Ni5P4/g-C3N4复合光催化剂的制备及光催化性能

使用尿素、 红磷和氯化镍为原料, 通过一种简单的焙烧方法合成了Ni₅P₄/g-C₃N₄光催化剂. 该催化剂形成的异质结可以降低界面电阻, 有效抑制光生电子-空穴对复合率. 以罗丹明B模拟污染物进行降解测试, 发现3NPC的反应速率常数最高, 几乎是g-C₃N₄的7倍, 并具有最高的光催化产氢能力, 制氢速率高达1013.88 μmol·g^-1·h^-1, 明显高于g-C₃N₄(664.38 μmol·g^-1·h^-1).     

不同半导体体系中磷化镍光催化甲酸分解的助催化作用

研究了在不同的半导体体系(TiO₂, CdS和C₃N₄)中, Ni₂P光催化甲酸(HCOOH)分解制氢的助催化效应. 作为助催化剂, Ni₂P与3种半导体形成的复合光催化剂均表现出良好的HCOOH分解制氢活性. Ni₂P/TiO₂, Ni₂P/CdS, Ni₂P/C₃N₄ 3种光催化剂最优的产氢活性分别为41.69, 22.45和47.67 μmol·mg^-1·h^-1, 分别为纯TiO₂, CdS和C₃N₄的3.8倍、 10倍和210倍, 表明Ni₂P在光催化HCOOH分解制氢体系中具有普适性. 研究了光催化HCOOH分解制氢的机理, Ni₂P的加入使光生电子从半导体转移至Ni₂P, 提高了光生电子-空穴对的分离效率; Ni₂P还促进了活性物种·OH的生成, 提高了光催化HCOOH分解的产氢速率.     

亚甲基蓝嵌入的供体受体型g-C3N4纳米片光催化剂用于产H2(英文)

石墨相氮化碳(g-C₃N₄)是一种优异的产H₂光催化剂,但是其存在载流子分离效率低、光吸收能力较差和比表面积小的问题。本研究通过对二氰二胺和亚甲基蓝(MB)进行热共聚合,结合后续热剥离策略,成功合成了一种新型分子内供体-受体(D-A)结构g-C₃N₄纳米片光催化剂。实验结果和密度泛函理论(DFT)计算表明,将亚甲基蓝掺入g-C₃N₄框架中扩大了光吸收范围,促进了载流子的分离。此外,热剥离增加了催化剂的比表面积且进一步促进了载流子的分离。因此,D-A结构g-C₃N₄纳米片显示出大幅提升的光催化产氢活性(2275.6μmol·h^-1·g^-1),分别是块状g-C₃N₄、D-A结构g-C₃N₄、g-C₃N₄纳米片的5.30,2...     

原位光沉积制备Z型α-Fe2O3/g-C3N4异质结及其可见光驱动光解水产氢性能

采用原位光沉积-煅烧法制得了Z型α-Fe₂O₃/g-C₃N₄异质结复合光催化剂。分别采用透射电子显微镜、X射线衍射、X射线光电子能谱、紫外可见漫反射光谱、荧光光谱以及电化学测试对样品进行了表征,并考察了可见光下光解水产氢活性。结果表明:当α-Fe₂O₃的负载量为2.9%时,α-Fe₂O₃/g-C₃N₄复合光催化剂具有最优的产氢催化活性,产氢速率高达1841.9μmol·g^-1·h^-1,约为g-C₃N₄的3.3倍。光催化性能的提高主要归因于3方面:(1)高温煅烧过程中α-Fe₂O₃的形成,有效促进了氮化碳片层的热剥离,增大了比表面积,从而为光催化反应提供了更多反应活性位;(2)超细α-Fe₂O₃颗粒(5~8 nm)高度均匀地分散在g-C₃N₄表面,并且与其紧密结合,形成了高质量的Z型异质结;(3)Z型异质结不仅有效抑制地了光生载流子的复合,同时极大地保留了g-C₃N₄导带电子的强还原性和α-Fe₂O₃价带空穴的强氧化性。     

金属相1T´ MoS2增强类石墨相C3N4的可见光催化性能

通过煅烧和静电自组装的方法制备了1T′ MoS₂超薄纳米片和类石墨烯相氮化碳(g-C₃N₄)纳米片的复合材料. 该材料在光催化实验中展现出6.24 μmol?g^?1?h^?1的产氢速率, 优于贵金属铂修饰的g-C₃N₄纳米片的性能(4.64 μmol?g^?1?h^?1). 此外, 该复合材料在光催化降解有机染料甲基橙的实验中表现出0.19 min^?1的催化速率, 而纯g-C₃N₄纳米片只有0.053 min^?1的催化速率. 材料光催化性能的提升可归结于1T′MoS₂ 和g-C₃N₄之间的协同效应, 包括光吸收的增强以及因1T′MoS₂优异电子导电性而得到的高效电荷分离.     

