Progress in defect modulation of g-C3N4 based materials and its photocatalytic property
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摘要:
半导体光催化材料已成为有效应对环境污染和能源危机关键技术的核心要素。其中，石墨相氮化碳(g-C3N4)作为一种新兴的高效催化材料展现出了巨大的应用潜力。然而，未改性的g-C3N4存在诸如可见光响应范围有限、活性位点偏少及光生载流子复合速率高等缺点，严重制约了其实际应用。为了解决上述问题，研究人员采取了多种策略，如设计和开发异质结构、实施缺陷工程和进行形貌调控等。其中，缺陷调控因能有效地调制光催化材料的电子能带结构、延缓载流子的复合和增加表面活性位点等原因备受关注。本文阐述了缺陷修饰的类型、缺陷调控策略，最后对g-C3N4基材料的开发和光催化应用进行了总结并给出了展望。
Abstract:Semiconductor photocatalytic materials have become a key factor of photocatalytic technologies to solve environmental pollution and energy crisis. Among them, graphitic phase carbon nitride (g-C3N4) has shown great potential for application as an emerging highly efficient catalytic material. However, the unmodified g-C3N4 has disadvantages such as limited visible light response range, less reactive sites and high photogenerated carrier complexation rate, which severely limit its practical applications. Thus, researchers have adopted various strategies, such as designing and developing heterogeneous structures, defect engineering and morphological modulation to solve the problems mentioned above. Among them, defect modulation has attracted much attention because it can effectively modulate the electronic band structure of photocatalytic materials, delay carrier recombination and increase the surface reactive sites. This paper describes the types of defect modulations, defect modulation strategies, and finally summarizes the development and application of g-C3N4 based photocatalytic materials and gives an outlook.
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乙烯-四氟乙烯(ETFE)薄膜凭借其良好的物理特性及力学性能，在新型建筑、能源等领域中已被广泛应用。在实际工程应用中，ETFE膜结构的撕裂破坏可归结为内部因素与外部环境因素的协同作用。膜面处膜材在制造与安装过程中，不可避免地会存在微小孔洞、细微折痕和微裂纹等初始缺陷，以及偶发的外来飞致物刺穿引起的切缝；这使膜材在预应力、极端风荷载及雨雪荷载的复合作用下，极易产生应力集中而诱发缺陷不断扩展，最终膜材撕裂损伤，严重情况下甚至会引发膜结构的整体失效，对结构安全构成重大威胁。并且当膜材在中心区域处受到集中载荷或存在制造缺陷时，极有可能会出现显著的中心撕裂行为[1, 2]。因此，除了需对ETFE薄膜的常规力学性能进行研究，也有必要对其撕裂力学行为开展深入研究。
吴明儿[3-5]、崔家春[6, 7]、胡建辉[8]、Zhang[9]、Surholt[10]和Zhao[11-13]等分别对ETFE薄膜进行了系列试验与分析，揭示了薄膜的单轴和双轴力学行为，研究了弹性模量、屈服强度、断裂强度和徐变等力学参数和规律。整体上，现有研究多集中在ETFE母材的粘-弹塑性行为及本构关系等，在撕裂性能的研究尚十分欠缺。而随着ETFE膜结构的社会需求增长，对其撕裂性能研究的欠缺势必会阻碍ETFE膜结构的进一步应用和发展。另外，国内外学者已对织物类膜材的撕裂强度及破坏规律开展了深入研究[14-20]，可为ETFE薄膜撕裂力学性能的研究提供一定参考。Chen等[14, 15]对层压织物进行了系统的单轴撕裂试验，分析了切缝长度、切缝角度、偏轴角对其撕裂行为和撕裂强度的影响；Sun等[18, 19]深入研究了单轴拉伸下切缝长度和切缝角度对PTFE涂层织物撕裂性能的影响；Zhang等[20]论证了切口样式、切缝尺寸和试样尺寸对PVC涂层织物单轴中心撕裂特性的影响。
鉴于此，本文针对典型ETFE薄膜，进行单轴中心撕裂试验，研究切缝长度、切缝角度和切口样式对ETFE薄膜的破坏形态特征及撕裂力学行为的影响。另外，数字图像相关(DIC)技术具有全场测量、非接触、高分辨率等优势[21-23]，可为撕裂力学行为分析提供准确可靠的数据支撑，将用于薄膜撕裂全过程薄膜位移场和应变场的测量与重构。所得结论可为ETFE薄膜材料的撕裂力学性能研究和ETFE膜结构的安全性评估提供有益参考。
1. 试验概况
1.1 试验材料及试件尺寸
试验采用ETFE #250/NJ/
1600 /NT薄膜，其厚度为250μm，密度为1.75 g·cm−3。材料由乙烯和四氟乙烯聚合生成，无色透明，具有优秀的耐化学腐蚀性能和自洁性能[24]。考虑到当前暂无专门的ETFE膜材撕裂性能检测标准，因此参照GB/T 1040.3-2006[25]，以ETFE薄膜单轴拉伸试验的长条形试件的尺寸，直接作为单轴中心撕裂试验的试样尺寸，以实现测试需求。试件尺寸为150 mm×25 mm，夹持端长为25 mm，有效测试区域为100 mm×25 mm。散斑区域设置为50 mm×25 mm，散斑直径为0.5 mm。其中，切缝长度为5 mm，切缝方向角以膜材机器展开方向(MD)的垂直线为基准线，逆时针旋转θ。试件示意图如图1所示。另外，为保证试件在拉伸过程中的滑移量可控，采用在试件夹持端处使用粘结剂粘附砂纸的方法，通过增大夹具与试件接触面之间的摩擦系数，提升夹持的稳定性与可靠性。![]()
图 1 含中心切缝的乙烯-四氟乙烯(ETFE)薄膜典型试件示意图Figure 1. Schematic diagram of a typical specimen of ethylene tetrafluoroethylene (ETFE) foils with a central slit1.2 试验设备
试验选用深圳三思UTM4000型电子万能试验机和尼康D3200高像素照相机。其中，试验机位移速率范围为0.001~500.000 mm·min−1；变形测量范围为10~800 mm，±1‰变形精度；拉压力传感器量程为200 N、精度为0.2 N；尼康D3200高像素照相机拥有
2400 万像素。含中心切缝的ETFE薄膜加载过程中的夹持示意图如图2所示。试验中先对试件施加5 N的预张力，再匀速(50 mm·min−1)加载至试件破坏，并记录试件在试验过程中的变形、荷载和图像数据。![]()
图 2 含中心切缝的ETFE薄膜加载过程中的夹持示意图Figure 2. Clamping schematic of ETFE foils with a central slit during loading1.3 试验工况及环境
