Song Shaojia, Wu Kun, Wu Huadong, Guo Jia, Zhang Linfeng
Key Laboratory for Green Chemical Process of Ministry of Education, Wuhan Institute of Technology Wuhan 430205 PR China
Key Laboratory of Novel Reactor and Green Chemical Technology of Hubei Province, Wuhan Institute of Technology Wuhan 430205 PR China.
RSC Adv. 2019 Mar 6;9(13):7362-7374. doi: 10.1039/c9ra00168a. eCollection 2019 Mar 1.
The presence of organic dyes in wastewater has posed a huge threat to aquatic life and human health. In this study, nitrogen and phosphorus co-doped carbon quantum dot (CQD)-decorated multi-shelled ZnO microsphere photocatalysts (NPCQD/ZnO) were obtained a simple absorption process; ZnO was prepared by calcining carbon microspheres as the sacrificial template. The as-prepared NPCQD/ZnO showed an obvious multi-shelled structure with the nitrogen and phosphorus co-doped CQDs homogeneously attached onto the inner and outer shells of ZnO. According to the UV-Vis DRS results, all the co-doped, single-doped and undoped carbon quantum dots could enhance the efficiency of absorption of visible light and reduce the optical band gap. Furthermore, the PL characterization results showed that the NPCQD/ZnO composites had lowest fluorescence intensity because the decoration of ZnO with NPCQDs could effectively reduce the recombination rate of photogenerated electron-hole pairs in the ZnO semiconductor photocatalyst. Importantly, 2 g-NPCQD/ZnO composites exhibited higher photodegradation performance towards methylene blue (MB) than pure ZnO and even the newly reported series of ZnO catalysts under the same conditions. Moreover, the degradation obeyed the pseudo-first-order and Langmuir-Hinshelwood kinetics models with a reaction constant of 0.0725 min, which was 1.05 times that of pure ZnO (0.0353 min). The NPCQD/ZnO composites not only showed good photocatalytic performance, but also had excellent stability since the photocatalytic activity did not significantly decrease after five cycling tests. In addition, compared with single-doped and undoped carbon quantum dots, N and P co-doped carbon quantum dots have more significant efficiency for the modification of semiconductor photocatalysts. The present study shows that the CQD-decorated multi-shelled ZnO can be regarded as an excellent photocatalyst candidate in the field of water treatment. Moreover, this new concept is helpful in the controllable construction of other multi-shelled metal oxides decorated with co-doped carbon quantum dots with enhanced photocatalytic properties.
废水中有机染料的存在对水生生物和人类健康构成了巨大威胁。在本研究中，通过简单的吸附过程获得了氮磷共掺杂碳量子点（CQD）修饰的多壳层ZnO微球光催化剂（NPCQD/ZnO）；以碳微球为牺牲模板通过煅烧制备ZnO。所制备的NPCQD/ZnO呈现出明显的多壳层结构，氮磷共掺杂的CQDs均匀地附着在ZnO的内壳和外壳上。根据紫外-可见漫反射光谱（UV-Vis DRS）结果，所有共掺杂、单掺杂和未掺杂的碳量子点都能提高可见光吸收效率并减小光学带隙。此外，光致发光（PL）表征结果表明，NPCQD/ZnO复合材料的荧光强度最低，因为用NPCQDs修饰ZnO可以有效降低ZnO半导体光催化剂中光生电子-空穴对的复合率。重要的是，在相同条件下，2 g-NPCQD/ZnO复合材料对亚甲基蓝（MB）的光降解性能高于纯ZnO，甚至高于新报道的一系列ZnO催化剂。而且，降解过程符合准一级和朗缪尔-欣谢尔伍德动力学模型，反应常数为0.0725 min，是纯ZnO（0.0353 min）的1.05倍。NPCQD/ZnO复合材料不仅表现出良好的光催化性能，还具有优异的稳定性，因为经过五次循环测试后光催化活性没有显著降低。此外，与单掺杂和未掺杂的碳量子点相比，氮磷共掺杂的碳量子点对半导体光催化剂的改性效率更高。本研究表明，CQD修饰的多壳层ZnO可被视为水处理领域中一种优异的光催化剂候选材料。此外，这一新概念有助于可控构建其他具有增强光催化性能的共掺杂碳量子点修饰的多壳层金属氧化物。
