Kong Dan, Han Xiaoyu, Xie Jijia, Ruan Qiushi, Windle Christopher D, Gadipelli Srinivas, Shen Kai, Bai Zhiming, Guo Zhengxiao, Tang Junwang
Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, United Kingdom.
Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, United Kingdom.
ACS Catal. 2019 Sep 6;9(9):7697-7707. doi: 10.1021/acscatal.9b02195. Epub 2019 Jul 16.
Covalent triazine-based frameworks (CTFs), a group of semiconductive polymers, have been identified for photocatalytic water splitting recently. Their adjustable band gap and facile processing offer great potential for discovery and development. Here, we present a series of CTF-0 materials fabricated by two different approaches, a microwave-assisted synthesis and an ionothermal method, for water splitting driven by visible-light irradiation. The material (CTF-0-M) synthesized by microwave technology shows a high photocatalytic activity for hydrogen evolution (up to 7010 μmol h g), which is 7 times higher than another (CTF-0-I) prepared by conventional ionothermal trimerization under identical photocatalytic conditions. This leads to a high turnover number (TON) of 726 with respect to the platinum cocatalyst after seven cycles under visible light. We attribute this to the narrowed band gap, the most negative conduction band, and the rapid photogenerated charge separation and transfer. On the other hand, the material prepared by the ionothermal method is the most efficient one for oxygen evolution. CTF-0-I initially produces ca. 6 times greater volumes of oxygen gas than CTF-0-M under identical experimental conditions. CTF-0-I presents an apparent quantum efficiency (AQY) of 5.2% at 420 nm for oxygen production without any cocatalyst. The activity for water oxidation exceeds that of most reported CTFs due to a large driving force for oxidation and a large number of active sites. Our findings indicate that the band positions and the interlayer stacking structures of CTF-0 were modulated by varying synthesis conditions. These modulations impact the optical and redox properties, resulting in an enhanced performance for photocatalytic hydrogen and oxygen evolution, confirmed by first-principles calculations.
共价三嗪基框架材料（CTFs）是一类半导体聚合物，最近已被确定可用于光催化水分解。它们可调节的带隙和简便的加工方法为其发现和开发提供了巨大潜力。在此，我们展示了通过两种不同方法制备的一系列CTF-0材料，即微波辅助合成法和离子热法，用于可见光照射驱动的水分解。通过微波技术合成的材料（CTF-0-M）对析氢显示出高光催化活性（高达7010 μmol h g），在相同光催化条件下比通过传统离子热三聚反应制备的另一种材料（CTF-0-I）高7倍。在可见光下经过七个循环后，相对于铂助催化剂，这导致了高达726的高周转数（TON）。我们将此归因于带隙变窄、最负的导带以及快速的光生电荷分离和转移。另一方面，通过离子热法制备的材料对于析氧是最有效的。在相同实验条件下，CTF-0-I最初产生的氧气量比CTF-0-M大约多6倍。CTF-0-I在420 nm处无任何助催化剂时析氧的表观量子效率（AQY）为5.2%。由于氧化驱动力大且活性位点数量多，水氧化活性超过了大多数已报道的CTF材料。我们的研究结果表明，通过改变合成条件可调节CTF-0的能带位置和层间堆积结构。这些调节影响了光学和氧化还原性质，导致光催化析氢和析氧性能增强，这一点得到了第一性原理计算的证实。