高分散Co0.2Ni1.6Fe0.2P助催化剂改性P掺杂g-C3N4纳米片高效光催化析氢的研究

随着化石燃料使用的增加和温室气体排放量持续上升,20世纪以来气温上升得更快。开发环境友好型能源取代传统化石燃料是当务之急。氢能源作为一种清洁、高效的能源,被认为是最有希望取代传统化石燃料的能源。光催化水分解水产氢作为为一种环保型技术被认为是最有前景的氢能生产方法。提高光生电子-空穴对分离效率是构建高效光催化剂的关键。然而,利用高度分散的助催化剂构建高效、稳定的产氢光催化剂仍然是一个挑战。本文首次成功地采用一步原位高温磷化法制备了高度分散的非贵金属三金属过度金属磷化Co_0.2Ni_1.6Fe_0.2P助催化剂(PCNS-CoNiFeP)掺杂P的石墨相氮化碳纳米片(PCNS)。有趣的是,PCNS-CoNiFeP与传统氢氧前驱体磷化法制备的CoNiFeP相比,没有聚集性,分散性高。X射线衍射(XRD)、X射线光电子能谱(XPS)、元素映射图像和高分辨率透射电镜(HRTEM)结果表明,PCNS-CoNiFeP已成功合成。紫外-可见吸收光谱结果表明,PCNS-CoNiFeP在200–800 nm波长范围内较PCNS略有增加。光致发光光谱、电化学阻抗谱(EIS)和光电流分析结果表明,CoNiFeP助催化剂能有效促进光生电子-空穴对的分离,加速载流子的迁移。线性扫描伏安法(LSV)结果还表明,负载CoNiFeP助催化剂可大大降低CNS的过电位。结果表明,以三乙醇胺溶液为牺牲剂的PCNS-CoNiFeP最大产氢速率为1200 μmol·h^-1·g^-1,是纯CNS-Pt (320 μmol·h^-1·g^-1)的4倍。在420 nm处的表观量子效率为1.4%。PCNS-CoNiFeP在光催化反应中也表现出良好的稳定性。透射电镜结果表明,6–8 nm的CoNiFeP高度分散在PCNS表面。高度分散的CoNiFeP比聚集的CoNiFeP具有更好的电荷分离能力和更高的电催化析氢活性。由此可见,聚合的CoNiFeP-PCNs (300 μmol·h^-1·g^-1)的产氢速率远低于PCNS-CoNiFeP。此外,CNS的P掺杂可以改善其电导率和电荷传输。     

熔盐辅助法制备g-C3N4纳米结构及其光催化制氢性能

以尿素作为原料, 采用熔盐辅助热聚合法在KCl-NaCl-BaCl₂体系中制备了带隙可调的g-C₃N₄纳米结构. 采用X射线衍射仪、 扫描电子显微镜、 X射线光电子能谱仪、 紫外-可见漫反射光谱仪及荧光光谱仪对产物的结构、 形貌、 成分及光学性能进行了表征. 对g-C₃N₄纳米结构可见光条件下的光催化制氢性能进行了测试, 研究了不同的尿素/熔盐比对其光催化性能的影响. 结果表明, 熔盐辅助热聚合法制备的g-C₃N₄ 纳米结构吸收光谱出现明显宽化, 吸收边由普通热聚合法制备g-C₃N₄的约450 nm红移至约500 nm左右. 同时光生载流子复合几率明显降低, 从而有效提升其光催化制氢性能. 最优化的g-C₃N₄(60)样品析氢速率达到12301.1 μmol?g^?1?h^?1, 为普通热聚合法制备g-C₃N₄析氢速率的4倍.     

