Enhanced photocatalytic H2 production over dual-cocatalyst-modified g-C3N4 heterojunctions

Ag nanoparticles (NPs) were deposited on the surface of g-C₃N₄ (CN) by an in situ calcination method. NiS was successfully loaded onto the composites by a hydrothermal method. The results showed that the 10 wt%-NiS/1.0 wt%-Ag/CN composite exhibits excellent photocatalytic H₂ generation performance under solar-light irradiation. An H₂ production rate of 9.728 mmol·g^?1·h^?1 was achieved, which is 10.82-, 3.45-, and 2.77-times higher than those of pure g-C₃N₄, 10 wt%-NiS/CN, and 1.0 wt%-Ag/CN composites, respectively. This enhanced photocatalytic H₂ generation can be ascribed to the co-decoration of Ag and NiS on the surface of g-C₃N₄, which efficiently improves light harvesting capacity, photogenerated charge carrier separation, and photocatalytic H₂ production kinetics. Thus, this study demonstrates an effective strategy for constructing excellent g-C₃N₄-related composite photocatalysts for H₂ production by using different co-catalysts.     

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.     

Engineering oxygen into ultrathin graphitic carbon nitride: synergistic improvement of electron reduction and charge carrier dynamics for efficient photocatalysis

The fast separation rate of photogenerated carriers and the high utilization of sunlight are still a major challenge that restricts the practical application of carbon nitride (g-C₃N₄) materials in the field of photocatalytic hydrogen (H₂) evolution. Here, ultrathin oxygen (O) engineered g-C₃N₄ (named UOCN) was successfully obtained by a facial gaseous template sacrificial agent-induced bottom-up strategy. The synergy of O doping and exfoliating bulk into an ultrathin structure is reported to simultaneously achieve high-efficiency separation of photogenerated carriers, enhance the utilization of sunlight, and improve the reduction ability of electrons to promote photocatalytic H₂ evolution of UOCN. As a proof of concept, UOCN affords enhanced photocatalytic H₂ evolution (93.78 μmol h^?1) under visible light illumination, which was significantly better than that of bulk carbon nitride (named CN) with the value of 9.23 μmol h^?1. Furthermore, the H₂ evolution rate of UOCN at a longer wavelength (λ = 450 nm) was up to 3.92 μmol h^?1 due to its extended light absorption range. This work presents a practicable strategy of coupling O dopants with ultrathin structures about g-C₃N₄ to achieve efficient photocatalytic H₂ evolution. This integrated engineering strategy can develop a unique example for the rational design of innovative photocatalysts for energy innovation.     

Tuning band structure of graphitic carbon nitride for efficient degradation of sulfamethazine: Atmospheric condition and theoretical calculation

Numerous approaches have been used to modify graphitic carbon nitride（g-C₃N₄） for improving its photocatalytic activity. In this study, we demonstrated a facial post-calcination method for modified graphitic carbon nitride（g-C₃N₄-Ar/Air） to direct tuning band structure, i.e., bandgap and positions of conduction band（CB）/valence band（VB）, through the control of atmospheric condition without involving any additional elements or metals or semiconductors. ...     

Defect-assisted surface modification enhances the visible light photocatalytic performance of g-C3N4@C-TiO2 direct Z-scheme heterojunctions

To increase the number of active sites and defects in TiO₂ and promote rapid and efficient transfer of photogenerated charges, a g-C₃N₄@C-TiO₂ composite photocatalyst was prepared via in situ deposition of g-C₃N₄ on a carbon-doped anatase TiO₂ surface. The effects of carbon doping state and surface modification of g-C₃N₄ on the performance of g-C₃N₄@C-TiO₂ composite photocatalysts were studied by X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse-reflectance spectroscopy, transmission electron microscopy, electrochemical impedance spectroscopy, photoluminescence, and electron paramagnetic resonance. With increasing carbon doping content, the carbon doping state in TiO₂ gradually changed from gap to substitution doping. Although the number of oxygen vacancies gradually increased, the degradation efficiency of g-C₃N₄@C-TiO₂ for RhB (phenol) initially increased and subsequently decreased with increasing carbon content. The g-C₃N₄@10C-TiO₂ sample exhibited the highest apparent reaction rate constant of 0.036 min^?1 (0.039 min^?1) for RhB (phenol) degradation, which was 150 (139), 6.4 (6.8), 2.3 (3), and 1.7 (2.1) times higher than that of pure TiO₂, 10C-TiO₂, g-C₃N₄, and g-C₃N₄@TiO₂, respectively. g-C₃N₄ was grown in situ on the surface of C-TiO₂ by surface carbon hybridization and bonding. The resultant novel g-C₃N₄@C-TiO₂ photocatalyst exhibited direct Z-scheme heterojunctions with non-local impurity levels. The high photocatalytic activity can be attributed to the synergistic effects of the improved visible light response ability, higher photogenerated electron transfer efficiency, and redox ability arising from Z-type heterojunctions.     

