钾离子掺杂对石墨型氮化碳光催化剂能带结构及光催化性能的影响

以双氰胺和氢氧化钾为原料制备了能带可控的钾离子掺杂石墨型氮化碳(g-C3N4)光催化剂,并与碱处理的g-C3N4及g-C3N4/KOH复合催化剂进行了对比。采用X射线衍射(XRD)光谱、紫外-可见(UV-Vis)光谱、傅里叶变换红外(FTIR)光谱、N2吸附、电感耦合等离子体-原子发射光谱(ICP-AES)、荧光(PL)光谱、X 光电子能谱(XPS)等分析手段对制备的催化剂进行了表征。结果表明,钾离子含量对氮化碳催化剂的价带及导带位置有显著影响。此外,钾离子的引入抑制了氮化碳晶粒的生长,提高了氮化碳的比表面积以及对可见光的吸收,降低了光生电子-空穴对的复合几率。以染料罗丹明B的降解为探针反应系统研究了钾离子掺杂对g-C3N4在可见光下催化性能的影响,研究了光催化反应机理。结果表明,钾离子掺杂后氮化碳的光催化性能显著提高。制备的钾离子掺杂氮化碳催化剂表现出良好的结构及催化稳定性。     

铈掺杂石墨相氮化碳的合成及可见光光催化性能

以硝酸铈和三聚氰胺为原料,采用热解法合成系列Ce掺杂石墨相氮化碳(g-C_3N_4).采用X射线衍射仪(XRD)、透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FTIR)、紫外-可见漫反射光谱仪(UV-Vis DRS)、荧光光谱仪(PL)和X射线光电子能谱仪(XPS)等对样品进行了表征.结果表明,Ce掺杂使g-C_3N_4晶粒尺寸减小,比表面积增大,光生电子/空穴对复合几率降低,并影响到能带结构.在可见光下光催化降解亚甲基蓝水溶液的结果表明,Ce掺杂g-C_3N_4的可见光光催化活性远优于纯g-C_3N_4.其中,0.10-Ce-C_3N_4样品80 min内对亚甲基蓝的降解率高达98.51%,速率常数达0.0506 min~(-1),是纯g-C_3N_4的4.9倍.     

Fe-P共掺杂石墨相氮化碳催化剂可见光下催化性能研究

采用双氰胺、硝酸铁和磷酸氢二铵为原料制备Fe-P共掺杂石墨相氮化碳(g-C3N4).使用X射线衍射光谱(XRD)、N2吸附、紫外可见光谱(UV-Vis)、傅里叶红外光谱(FT-IR)、荧光光谱(PL)、X射线光电子能谱(XPS)等分析手段对制备的催化剂进行了表征.结果表明,引入掺杂剂可以抑制g-C3N4的晶粒生长,提高催化剂比表面积,降低带隙能,抑制光生电子和空穴的复合.在可见光下降解罗丹明B的实验表明Fe-P共掺杂g-C3N4的反应速率常数是纯g-C3N4的6倍.我们推测了P和Fe可能的掺杂态以及光催化反应机理.     

大豆蛋白改性TiO_2的制备及其可见光催化性能

采用溶胶-凝胶法制备了系列大豆蛋白改性TiO_2复合催化剂.通过元素分析、粒度分析、X射线衍射(XRD)、场发射扫描电镜(FESEM)、紫外-可见漫反射光谱(UV-Vis)、电化学等方法对所制备的样品进行了表征,以亚甲基蓝为目标降解物,研究了大豆蛋白改性TiO_2的可见光催化性能.结果表明,大豆蛋白改性可以一步实现C、N、H多种非金属元素共掺杂;相比纯TiO_2,改性后复合催化剂的比表面积增大;所有样品均为锐钛矿相;煅烧温度为400℃时,复合催化剂的可见光吸收发生明显红移,其禁带宽度较纯TiO_2窄化了0.32 e V;大豆蛋白改性后,复合材料的光电流密度增大;在可见光照射下,光催化反应2 h时,大豆蛋白改性TiO_2的亚甲基蓝降解效率最高可达79.4%.     