试验工况设置为切缝长度、切缝角度和切口样式。其中，切缝长度以2.5 mm为梯度，选取为2.5、5.0、7.5、10.0、12.5和15.0 mm；切缝角度以MD方向为基准，逆时针每旋转15°为一个梯度，选取0°、15°、30°、45°、60°、75°和90°七个角度；切口样式则将典型试件的“一”形切缝更换为其它切口样式，且切口样式可分为开放性切缝(如“一、V、X和十”形等)和封闭性切口(如圆形、椭圆形和矩形切口等)[26]；不同切缝角度和切口样式的示意图如图3所示。每个工况的有效试件为3个，以保证试验的有效性。
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图 3 切缝角度和切口样式的切缝示意图(单位：mm)Figure 3. Slit diagram of slit angles and notch shapes (Unit: mm)试验温度控制在(20±2.0)℃，相对湿度控制在(65±4.0)%。
2. 试验结果及分析
2.1 撕裂过程及破坏形态
ETFE薄膜在不同工况下典型撕裂过程如图4所示，其膜面含散斑贴膜以便于观察，三种工况下的ETFE薄膜的撕裂过程均呈现出4个特征状态：
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图 4 不同工况下ETFE薄膜典型撕裂过程：(a)切缝长度、(b)切缝角度和(c)切口样式Figure 4. Typical tearing process of ETFE foils under different conditions: (a) Slit length; (b) Slit angle; (c) Notch shape(ⅰ)切缝初始状态：在外加5 N预张力时，因其外加荷载较小，切缝保持未张开状态。
(ⅱ)切缝张开状态：随着外加荷载不断增加，切缝逐渐张开，切缝张开形状近似呈现椭圆形；薄膜在切缝尖端上下邻域展现出显著的面外屈曲现象。
(ⅲ)极限撕裂状态：随着外加荷载进一步增大，切缝开口进一步扩大，面外屈曲现象也变得更加明显，薄膜的塑性变形显著增加；其切缝尖端处由于应力集中效应显著，会形成撕裂三角区，出现明显的颈缩现象，并且切缝开始沿着垂直于加载方向扩展。
(ⅳ)完全破坏状态：在薄膜到达极限撕裂状态以后，随着荷载的增大，切缝扩展速度加剧，薄膜的承载能力不断下降，薄膜最终达到完全破坏状态，丧失所有承载能力，并且不同切口样式导致薄膜呈现的破坏形态各异。
图5为ETFE薄膜在切缝张开状态下的切缝邻域εxy应变云图，该云图可直观的展现出薄膜面外屈曲的位置分布及其方向。据图可知，薄膜的面外屈曲的位置集中分布于切口上下邻域；εxy应变云图集中区呈现“X”型分布，其中，“X”型的中心点与切口的中心点重合。在构成“X”型的同一边上，面外屈曲的方向相同；而在构成“X”型的不同边上，面外屈曲的方向相反。随着切缝长度变化，薄膜面外屈曲的位置几乎保持不变。随着切缝角度变化，面外屈曲的位置仍处于切口上下邻域，随之发生相同角度的倾斜。随着切口样式变化，切口会沿着拉伸方向发生不同的张开变形，从而使薄膜面外屈曲的位置随之变化。
2.2 切缝长度影响
不同切缝长度的ETFE薄膜的撕裂抗力-位移曲线如图6(a)所示，撕裂曲线随切缝长度改变存在规律性衍变，但存在典型共同特征，不妨提取典型撕裂曲线对ETFE薄膜撕裂力学行为进行深入阐释(见图6(b))。
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图 5 不同工况下ETFE薄膜切缝邻域的εxy应变云图Figure 5. εxy strain nephogram of ETFE foils in the neighborhood of the slit under different conditions![]()
图 6 不同切缝长度的ETFE薄膜撕裂抗力-位移曲线及其典型撕裂曲线Figure 6. Tearing strength-displacement curves and typical tearing curve of ETFE foils with different slit lengths如图6(a)所示，随着切缝长度增大，撕裂抗力-位移曲线的撕裂前段的斜率不发生变化。在撕裂抗力上升阶段，曲线斜率增加的部分随切缝长度增大而逐渐消失；当切缝长度为2.5 mm、5.0 mm时，可明显观察到曲线斜率上升的趋势，而当切缝长度增大至7.5 mm后，曲线的斜率随着位移的增大而越来越小，无法观察到曲线斜率上升。在撕裂后段，当薄膜的切缝长度从2.5 mm增大到15.0 mm，薄膜有效承载截面不断减小，其极限撕裂抗力从130.74 N下降至57.94 N，下降55.68%；断裂位移由45.48 mm下降至11.05 mm，下降75.70%。
如图6(b)所示，典型撕裂曲线以4个特征点为界，可分为3个特征阶段。其中，初始点O为曲线与纵轴的交点，类屈服点A为曲线斜率首次发生变化点，峰值点B为曲线撕裂抗力最大点和破坏点C为曲线与横轴的交点；4特征点分别与典型撕裂过程的4个特征状态相对应。
(OA)撕裂前段：曲线从不为零的初始点O开始，对应着试验前施加的预张力状态；在该阶段ETFE薄膜呈现出显著的线弹性行为，薄膜的初始弹性模量较大。
(AB)撕裂抗力上升阶段：曲线到达类屈服点A后，斜率迅速减小，明显小于撕裂前段的斜率，开始出现较大的塑性变形；随着位移增大，薄膜内部结构会充分发生变化，撕裂抗力不断增加，曲线斜率明显上升；随后由于变形继续增大导致刚度下降，撕裂抗力增加的速度变缓，曲线斜率又开始下降至零。
(BC)撕裂后段：曲线到达峰值点B时，薄膜达到极限撕裂抗力，开始发生显著的撕裂扩展；随着位移增加，撕裂抗力不断下降，并且撕裂扩展的速度不断加快，撕裂抗力下降幅度逐渐变大，最终下降到破坏点C，对应着薄膜完全破坏。
2.3 切缝角度影响
不同切缝角度的ETFE薄膜撕裂抗力-位移曲线如图7所示。随着切缝角度增大，撕裂抗力-位移曲线的撕裂前段的斜率不发生变化，并且类屈服点对应的位移由1.52 mm上升至1.57 mm，撕裂前段所历经的位移仅增加1.97%，曲线几乎同时进入下一阶段。在撕裂抗力上升阶段，不同切缝角度的薄膜的曲线均会呈现出斜率增大的趋势，并且撕裂抗力上升阶段随切缝角度增加而显著变长。在撕裂后段，当切缝角度由0°增大至90°时，对应的等效切缝长度[27]由5 mm减少至0 mm，其极限撕裂抗力由107.69 N上升至134.25 N，断裂位移由24.39 mm上升至79.90 mm。
可见，随着切缝角度的增大，对应的等效切缝长度随之减小，薄膜的承载途径逐渐恢复，用来承受拉伸荷载的有效截面增大，薄膜的极限撕裂强度增强，使薄膜不易到达极限撕裂状态，使得其断裂位移也随之增大。并且当切缝长度保持为5 mm时，切缝角度由0°增大到90°，其极限撕裂抗力和断裂位移分别上升了24.66%和227.59%，断裂位移的变化率远大于极限撕裂抗力的变化率。因此，切缝角度的改变对薄膜的极限撕裂抗力影响较小，而会显著影响薄膜完全破坏时对应的断裂位移。
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图 7 不同切缝角度的ETFE薄膜撕裂抗力-位移曲线Figure 7. Tearing strength-displacement curves for ETFE foils with different slit angles图8为不同切缝角度的ETFE薄膜的切缝尖端邻域的竖向应变场云图。据图可知，当预制切缝长度为5 mm的“一”形切缝时，薄膜在切缝邻域出现明显的应变集中区(红色区域)，并且其应变集中区分布于切缝尖端邻域上，随切缝角度的增加而发生相应的偏转。这是由于薄膜在预制初始切缝后，在切缝尖端邻域，随着拉伸应力的增大，切缝张开导致薄膜沿着切缝方向发生横向收缩，并且在切缝上下邻域处发生面外屈曲，薄膜会向面外凸出，导致切缝尖端邻域处承受的应力远高于其它区域，从而使薄膜在该区域处的竖向应变较大而出现应变集中区。因此，随着切缝角度的增大，薄膜切缝张开所致的横向收缩效应及面外屈曲现象发生相应的变化，使薄膜的应变集中区始终分布于切缝尖端邻域，从而使得薄膜的应变集中区发生相应的偏转。
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图 8 不同切缝角度的ETFE薄膜切缝尖端邻域的竖向应变场云图Figure 8. Vertical strain field nephograms in the neighborhood of the slit tip of ETFE foils with different slit angles2.4 切口样式影响
