Separation Efficiency Of Carriers Research Articles

Engineering of g-C3N4 for Photocatalytic Hydrogen Production: A Review.

Graphitic carbon nitride (g-C3N4)-based photocatalysts have garnered significant interest as a promising photocatalyst for hydrogen generation under visible light, to address energy and environmental challenges owing to their favorable electronic structure, affordability, and stability. In spite of that, issues such as high charge carrier recombination rates and low quantum efficiency impede its broader application. To overcome these limitations, structural and morphological modification of the g-C3N4-based photocatalysts is a novel frontline to improve the photocatalytic performance. Therefore, we briefly summarize the current preparation methods of g-C3N4. Importantly, this review highlights recent advancements in crafting high-performance g-C3N4-based photocatalysts, focusing on strategies like elemental doping, nanostructure design, bandgap engineering, and heterostructure construction. Notably, sophisticated doping techniques have propelled hydrogen production rates to a 104-fold increase. Ingenious nanostructure designs have expanded the surface area by a factor of 26, concurrently extending the fluorescence lifetime of charge carriers by 50%. Moreover, the strategic assembly of heterojunctions has not only elevated charge carrier separation efficiency but also preserved formidable redox properties, culminating in a dramatic hundredfold surge in hydrogen generation performance. This work provides a reliable and brief overview of the controlled modification engineering of g-C3N4-based photocatalyst systems, paving the way for more efficient hydrogen production.

The cooperative p-n heterojunction and Schottky junction in Au-decorated hierarchical CuS@SnS2 hollow cubes for boosted charge transport and CO2 photoreduction

During the photocatalytic CO2 reduction process, fast charge transport, abundant active sites, and high visible light utilization in photocatalysts are key to achieving excellent CO2 conversion efficiency. In this work, we have designed and prepared hierarchical CuS@SnS2p-n heterostructure hollow cubes for photocatalytic CO2 reduction. First, a monolayer of CuS was in situ generated on the pre-prepared Cu2O cubes to construct core–shell Cu2O@CuS cubes by sulfidation of Cu2O cubes. The following etching process led to the formation of CuS hollow cubes. Finally, the hierarchical CuS@SnS2p-n heterostructure hollow cubes were obtained by growing SnS2 nanosheets on the CuS hollow cubes. The prepared CuS@SnS2p-n heterostructure hollow cubes showed an improved photocatalytic CO2 reduction activity compared with the bare CuS and SnS2 control samples. The p-n heterojunction formed between SnS2 and CuS as well as its hollow structure enhanced the charge carrier separation efficiency and the light absorption capacity of the hybrid catalyst. Furthermore, after the decoration of Au nanoparticles, the formed Schottky junction further discouraged the charge carrier recombination. Thus, the cooperative p-n heterojunction and Schottky junction greatly facilitated photocatalytic CO2 reduction, and exhibiting the maximum CO and CH4 yields of 140.1 and 77.5 μmol g−1 h−1, respectively. This work presents an efficient design of high-performance catalysts for photocatalytic CO2 reduction.

Tuning oxygen vacancies via photoinduced defect engineering in plasma pre-treated TiO2 for efficient solar-light-driven oxidation of trace methane

Photocatalysis employing cost-effective commercial titanium dioxide offers an ideal solution for eliminating trace methane emissions from livestock and poultry farming. However, significant challenges such as the rapid recombination of photogenerated carriers, a limited light absorption spectrum, and weak adsorption capabilities considerably hinder the effectiveness of titanium dioxide in the photocatalytic treatment of trace methane. This study proposes a novel approach to activate plasma pre-treated N-doped commercial anatase TiO2 into dual-defect TiO2 (N-doped TiO2-x) featuring stable and controllable oxygen vacancies (OV) through photoinduced defect engineering. Characterizations of the photocatalyst confirm the successful creation of surface defects, further evaluated through solar-light-driven CH4 (ppm level) removal investigations. The yield of this N-doped TiO2-x in converting CH4 is 4.84 μmol h−1, 44 times greater than that of unmodified TiO2, significantly outperforming previous studies. UV–Vis diffuse reflection spectra, and photoluminescence indicate that the modified commercial anatase TiO2 possesses a narrower band gap, efficient photogenerated carrier separation, and enhanced charge transfer. Furthermore, density functional theory (DFT) calculations demonstrate that the synergistic effects of oxygen vacancies and N doping enhance the adsorption and activation of both O2 and CH4 in the rate-determining step of the reaction. This innovative strategy holds considerable promise for modifying various materials for more efficient photocatalytic applications.