生物质多元自掺杂TiO_2的超声同步合成及其表征分析

采用溶胶-超声空化技术同步合成了生物质多元自掺杂TiO_2复合催化剂,通过场发射扫描电镜(FESEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外-可见漫反射光谱(UV-vis)、傅里叶变换红外光谱(FT-IR)、光致发光光谱(PL)等对样品进行了表征分析。结果表明,复合催化剂实现了C、N、P、Cl、K等元素的同步掺杂,合成了多元共掺杂复合TiO_2;相比纯TiO_2,复合催化剂的禁带宽度窄化了0.21 e V,表面羟基与活性位点增多,光生载流子复合几率降低,结晶度提高,比表面积增大。以亚甲基蓝(MB)为目标污染物,研究了复合催化剂的可见光光催化性能。实验结果表明,在可见光照射下,光催化反应2 h时,复合催化剂对亚甲基蓝的降解效率最高可达98%。     

C-I共掺杂多孔g-C3N4光催化分解水制氢

氢气是一种可替代传统燃料的理想清洁能源,利用光催化技术分解水制氢是制取氢气的有效途径之一.无机半导体光催化材料具有较高的活性和稳定性,且原料丰富,易加工改性.目前针对光催化技术的应用,大量的研究工作都集中在开发可见光响应光催化剂,以提高对可见光的利用率.同时,非金属聚合物半导体因其特殊的光电性质,在光催化应用研究中越来越受到关注,如庚嗪基微孔聚合物(HMP)和共价三嗪基骨架(CTF).石墨相碳化氮(g-C3N4)是一种典型非金属二维聚合物半导体,被认为是一种非常有价值的光催化材料.然而,其较低的光生电子的传输效率限制了其实际应用,因此诸多研究对g-C3N4的物理化学结构进行优化,如半导体耦合、共聚合、纳米结构设计和掺杂.非金属掺杂是一种有效的方法,由于原子电负性差异引起的电荷分离可有效改善载流子传输效率,且保持半导体的非金属性质.通过O,B,P和S等掺杂可以扩大可见光响应范围,并调节能带位置以改善光催化活性.除了常见的单一非金属掺杂,金属和非金属元素或多非金属元素共掺杂的办法同样可提高g-C3N4的光催化性能.本工作通过两步法对双氰胺、尿素和碘化1-乙基-3-甲基咪唑的混合物直接热聚合,合成C-I共掺杂的多孔g-C3N4,其在可见光照射下表现出较高的产氢活性和稳定性.采用X射线衍射(XRD)、X射线光电子能谱(XPS)、荧光光谱(PL)和电化学实验等方法对多孔掺杂g-C3N4结构进行详细表征和分析.在助催化剂Pt和电子牺牲剂(三乙醇胺)存在的条件下,采用可见光(>400 nm)照射分解水产氢的方法评价其光催化活性.结果表明,后热处理和碘离子液掺杂对g-C3N4材料的结构和性能具有较大影响.C-I共掺杂和后热处理使催化剂产物颗粒尺寸减小,形成多孔片层状紧密堆积,比表面积和孔隙率显著增加,吸收带边发生蓝移.后热处理使样品层间距减小,聚合度增加,有利于电荷传输,C-I共掺杂后出现更多的缺陷,但没有改变其层状堆积的特性.XPS结果表明,样品中碘元素以I-和I5+的形式存在,改性后催化剂C/N比明显增加,sp2芳环N含量增加,表面氨基含量降低,表明后热处理和C-I共掺杂没有改变多孔g-C3N4的基本骨架,共轭结构更加完善.PL和光电流结果表明,改性后样品的PL强度均显著降低,并且随着掺杂量的增加而逐渐降低,表明共掺杂可抑制光生电荷的复合.电化学测试结果表明,后热处理和C-I共掺杂的样品界面电荷转移电阻降低,导电率和电荷迁移率增加,从而有助于提高光催化性能.光解水产氢性能测试表明,后热处理和C-I共掺杂有利于催化剂产氢速率的提高,改性后CNIN0.2的产氢速率达168.2μmol/h,是纯氮化碳的9.8倍.经过多次循环测试,其产氢性能保持稳定而没有显著下降,表明其产氢稳定性较好.     