图9为不同切口样式的ETFE薄膜的撕裂抗力-位移曲线。不同切口样式对薄膜撕裂曲线的撕裂后段影响显著，导致含不同切口样式的薄膜在完全破坏时，整体上表现出两种破坏模式：类脆性破坏和类延性破坏。如图9(a)和图9(f)所示，对于无切缝和含圆形切口的ETFE薄膜，撕裂曲线到达峰值点后立即发生破坏，在撕裂后段历经的位移占整个撕裂过程发生的位移比例极小；并且在试验过程中可听到轻脆的崩断声，薄膜突然发生破坏，展现出类脆性破坏特性。而对于图9其它切口样式的ETFE薄膜，则呈现类延性破坏特性。撕裂曲线到达峰值点后，薄膜虽然达到了极限撕裂强度，但并不会立即发生断裂破坏；薄膜的切缝不断扩展，有效承载截面逐渐减小，薄膜在历经较大的位移后才完全破坏，可观察到明显预兆。
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图 9 不同切口样式的ETFE薄膜撕裂抗力-位移曲线Figure 9. Tearing strength-displacement curves of ETFE foils with different notch shapes图10为撕裂试样典型损伤模式示意图。可知，含切口的ETFE薄膜，在拉伸撕裂过程中，切口破坏了薄膜的完整性，使薄膜较易出现面外屈曲和颈缩，从而使薄膜在切口邻域处出现显著的大变形区。这会导致薄膜的应力分布不均匀，在大变形区出现应力集中，从而引发撕裂，使薄膜在切口尖端处出现撕裂三角区，薄膜的承载性能下降。并随着撕裂三角区的逐渐扩展，薄膜的有效承载区域不断减小，薄膜的承载性能逐渐下降为零。并且，不同切口样式会使薄膜的大变形区不同，从而使其应力集中各不相同，导致不同切口样式使薄膜承载性能的衰减程度各异。
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图 10 典型撕裂试样损伤模式示意图：(a)“一”形切缝和(b)圆形切口Figure 10. Schematic representation of typical damage modes of the tearing specimens: (a) “—” shaped slit ,and (b) circle notch图11为不同切口样式的ETFE薄膜对应的极限撕裂抗力。对于含开放性切缝的薄膜，相较于无切缝薄膜，含“V、X和十”形切缝的薄膜的极限撕裂抗力均约为138.13 N，下降40.58%，而含“一”形切缝的薄膜仅为107.25 N，下降53.86%。因此，当切缝的横向尺寸相同时，“一”形切缝贯穿了薄膜的主要受力方向，应力集中显著，对薄膜的极限撕裂强度的不利影响最大。对于含封闭性切口的薄膜，相较于无切缝薄膜，含圆形和椭圆形切口的薄膜的极限撕裂强度约为151.88 N，下降34.66%，含矩形-I切口的薄膜仅为115.19 N，下降50.44%。因此，当切口的横向尺寸相同时，矩形-I切口由于具有直角边缘等特性，使薄膜的应力集中程度远大于含圆形和椭圆形切口的薄膜，使薄膜承载性能的衰减程度更大。另外，含矩形-II切口的薄膜的极限撕裂强度为129.63 N，相较于无切缝薄膜的下降44.23%。可见，当切口几何外形相同时，对于横向尺寸较大的切口，其周围的应力集中区域较大，薄膜较易产生撕裂扩展，故对薄膜极限撕裂强度的不利影响更大。
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图 11 不同切口样式的ETFE薄膜极限撕裂抗力Figure 11. Ultimate tearing strength of ETFE foils with different notch shapes3. 结 论
结合系列试验与数字图像相关(DIC)技术，深入分析了乙烯-四氟乙烯(ETFE)薄膜的单轴中心撕裂行为，主要结论如下：
(1) ETFE薄膜的典型撕裂扩展过程呈现出4个特征状态；不同切缝参数显著影响薄膜面外屈曲的位置和破坏形态，但不影响薄膜切缝扩展的方向始终为垂直于加载方向；
(2) ETFE薄膜的撕裂抗力-位移曲线随不同工况的变化而发生非线性衍变，但存在典型共同特征，可划分为3个特征阶段：撕裂前段、撕裂抗力上升阶段和撕裂后段；
(3)当切缝长度从2.5 mm增大到15.0 mm时，薄膜的有效承载截面变小，其极限撕裂强度和断裂位移分别减小了55.75%和75.70%；当切缝角度从0°增大到90°时，薄膜承载途径逐渐恢复，其极限撕裂强度增大了24.67%，而断裂位移却增大了227.59%；
(4)切口样式使薄膜在完全破坏时呈现出类脆性破坏特征或类延性破坏特征。当横向尺寸相同时，在开放性切缝中，“一”形切缝贯穿薄膜主要受力方向，应力集中显著，对薄膜极限撕裂强度的不利影响最大；在封闭性切口中，与光滑边缘切口相比，直角边缘切口使薄膜的应力集中效应更显著，使薄膜易在切口尖角处发生撕裂，造成薄膜承载性能的显著衰减。所得结论可为相关均质性膜材的撕裂力学性能研究和膜结构的安全性评估提供有益参考。
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图 1 石墨相氮化碳(g-C3N4)常见缺陷类型的示意图
Figure 1. Schematic diagram of common defect types in graphitic phase carbon nitride (g-C3N4)
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图 2 g-C3N4空位缺陷的结构示意图
Figure 2. Structural schematic diagram of vacancy defects in g-C3N4
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图 3 (a)原始石墨氮化碳(CN)和680℃改性石墨氮化碳(CNQ680)的带状结构示意图；(b)转换后的Kubelka-Munk与光能图；((c), (d)) CNQ680和CN的典型TEM图像[19]
VB—Valence band; CB—Conduction band; CNQ500, CNQ600, CNQ650, CNQ680, CNQ700, CNQ720—Modified graphite carbon nitride obtained at 500℃, 600℃, 650℃, 680℃, 700℃, 720℃ calcination temperatures; α—Light absorption coefficient; hv—Photon energy
Figure 3. (a) Schematic band structure of primary graphite carbon nitride (CN) and modified graphite carbon nitride obtained at 680℃ (CNQ680); (b) Converted Kubelka-Munk vs. light energy maps; ((c), (d)) Typical TEM images of CNQ680 and CN[19]
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图 4 (a) K(x)-CN中K离子的可能掺杂位点；(b)所制备的g-C3N4和K(x)-CN的带隙结构；(c) g-C3N4的SEM图像； (d) K(0.05)-CN的SEM图像[30]
SCE—Saturated calomel electrode; RhB—Rhodamine B
Figure 4. (a) Possible doping site for K ions in K(x)-CN; (b) Band gap structures of as-prepared g-C3N4 and K(x)-CN; (c) SEM image of g-C3N4; (d) SEM image of K(0.05)-CN[30]
