Synthesis and photocatalytic H2-production activity of plasma-treated Ti3C2Tx MXene modified graphitic carbon nitride

Plasma processing technology, as a promising method to enhance photocatalytic activity of catalyst, is gradually attracting extensive interest from researchers. However, the main mechanism of plasma-treated photocatalyst on hydrogen production is not clear. In this work, 2D Ti₃C₂T_x MXene is selected as a co-catalyst of graphitic carbon nitride (g-C₃N₄), which carries out a plasma treatment (500°C) under N₂/H₂ atmosphere. Due to plasma treatment, there is a higher proportion Ti–O functional groups on surface of layered Ti₃C₂T_x MXene, especially for Ti⁴⁺. The obtained g-C₃N₄/p-Ti₃C₂T_x photocatalyst with sandwich-like structure shows an enhanced photocatalytic activity. The rate of hydrogen generation of CN/pTC3.0 sample without Pt co-catalyst is 25.4 and 2.4 times that of pure g-C₃N₄ and CN/TC3.0 samples, respectively. The improved photocatalytic activity is attributed to presence of Ti⁴⁺ due to plasma treatment, which can capture photo-induced electron from g-C₃N₄ and improve the separation of electrons and holes after visible light irradiation. The cyclic hydrogen production of the photocatalyst demonstrates good photocatalytic stability. In addition, this method of plasma treatment under N₂/H₂ atmosphere is feasible to develop a high-performance co-catalyst, which can be extended to other photocatalysts with two-dimensional structure for photocatalytic water-splitting applications.     

Tailoring the bandgap of N-rich graphitic carbon nitride for enhanced photocatalytic activity

Nitrogen - rich graphitic carbon nitride (Ng-C₃N₄) with improved photocatalytic activity was engineered using a facile post-annealing treatment of pristine g-C₃N₄ in N₂ atmosphere. The thermal annealing did not modify the crystal structure, vibrational modes, or morphology of the N-rich g-C₃N₄ (Ng-C₃N₄). However, it decreased the crystallinity by broadening the dominant X-ray diffraction (XRD) peak and increased the surface area and mesoporous nature because of the formation of carbon vacancies. Diffuse reflectance spectroscopy indicated that the bandgap of the annealed Ng-C₃N₄ decreased from 2.82 to 2.77 eV compared to pristine g-C₃N₄. The increase of nitrogen content in the annealed Ng-C₃N₄ was quantified by X-ray photoelectron spectroscopy (XPS), which was also used to examine the formation of carbon vacancies. Photocurrent and electrochemical impedance spectroscopy measurements showed that the annealed Ng-C₃N₄ had higher light absorption capacity than the pristine g-C₃N₄. The photocatalytic performance of the samples was investigated for the degradation of crystal violet (CV) under ultra-violet light irradiation. The annealed Ng-C₃N₄ sample exhibited superior photodegradation of CV over pristine g-C₃N₄.     

煤基碳量子点/氮化碳复合材料制备及其光催化还原CO2性能

以太西无烟煤为原料,采用化学氧化法制备煤基碳量子点(C-CQDs),进一步以C-CQDs和尿素为前体,原位复合制备得到煤基碳量子点/氮化碳(C-CQDs/g-C₃N₄)复合材料。采用TEM、XRD、FT-IR、UV-Vis、PL等手段对样品结构性能进行了表征和分析,进而考察了其在光催化还原CO₂合成甲醇过程的催化性能。研究表明：C-CQDs均匀地负载在g-C₃N₄的表面,且掺杂适量的C-CQDs有利于提高C-CQDs/g-C₃N₄的光催化活性,当可见光照12 h时,其光催化还原CO₂甲醇产量最高可达28.69 μmol/(g cat),约为相同条件下纯石墨相g-C₃N₄作用时甲醇产量的2.2倍。     

硫酸根改性g-C3N4制备与催化性能研究

采用酸水热后处理法制备了具有优异光催化合成双氧水性能的硫酸根改性石墨相氮化碳纳米棒催化剂。采用XRD、N2吸附脱附、UV-Vis、FTIR、SEM、XPS、TPD、EIS及PL对催化剂进行表征。结果显示：硫酸根的引入改变了催化剂的结构性质，光学性质和氧气吸附能力。所制备的硫酸根改性氮化碳催化剂的双氧水平衡浓度为2.7 mmol/L，是纯氮化碳的2.7倍。     

Tetraethylorthosilicate induced preparation of mesoporous graphitic carbon nitride with improved visible light photocatalytic activity