Fe掺杂g-C_3N_4的制备及其可见光催化性能

以硝酸铁和三聚氰胺为原料制备不同含铁量的Fe掺杂石墨氮化碳(g-C3N4).采用X射线衍射光谱(XRD)、紫外-可见(UV-Vis)光谱、傅里叶变换红外(FT-IR)光谱、电感耦合等离子体-原子发射光谱(ICP-AES)、荧光(PL)光谱、X光电子能谱(XPS)等分析手段对制备的催化剂进行了表征.结果表明,铁以离子形式镶嵌在gC3N4的结构单元中,影响了g-C3N4的能带结构,增加了g-C3N4对可见光的吸收,降低了光生电子-空穴对的复合几率.以染料罗丹明B的降解为探针反应系统研究了不同含铁量对g-C3N4在可见光下催化性能的影响.结果表明,m(Fe)/m(g-C3N4)=0.14%时,制备的Fe掺杂g-C3N4表现出最佳的光催化性能,120 min内罗丹明B的降解率高达99.7%,速率常数达到0.026 min-1,是纯g-C3N4的3.2倍.以叔丁醇、对苯醌、乙二胺四乙酸二钠为自由基(·OH)、自由基(O2-·)和空穴(h+VB)的捕获剂,研究了光催化反应机理.     

利用硫化铋纳米颗粒增强类石墨相氮化碳的光生载流子分离效率和光催化活性（英文）

二氧化钛,氧化锌,磷酸铋等传统的紫外光响应光催化剂虽然具有良好的光催化性能,但是对太阳能利用率很低(紫外光只占太阳光能量的4%左右).近年来,类石墨相氮化碳(g-C3N4)受到了广泛的关注.g-C3N4的带隙约2.7 eV,它只能吸收460nm以下的光,对太阳能的利用率依然比较低.构筑异质结是一种有效的提高光催化活性的方法.BiOCl/g-C3N4,TiO2/g-C3N4, Bi2MoO6/g-C3N4, Al2O3/g-C3N4, Ag3PO4/g-C3N4等异质结光催化剂曾被广泛的报道.硫化铋是属于正交晶系的窄带隙半导体,它的带隙约1.3–1.7 e V.由于其独特的电子结构和光学特性,硫化铋在光催化,光检测器和医药成像等领域有着广泛的应用.另外,硫化铋还具有优异的光热转换性能,在光热癌症治疗领域有显著的效果.微波辅助法,水热法,惰性气体下高温煅烧法等都曾被用来合成g-C3N4/Bi2S3异质结光催化剂.不同的文献也提出了不同的催化机理.如何使用更简单环保的方法来合成g-C3N4/Bi2S3异质结光催化剂?电子和空穴的转移路径是怎样的?本文利用简单的低温方法合成了硫化铋,利用超声法得到了g-C3N4/Bi2S3异质结光催化剂,分析了其微观形貌,结构,并探讨了光催化的反应机理和提高光催化性能的因素.X射线衍射,傅里叶变换红外光谱, X射线光电子能谱和透射电子显微镜的结果表明,硫化铋纳米颗粒被成功地引入到g-C3N4中.使用亚甲基蓝为分子探针研究了所制材料在模拟太阳光下的光催化活性.结果发现, CN-BiS-2表现出最佳的光催化活性,是g-C3N4的2.05倍,是Bi2S3的4.42倍.利用液相色谱二级质谱联用分析了亚甲基蓝的降解路径.硫化铋的引入拓展了复合材料的吸收边,使其向可见光区红移,且在整个可见光区的光吸收能力都有明显的增强.光电流的增强和交流阻抗谱圆弧半径的减小,表明光生载流子的迁移与分离速率得到了增强.自由基捕获试验表明,最主要的活性物种是光生空穴,次之是羟基自由基和超氧自由基.在CN-Bi S-2样品中羟基自由基和超氧自由基的电子顺磁共振信号都比g-C3N4有明显的增强,表明复合样品中能够产生更多的羟基自由基和超氧自由基.基于光电流,交流阻抗,荧光光谱,自由基捕获和电子顺磁共振的结果,我们提出了高能电子由硫化铋转移到g-C3N4,同时空穴由g-C3N4转移到硫化铋的电子空穴转移机制.此外,红外热成像的结果表明, g-C3N4/Bi2S3异质结材料具有更强的光热转换能力,从而有利于加速光生载流子分离.     