An Efficient MnO2 Photocathode with an Excellent SnO2 Electron Transport Layer for Photo-Accelerated Zinc Ion Batteries.

Photo-accelerated rechargeable batteries play a crucial role in fully utilizing solar energy, but it is still a challenge to fabricate dual-functional photoelectrodes with simultaneous high solar energy harvesting and storage. This work reports an innovative photo-accelerated zinc-ion battery (PAZIB) featuring a photocathode with a SnO2@MnO2 heterojunction. The design ingeniously combines the excellent electronic conductivity of SnO2 with the high energy storage and light absorption capacities of MnO2. The capacity of the SnO2@MnO2-based PAZIB is ≈598mAh g-1 with a high photo-conversion efficiency of 1.2% under illumination at 0.1 A g-1, which is superior to that of most reported MnO2-based ZIB. The boosting performance is attributed to the synergistic effect of enhanced photogenerated carrier separation efficiency, improved conductivity, and promoted charge transfer by the SnO2@MnO2 heterojunction, which is confirmed by systematic experiments and theoretical simulations. This work provides valuable insights into the development of dual-function photocathodes for effective solar energy utilization.

Boosting the Activation of Molecular Oxygen and the Degradation of Rhodamine B in Polar-Functional-Group-Modified g-C3N4.

Molecular oxygen activation often suffers from high energy consumption and low efficiency. Developing eco-friendly and effective photocatalysts remains a key challenge for advancing green molecular oxygen activation. Herein, graphitic carbon nitride (g-C3N4) with abundant hydroxyl groups (HCN) was synthesized to investigate the relationship between these polar groups and molecular oxygen activation. The advantage of the hydroxyl group modification of g-C3N4 included narrower interlayer distances, a larger specific surface area and improved hydrophilicity. Various photoelectronic measurements revealed that the introduced hydroxyl groups reduced the charge transfer resistance of HCN, resulting in accelerated charge separation and migration kinetics. Therefore, the optimal HCN-90 showed the highest activity for Rhodamine B photodegradation with a reaction time of 30 min and an apparent rate constant of 0.125 min-1, surpassing most other g-C3N4 composites. This enhanced activity was attributed to the adjusted band structure achieved through polar functional group modification. The modification of polar functional groups could alter the energy band structure of photocatalysts, narrow band gap, enhance visible-light absorption, and improve photogenerated carrier separation efficiency. This work highlights the significant potential of polar functional groups in tuning the structure of g-C3N4 to enhance efficient molecular oxygen activation.

Construction of S-scheme heterojunction via Cu2ZnSnS4 coupled with g-C3N4 for enhancing HER performance

It is shown that replacing non-noble metals with noble metals in photocatalytic water splitting is pivotal for increased and sustained hydrogen production. However, the challenge persists in designing and developing a cost-effective, highly active catalyst with effective carrier separation and providing sufficient H+ reduction sites to enhance photocatalytic H2 evolution efficiency. Herein, a series of S-scheme Cu2ZnSnS4/g-C3N4 (CZTS/CN) heterojunction composites were prepared via the hydrothermal method, followed by comprehensive characterizations for in-depth investigation. The TEM image exhibits a clear interface, showing the heterojunction formation between CZTS and CN nanosheets. The results show that incorporating CZTS cocatalyst significantly improves CN photocatalytic hydrogen evolution reaction (HER) and its performance is notably influenced by CZTS to CN mass ratio. Among CZTS/CN heterojunction composites, the 5% CZTS/CN heterojunction composite exhibited a significantly improved HER of 243.64 μmol g−1h−1, which is 29.4 and 7.08 folds superior as compared to CN (8.29 μmol g−1h−1) and CZTS (34.42 μmol g−1h−1), respectively. The mechanism study revealed that the excellent superior H2 evolution performance resulted from the established internal electric field (IEF) in p-n heterojunction, which expedites the efficient separation and migration of photoinduced carriers coupled with the distinctive flower-like configuration of CZTS offering a substantial surface area and enough active reduction sites for photocatalysis process. This work presents a rational design and an inexpensive and efficient heterojunction photocatalysis system suitable for diverse applications.