Mesoporous graphitic carbon nitride (mg-C₃N₄) has been prepared by the in situ formed silica from tetraethylorthosilicate (TEOS) as a mesoporous template. The resultant mg-C₃N₄ possessed a large surface area (152 m² g^− 1), and enhanced photodegradation performance for Rhodamine B pollutant when energized with visible light. Moreover, mg-C₃N₄ also exhibited good stability after three recycles. The significant enhancement in photodegradation activity over mg-C₃N₄ catalyst could be ascribed to the large surface area, high adsorption ability to dye and enhanced separation efficiency of photogenerated electron-hole pairs. The simple strategy for the fabrication of mg-C₃N₄ may facilitate its wide applications in various fields.     

钴掺杂聚合氮化碳光催化还原二氧化碳性能研究

聚合氮化碳(CN)具有可见光响应、化学性质稳定、廉价易得、无毒等优点,在光催化领域得到了广泛的研究和应用,但是存在比表面积较小、电子-空穴对易复合等不足之处,严重限制了其光催化性能。以尿素和常见的两种钴盐[CoCl₂和Co(NO₃)₂]为前驱体,通过一步煅烧法制备了钴(Co)掺杂CN,研究了不同Co源对材料光催化还原二氧化碳(CO₂)性能的影响。实验证明,由适量氯化钴(CoCl₂)为Co源得到的Co掺杂CN,其光催化还原CO₂生成一氧化碳(CO)的速率可由纯CN的82.7μmol/(g·h)提升至374.5μmol/(g·h),同时CO选择性由79.1%提高至88.5%;而以硝酸钴[Co(NO₃)₂]为Co源得到的Co掺杂CN倾向于产氢,其光催化还原CO₂性能基本不能得到提升。通过对光催化剂进行电感耦合等离子体(ICP)、X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、X射线光电子能谱(...     

Facile synthesis of Y-doped graphitic carbon nitride with enhanced photocatalytic performance

Yttrium-doped graphitic carbon nitride (Y/g-C₃N₄) catalysts were prepared via a facile pyrolysis method with urea used as a precursor and yttrium nitrate as the Y source. Characterization results show that an appropriate doping ratio of Y can be embedded into in-planes of g-C₃N₄. The Y/g-C₃N₄ catalysts are characterized by hierarchical porosity, large specific surface area, and large pore volume. Introduction of Y species effectively extends the spectral response of g-C₃N₄ from ultraviolet to visible region and decelerates the recombination of photogenerated electrons and holes. Because of these properties, the Y/g-C₃N₄ catalysts show an enhanced photocatalytic performance in rhodamine B degradation under visible light.     

铁基催化剂光催化还原CO2研究进展

利用可再生清洁能源——太阳能,将CO₂转化为一氧化碳、甲烷、甲醇等,因同时具有提供可持续燃料和解决全球变暖问题的潜力而受到越来越多的关注。铁基材料因具有金属/半导体的特性和独特的电子结构,在光催化还原CO₂领域具有广阔的应用潜力。基于此,各种具有高催化活性的铁基催化剂已经被设计来提高光催化还原CO₂的效率。概述了近年来铁基催化剂在光催化还原二氧化碳中的研究进展,对它们的结构特征和催化活性进行了阐述和比较,最后总结了铁基催化剂在光催化还原CO₂领域中待解决的问题,并展望了未来发展的方向。     

Onion-like carbon modified porous graphitic carbon nitride with excellent photocatalytic activities under visible light

A series of onion-like carbon modified porous g-C₃N₄ (OLC/pg-C₃N₄) composites have been fabricated by a simple ultrasonic adsorption approach. The resultant OLC/pg-C₃N₄ composites exhibit excellent photocatalytic activity and stability towards the degradation of the dyes and phenol in aqueous solution under visible-light irradiation. The composite with 2.0 wt% OLC content shows the optimal photocatalytic activity for degrading rhodamine B (RhB), its rate constant is about three times that of pure pg-C₃N₄. The improved photocatalytic activity is mainly attributed to the synergetic effect of pg-C₃N₄ and OLC, including larger surface area, stronger visible light adsorption and efficient separation of photogenerated electrons and holes. Moreover, a possible mechanism of photocatalytic reaction over OLC/pg-C₃N₄ composite is proposed.     