Ag@AgBr光催化剂的制备及其可见光催化降解亚甲基蓝反应性能

采用沉积-沉淀及光还原法制备了Ag@AgBr等离子体光催化剂,利用X射线衍射、扫描电镜和紫外-可见漫反射光谱对其进行了表征,并考察了该等离子体光催化剂在可见光(λ420nm)下的催化性能,探讨了催化剂用量、pH值、亚甲基蓝初始浓度、H2O2添加量、循环使用及捕获剂对Ag@AgBr催化性能的影响.结果表明,当亚甲基蓝的初始浓度为10mg/L,催化剂用量为1g/L,pH=9.8时,光照12min后,亚甲基蓝的降解率高达96%,且样品经5次循环使用后活性基本保持不变;而少量H2O2的添加对光催化活性影响不大,过量的H2O2会降低光催化活性;乙二胺四乙酸捕获空穴后比异丙醇捕获·OH后的光催化活性降得更低.同时,对Ag@AgBr等离子体光催化剂可见光降解亚甲基蓝的催化机理进行了分析.     

瓜环和金属改性的硫化镉光催化性质

以硫代乙酰胺为硫源,氯化镉为镉源,超声法制备银、钴离子掺杂的六元瓜环-硫化镉复合物。采用X射线粉末衍射、傅里叶变换红外光谱和扫描电子显微镜对催化剂结构和形貌进行表征,并进行催化降解染料的测试,考察Q[6]和金属离子对催化剂催化性能的影响。结果表明:采用瓜环复合和适量金属掺杂能使硫化镉可见光催化降解亚甲基蓝的性能显著提高约20%,且以瓜环对硫化镉协同增效作用为主。     

ZnO-based ternary nanocomposite for decolorization of methylene blue by photocatalytic dynamic membrane

In this article, novel Ag–ZnO/g-C₃N₄/GO ternary nanocomposites were prepared via co-precipitation method by 1%w Ag, 50% w g-C₃N₄, 10% w GO concentration and applied in dynamic membranes. The characteristics of Ag–ZnO/g-C₃N₄/GO nanocomposite were evaluated by various techniques such as X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray map, transmission electron microscopy, X-ray photoelectron spectroscopy, photocatalyst. The photocatalytic degradation of methylene blue was investigated under visible light. The photocatalytic efficiency of 93.43% for methylene blue degradation was obtained for Ag–ZnO/g-C₃N₄/GO nanocomposite after 50 min of irradiation, which was remarkably higher than that of pure ZnO, bare g-C₃N₄, Ag–ZnO, and Ag–ZnO/g-C₃N₄ at the same irradiation time. Likewise, in self-forming and pre-coated membranes, ternary nanocomposites can play a vital role in the membrane surface properties, as well as their decolorization performance. The rejection of methylene blue was 30% in pure polyethersulfone membrane, while the photocatalytic degradation of methylene blue in Ag–ZnO/g-C₃N₄/GO nanocomposites was 88.46% and 98.86% after 10 and 15 min of irradiation in both self-forming and pre-coated dynamic membranes, respectively. Experimental results show that the dynamic membrane possesses a higher ability for degradation of MB in a shorter period of time than the static system.     