Integrating non-precious-metal cocatalyst Ni3N with g-C3N4 for enhanced photocatalytic H2 production in water under visible-light irradiation

Photocatalytic H₂ production via water splitting in a noble-metal-free photocatalytic system has attracted much attention in recent years. In this study, noble-metal-free Ni₃N was used as an active cocatalyst to enhance the activity of g-C₃N₄ for photocatalytic H₂ production under visible-light irradiation (λ > 420 nm). The characterization results indicated that Ni₃N nanoparticles were successfully loaded onto the g-C₃N₄, which accelerated the separation and transfer of photogenerated electrons and resulted in enhanced photocatalytic H₂ evolution under visible-light irradiation. The hydrogen evolution rate reached ～305.4 μmol h^?1 g^?1, which is about three times higher than that of pristine g-C₃N₄, and the apparent quantum yield (AQY) was ～0.45% at λ = 420. Furthermore, the Ni₃N/g-C₃N₄ photocatalyst showed no obvious decrease in the hydrogen production rate, even after five cycles under visible-light irradiation. Finally, a possible photocatalytic hydrogen evolution mechanism for the Ni₃N/g-C₃N₄ system is proposed.     

CdS nanospheres hybridized with graphitic C3N4 for effective photocatalytic hydrogen generation under visible light irradiation

Graphitic carbon nitride (g‐C₃N₄)‐based photocatalysts have received considerable attention in the field of photocatalysis, especially for photocatalytic H₂ evolution. However, the intrinsic disadvantages of g‐C₃N₄ seriously limit its practical application. Herein, CdS nanospheres with an average diameter of 135 nm prepared using a solvothermal method were used as co‐catalysts to form CdS/g‐C₃N₄ composites (CSCN) to enhance the photocatalytic activity. Various techniques were employed to characterize the structure, composition and optical properties of the as‐prepared samples. It was found that the CdS nanospheres were relatively uniformly dispersed on the surface of g‐C₃N₄. Moreover, the photocatalytic H₂ generation activity of the samples was evaluated using lactic acid as sacrificial reagent in water under visible light irradiation. When the amount of CdS nanospheres loaded in the hybridized composites was 5 wt%, the optimal H₂ evolution rate reached 924 μmol g^?1 h^?1, which was approximately 1.4 times higher than that (680 μmol g^?1 h^?1) of Pt/g‐C₃N₄ (3 wt%). Based on the results of analysis, a possible mechanism for the photocatalytic activity of CSCN is proposed tentatively.     

NiS2/NiFe LDH/g-C3N4 ternary heterostructure-based label-free photoelectrochemical aptasensing for highly sensitive determination of enrofloxacin

Photoelectrochemical (PEC) aptasensor based on photoactive species with remarkable and stable PEC response is a rising analytical method to implement highly efficient and sensitive detection of residual antibiotics in the field of food. Herein, NiS₂/NiFe-layered double/graphitic carbon nitride (NiS₂/NiFe LDH/g-C₃N₄) ternary heterostructure designed by the surface vulcanization of flower-like NiFe LDH/g-C₃N₄ was used for developing a label-free PEC aptasensing platform to detect enrofloxacin (ENR). The introduction of NiS₂ with narrow bandgap can strengthen the light harvesting of solar energy, producing large amounts of photoinduced carriers. NiS₂ as the electrons conduction bridge further accelerates the transmission efficiency of electrons in contrast to binary heterojunction, endowing ternary heterostructure with superior photocurrent signal. A label-free PEC aptasensor detected ENR with an amplified detection signal because of the oxidation of ENR molecules by photoinduced holes. This PEC aptasensing platform of ENR manifested a wide detection range from 3.6 × 10^?7 to 30 ng/mL with a low detection limit of 1.2 × 10^?7 ng/mL as well as can provide a sensitive and stable analysis with feasible application to monitor milk and honey samples. This design can open the utilization of ternary heterostructure by surface vulcanization to improve the sensitivity of PEC aptasensing platform for monitoring environmental pollutants.     