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图 6 (a) 块状g-C3N4纳米片、纯g-C3N4纳米片和Fe掺杂g-C3N4纳米片在阳光照射下对水溶液中罗丹明B (RhB)降解的光催化活性对比；(b)在阳光照射下Fe掺杂g-C3N4纳米片在水溶液中降解RhB的高光催化活性示意图[33]
Eg—Optical band gap of the material; LUMO—Lowest unoccupied molecular orbital; HOMO—Highest occupied molecular orbital; C/C0—Absorbance after degradation/original absorbance; E—Electrode potential; NHE—Standard hydrogen electrode
Figure 6. (a) Comparison of the photocatalytic activities of bulk g-C3N4, pure and Fe-doped g-C3N4 nanosheets for the degradation of Rhodamine B (RhB) in aqueous solution under sunlight irradiation; (b) Schematic diagram of the high photocatalytic activity of Fe-doped g-C3N4 nanosheets for the degradation of RhB in aqueous solution under sunlight irradiation[33]
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图 7 (a)介电隔离层放电(DBD)法40 min制备的硫掺杂碳氮化物(PSN-40)的SEM图像；已制备的原始g-C3N4 (g-CN)、650℃制备的硫掺杂碳氮化物(SN-650)和PSN-40 的光致发光图谱(PL) (b)和电化学阻抗谱(EIS) (c)[38]
ZR0—Real part of impedance; ZIm—Imaginary part of impedance
Figure 7. (a) SEM image of sulfur doped carbon nitride (PSN-40) prepared by dielectric isolation layer discharge (DBD) method for 40 min; Photoluminescence spectroscopy (PL) (b) and electrochemical impedance spectroscopy (EIS) (c) ofas-prepared original g-C3N4 (g-CN), sulfur doped carbon nitride prepared at 650℃ (SN-650) and PSN-40[38]
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图 8 (a)不同温度下合成的缺氮氮化碳(ACN)及块状氮化碳(BCN)的红外图谱[72]；(b)聚合物氮化碳(CN)和含N缺陷氮化碳(SCN)在不同煅烧温度下的电子顺磁共振(EPR)图谱[73]
ACN-450, ACN-500, ACN-550—Nitrogen-deficient carbon nitride calcined in NH3 at 450℃, 500℃, 550℃ for 2 h; CN550—Polymer carbon nitride obtained at 550°C; SCN500, SCN550, SCN600—N-defective nitride carbons obtained by heating at 500℃, 550℃, and 600℃, respectively
Figure 8. (a) FTIR spectra of nitrogen-deficient carbon nitride (ACN) and bulk carbon nitride (BCN) synthesized at different temperatures[72]; (b) Electron paramagnetic resonance (EPR) spectra for polymer carbon nitride (CN) and N-deficient carbon nitride (SCN) at different calcination temperatures[73]
表 1 氮化碳改性的各种参数和应用
Table 1 Various parameters and applications of carbon nitride modification
Control strategy Type of defect Add
substancesEg/eV BET/(m2·g−1) Application Ref. Pre-polymerization adjustment Carbon vacancy (Cv) Ar 2.79 160 HER [62] Cv CO2 2.84 147 No oxidization [63] Nitrogen vacancy (NV) HNO3 2.78 421.59 HER, pollutant removal [64] NV, nitrogen and
cyanide vacancies (—C≡N)NaBH4 2.71 53.7 HER [65] NV NaBH4 2.66 56.05 No removal [66] NV H2 2.0 – HER [67] Polymerization time adjustment NV N2 2.78 67.5 No removal [68] NV N2 2.07 65.6 Overall water splitting [69] Cv Acetone 2.33 153.78 HER [70] Cv – 2.92 75.24 Nitrogen fixation [71] Notes: BET—Specific surface area; HER—Hydrogen evolution reaction. 
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[1] ONG W J, TAN L L, NG Y H, et al. Graphitic carbon nitride (g-C3N4)-based photocatalysts for artificial photosynthesis and environmental remediation: Are we a step closer to achieving sustainability?[J]. Chemical Reviews, 2016, 116(12): 7159-7329. DOI: 10.1021/acs.chemrev.6b00075
[2] MA Y, WANG X, JIA Y, et al. Titanium dioxide-based nanomaterials for photocatalytic fuel generations[J]. Chemical Reviews, 2014, 114(19): 9987-10043. DOI: 10.1021/cr500008u
[3] CHEN X, SHEN S, GUO L, et al. Semiconductor-based photocatalytic hydrogen generation[J]. Chemical Reviews, 2010, 110(11): 6503-6570. DOI: 10.1021/cr1001645
[4] YAN S C, LI Z S, ZOU Z G. Photodegradation performance of g-C3N4 fabricated by directly heating melamine[J]. Langmuir: The ACS Journal of Surfaces and Colloids, 2009, 25(17): 10397-10401.