One-step fabrication and high photocatalytic activity of porous graphitic carbon nitride/graphene oxide hybrid by direct polymerization of cyanamide without templates

Graphene oxide modified porous g-C₃N₄ (porous g-C₃N₄/GO) had been synthesized by means of one-step calcination of cyanamide for efficient photocatalysis under visible light irradiation (λ > 400 nm). We expect that the photocatalytic activity of this hybrid photocatalyst could be enhanced by the efficient visible light absorption due to the porous structure and efficient photo generated charge separation at the heterojunction formed between porous g-C₃N₄ and GO. Scanning electron microscopy (SEM) images demonstrated that the as prepared photocatalyst is composed of GO and porous g-C₃N₄. The UV-vis diffuse reflectance spectrum shows that optical absorption of porous g-C₃N₄/GO is more intensive than for pristine g-C₃N₄. The enhanced generation of photocurrent under visible light irradiation (λ > 400 nm) is observed for the porous g-C₃N₄/GO. The results of photocatalytic experiments reveal that the pseudofirst-order kinetic constant of photocatalytic degradation of methylene blue (MB) using the porous g-C₃N₄/GO is 6 times higher than that of pristine g-C₃N₄.     

Microwave-assisted synthesis of the Fe2O3/g-C3N4 nanocomposites with enhanced photocatalytic activity for degradation of methylene blue

The preparation and photocatalytic performance of the Fe₂O₃/g-C₃N₄ nanocomposites with different weight percentage of iron was investigated in this study. Samples were successfully synthesized using melamine and ferric nitrate as the precursors via the green and facile microwave-assisted method. The physicochemical and structural properties of the Fe₂O₃-doped g-C₃N₄ were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), the Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and ultraviolet–visible spectroscopy (UV–Vis). The photocatalytic activity of the Fe₂O₃/g-C₃N₄ catalysts was evaluated by the degradation of methylene blue (MB) at room temperature under visible light irradiation. As expected, the as-synthesized samples exhibited considerable improvement in the photodegradation of MB. The Fe₂O₃/g-C₃N₄ (1.0 wt%) nanocomposite had superior photocatalytic activity, with almost 70% degradation efficiency within 90 min of irradiation. The enhanced performance was ascribed to the separation and migration of the photoinduced electron–hole pairs and taking part of the charge carriers in the chemical redox reactions at the surface of the photocatalyst. In this work, the effect of Fe weight percentage on the degradation potential was also studied, and the photocatalytic mechanism was proposed with the main reactive species •OH.     

g-C3N4-BiOBr复合材料制备及可见光催化性能

利用原位沉积法将BiOBr纳米片生长到g-C₃N₄表面,制得g-C₃N₄-BiOBr p-n型异质结复合光催化剂。采用X射线衍射(XRD)、红外光谱(FTIR)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、紫外可见漫反射(UV-Vis-DRS)和荧光光谱(PL)等测试对光催化剂结构和性能进行表征。通过可见光辐照降解甲基橙水溶液检测评估复合光催化剂光催化活性。研究结果表明:复合光催化剂由BiOBr和g-C₃N₄两相组成,BiOBr纳米片在片状g-C₃N₄表面快速形核生长形成面-面复合结构。相比于纯相g-C₃N₄和BiOBr,g-C₃N₄-BiOBr复合材料具有更强可见光吸收能力,吸收带边红移。在可见光辐照100 min后,性能最佳的2:8 g-C₃N₄-BiOBr复合光催化剂光催化活性分别是纯相g-C₃N₄和BiOBr的1.8和1.2倍,经过4次循环实验后,其降解率仍达84%,说明复合结构光催化剂催化性能和稳定性增强。复合光催化剂的荧光强度显著降低,说明光生载流子复合得到了有效抑制。复合光催化剂催化性能的提高归因于p-n型异质结促进电荷有效分离、抑制电子-空穴复合和吸收光波长范围的扩展,相比单一成分材料具有更好的催化活性和稳定性。自由基捕获实验证明,可见光降解甲基橙光催化过程中的主要活性成分为空穴,并据此提出了可能的光催化机理。     