Synergistic improvement of Cr(VI) reduction and RhB degradation using RP/g-C3N4 photocatalyst under visible light irradiation

The RP/g-C₃N₄ heterojunction photocatalyst was fabricated by a facile heat treatment strategy. The obtained composite has excellent light harvesting ability and charge separation performance. Compared to single RP and g-C₃N₄, the 50%-RP/g-C₃N₄ exhibited enhanced photocatalytic activity for simultaneously removing Cr(VI) and RhB, and the removal rates can reach 92% and 99% in 25 min, respectively. The enhanced mechanism was revealed by active species capturing experiments, showing that electrons can reduce Cr(VI) and produce O₂^– in air and that holes can directly oxidize the dyes. The coexistence of Cr(VI) and RhB will lead to a synergistic improvement of Cr(VI) reduction and RhB degradation due to rapid surface reactions. This further improves the charge separation except for the heterojunction effect. In addition, the COD analysis demonstrates that organic dyes are mainly degraded into CO₂, H₂O and some intermediates.     

Engineering FeS2 nanoparticles on tubular g-C3N4 for photo-Fenton treatment of paint wastewater

An efficient photo-Fenton catalyst （Fe S₂@HTCN） was designed by maximizing the synergistic effect of Fe S₂nanoparticles and hollow tubular g-C₃N₄（HTCN）.Molecule self-assembly and molten salts-assisted calcination were used to engineering the hollow structured g-C₃N₄before anchoring Fe S₂nanoparticles on the walls of HTCN via reflux method.Compared to bulk g-C₃N₄,the unique structure of HTCN and het...     

g-C3N4碳位掺杂电学及光学性质的分析

使用第一性原理研究了C位掺杂的g-C₃N₄的电学性质和光学性质,掺杂原子为B、P、S. g-C₃N₄有C1位和C2 位两种对称位碳原子,其中在C1 位上的掺杂易于C2 位,掺杂体系也较C2 位稳定. 相比于磷和硫在g-C₃N₄上的掺杂,硼掺杂最易于进行. 掺杂后体系的晶体结构之间差别较大,这与掺杂原子的大小以及电负性有关. 由轨道布居分布可知,掺杂后的硼、磷、硫原子价电子发生了变化,表明掺杂原子发生了杂化,与相邻原子以强的共价键相连. 掺杂原子与被取代的碳原子之间的价电子差异导致了能带的增加. 在原来的体系中,掺杂后的体系出现了一条新的能带,因此导致实际带隙下降,表明了掺杂后的体系导电性能增强. 对纯g-C₃N₄及掺杂g-C₃N₄的光学性质分析表明,g-C₃N₄的光学吸收主要在紫外光区,掺杂磷和硫后对g-C₃N₄的光吸收波长范围无改变,掺杂硼后的g-C₃N₄光吸收不再局限于紫外光区,而且延伸至可见光区和红外光区,并在红外光区有很强的吸收,表明g-C₃N₄掺杂硼后能大大地提高光催化效率. 电子能量损失光谱和光导率谱以及介电常数都佐证了上述观点.     

A novel P-doped and NCDs loaded g-C3N4 with enhanced charges separation for photocatalytic hydrogen evolution

Graphite carbon nitride(g-C₃N₄) is a promising non-metal photocatalyst for photocatalytic hydrogen production, but its performance is still limited due to sluggish charges separation and low utilization of light.In this work, P-doped and N-doped carbon dots(NCDs) supported g-C₃N₄were successfully prepared via hydrothermal and polymerization reactions. The sub-bandgap formed by P-doping enhances the utilization of visible light, and the high electron de...     

Nanocavity-assisted single-crystalline Ti3+ self-doped blue TiO2(B) as efficient cocatalyst for high selective CO2 photoreduction of g-C3N4

Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) has invoked significant interest for photocatalytic applications for its excellent features such as high surface area, visible light absorption, and easy transportation of photogenerated charge carriers, but the most reported g-C₃N₄ show relatively low photoactivity due to inferior conductivity and rapid recombination of carriers. These can be overcome by inducing porosity in g-C₃N₄, followed by exfoliation and combining with other materials. Herein, we synthesize nanocavity-assisted oxygen-deficient Ti³⁺ self-doped blue TiO₂(B) nanorods (BT) and integrate them on exfoliated porous g-C₃N₄ (PCN). The synthesized materials are tested for photocatalytic conversion of CO₂ into solar fuels (H₂, CO, and CH₄). The fabricated BT/PCN heterostructures exhibit higher photocatalytic CO₂ conversion activity and 92% CO-evolving selectivity than BT and PCN. The enhancement in activity of BT/PCN can be attributed to the efficient separation and transportation of charge carriers, facilitated by the unique properties of BT, PCN, and their synergistic interactions. We believe that these results can contribute to the improvement of cost-effectiveness, feasibility, and overall performance for real photocatalytic systems.     

