了电荷分离。数据表明，电荷转移与碳纳米管的壁数成反比，光活性直接由所用碳纳米管的尺寸控制。在CNTs/CN纳米复合材料中，当使用SWCNTs时，光生电子可以更有效地从CN转移，为H-2的生产提供更多的可用电子。
Hydrogen generation from water using solar energy has grown into a promising approach for sustainable energy production. Over the last years, graphitic carbon nitrides (g-C3N4, CN), polymers based on the heptazine-group, have been widely applied as photocatalysts for H-2 evolution. The poor charge separation efficiency of CN is considered the major drawback. Here, we investigated the effect of coupling CN with different types of carbon nanotubes on the charge transfer properties and the photocatalytic H-2 evolution. We used carbon nanotubes (CNTs) of different wall number (single (SWCNTs), double (DWCNTs) and multi-walled (MWCNTs) CNTs) for the development of full-organic CN based composite photocatalysts. Photoactivity was drastically affected by the content but more importantly by the nature of the CNTs. The SWCNTs functionalized CN composites were the most active presenting approximately 2-5 times higher H-2 evolution than the corresponding DWCNTs and MWCNTs functionalized CN under both solar and pure visible light irradiation. Photoactivity was primarily controlled by the improved electronic properties linked with the abundance and stability of photogenerated charges as evidenced by electron paramagnetic resonance spectroscopy. Transient absorption spectroscopy verified the transfer of reactive electrons from CN to CNTs. CNTs functioned as electron acceptors improving charge separation. The data suggest that charge transfer is inversely proportional to the wall number of the CNTs and that photoactivity is directly controlled by the size at the nanoscale of the CNTs used. In the CNTs/CN nanocomposites, photogenerated electrons are transferred more efficiently from CN when SWCNTs are used, providing more available electrons for H-2 production.