B,N共掺杂的In2O3/TiO2制备与光催化产氢性能研究

为拓宽TiO₂的光吸收范围以及提高光生载流子的利用率,本工作利用B,N共掺杂改性的方法,通过聚合物前驱体法设计并制备了In₂O₃改性的TiO₂光催化剂.在前驱体合成中引入了聚乙二醇（PEG）作为致孔剂.PEG在前驱体转化为无机氧化物的热处理过程中分解离去、形成介孔等不同尺度的孔隙,提高了样品的比表面积.异质结结构在产物中得到有效构筑,带隙宽度由P25的3.09 eV缩窄至2.71 eV（样品IT-500,500℃退火产物）.B,N掺杂进入TiO₂晶格内,形成了Ti-N-B和Ti-O-B结构,同时也存在N的填隙掺杂,有助于带隙的缩窄、并拓宽可见光吸收范围.In₂O₃/TiO₂异质结结构的构筑,促进了电子-空穴对的分离与转移,提高了光生载流子的利用率.在大于380 nm可见光的照射下,样品IT-500的可见光催化产氢速率达到了5961 μmol·g^-1·h^-1,催化剂经过分离回收后进行循环实验,仍能保持良好的光催化活性.为了进一步提高其回收性,利用气纺丝制备了B,N掺杂的In₂O₃/TiO₂纳米纤维棉,在最佳焙烧温度500℃下,所获得的纤维棉状光催化剂的氢气产生速率达到1186 μmol·g^-1·h^-1,纤维棉简化了回收再利用的过程,经过5次循环实验后仍能达到初始产氢速率的97%.     

Au/N-g-C3N4复合材料的制备及其可见光催化产氢性能

首先以尿素和柠檬酸作为前驱体,通过热处理工艺合成N掺杂的g-C₃N₄(N-g-C₃N₄),然后利用化学还原的方法将Au沉积到N-g-C₃N₄表面,形成Au修饰的N掺杂的g-C₃N₄复合光催化材料(Au/N-g-C₃N₄)。通过XRD、XPS、TEM、UV-Vis和光电流测试对其进行了表征,与同等条件下制备的N-g-C₃N₄和g-C₃N₄相比,Au/N-g-C₃N₄具有更强的光吸收性能和更大的光电流。同时对材料的可见光产氢性能进行了研究,结果发现：当Au含量为1%时,复合材料呈现最佳的光催化产氢性能,其产氢速率为974μmol·g^-1·h ^-1,为N-g-C₃N₄     

ZnIn2S4/g-C3N4复合材料的制备及可见光催化制氢性能

采用水热方法制备了ZnIn₂S₄/g-C₃N₄复合材料, 并通过X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 紫外-可见漫反射光谱(UV-Vis DRS)、 透射电子显微镜(TEM)和荧光光谱(PL)等手段对其结构和性能进行表征. 结果表明, 当ZnIn₂S₄的负载量为20%(质量分数)时, 复合材料表现出最佳的光催化制氢性能, 制氢速率可达到637.08 μmol·g^-1·h^-1, 分别为纯ZnIn₂S₄和纯g-C₃N₄的4倍和37倍. 其原因在于ZnIn₂S₄和g-C₃N₄之间具有紧密的异质结结构, 两者有效的结合改善了组分的能带匹配和界面电荷转移, 从而大幅增强了载流子的分离和迁移, 进而提高光催化的性能.     