[5] ZHANG X, XIE X, WANG H, et al. Enhanced photoresponsive ultrathin graphitic-phase C3N4 nanosheets for bioimaging[J]. Journal of the American Chemical Society, 2013, 135(1): 18-21. DOI: 10.1021/ja308249k
[6] DONG F, ZHAO Z, XIONG T, et al. In situ construction of g-C3N4/g-C3N4 metal-free heterojunction for enhanced visible-light photocatalysis[J]. ACS Applied Materials & Interfaces, 2013, 5(21): 11392-11401.
[7] 徐杨, 刘成宝, 郑磊之, 等. 高结晶度g-C3N4在光催化领域的研究进展[J]. 材料导报, 2024, 3(1): 1-20. XU Yang, LIU Chengbao, ZHENG Leizhi, et al. Research progress of high crystallinity g-C3N4 in photocatalysis[J]. Materials Reports, 2024, 3(1): 1-20(in Chinese).
[8] WANG Y, CHEN J, LIU L, et al. Novel metal doped carbon quantum dots/CdS composites for efficient photocatalytic hydrogen evolution[J]. Nanoscale, 2019, 11(4): 1618-1625. DOI: 10.1039/C8NR05807E
[9] TAY Q, WANG X, ZHAO X, et al. Enhanced visible light hydrogen production via a multiple heterojunction structure with defect-engineered g-C3N4 and two-phase anatase/brookite TiO2[J]. Journal of Catalysis, 2016, 342: 55-62. DOI: 10.1016/j.jcat.2016.07.007
[10] FU J, MO Z, CHEN H, et al. Three coordinate nitrogen (N3c) vacancies from in-situ hydrogen bond breaking over polymeric carbon nitride for efficient photocatalysis[J]. Journal of Environmental Chemical Engineering, 2023, 11(2): 109495. DOI: 10.1016/j.jece.2023.109495
[11] YE X, CHEN Y, YANG N, et al . WC1-x-coupled 3D porous defective g-C3N4 for efficient photocatalytic overall water splitting [J]. Solar RRL, 2019, 3 (5): 1800341.
[12] WANG K, FU J, ZHENG Y. Insights into photocatalytic CO2 reduction on C3N4: Strategy of simultaneous B, K co-doping and enhancement by N vacancies[J]. Applied Catalysis B: Environmental, 2019, 254: 270-282. DOI: 10.1016/j.apcatb.2019.05.002
[13] WANG X, MAEDA K, THOMAS A, et al. A metal-free polymeric photocatalyst for hydrogen production from water under visible light[J]. Nature Materials, 2009, 8(1): 76-80. DOI: 10.1038/nmat2317
[14] YU H, SHI R, ZHAO Y, et al. Alkali-assisted synthesis of nitrogen deficient graphitic carbon nitride with tunable band structures for efficient visible-light-driven hydrogen evolution[J]. Advanced Materials, 2017, 29(16): 1605148. DOI: 10.1002/adma.201605148
[15] YANG P, ZHU Z H, WANG R, et al. Carbon vacancies in a melon polymeric matrix promote photocatalytic carbon dioxide conversion[J]. Angewandte Chemie (International Edition in English), 2019, 58(4): 1134-1137. DOI: 10.1002/anie.201810648
[16] LI F, YUE X, ZHANG D, et al. Targeted regulation of exciton dissociation in graphitic carbon nitride by vacancy modification for efficient photocatalytic CO2 reduction[J]. Applied Catalysis B: Environmental, 2021, 292: 120179. DOI: 10.1016/j.apcatb.2021.120179
[17] SHAO W, WANG L, WANG H, et al. Efficient exciton dissociation in heterojunction interfaces realizing enhanced photoresponsive performance[J]. The Journal of Physical Chemistry Letters, 2019, 10(11): 2904-2910. DOI: 10.1021/acs.jpclett.9b01020
[18] LIU Y, XIAO C, LI Z, et al. Vacancy engineering for tuning electron and phonon structures of two-dimensional materials[J]. Advanced Energy Materials, 2016, 6(23): 1600436. DOI: 10.1002/aenm.201600436
[19] NIU P, QIAO M, LI Y, et al. Distinctive defects engineering in graphitic carbon nitride for greatly extended visible light photocatalytic hydrogen evolution[J]. Nano Energy, 2018, 44: 73-81. DOI: 10.1016/j.nanoen.2017.11.059
[20] IGLESIAS D, GIULIANI A, MELCHIONNA M, et al. N-doped graphitized carbon nanohorns as a forefront electrocatalyst in highly selective O2 reduction to H2O2[J]. Chem, 2018, 4(1): 106-123. DOI: 10.1016/j.chempr.2017.10.013
[21] LIN F, WANG T, REN Z, et al. Central nitrogen vacancies in polymeric carbon nitride for boosted photocatalytic H2O2 production[J]. Journal of Colloid and Interface Science, 2023, 636: 223-229. DOI: 10.1016/j.jcis.2023.01.036
[22] XIE Y, LI Y, HUANG Z, et al. Two types of cooperative nitrogen vacancies in polymeric carbon nitride for efficient solar-driven H2O2 evolution[J]. Applied Catalysis B: Environmental, 2020, 265: 118581. DOI: 10.1016/j.apcatb.2019.118581
[23] DONG G, JACOBS D L, ZANG L, et al. Carbon vacancy regulated photoreduction of NO to N2 over ultrathin g-C3N4 nanosheets[J]. Applied Catalysis B: Environmental, 2017, 218: 515-524. DOI: 10.1016/j.apcatb.2017.07.010
[24] LIU M, ZHANG D, HAN J, et al. Adsorption enhanced photocatalytic degradation sulfadiazine antibiotic using porous carbon nitride nanosheets with carbon vacancies[J]. Chemical Engineering Journal, 2020, 382: 123017. DOI: 10.1016/j.cej.2019.123017
[25] LIANG Q, LI Z, HUANG Z H, et al. Hydrogen evolution: Holey graphitic carbon nitride nanosheets with carbon vacancies for highly improved photocatalytic hydrogen production[J]. Advanced Functional Materials, 2015, 25(44): 6952. DOI: 10.1002/adfm.201570285
[26] WANG J, HUANG J, XIE H, et al. Synthesis of g-C3N4/TiO2 with enhanced photocatalytic activity for H2 evolution by a simple method[J]. International Journal of Hydrogen Energy, 2014, 39(12): 6354-6363. DOI: 10.1016/j.ijhydene.2014.02.020
[27] ZHENG Y, LIN L, WANG B, et al. Graphitic carbon nitride polymers toward sustainable photoredox catalysis[J]. Angewandte Chemie International Edition, 2015, 54(44): 12868-12884. DOI: 10.1002/anie.201501788
[28] XU J, BRENNER T, CHEN Z, et al. Upconversion-agent induced improvement of g-C3N4 photocatalyst under visible light[J]. ACS Applied Materials & Interfaces, 2014, 6(19): 16481-16486.
