Constructing CdS/Cd/doped TiO2 Z-scheme type visible light photocatalyst for H2 production
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Constructing Z-scheme type photocatalyst is an efficient way to improve the charge separation efficiency and enhance the photocatalytic activity. In this report, the Cd:TiO2 nanoparticles are prepared via the sol-gel route and employed as a starting material. When it was reduced by NaBH4 at 300°C, the surface oxygen vacancies were produced and Cd2+ was reduced into metal Cd0 nanoparticle (denoted as R-Cd:TiO2). Subsequently, the formed R-Cd:TiO2 was treated with thioureain the hydrothermal reaction. Through the decomposition of thiourea, the oxygen vacancies were refilled by S2− from thiourea to form S:TiO2/TiO2 (d-TiO2) and Cd was partially converted into CdS to form CdS/Cd/d-TiO2 composite. The formed CdS/Cd/d-TiO2 composite exhibits improved photocatalytic activity. Under visible light irradiation (λ>400 nm), the H2 production rate of CdS/Cd/d-TiO2 reaches 119 μmol h−1 with 50 mg of photocatalyst without any cocatalyst, which is about 200 and 60 times higher than that of S:TiO2/TiO2 (0.57 μmol h−1), CdS (2.03 μmol h−1) and heterojunction CdS/d-TiO2 (2.17 μmol h-1) materials, respectively. The results illustrate that metal Cd greatly promotes the charge separation efficiency due to the formation of Z-scheme type composite. In addition, the photocatalytic activity in the visible light region was dramatically enhanced due to the contribution of both CdS and d-TiO2. The method could be easily extended to other wide bandgap semiconductors for constructing visible light responsive Z-scheme type photocatalysts.
KeywordsZ-scheme CdS doped TiO2 Cd H2 production
构建Z型光催化体系是提高光生电荷分离效率和光催化活性的一种有效途径. 本文通过溶胶凝胶方法制备了Cd掺杂的TiO2纳米颗粒, 并通过一步NaBH4固相热还原的方式在材料表面可控地引入氧空位(VO), 同时掺入的Cd2+可被还原为金属Cd0纳米粒子(即R-Cd:Ti〇2). 进一步将获得的R-Cd:TiO2材料与硫脲热水反应, 材料表面VO的可被S2−替代同时部分金属Cd0硫化, 从而获得CdS/Cd/d-TiO2 Z型光催化复合材料. 研究结果表明该Z型光催化复合材料具有优异的模拟太阳光及可见光区光催化活性和稳定性. 通过实验分析证明掏建这种全固态金属-无机半导体Z型光催化复合材料, 金属介质层显著促进了光生电荷的分离与迁移; 此外, 由于CdS和d-TiO2在可见光区的光吸收作用, 该CdS/Cd/d-TiO2 Z型光催化复合材料在可见光区的光催化活性获得了显著增强.
Sun Z thanks the financial support from the National Natural Science Foundation of China (21671011), Beijing High Talent Program, Beijing Natural Science Foundation (KZ201710005002). The authors thank China Postdoctoral Science Foundation, Beijing Postdoctoral Research Foundation, and Dongguan Program for International S&T Cooperation. Zhao Z thanks the support from China Scholarship Council. This research was also supported by the National Science Foundation (DMR-1506661, Feng P).