非贵金属助剂Ni2P修饰类石墨碳氮化物光催化剂增强可见光光催化产氢性能

Energy crisis has become a serious global issue due to the increasing depletion of fossil fuels; therefore, it is crucial to develop environmentally friendly and renewable energy resources, such as hydrogen (H₂), to replace fossil fuels. From this viewpoint, photocatalytic H₂ production is considered as one of the most promising technologies. Noble metal platinum (Pt) can be applied as an efficient cocatalyst for improving the H₂ production performance of photocatalytic systems; however, its high cost limits its further application. Thus, the development of novel, high-activity, and low-cost cocatalysts for replacing noble metal cocatalysts is of great significance for use in photocatalytic H₂ evolution techniques. Herein, we successfully synthesized a Ni₂P/graphite-like carbonitride photocatalyst (Ni₂P/CN) using a conjugated polymer (SCN)_n as precursor for enhanced photocatalytic H₂ production under visible light illumination. Various characterization techniques, including optical and photoelectronic chemical tests, were used to investigate the structural composition, morphology, and light adsorption ability of these materials. X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy results showed that Ni₂P/CN nanocomposites with good crystal structure were obtained. Scanning electron microscopy and transmission electron microscopy results revealed that the Ni₂P/CN samples had a typical two-dimensional layered structure, and the Ni₂P nanoparticles were uniformly loaded on the surface of the CN to form a non-noble metal promoter. UV-Vis diffuse reflectance spectra results demonstrated that the loading of Ni₂P nanoparticles effectively enhances the adsorption capacity of CN to visible light. Photoluminescence spectroscopy and photocurrent (PL) results suggested that Ni₂P loading to CN is beneficial for promoting the migration and separation efficiency of photogenerated carriers. Photocatalytic H₂ production was conducted under visible light irradiation with triethanolamine as a sacrificial agent. The results suggest that the Ni₂P/CN composite photocatalysts exhibit excellent photocatalytic reduction performance. In particular, the H₂ evolution rate of the optimal Ni₂P/CN nanocomposite is 623.77 μmol·h^-1·g^-1, which is higher than that of CN modified by noble metal Pt, i.e., 524.63 μmol·h^-1·g^-1. In conclusion, Ni₂P nanoparticles are homogeneously attached to the surface of CN, and a strong interfacial effect exists between them, thereby forming an electron transfer tunnel that greatly inhibits the recombination of photoinduced carriers and promotes the migration of electrons from CN to Ni₂P. In addition, a possible photocatalytic mechanism is proposed based on the experiments and characterizations. This work has profound significance for developing non-noble metal cocatalysts for the substitution of noble metal cocatalysts for high-efficiency photocatalytic H₂ evolution.      

二维/二维FeNi-LDH/g-C3N4复合光催化剂用于促进CO2光还原反应

Photocatalytic reduction of carbon dioxide into chemical fuels is a promising route to generate renewable energy and curtail the greenhouse effect. Therefore, various photocatalysts have been intensively studied for this purpose. Among them, g-C₃N₄, a 2D metal-free semiconductor, has been a promising photocatalyst because of its unique properties, such as high chemical stability, suitable electronic structure, and facile preparation. However, pristine g-C₃N₄ suffers from low solar energy conversion efficiency, owing to its small specific surface area and extensive charge recombination. Therefore, designing g-C₃N₄ (CN) nanosheets with a large specific surface area is an effective strategy for enhancing the CO₂ reduction performance. Unfortunately, the performance of CN nanosheets remains moderate due to the aforementioned charge recombination. To counter this issue, loading a cocatalyst (especially a two-dimensional (2D) one) can enable effective electron migration and suppress electron-hole recombination during photo-irradiation. Herein, CN nanosheets with a large specific surface area (97 m²·g^-1) were synthesized by a two-step calcination method, using urea as the precursor. Following this, a 2D/2D FeNi-LDH/g-C₃N₄ hybrid photocatalyst was obtained by loading a FeNi layered double hydroxide (FeNi-LDH) cocatalyst onto CN nanosheets by a simple hydrothermal method. It was found that the production rate of methanol from photocatalytic CO₂ reduction over the FeNi-LDH/g-C₃N₄ composite is significantly higher than that of pristine CN. Following a series of characterization and analysis, it was demonstrated that the FeNi-LDH/g-C₃N₄ composite photocatalyst exhibited enhanced photo-absorption, which was ascribed to the excellent light absorption ability of FeNi-LDH. The CO₂ adsorption capacity of the FeNi-LDH/g-C₃N₄ hybrid photocatalyst improved, owing to the large specific surface area and alkaline nature of FeNi-LDH. More importantly, the introduction of FeNi-LDH on the CN nanosheet surface led to the formation of a 2D/2D heterojunction with a large contact area at the interface, which could promote the interfacial separation of charge carriers and effectively inhibit the recombination of the photogenerated electrons and holes. This subsequently resulted in the enhancement of the CO₂ photo-reduction activity. In addition, by altering the loading amount of FeNi-LDH for photocatalytic performance evaluation, it was found that the optimal loading amount was 4% (w, mass fraction), with a methanol production rate of 1.64 μmol·h^-1·g^-1 (approximately 6 times that of pure CN). This study provides an effective strategy to improve the photocatalytic CO₂ reduction activity of g-C₃N₄ by employing 2D layered double hydroxide as the cocatalyst. It also proposes a protocol for the successful design of 2D/2D photocatalysts for solar energy conversion.      