[29] ZHANG M, BAI X, LIU D, et al. Enhanced catalytic activity of potassium-doped graphitic carbon nitride induced by lower valence position[J]. Applied Catalysis B: Environmental, 2015, 164: 77-81. DOI: 10.1016/j.apcatb.2014.09.020
[30] HU S, LI F, FAN Z, et al. Band gap-tunable potassium doped graphitic carbon nitride with enhanced mineralization ability[J]. Dalton Transactions, 2015, 44(3): 1084-1092. DOI: 10.1039/C4DT02658F
[31] XIONG T, CEN W, ZHANG Y, et al. Bridging the g-C3N4 interlayers for enhanced photocatalysis[J]. ACS Catalysis, 2016, 6(4): 2462-2472. DOI: 10.1021/acscatal.5b02922
[32] WANG N, WANG J, HU J, et al. Design of palladium-doped g-C3N4 for enhanced photocatalytic activity toward hydrogen evolution reaction[J]. ACS Applied Energy Materials, 2018, 1(6): 2866-2873. DOI: 10.1021/acsaem.8b00526
[33] TONDA S, KUMAR S, KANDULA S, et al. Fe-doped and -mediated graphitic carbon nitride nanosheets for enhanced photocatalytic performance under natural sunlight[J]. Journal of Materials Chemistry A, 2014, 2(19): 6772-6780. DOI: 10.1039/c3ta15358d
[34] ZHANG Y, MORI T, YE J, et al. Phosphorus-doped carbon nitride solid: Enhanced electrical conductivity and photocurrent generation[J]. Journal of the American Chemical Society, 2010, 132(18): 6294-6295. DOI: 10.1021/ja101749y
[35] ZHANG L, CHEN X, GUAN J, et al. Facile synthesis of phosphorus doped graphitic carbon nitride polymers with enhanced visible-light photocatalytic activity[J]. Materials Research Bulletin, 2013, 48(9): 3485-3491. DOI: 10.1016/j.materresbull.2013.05.040
[36] HU S, MA L, YOU J, et al. A simple and efficient method to prepare a phosphorus modified g-C3N4 visible light photocatalyst[J]. RSC Advances, 2014, 4(41): 21657-21663. DOI: 10.1039/C4RA02284J
[37] LIU G, NIU P, SUN C, et al. Unique electronic structure induced high photoreactivity of sulfur-doped graphitic C3N4[J]. Journal of the American Chemical Society, 2010, 132(33): 11642-11648. DOI: 10.1021/ja103798k
[38] MA L, HU S, LI P, et al. In situ synthesis of sulfur doped carbon nitride with enhanced photocatalytic performance using DBD plasma treatment under H2S atmosphere[J]. Journal of Physics and Chemistry of Solids, 2018, 118: 166-171. DOI: 10.1016/j.jpcs.2018.03.017
[39] FAN Q, LIU J, YU Y, et al. A simple fabrication for sulfur doped graphitic carbon nitride porous rods with excellent photocatalytic activity degrading RhB dye[J]. Applied Surface Science, 2017, 391: 360-368. DOI: 10.1016/j.apsusc.2016.04.055
[40] ROOSE B, PATHAK S, STEINER U. Doping of TiO2 for sensitized solar cells[J]. Chemical Society Reviews, 2015, 44(22): 8326-8349. DOI: 10.1039/C5CS00352K
[41] NASIR M, BAGWASI S, JIAO Y, et al. Characterization and activity of the Ce and N co-doped TiO2 prepared through hydrothermal method[J]. Chemical Engineering Journal, 2014, 236: 388-397. DOI: 10.1016/j.cej.2013.09.095
[42] SHEN X Z, LIU Z C, XIE S M, et al. Degradation of nitrobenzene using titania photocatalyst co-doped with nitrogen and cerium under visible light illumination[J]. Journal of Hazardous Materials, 2009, 162(2): 1193-1198.
[43] HU S, MA L, YOU J, et al. Enhanced visible light photocatalytic performance of g-C3N4 photocatalysts co-doped with iron and phosphorus[J]. Applied Surface Science, 2014, 311: 164-171. DOI: 10.1016/j.apsusc.2014.05.036
[44] ZHANG S, LI J, ZENG M, et al. Bandgap engineering and mechanism study of nonmetal and metal ion codoped carbon nitride: C+Fe as an example[J]. Chemistry–A European Journal, 2014, 20(31): 9805-9812. DOI: 10.1002/chem.201400060
[45] HU S, MA L, XIE Y, et al. Hydrothermal synthesis of oxygen functionalized S–P codoped g-C3N4 nanorods with outstanding visible light activity under anoxic conditions[J]. Dalton Transactions, 2015, 44(48): 20889-20897. DOI: 10.1039/C5DT04035C
[46] MA H, ZHAO S, LI S, et al. A facile approach to synthesizing S–Co–O tridoped g-C3N4 with enhanced oxygen-free photocatalytic performance via a hydrothermal post-treatment[J]. RSC Advances, 2015, 5(97): 79585-79592. DOI: 10.1039/C5RA14081A
[47] DI J, JIE X X, LI X, et al. Constructing confined surface carbon defects in ultrathin graphitic carbon nitride for photocatalytic free radical manipulation[J]. Carbon, 2016, 107: 1-10.
[48] YANG X, YANG H, HO W, et al. Promoting the photocatalytic NO oxidation activity of hierarchical porous g-C3N4 by introduction of nitrogen vacancies and charge channels [J]. Applied Catalysis B: Environmental, 2024, 344: 123604.
[49] LIAO J, CUI W, LI J, et al. Nitrogen defect structure and NO+ intermediate promoted photocatalytic NO removal on H2 treated g-C3N4[J]. Chemical Engineering Journal, 2020, 379: 122282. DOI: 10.1016/j.cej.2019.122282
[50] ZHAO D, DONG C L, WANG B, et al. Synergy of dopants and defects in graphitic carbon nitride with exceptionally modulated band structures for efficient photocatalytic oxygen evolution[J]. Advanced Materials, 2019, 31(43): 1903545. DOI: 10.1002/adma.201903545
[51] GU Z, CUI Z, WANG Z, et al. Carbon vacancies and hydroxyls in graphitic carbon nitride: Promoted photocatalytic NO removal activity and mechanism[J]. Applied Catalysis B: Environmental, 2020, 279: 119376. DOI: 10.1016/j.apcatb.2020.119376
[52] LIU G, ZHAO G, ZHOU W, et al. In situ bond modulation of graphitic carbon nitride to construct p-n homojunctions for enhanced photocatalytic hydrogen production[J]. Advanced Functional Materials, 2016, 26(37): 6822-6829. DOI: 10.1002/adfm.201602779
[53] TIAN J, WANG D, LI S, et al. KOH-assisted band engineering of polymeric carbon nitride for visible light photocatalytic oxygen reduction to hydrogen peroxide[J]. ACS Sustainable Chemistry & Engineering, 2020, 8(1): 594-603.