Ti基CO2光催化还原及其影响因素研究进展

综述了Ti基CO2光催化还原的研究进展,简要介绍了近年来用于光催化还原CO2的Ti基催化剂,包括纯TiO2催化剂、金属掺杂TiO2催化剂、非金属掺杂TiO2催化剂、共掺杂TiO2催化剂、Ti基纳米复合催化剂、有机光敏化剂修饰TiO2催化剂及其它TiO2催化剂等,比较了各类TiO2基催化剂光催化活性,介绍了其相应的反应机理及优缺点,讨论了光照时间、反应温度、CO2分压力、H2O和CO2摩尔比、光反应器等因素对光催化活性的影响。通过综合运用多种改性措施,开发高效Ti基催化剂并优化反应系统以提高光催化反应活性及光利用率将会成为CO2光催化还原领域重点研究内容与发展趋势,最后展望了利用该技术光催化还原工业烟气,尤其是富氧燃烧烟气的潜在应用前景与挑战。     

Preferential CO oxidation over activated carbon supported catalysts in H2-rich gas streams containing CO2 and H2O

Selective CO oxidation (PROX) was studied at 423 K over 1% Pt–0.25% SnO_x and 1% Pt–1% CeO_x catalysts supported on un-oxidized and oxidized activated carbon (AC) using feed mixtures simulating the reformate coming from fuel processors. Effects of the addition of 15% CO₂ or (15% CO₂ + 10% H₂O) into feed mixtures containing 1% CO, 1% O₂, 60% H₂ and He were determined for nine different AC-supported catalysts, and the results were compared with those obtained with pure H₂-rich feed. Unlike other PROX catalysts having oxide supports, introduction of CO₂ into pure feed drastically increased CO conversion on all nine catalysts supported on oxidized or un-oxidized AC regardless of impregnation strategy.1% Pt–0.25% SnO_x supported on HNO₃-oxidized AC stands out as a potential candidate for commercial use in PROX since it yields 100% CO conversion under realistic feed conditions. 1% Pt–1% CeO_x catalysts prepared by sequential or co-impregnation and supported on air-oxidized AC also give 100% CO conversion in H₂-rich feed containing (CO₂ + H₂O) during extended run times and hence hold promise as PROX catalysts.     

稀土掺杂TiO2光催化还原CO2

采用溶胶-凝胶法制备了稀土掺杂TiO₂纳米光催化剂,并应用于光催化还原CO₂/H₂O体系中。通过XRD对光催化性能进行表征,研究稀土离子掺杂和焙烧温度对光催化性能的影响。结果表明,稀土La和Ce的加入可以抑制TiO2的晶相转变,提高光催化性能。催化剂800 ℃焙烧可达到最好的光催化活性,在反应时间7 h、CO₂流量200 mL·min^-1和反应液中NaOH与Na₂SO₃浓度均为0.10 mol·L^-1条件下,甲醇产率高达315.49 μmol·g^-1。并对稀土掺杂TiO₂催化剂光催化还原CO₂的机理进行了探究。     

Controlled synthesis of graphitic carbon nitride/beta bismuth oxide composite and its high visible-light photocatalytic activity

g-C₃N₄/β-Bi₂O₃ composites with high visible-light-driven photocatalytic activity were prepared through calcination of g-C₃N₄/Bi₂O₂CO₃ of different proportions. They were characterized by powder X-ray diffraction (XRD), Fourier Translation infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy TEM (high resolution transmission electron microscopy HRTEM), UV–vis diffuse reflectance spectra (UV–vis DRS) and photoluminescence spectra (PL) techniques. It was observed that the phase structure of Bi₂O₃ is subject to the amount of g-C₃N₄ in the g-C₃N₄/Bi₂O₂CO₃ precursor. Based on the results of light absorption and photocurrent measurement as well as the energy levels of β-Bi₂O₃ and g-C₃N₄, we propose a mechanism for the degradation of organic compounds over this class of catalysts.     

Enhanced mechanical and photocatalytic performances of epoxy nanocomposites filled with potassium-modified graphitic carbon nitride nanosheets

The unique structure and property of K⁺-modified graphitic carbon nitride (K-CN) nanosheets would be beneficial for developing advanced epoxy nanocomposites. However, the compatibility between K-CN nanosheets and epoxy matrix is a big challenge. In this study, we demonstrate a new and effective method to improve the compatibility of K-CN nanosheets and epoxy by using 1-(oxiran-2-ylmethyl)-1H-indole (IN) as surface modifier through the cation-π interaction between K⁺ on the surface of K-CN nanosheets and indole group of IN. In addition, the covalent bond between epoxy group of IN and amino group of curing agent could be used to participate in the formation of the epoxy network. When the content of K-CN nanosheets is 0.5 wt%, the tensile strength of prepared epoxy nanocomposites increases by 60.7% and extensibility of prepared epoxy nanocomposites increases by 53.4% compared to neat epoxy resin. In addition, the prepared epoxy nanocomposites are used as efficient reusable photocatalysts for degradation of methylene blue (MB). The efficiency of MB degradation is 98% within 60 min. This work opens up a new avenue to fabricate high-performance epoxy nanocomposites with multifunctional properties for advanced engineering applications.     