Thiophene-based vinylene-linked donor-acceptor covalent organic frameworks for photocatalytic organic transformations

Donor-acceptor (D-A) type vinylene-linked covalent organic frameworks (COFs) exhibit promising potential as catalysts for photocatalytic organic conversion. However, the correlation between the strength of the D-A system and D-A COFs’ photocatalytic performance remains ambiguous. Herein, two thiophene-based vinylene-linked D-A COFs with different D-A effects, namely TTDA-COF and TPDA-COF, were designed and synthesized, and their photocatalytic performance was evaluated. The triazine-containing TTDA-COF exhibited superior photocatalytic activity compared to the pyridine-containing TPDA-COF, achieving conversion rates of 95 % for sulfide and 92 % for phenylboronic acid under optimized conditions. Additionally, TTDA-COF demonstrated excellent substrate adaptability and recyclability. The plausible catalytic mechanisms of two photocatalytic reactions were speculated. Further material characterization and theoretical calculations revealed that the enhancement of D-A effect could significantly amplify charge transfer between the donor and acceptor, thereby facilitating more efficient separation and migration of carriers. This study may provide valuable insights for the development of highly efficient D-A COF photocatalysts.

Optimizing photocatalytic hydrogen evolution performance by rationally constructing S-scheme heterojunction to modulate the D-band center

The research in the field of photocatalysis has progressed, with the development of heterojunctions being recognized as an effective method to improve carrier separation efficiency in light-induced processes. In this particular study, CuCo2S4 particles were attached to a new cubic CdS surface to create an S-scheme heterojunction, thus successfully addressing this issue. Specifically, owing to the higher conduction band and Fermi level of CuCo2S4 compared to CdS, they serve as the foundation and driving force for the formation of an S-scheme heterojunction. Through in-situ X-ray photoelectron spectroscopy and electron paramagnetic resonance analysis, the direction of charge transfer in the composite photocatalyst under light exposure was determined, confirming the charge transfer mechanism of the S-scheme heterojunction. By effectively constructing the S-scheme heterojunction, the d-band center of the composite photocatalyst was adjusted, reducing the energy needed for electron filling in the anti-bonding energy band, promoting the transfer of photogenerated carriers, and ultimately enhancing the photocatalytic hydrogen production. performance. After optimization, the hydrogen evolution activity of the composite photocatalyst CdS-C/CuCo2S4-3 reached 5818.9 μmol g−1h−1, which is 2.6 times higher than that of cubic CdS (2272.3 μmol g−1h−1) and 327.4 times higher than that of CuCo2S4 (17.8 μmol g−1h−1), showcasing exceptional photocatalytic activity. Electron paramagnetic resonance and in situ X-ray photoelectron spectroscopy have established a theoretical basis for designing and constructing S-scheme heterojunctions, offering a viable method for adjusting the D-band center to enhance the performance of photocatalytic hydrogen evolution.

Ultrafast carrier dynamics triggered by Ga-S bond in GaZnON/CdS heterojunction for efficient photocatalytic hydrogen evolution

Constructing heterojunction has been regarded as a valid strategy of photocatalysts to promote the catalytic process. However, beyond the possible synergistic advantage from the component catalysts, the understanding of the interface effect on the photocatalytic process within heterojunction remains challenging. Herein, we prepare a novel GaZnON/CdS heterojunction photocatalyst via a robust electrostatic assembly method. The sulfur atoms in CdS are found to occupy the nitrogen vacancy over the GaZnON surface to form interfacial Ga-S bonds, which is proved as electron-transfer channel between CdS and GaZnON to realize efficient photo-induced carrier separation. The dynamic study quantificationally reveals interfacial electron transfer with a fast transfer rate of 143.8 ns−1. Thereby, the optimal composite photocatalyst reached an impressive hydrogen evolution rate of 14.76 mmol g-1h−1, as well as an impressive AQY of 36.1 % (450 nm). This work expounds the ultrafast carrier dynamics underlying interface bonds within heterojunction for weakened photo-induced carrier recombination.

Interface Engineering in Gradient Core/Shell Quantum Dots Enables Efficient Photoelectrochemical Hydrogen Production

Semiconductor core/shell quantum dots (QDs) are considered promising building blocks to fabricate photoelectrochemical (PEC) cells for the direct conversion of solar energy into hydrogen (H2). However, the lattice mismatch between core and shell in such QDs results in undesirable defects and severe carrier recombination, limiting photo-induced carrier separation/transfer and solar-to-fuel conversion efficiency. Here, we explore an interface engineering approach to minimize the core-shell lattice mismatch in CdS/CdSexS1-x (x=0.09~1) core/shell QDs (g-CSG). As a proof-of-concept, PEC cells based on g-CSG QDs yield a remarkable photocurrent density of 13.1 mA/cm2 under AM 1.5 G one-sun illumination (100 mW/cm2), which is ~54.1% and ~33.7% higher compared to that in CdS/CdSe0.5S0.5 (g-CSA) and CdS/CdSe QDs (g-CS), respectively. Theoretical calculations and carrier dynamics confirm more efficient carrier separation and charge transfer rate in g-CSG QDs with respect to g-CSA and g-CS QDs. These results are attributed to the minimization of the core-shell lattice mismatch by the cascade gradient shell in g-CSG QDs, which modifies carrier confinement potential and reduces interfacial defects. This work provides fundamental insights into the interface engineering of core/shell QDs and may open up new avenues to boost the performance of PEC cells for H2 evolution and other QDs-based optoelectronic devices.