Ni,Co基硒化物修饰g-C3N4光催化产氢研究

Developing novel and efficient catalysts is a significant way to break the bottleneck of low separation and transfer efficiency of charge carriers in pristine photocatalysts. Here, two fresh photocatalysts, g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ hybrids, are first synthesized by anchoring Ni₃Se₄ and CoSe₂ nanoparticles on the surface of well-dispersed g-C₃N₄ nanosheets. The resulting materials show excellent performance for photocatalytic in situ hydrogen generation. Pristine g-C₃N₄ has poor photocatalytic hydrogen evolution activity (about 1.9 μmol·h^-1) because of the rapid recombination of electron-hole pairs. However, the hydrogen generation activity is well improved after growing Ni₃Se₄ and CoSe₂ on the surface of g-C₃N₄, owing to the unique effect of these selenides in accelerating the separation and migration of charge carriers. The hydrogen production activities of G-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ are about 16.4 μmol·h^-1 and 25.6 μmol·h^-1, which are 8-fold and 13-fold that of pristine g-C₃N₄, respectively. In detail, coupling Ni₃Se₄ and CoSe₂ with g-C₃N₄ greatly improves the light absorbance density and extends the light response region. The photoluminescence intensity of the photoexcited Eosin Y dye in the presence of g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ is weaker than that in the presence of pure g-C₃N₄. On the other hand, the upper limit of the electron-transfer rate constants in the presence of g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ is greater than that in the presence of pure g-C₃N₄. Among the g-C₃N₄@Ni₃Se₄@FTO, g-C₃N₄@CoSe₂@FTO, and g-C₃N₄@FTO electrodes, the g-C₃N₄@FTO electrode has the lowest photocurrent density and the highest electrochemical impedance, implying that the introduction of CoSe₂ and Ni₃Se₄ onto the surface of g-C₃N₄ enhances the separation and transfer efficiency of photogenerated charge carriers. In other words, the formation of two star metals selenide based on g-C₃N₄ can efficiently inhibit the recombination of photogenerated charge carriers and accelerate photocatalytic water splitting to generate H₂. Meanwhile, the right shift of the absorption band edge effectively reduces the transition threshold of the photoexcited electrons from the valence band to the conduction band. In addition, the more negative zeta potential for the g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ catalysts as compared with that for pure g-C₃N₄ leads to a notable enhancement in the adsorption of protons by the sample surface. Moreover, the results of density functional theory calculations indicate that the hydrogen adsorption energy of the N sites in g-C₃N₄ is -0.22 eV; further, the hydrogen atoms are preferentially adsorbed at the bridge site of two selenium atoms to form a Se―H―Se bond, and the adsorption energy is 1.53 eV. In-depth characterization has been carried out by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, transient photocurrent measurements, and Fourier transform infrared spectroscopy; the results of these experiments are in good agreement with one another.     

反蛋白石结构的g-C3N4可控合成及其优异的光催化产氢性能

The growing frustration from facing energy shortages and unbalanced environmental issues has obstructed the long-term development of human society. Semiconductor-based photocatalysis, such as water splitting, transfers solar energy to storable chemical energy and is widely considered an economic and clean solution. Although regarded as a promising photocatalyst, the low specific surface area of g-C₃N₄ crucially restrains its photocatalytic performance. The macro-mesoporous architecture provides effective channels for mass transfer and full-light utilization and improved the efficiency of the photocatalytic reaction. Herein, g-C₃N₄ with an inverse opal (IO) structure was rationally fabricated using a well-packed SiO₂ template, which displayed an ultrahigh surface area (450.2 m²·g^-1) and exhibited a higher photocatalytic H₂ evolution rate (21.22 μmol·h^-1), almost six times higher than that of bulk g-C₃N₄ (3.65 μmol·h^-1). The IO g-C₃N₄ demonstrates better light absorption capacity than bulk g-C₃N₄, primarily in the visible spectra range, owing to the multiple light scattering effect of the three-dimensional (3D) porous structure. Meanwhile, a lower PL intensity, longer emission lifetime, smaller Nyquist semicircle, and stronger photocurrent response (which synergistically give rise to the suppressed recombination of charge carriers) decrease the interfacial charge transfer resistance and boost the formation of photogenerated electron-hole pairs. Moreover, the existing N vacancies intensify the local electron density, helping increase the number of photoexcitons. The N₂ adsorption-desorption test revealed the existence of ample mesopores and macropores and high specific surface area in IO g-C₃N₄, which exposes more active edges and catalytic sites. Optical behavior, electron paramagnetic resonance, and electrochemical characterization results revealed positive factors, including enhanced light utilization, improved photogenerated charge separation, prolonged lifetime, and fortified IO g-C₃N₄ with excellent photocatalytic performance. This work provides an important contribution to the structural design and property modulation of photocatalysts.      