g-C3N4-BiOBr复合材料制备及可见光催化性能

利用原位沉积法将Bi OBr纳米片生长到g-C_3N_4表面,制得g-C_3N_4-Bi OBr p-n型异质结复合光催化剂。采用X射线衍射(XRD)、红外光谱(FTIR)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、紫外可见漫反射(UV-Vis-DRS)和荧光光谱(PL)等测试对光催化剂结构和性能进行表征。通过可见光辐照降解甲基橙水溶液检测评估复合光催化剂光催化活性。研究结果表明:复合光催化剂由Bi OBr和g-C_3N_4两相组成,Bi OBr纳米片在片状g-C_3N_4表面快速形核生长形成面-面复合结构。相比于纯相g-C_3N_4和Bi OBr,g-C_3N_4-Bi OBr复合材料具有更强可见光吸收能力,吸收带边红移。在可见光辐照100 min后,性能最佳的2:8 gC_3N_4-Bi OBr复合光催化剂光催化活性分别是纯相g-C_3N_4和Bi OBr的1.8和1.2倍,经过4次循环实验后,其降解率仍达84%,说明复合结构光催化剂催化性能和稳定性增强。复合光催化剂的荧光强度显著降低,说明光生载流子复合得到了有效抑制。复合光催化剂催化性能的提高归因于p-n型异质结促进电荷有效分离、抑制电子-空穴复合和吸收光波长范围的扩展,相比单一成分材料具有更好的催化活性和稳定性。自由基捕获实验证明,可见光降解甲基橙光催化过程中的主要活性成分为空穴,并据此提出了可能的光催化机理。     

In-situ polymerization for PPy/g-C3N4 composites with enhanced visible light photocatalytic performance

Polypyrrole-modified graphitic carbon nitride composites (PPy/g-C₃N₄) are fabricated using an in-situ polymerization method to improve the visible light photocatalytic activity of g-C₃N₄. The PPy/g-C₃N₄ is applied to the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Various characterization techniques are employed to investigate the relationship between the structural properties and photoactivities of the as-prepared composites. Results show that the specific surface area of the PPy/g-C₃N₄ composites increases upon assembly of the amorphous PPy nanoparticles on the g-C₃N₄ surface. Owing to the strong conductivity, the PPy can be used as a transition channel for electrons to move onto the g-C₃N₄ surface, thus inhibiting the recombination of photogenerated carriers of g-C₃N₄ and improving the photocatalytic performance. The elevated light adsorption of PPy/g-C₃N₄ composites is attributed to the strong absorption coefficient of PPy. The composite containing 0.75 wt% PPy exhibits a photocatalytic efficiency that is 3 times higher than that of g-C₃N₄ in 2 h. Moreover, the degradation kinetics follow a pseudo-first-order model. A detailed photocatalytic mechanism is proposed with ·OH and ·O₂^? radicals as the main reactive species. The present work provides new insights into the mechanistic understanding of PPy in PPy/g-C₃N₄ composites for environmental applications.     

Photocatalytic activity under visible light illumination of organic dyes over g-C3N4/MgAl2O4 nanocomposite

Using a grinding method, nanocomposites of graphitic carbon nitride (g-C₃N₄) and magnesium aluminate (MgAl₂O₄) spinel were successfully synthesized for the photocatalytic degradation of methylene blue (MB) and methyl orange (MO). Variously formulated g-C₃N₄/MgAl₂O₄ nanocomposites were characterized by thermal gravimetric analysis (TGA), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM) and surface area and micropore analysis (BET surface area). The g-C₃N₄ powder exhibited a nanosheet structure whereas the MgAl₂O₄ spinel comprised agglomerated nanoparticles. The optical properties of the g-C₃N₄/MgAl₂O₄ nanocomposites were investigated by diffuse reflectance spectroscopy (DRS). As the g-C₃N₄ loading content increased from 0 to 30%, the optical band gap energy of the nanocomposite decreased from 3.84 to 2.86 eV, the specific surface area decreased from 153.78 to 114.45 m²/g, and the porosity decreased from 0.447 to 0.347 cm³/g. A 20%g-C₃N₄/MgAl₂O₄ nanocomposite proved to be the most effective photocatalyst and degraded MB faster and more completely than MO. The degradation rates of both MO (0.0107 min^?1) and MB (0.0386 min^?1) in a mixed MO-MB system were greater than the degradation rates in their single systems. The key factor that improved the photocatalytic degradation of MO was the synergistic effect whereas the synergistic effect and photosensitization were the key factors that enhanced the photocatalytic degradation of MB. The g-C₃N₄/MgAl₂O₄ nanocomposite is suitable for the photocatalytic degradation of mixed dyes because its point of zero charge is neutral and it is stable and recyclable.     

