Double element co-doped carbon quantum dots (CQDs) have unique electron properties and broad prospects in photocatalysis. In this paper, the phosphorus and nitrogen co-doped CQDs (PNCQDs) were loaded on TiO2 nanosheets by in-situ synthesis method. Physical structure and chemical composition of samples were analyzed by XRD, FT-IR, XPS, SEM and TEM. UV–Vis spectra show the donor–acceptor coupling between PNCQDs and TiO2 and enhanced strong UV light absorption. Photoluminescence spectra indicate that PNCQDs effectively promote charge separation, which is different from nitrogen doped CQDs. The sample 1-PNCT with the optimal phosphorus doping amount has the highest kinetic constant for photodegradation of Methylene Blue (MB), which is 3.4 times pure TiO2. A possible Z-scheme photodegradation mechanism is proposed according to the active species scavenge experiment results in which PNCQDs can not only accept but also localize photogenerated electrons to dopant sites due to the quantum wells created by P and N doping energy barriers.

中文翻译：

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磷氮共掺杂碳量子点/TiO2纳米片的光催化活性

双元素共掺杂碳量子点（CQDs）具有独特的电子特性和广阔的光催化应用前景。在本文中，磷和氮共掺杂的 CQDs (PNCQDs) 负载在 TiO2 上。2采用原位合成法制备纳米片。采用XRD、FT-IR、XPS、SEM、TEM等手段对样品的物理结构和化学成分进行分析。UV-Vis 光谱显示 PNCQD 和 TiO2 之间的供体-受体耦合2并增强了强烈的紫外线吸收。光致发光光谱表明，PNCQDs 有效地促进了电荷分离，这与氮掺杂 CQDs 不同。具有最佳磷掺杂量的样品1-PNCT对亚甲基蓝（MB）的光降解动力学常数最高，是纯TiO的3.4倍2. 根据活性物质清除实验结果提出了一种可能的 Z 型光降解机制，其中 PNCQD 不仅可以接受而且可以将光生电子定位到掺杂位点，这是由于 P 和 N 掺杂能垒产生的量子阱。