[54] LIN W, LU K, ZHOU S, et al. Defects remodeling of g-C3N4 nanosheets by fluorine-containing solvothermal treatment to enhance their photocatalytic activities[J]. Applied Surface Science, 2019, 474: 194-202. DOI: 10.1016/j.apsusc.2018.03.140
[55] NIU P, LIU G, CHENG H M. Nitrogen vacancy-promoted photocatalytic activity of graphitic carbon nitride[J]. The Journal of Physical Chemistry C, 2012, 116(20): 11013-11018. DOI: 10.1021/jp301026y
[56] KANG Y, YANG Y, YIN L C, et al. An amorphous carbon nitride photocatalyst with greatly extended visible-light-responsive range for photocatalytic hydrogen generation[J]. Advanced Materials, 2015, 27(31): 4572-4577. DOI: 10.1002/adma.201501939
[57] HAN Q, CHENG Z, WANG B, et al. Significant enhancement of visible-light-driven hydrogen evolution by structure regulation of carbon nitrides[J]. ACS Nano, 2018, 12(6): 5221-5227. DOI: 10.1021/acsnano.7b08100
[58] DENG Y, ZHOU Z, ZENG H, et al. Phosphorus and kalium co-doped g-C3N4 with multiple-locus synergies to degrade atrazine: Insights into the depth analysis of the generation and role of singlet oxygen[J]. Applied Catalysis B: Environmental, 2023, 320: 121942. DOI: 10.1016/j.apcatb.2022.121942
[59] CHEN Z, CHEN W, LIAO G, et al. Flexible construct of N vacancies and hydrophobic sites on g-C3N4 by F doping and their contribution to PFOA degradation in photocatalytic ozonation[J]. Journal of Hazardous Materials, 2022, 428: 128222. DOI: 10.1016/j.jhazmat.2022.128222
[60] CUI Y, ZHANG G, LIN Z, et al. Condensed and low-defected graphitic carbon nitride with enhanced photocatalytic hydrogen evolution under visible light irradiation[J]. Applied Catalysis B: Environmental, 2016, 181: 413-419. DOI: 10.1016/j.apcatb.2015.08.018
[61] TU W, XU Y, WANG J, et al. Investigating the role of tunable nitrogen vacancies in graphitic carbon nitride nanosheets for efficient visible-light-driven H2 evolution and CO2 reduction[J]. ACS Sustainable Chemistry & Engineering, 2017, 5(8): 7260-7268.
[62] GHOLIPOUR M R, BÉLAND F, DO T O J A S C, et al. Post-calcined carbon nitride nanosheets as an efficient photocatalyst for hydrogen production under visible light irradiation[J]. ACS Sustainable Chemistry & Engineering, 2017, 5: 213-220.
[63] LI Y, HO W, LYU K, et al. Carbon vacancy-induced enhancement of the visible light-driven photocatalytic oxidation of NO over g-C3N4 nanosheets[J]. Applied Surface Science, 2018, 430: 380-389. DOI: 10.1016/j.apsusc.2017.06.054
[64] CHE H, LIU L, CHE G, et al. Control of energy band, layer structure and vacancy defect of graphitic carbon nitride by intercalated hydrogen bond effect of NO3− toward improving photocatalytic performance[J]. Chemical Engineering Journal, 2019, 357: 209-219. DOI: 10.1016/j.cej.2018.09.112
[65] WEN Y, QU D, AN L, et al. Defective g-C3N4 prepared by the NaBH4 reduction for high-performance H2 production[J]. ACS Sustainable Chemistry & Engineering, 2019, 7(2): 2343-2349.
[66] CAO J, ZHANG J, DONG X A, et al. Defective borate-decorated polymer carbon nitride: Enhanced photocatalytic NO removal, synergy effect and reaction pathway[J]. Applied Catalysis B: Environmental, 2019, 249: 266-274. DOI: 10.1016/j.apcatb.2019.03.012
[67] TAY Q, KANHERE P, NG C F, et al. Defect engineered g-C3N4 for efficient visible light photocatalytic hydrogen production[J]. Chemistry of Materials, 2015, 27(14): 4930-4933. DOI: 10.1021/acs.chemmater.5b02344
[68] WANG Z, HUANG Y, CHEN M, et al. Roles of N-vacancies over porous g-C3N4 microtubes during photocatalytic NOx removal[J]. ACS Applied Materials & Interfaces, 2019, 11(11): 10651-10662.
[69] ZENG Y, LI H, LUO J, et al. Sea-urchin-structure g-C3N4 with narrow bandgap (~2.0 eV) for efficient overall water splitting under visible light irradiation[J]. Applied Catalysis B: Environmental, 2019, 249: 275-281. DOI: 10.1016/j.apcatb.2019.03.010
[70] JIANG L, LI J, WANG K, et al. Low boiling point solvent mediated strategy to synthesize functionalized monolayer carbon nitride for superior photocatalytic hydrogen evolution[J]. Applied Catalysis B: Environmental, 2020, 260: 118181. DOI: 10.1016/j.apcatb.2019.118181
[71] CAO S, FAN B, FENG Y, et al. Sulfur-doped g-C3N4 nanosheets with carbon vacancies: General synthesis and improved activity for simulated solar-light photocatalytic nitrogen fixation[J]. Chemical Engineering Journal, 2018, 353: 147-156. DOI: 10.1016/j.cej.2018.07.116
[72] MENG F, TIAN W, TIAN Z, et al. Enhanced photocatalytic organic pollutant degradation and H2 evolution reaction over carbon nitride nanosheets: N defects abundant materials[J]. Science of the Total Environment, 2022, 851: 158360. DOI: 10.1016/j.scitotenv.2022.158360
[73] BAI X, LI M, LI J, et al. Chemical cutting of network nodes in polymeric carbon nitride for enhanced visible-light photocatalytic hydrogen generation[J]. ACS Applied Nano Materials, 2022, 5(1): 691-701. DOI: 10.1021/acsanm.1c03419
[74] DUAN Y, WANG Y, GAN L, et al. Amorphous carbon nitride with three coordinate nitrogen (N3C) vacancies for exceptional NOx abatement in visible light[J]. Advanced Energy Materials, 2021, 11(19): 2004001. DOI: 10.1002/aenm.202004001
[75] ZHANG D, GUO Y, ZHAO Z. Porous defect-modified graphitic carbon nitride via a facile one-step approach with significantly enhanced photocatalytic hydrogen evolution under visible light irradiation[J]. Applied Catalysis B: Environmental, 2018, 226: 1-9. DOI: 10.1016/j.apcatb.2017.12.044
[76] GUO S, DENG Z, LI M, et al. Phosphorus-doped carbon nitride tubes with a layered micro-nanostructure for enhanced visible-light photocatalytic hydrogen evolution[J]. Angewandte Chemie International Edition, 2016, 55(5): 1830-1834. DOI: 10.1002/anie.201508505
[77] 曹一达, 刘成宝, 陈丰, 等. CeO2/BiOI/g-C3N4三相复合材料的制备及可见光催化降解RhB性能研究[J]. 材料导报, 2023, 37(3): 136-142. CAO Yida, LIU Chengbao, CHEN Feng, et al. Preparation of CeO2/BiOI/g-C3N4 composite and its photocatalytic degradation property for RhB under visible light[J]. Materials Reports, 2023, 37(3): 136-142(in Chinese).