碳纳米管改性g-C3N4提升可见光催化降解性能

以尿素为原料,引入少量的多壁碳纳米管(CNT)改性,采用简便方法制备CNT/g-C_3N_4催化剂。利用扫描电镜(SEM)、透射电镜(TEM)、傅里叶红外光谱仪(FT-IR)、X射线衍射(XRD)、X射线光电子能谱(XPS)、紫外-可见-近红外分光光度计(UV-Vis-NIR Spectrophotometer)、荧光光谱(PL)等手段对CNT/g-C_3N_4催化剂进行表征。结果表明,g-C_3N_4与CNT之间的协同作用,影响了gC_3N_4的能带结构,增强了其对可见光的吸收,改善了光生载流子的分布,提高了电子-空穴对的分离效率。并以罗丹明B(RhB)水溶液模拟废水,在可见光下考察催化剂的光催化降解性能,发现当CNT掺杂量为0.1%(w/w)时效果最佳,降解速率常数是体相g-C_3N_4的3.1倍,且研究发现超氧自由基是该体系下的主要活性物种。     

Novel visible-light-driven photocatalyst of NiO/Cd/g-C3N4 for enhanced degradation of methylene blue

Novel NiO/Cd/g-C₃N₄ photocatalysts were synthesized using a green and straightforward microwave-assisted method and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), the Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and ultraviolet–visible spectroscopy (UV–Vis). The ternary NiO/Cd/g-C₃N₄ nanocomposites were evaluated for the degradation of methylene blue (MB) at room temperature under the visible light irradiation. Experimental results revealed that the weight percent of cadmium had a remarkable effect on the photodegradation efficiency. The NiO/Cd/g-C₃N₄ (0.1%) sample exhibited superior activity in the degradation reaction. The activity of this nanocomposite was about 4.5 and 3.25 fold higher than those of the pure g-C₃N₄ and NiO/g-C₃N₄ samples in the degradation of MB, respectively. The enhanced photocatalytic activity was attributed to the low energy gap, increased absorption capacity of the visible light, and efficient suppression of the recombination of photogenerated electron-hole pairs. A detailed photocatalytic mechanism over the nanocomposite of NiO/Cd/g-C₃N₄ (0.1%) was proposed with superoxide radical anion O₂^– as the main reactive species. The stability of the nanocomposite was confirmed after four consecutive runs as well.     

Novel PtPd alloy nanoparticle-decorated g-C3N4 nanosheets with enhanced photocatalytic activity for H2 evolution under visible light irradiation

PtPd bimetallic alloy nanoparticle (NP)-modified graphitic carbon nitride (g-C₃N₄) nanosheet photocatalysts were synthesized via chemical deposition precipitation. Characterization of the photocatalytic H₂ evolution of the g-C₃N₄ nanosheets shows that it was significantly enhanced when PtPd alloy NPs were introduced as a co-catalyst. The 0.2 wt% PtPd/g-C₃N₄ composite photocatalyst gave a maximum H₂ production rate of 1600.8 μmol g^–1 h^–1. Furthermore, when K₂HPO₄ was added to the reaction system, the H₂ production rate increased to 2885.0 μmol g^–1 h^–1. The PtPd/g-C₃N₄ photocatalyst showed satisfactory photocatalytic stability and was able to maintain most of its photocatalytic activity after four experimental photocatalytic cycles. In addition, a possible mechanism for the enhanced photocatalytic activity was proposed and verified by various photoelectric techniques. These results demonstrate that the synergistic effect between PtPd and g-C₃N₄ helps to greatly improve the photocatalytic activity of the composite photocatalyst.