双功能复合材料g-C3N4/CdS/Ni催化光解水产氢和5-羟甲基糠醛氧化性能

采用高温煅烧法、 原位生长法和光还原法分三步制备出双功能复合光催化剂g-C₃N₄/CdS/Ni. 材料中CdS的引入可以增强光生电子和空穴的分离效率, Ni可以进一步提高光致产氢速率. 在以三乙醇胺(TEOA)为电子给体的水溶液中对所制备的材料进行了催化产氢性能测试, 并对材料中CdS的含量进行了优化. 结果表明, 25% (质量分数)CdS负载量的复合材料催化产氢性能最佳, 其催化产氢速率为4134.5 μmol·g^-1·h^-1, 是 g-C₃N₄/Ni催化产氢速率的115倍. 且Ni是一种良好的质子催化剂. 在此基础上, 以5-羟甲基糠醛(HMF)替代TEOA作为体系的电子给体, 其可以被选择性地催化氧化为增值化学品2, 5-二甲酰基呋喃(DFF). 当体系中HMF的转化率为82.3%, DFF的选择性为69.4%时, DFF的产率(57.2%)达到最高, 体系中H₂的产量为 51.8 μmol/g. g-C₃N₄/CdS/Ni复合材料可以在同一体系中进行催化光致产氢和HMF的选择性氧化.     

全有机S型异质结PDI-Ala/S-C3N4光催化剂增强光催化性能

Organic photocatalysts have attracted attention owing to their suitable redox band positions, low cost, high chemical stability, and good tunability of their framework and electronic structure. As a novel organic photocatalyst, PDI-Ala (N, N'-bis(propionic acid)-perylene-3, 4, 9, 10-tetracarboxylic diimide) has strong visible-light response, low valence band position, and strong oxidation ability. However, the low photogenerated charge transfer rate and high carrier recombination rate limit its application. Due to the aromatic heterocyclic structure of g-C₃N₄ and large delocalized π bond in the planar structure of PDI-Ala, g-C₃N₄ and PDI-Ala can be tightly combined through π–π interactions and N―C bond. The band structure of sulfur-doped g-C₃N₄ (S-C₃N₄) matched well with PDI-Ala than that with g-C₃N₄. The electron delocalization effect, internal electric field, and newly formed chemical bond jointly promote the separation and migration of photogenerated carriers between PDI-Ala and S-C₃N₄. To this end, a novel step-scheme (S-scheme) heterojunction photocatalyst comprising organic semiconductor PDI-Ala and S-C₃N₄ was prepared by an in situ self-assembly strategy. Meanwhile, PDI-Ala was self-assembled by transverse hydrogen bonding and longitudinal π–π stacking. The crystal structure, morphology, valency, optical properties, stability, and energy band structure of the PDI-Ala/S-C₃N₄ photocatalysts were systematically analyzed and studied by various characterization methods such as X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, ultraviolet visible diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, and Mott-Schottky curve. The work functions and interface coupling characteristics were determined using density functional theory. The photocatalytic activities of the synthesized photocatalyst for H₂O₂ production and the degradation of tetracycline (TC) and p-nitrophenol (PNP) under visible-light irradiation are discussed. The PDI-Ala/S-C₃N₄ S-scheme heterojunction with band matching and tight interface bonding accelerates the intermolecular electron transfer and broadens the visible-light response range of the heterojunction. In addition, in the processes of the PDI-Ala/S-C₃N₄ photocatalytic degradation reaction, a variety of active species (h⁺, ·O₂^-, and H₂O₂) were produced and accumulated. Therefore, the PDI-Ala/S-C₃N₄ heterojunction exhibited enhanced photocatalytic performance in the degradation of TC, PNP, and H₂O₂ production. Under visible-light irradiation, the optimum 30%PDI-Ala/S-C₃N₄ removed 90% of TC within 90 min. In addition, 30%PDI-Ala/S-C₃N₄ displayed the highest H₂O₂ evolution rate of 28.3 μmol·h^-1·g^-1, which was 2.9 and 1.6 times higher than those of PDI-Ala and S-C₃N₄, respectively. These results reveal that the all organic photocatalyst comprising PDI-based supramolecular and S-C₃N₄ can be efficiently applied for the degradation of organic pollutants and production of H₂O₂. This work not only provides a novel strategy for the design of all organic S-scheme heterojunctions but also provides a new insight and reference for understanding the structure–activity relationship of heterostructure catalysts with effective interface bonding.      