[78] 于巧玲, 刘成宝, 金涛. 等. CuS/CQDs/g-C3N4复合材料的合成及其光催化性能研究[J]. 材料导报, 2024, 3(1): 1-15. YU Qiaoling, LIU Chengbao, JIN Tao, et al. Synthesis and photocatalytic properties of CuS/CQDs/g-C3N4[J]. Materials Reports, 2024, 3(1): 1-15(in Chinese).
[79] FANG H X, GUO H, NIU C G, et al. Hollow tubular graphitic carbon nitride catalyst with adjustable nitrogen vacancy: Enhanced optical absorption and carrier separation for improving photocatalytic activity[J]. Chemical Engineering Journal, 2020, 402: 126185. DOI: 10.1016/j.cej.2020.126185
[80] ZHU J, CARABINEIRO S A C, SHAN D, et al. Oxygen activation sites in gold and iron catalysts supported on carbon nitride and activated carbon[J]. Journal of Catalysis, 2010, 274(2): 207-214. DOI: 10.1016/j.jcat.2010.06.018
[81] HONG Z, SHEN B, CHEN Y, et al. Enhancement of photocatalytic H2 evolution over nitrogen-deficient graphitic carbon nitride[J]. Journal of Materials Chemistry A, 2013, 1(38): 11754-11761. DOI: 10.1039/c3ta12332d
[82] XU J, WANG Z, ZHU Y. Enhanced visible-light-driven photocatalytic disinfection performance and organic pollutant degradation activity of porous g-C3N4 nanosheets[J]. ACS Applied Materials & Interfaces, 2017, 9(33): 27727-27735.
[83] LIU H, MA S, SHAO L, et al. Defective engineering in graphitic carbon nitride nanosheet for efficient photocatalytic pathogenic bacteria disinfection[J]. Applied Catalysis B: Environmental, 2020, 261: 118201. DOI: 10.1016/j.apcatb.2019.118201
[84] ZHAO H, YU H, QUAN X, et al. Fabrication of atomic single layer graphitic-C3N4 and its high performance of photocatalytic disinfection under visible light irradiation[J]. Applied Catalysis B: Environmental, 2014, 152-153: 46-50. DOI: 10.1016/j.apcatb.2014.01.023
[85] XU J, WANG Z, ZHU Y. Highly efficient visible photocatalytic disinfection and degradation performances of microtubular nanoporous g-C3N4 via hierarchical construction and defects engineering[J]. Journal of Materials Science & Technology, 2020, 49: 133-143.
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目的
光催化技术由于可以利用太阳能降解水和空气中的污染物，或将太阳能转化为化学能，被视为解决能源危机和环境污染的最有前途的技术之一，在众多新型光催化材料中，g-CN具有独特的电子结构、稳定的理化性质、简单的制备工艺和廉价的制备成本等优点，但未改性的g-CN活性位点偏少以及光生载流子复合速率高等缺点，严重制约了其实际应用。通过缺陷调控有效地改善光催化材料的电子能带结构、延缓载流子的复合和增加表面活性位点进而提升光催化性能。
方法引入缺陷被证明是提高g-CN光催化材料性能的有效方法，特别是促进光生载流子的分离和传输，从而增强其催化活性。总结了如N空位、C空位以及元素掺杂等不同的缺陷类型研究现状，介绍了g-CN缺陷引入的策略，包括在聚合反应之前对条件进行精确控制以及在聚合时有意地调节反应条件，例如温度、反应时间和反应物比例等操作，将空位缺陷引入CN 中，如直接热处理、水处理、溶剂热处理和气体还原处理，同时对缺陷浓度的调节进行总结概括，这些缺陷可增宽光吸收带、改善电荷转移、延长载流子寿命和优化氧化还原能力。此外，对g-CN在光催化中的实际应用进行了分类描述，同时对缺陷调控所面临的挑战和未来发展前景进行了展望。
结果引入氮空位缺陷对g-CN光催化性能具有多重作用。首先，氮空位可作为光激发电子陷入的位点，有效抑制光生电子-空穴对的再组合，有助于提高光催化活性。其次，氮空位中的多余电子可与氧分子结合形成超氧自由基，或与金属物质结合形成光生电子的吸收位点，进一步促进光催化反应。与氮空位不同，C空位的引入会增加g-CN的价带能量，激发更多电子，缩小带隙。此外，C空位破坏C-N键并降低结构对称性，导致不饱和的N原子形成，可作为顺磁中心吸引导带中的电子，促进电子和空穴的有效分离，从而提升光催化性能。掺杂杂原子也是一种有效改性方法，金属掺杂可改变电子结构并参与催化反应，而非金属掺杂能够提高材料性能而不改变其非金属特性。这些方法为g-CN的光催化应用提供了新的可能性。在g-CN的缺陷调控中，合适的缺陷浓度对其光催化性能至关重要。适度的缺陷浓度可以提高光吸收效率和催化活性，但过高的缺陷浓度可能导致结晶度下降和光生载流子复合，从而降低催化效率。调控缺陷浓度可通过热聚合处理中的温度、升温时间和速率等参数进行，一般来说，随着煅烧温度升高，氮缺陷数量增加。然而，不同方法可能会导致不同的结果。此外，采用不同的引入缺陷方法，如溶剂、固体材料或还原气体，也可调控缺陷浓度。确保前驱体和添加剂充分混合均匀是控制缺陷浓度的关键。因此，精确调控g-CN中的缺陷浓度是优化其光催化性能的关键步骤。
结论本文综述了缺陷g-CN在光催化领域的研究进展，包括N空位、C空位和元素掺杂等缺陷类型的研究现状。介绍了引入缺陷的策略，如调控聚合反应条件、热处理和溶剂处理，并总结了对缺陷浓度的调节方法。这些缺陷可改善材料的光吸收、电荷转移、载流子寿命和氧化还原能力。然而，过多的缺陷会导致电荷复合，不利于光催化。为了充分利用缺陷的优势并避免其缺点，需要创新缺陷调控策略、开发直接带隙的掺杂方法，以及结合纳米结构制造来提高材料的光催化性能。
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