Development of versatile CdMoO4/g-C3N4 nanocomposite for enhanced photoelectrochemical oxygen evolution reaction and photocatalytic dye degradation applications

Fabrication of an efficient, stable, and versatile photocatalysts for the energy and environment remediation applications is an urgent task for the current researchers. In this work, we have successfully synthesized a versatile hybrid photocatalysts, i.e.; CdMoO₄/g-C₃N₄ (CMO/CN) by a facile and simple one-pot in-situ hydrothermal method. Here CdMoO₄ (CMO) microspheres were deposited on the g-C₃N₄ (CN) sheets. Fabricated CN, CMO, and CMO/CN composite photocatalysts were analyzed with various characterization techniques like UV–visible diffuse reflectance spectra (UV–Vis DRS), photoluminescence spectroscopy (PL), time-resolved fluorescence lifetime (TRFL), electrochemical impedance spectroscopy (EIS), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy–energy-dispersive X-ray analysis (SEM-EDX), transmission electron microscope (TEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET). The results reveal that the formation of a strong heterojunction between two semiconductors leads to the formation of active photocatalyst. Furthermore, as-synthesized materials were tested for the photoelectrocatalytic (PEC) oxygen evolution reactions (OERs) in acidic medium, and photocatalytic (PC) degradation of methylene blue (MB) under light irradiation. Among all tested samples, CMO/CN-10 has shown the highest current density 52.74 mA cm^?2 at 1.95 V with lowest over potential of 0.70 mV on glassy carbon electrode for OER in acidic medium under the light irradiation. The PC degradation rate constant of CMO/CN-10 composite in MB solution is k = 2.0 × 10^?2 min^?1, whereas for the pure CMO and CN degradation rate constant is k = 5.7 × 10^?3 min^?1 and k = 1.2 × 10^?2 min^?1, respectively. This enhancement in PEC and PC properties is due to the fast migration of photo-induced electrons in the case of CMO/CN-10 nanocomposite. Trapping experiment results reveal the major reactive species for PC degradation of MB is ?OH (hydroxyl radicals) and h⁺ (holes), respectively, and suitable PC reaction mechanism also proposed for CMO/CN-10 composites. Based on the above remarkable results, it would be a potential nanocomposite for the PEC oxygen evolution and PC degradation of MB under light illumination.     

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。     

C/g-C3N4/MoS2复合材料的制备及光催化性能

首先以尿素和葡萄糖为前驱体,通过热缩合方法制备了C/g-C₃N₄,然后利用溶剂热法合成C/g-C₃N₄/MoS₂三元复合材料。通过不同的手段对其进行了表征,结果表明,与C/g-C₃N₄相比,该三元复合材料不仅具有更强的光吸收性能和更大的表面积,而且更有利于电子的转移。同时对其可见光催化降解甲基橙性能进行研究,结果发现,C/g-C₃N₄/MoS₂-2.0%复合材料(含有质量分数为2.0%的MoS₂)表现出最高的反应速率常数(0.0086 min^-1),分别为g-C₃N₄/MoS₂-2.0%(0.0015 min^-1)和C/g-C₃N₄(0.0036min^-1)的5.7倍和2.3倍。     

Exited State Absorption Upconversion Induced by Structural Defects for Photocatalysis with a Breakthrough Efficiency

The nitrogen-deficient graphitic carbon nitride (g-C₃N₄) has been prepared, a new excited state absorption (ESA) up-conversion mode is discovered, which is directly induced by structural defects, showing distinct chemical characteristics from those based on lanthanide ions and triplet states chromophores. The abundant N_2C vacancies in g-C₃N₄ nanosheets work as the crucial intermediate excitation states, which lead to g-C₃N₄ upconverted emitting at the wavelength of 436 nm excited by the light with the wavelength of 800 nm. This process is proven to proceed via a two-photon involved ESA mode with a breakthrough quantum efficiency of 0.64 %. Further, we combine N_2C vacancies enriched g-C₃N₄ with In₂S₃ and CdS, and successfully achieved an infrared light driven photocatalytic reactions. These findings offered a new family of up-conversion materials; more semiconductors with various structural defects are potential complementary members.     