Explosive thermal exfoliation of intercalated graphitic carbon nitride for enhanced photocatalytic degradation properties

Dicyandiamide derived graphitic carbon nitride (g-C₃N₄) was chemically intercalated by concentrated H₂SO₄ firstly, followed by a rapid heating treatment. Molecules between the stacking layers of g-C₃N₄ produced an explosive effect upon rapid heating to thermally exfoliate g-C₃N₄ into porous structures. The appearance color of g-C₃N₄ changed from light yellow to grey after heating treatment indicating the enhanced light absorption properties, which were identified by the UV–vis absorption test. In addition, photoluminescence intensities of porous g-C₃N₄ were obviously suppressed compared to those of bulk g-C₃N₄ samples, indicating the prevention of the recombination process of photogenerated electron-hole pairs. As a result of these simultaneous modifications in texture, optical and electronic properties, the photodegradation kinetics of crystal violet on the catalyst surface can be improved by 4.75 times.     

氨基修饰片状氮化碳的制备及光催化性能

石墨相氮化碳是一种低成本易获得的可见光响应光催化剂,但由于比表面积小、光生载流子易复合等缺点限制了其应用。为克服传统氮化碳的缺陷,本实验以尿素和三聚氰胺为原料,通过水热预处理改性前体,再用高温煅烧法成功制备出氨基修饰片状氮化碳光催化材料。并通过X射线衍射（XRD）、扫描电子显微镜（SEM）和X射线光电子能谱仪（XPS）等手段对样品的晶格结构和形貌特征等进行表征。结果表明,成功引入氨基基团的片状氮化碳,比表面积增加且光生载流子复合率显著降低。以罗丹明B和壬基酚溶液的光降解考察材料光催化性能,发现氨基修饰片状氮化碳对其去除率分别为80.69%和50.7%,分别是传统块状氮化碳的2.45倍和2.19倍,是未修饰片状氮化碳的1.26倍和1.21倍。且氨基修饰片状氮化碳材料重复使用5次后仍具有较高光催化活性,光催化性能显著提高。     

薄层氮化碳光催化还原CO_2性能研究

以氮化碳(g-CN)为原料,采用水蒸汽焙烧剥离法在Ar/H2O氛围下制备薄层氮化碳(Hg-CN),并对其进行XRD、TEM、FT-IR、BET和UV-Vis DRS等表征。结果表明,进行剥离后,H-g-CN比表面积相比剥离前明显增大。H-g-CN的光催化还原CO_2活性大大高于未剥离gCN的活性,光照反应9 h,H-g-CN光催化还原CO_2活性由剥离前的11. 4μmol·g~(-1)提高至24. 6μmol·g~(-1),H-g-CN的CO选择性为91. 2%,未剥离的g-CN的CO选择性为89. 1%,并提出相应的反应机理。     

二维石墨相氮化碳纳米片的制备及其光催化性能

摘要：利用水热反应法,将三聚氰胺悬浊液在200 ℃下反应生成中间产物,然后煅烧中间产物直接制成了二维石墨相氮化碳g-C3N4纳米片（WCN）,并与本体g-C3N4(CN)、传统热氧剥离法得到的g-C3N4纳米片（OCN）进行了比较。采用SEM、XRD、FTIR、Raman、AFM、PL仪等对催化剂进行了表征,探讨了催化剂的光电化学性能和光催化性能。结果表明：两种方法均实现了对CN的剥离,WCN和OCN二维纳米片与CN 晶体结构和组成相同,WCN和OCN的比表面积分别是CN的4倍和3倍。光电化学分析显示WCN有更好的载流子的迁移与分离效率,具有较好的光催化活性。在可见光条件下,WCN对亚甲基蓝（MB）的光催化降解率达到82％,分别是OCN和CN的2.4 倍和6.7 倍,光催化降解过程符合一级动力学方程。WCN具有优良的稳定性和可重复利用性能。