Ni2P纳米片用于光催化二氧化碳还原

Artificial photosynthesis is an ideal method for solar-to-chemical energy conversion, wherein solar energy is stored in the form of chemical bonds of solar fuels. In particular, the photocatalytic reduction of CO₂ has attracted considerable attention due to its dual benefits of fossil fuel production and CO₂ pollution reduction. However, CO₂ is a comparatively stable molecule and its photoreduction is thermodynamically and kinetically challenging. Thus, the photocatalytic efficiency of CO₂ reduction is far below the level of industrial applications. Therefore, development of low-cost cocatalysts is crucial for significantly decreasing the activation energy of CO₂ to achieving efficient photocatalytic CO₂ reduction. Herein, we have reported the use of a Ni₂P material that can serve as a robust cocatalyst by cooperating with a photosensitizer for the photoconversion of CO₂. An effective strategy for engineering Ni₂P in an ultrathin layered structure has been proposed to improve the CO₂ adsorption capability and decrease the CO₂ activation energy, resulting in efficient CO₂ reduction. A series of physicochemical characterizations including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM) were used to demonstrate the successful preparation of ultrathin Ni₂P nanosheets. The XRD and XPS results confirm the successful synthesis of Ni₂P from Ni(OH)₂ by a low temperature phosphidation process. According to the TEM images, the prepared Ni₂P nanosheets exhibit a 2D and near-transparent sheet-like structure, suggesting their ultrathin thickness. The AFM images further demonstrated this result and also showed that the height of the Ni₂P nanosheets is ca 1.5 nm. The photoluminescence (PL) spectroscopy results revealed that the Ni₂P material could efficiently promote the separation of the photogenerated electrons and holes in [Ru(bpy)₃]Cl₂·6H₂O. More importantly, the Ni₂P nanosheets could more efficiently promote the charge transfer and charge separation rate of [Ru(bpy)₃]Cl₂·6H₂O compared with the Ni₂P particles. In addition, the electrochemical experiments revealed that the Ni₂P nanosheets, with their high active surface area and charge conductivity, can provide more active centers for CO₂ conversion and accelerate the interfacial reaction dynamics. These results strongly suggest that the Ni₂P nanosheets are a promising material for photocatalytic CO₂ reduction, and can achieve a CO generation rate of 64.8 μmol·h^-1, which is 4.4 times higher than that of the Ni₂P particles. In addition, the XRD and XPS measurements of the used Ni₂P nanosheets after the six cycles of the photocatalytic CO₂ reduction reaction demonstrated their high stability. Overall, this study offers a new function for the 2D transition-metal phosphide catalysts in photocatalytic CO₂ reduction.     

氨氛围热处理g-C_3N_4控制N空位浓度提高光催化制氢性能

热处理氧化石墨相氮化碳(g-C_3N_4)材料产生氮缺陷、提升其光催化制氢性能的研究备受关注,但其N空位浓度高且不可控、一定程度破坏g-C_3N_4晶体结构,降低g-C_3N_4的结晶度,导致光生电子-空穴对复合率高,致使其光催化制氢效率较低。基于上述问题,本研究以二氰二胺为前驱体制备了g-C_3N_4,与不同含量的尿素混合,在空气中加热快速热处理,通过X-射线衍射仪(XRD)、扫描电子显微镜(SEM)等测试手段,对其物相组成、微观形貌、光学吸收等进行了表征,在可见光条件下对样品进行了光催化制氢性能测试,研究了尿素的加入对热处理后g-C_3N_4材料的N空位浓度、结晶度及光催化制氢性能的影响。研究表明,尿素的加入降低了N空位的浓度,且提升了其结晶度。在优化的尿素添加量下,g-C_3N_4的可见光光催化制氢速率为6.5μmol·h-1,是没有添加尿素处理的样品的3倍。该研究结果表明,利用尿素原位分解产生的NH_3,可以抑制g-C_3N_4热处理过程中氮原子的氧化程度、实现调控N空位浓度,同时提高了结晶度,最终提升了其光催化制氢性能。