g-C_3N_4基多功能层光阳极在光电化学水分解中的应用（英文）

光电化学分解水制氢可以一并解决环境问题和能源危机,因而成为研究热点.由于TiO_2 禁带宽度较大,不能有效吸收太阳光中的可见光,使光电化学分解水制氢的应用受限.g-C_3N_4的禁带宽度约为2.7 e V,能有效吸收可见光,但g-C_3N_4薄膜制备研究较少.我们通过热聚缩合法直接在FTO导电玻璃上制备出g-C_3N_4薄膜,发现其光电化学分解水制氢稳定性不高,选择易制备的TiO_2 作为保护层可以提高g-C_3N_4的耐用性.此外,为提高g-C_3N_4光生电子空穴对的分离能力,依靠Co-Pi对光生空穴的捕获作用而将其覆盖在最外层.因此本文首次制备一种新型的g-C_3N_4/TiO_2 /Co-Pi光阳极用于光电化学分解水制氢,其中g-C_3N_4用作光吸收层,TiO_2 用作保护层,Co-Pi用作空穴捕获层.并在此基础上,通过扫描电子显微镜(SEM),X射线衍射(XRD),紫外可见光谱(UV-Vis)等手段研究了g-C_3N_4/TiO_2 /Co-Pi光阳极的形貌特征和光电化学性能.SEM、EDS和XRD结果表明,g-C_3N_4/TiO_2 /Co-Pi光阳极被成功制备在了FTO导电玻璃上,厚度约为3μm.UV-Vis测试表明,g-C_3N_4的光吸收边约为470 nm,可以有效地吸收可见光,并且g-C_3N_4的框架结构使光多次反射折射增加了光的捕获能力,由此可见,g-C_3N_4能够发挥很好的光吸收层作用.通过对g-C_3N_4光阳极,g-C_3N_4/TiO_2 光阳极和g-C_3N_4/TiO_2 /Co-Pi光阳极的电流电压测试发现,g-C_3N_4/TiO_2 光阳极的光电流密度小于g-C_3N_4光阳极,而g-C_3N_4/TiO_2 /Co-Pi光阳极的光电流密在可逆氢电极1.1 V下达到了0.346 mA?cm–2,约为单独g-C_3N_4光阳极的3.6倍.这说明Co-Pi是提升g-C_3N_4光电化学性能的主要因素.电化学阻抗测试结果发现,g-C_3N_4/TiO_2 /Co-Pi光阳极的界面电荷转移电阻小于g-C_3N_4光阳极的,这表明g-C_3N_4/TiO_2 /Co-Pi光阳极界面处载流子转移较快,同时也能促进内部光生电子空穴对的分离,整体性能的提高应该主要归因于Co-Pi对光生空穴的捕获作用.恒电压时间测试展示出g-C_3N_4/TiO_2 /Co-Pi光阳极的光电流密度在2 h测试过程中没有明显下降,表明g-C_3N_4/TiO_2 /Co-Pi光阳极是相当稳定的,具有良好的耐用性,归因于TiO_2 和Co-Pi的共同保护作用,主要归因于TiO_2 层对FTO导电玻璃上的g-C_3N_4薄膜保护,从电化学沉积Co-Pi到所有测试结束.总体而言,g-C_3N_4/TiO_2 /Co-Pi光阳极加强的光电化学性能归因于以下几个因素:(1)g-C_3N_4优异的光吸收能力;(2)TiO_2 稳定的保护提升了g-C_3N_4薄膜的耐用性;(3)Co–Pi对光生空穴的捕获有效促进了光生电子空穴对的分离.     

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。     

NiS-PdS/CdS光催化剂的水热法合成及其可见光分解水产氢性能

为提高太阳能转化效率, 高效响应可见光的光催化剂的研究十分必要. 本研究以硫化镉、氯化钯、醋酸镍和硫脲为原料, 利用水热法制备了NiS-PdS/CdS复合光催化剂. 通过X射线衍射(XRD)、紫外-可见光漫反射光谱(DRS)、透射电子显微镜(TEM)和光致发光(PL)光谱等手段对光催化剂进行了表征, 并在乳酸牺牲剂中对光解水制氢活性进行了测试. 结果表明: 助催化剂NiS 和PdS 能较好地分布在CdS 表面上, 形成共负载的NiS-PdS/CdS 光催化剂, 其可见光下的活性比CdS明显增强, 当NiS 和PdS 负载量分别在1.5%和0.41%(w)时, NiS-PdS/CdS获得最好活性, 最大产氢量达到6556 μmol·h^-1, 是CdS活性的7倍, 是NiS/CdS的近3倍, 测得在λ=420 nm时的表观量子效率为47.5%. 助催化剂NiS 和PdS分别起到传递光生电子和光生空穴的作用,两者共负载相比于单独负载, 能使光生载流子的迁移和分离效率更高, 因此提高了光催化产氢活性.