Facile SILAR deposited SnS/NiS vertical heterojunction for high performance flexible broadband photodetector

Low-cost, flexible broadband photodetectors fabricated from two-dimensional transition metal chalcogenides have garnered attention because of their excellent absorption coefficient and photoconductivity. Likewise, vertical heterojunctions fabricated from two two-dimensional (2D) transition metal chalcogenides (TMCs) also have drawn major curiosity lately owing to their superior optical performance. This work reports a p-p type II vertical Van der Waal's heterojunction structure by depositing thin film of NiS over SnS on a flexible paper substrate. Morphological and structural characterization confirms presence of a rhombohedral β-NiS crystal structure along with traces of Ni(OH)2 on orthorhombic SnS nanoparticles. The device fabrication method made use of the inexpensive, clean room free SILAR (Successive Ionic Layer Adsorption and Reaction) technique. A purposeful modification of narrow bandgap property of NiS is done by depositing it in an alkaline environment. The fabricated device records optical responsivity of 0.92 mA/W under UV illumination, 5.32 mA/W under Visible illumination, and 0.8 mA/W under NIR illumination. A maximum EQE of 1.3 % is observed along with superior response times of 0.114 s (UV),0.103 s (Visible) and 1.34 s (NIR). The acquired photo response is due to superior absorption property of NiS in UV region and SnS in the visible and NIR region. The difference in fermi level between two materials causes efficient separation of the charge carriers that results in junctional electric field upon light illumination. The device underwent flexibility testing and shown exceptional resistance to bending force making it suitable for numerous applications like wearable healthcare monitoring, security purposes and flexible image sensors.

Investigation of the mechanism and stability of highly efficient photocatalytic degradation of Methylene blue using Ni doped CdS photocatalyst

Methylene blue (MB) is commonly utilized in chemical indicators, dyes, biological colors, and pharmaceuticals. Its aqueous solution is poisonous and carcinogenic, posing a significant threat to the ecological environment. The wurtzite-phase NixCd1−xS was synthesized using the hydrothermal technique in this study. Ni doped CdS enhanced its photocatalytic efficiency and resistance to photocorrosion, enabling its application in the photocatalytic destruction of MB. The incorporation of Ni did not change the crystal structure and microstructure of CdS, but increased the visible light absorption range and decreased the band gap width slightly, which promoted the migration of photogenerated electrons and reduced their recombination with holes, resulting in higher photogenerated carrier separation efficiency of NixCd1−xS. The photocatalytic decolorization rate of Ni0.06Cd0.94S for 100 mL of 10 mg/L MB at 240 min is 91.3 %, and the reaction rate constant is 0.01102 min−1, which is 4.42 times that of wurtzite-phase CdS. The photocatalytic mechanism of NixCd1−xS and its composite was analyzed using trap experiments in conjunction with the band structure of the sample. Additionally, the stability of NixCd1−xS was evaluated. The results indicated that the stability was superior to that of CdS. The findings demonstrate that Ni0.06Cd0.94S exhibits good catalytic activity and stability, making it a viable catalyst for the photocatalytic degradation of organic pollutants in water.

CoP electrodeposited on TiO2 nanorod arrays as photoanode for enhanced photoelectrochemical water splitting

AbstractIt is of great significance to design photoelectrodes with high carrier separation and transport efficiency in photocatalytic water separation systems. In this study, we used a simple electrochemical deposition method to regulate the load of co‐catalyst CoP on TiO2 nanorods to improve the photoelectrochemical properties. The photocurrent density of TiO2/CoP (20) photoanode at 1.23 V increases to 1.57 mA/cm2, which is 3.4 times that of original TiO2. Long‐term photoelectrolysis reveals that this electrode has excellent stability. Mechanistic studies support the role of CoP nanoparticles in improving photoelectrochemical property and imply that the excellent photoelectrochemical property of TiO2/CoP photoanode is mainly ascribed to the suppress of surface photogenerated electrons and holes recombination due to the construction of built‐in electric field between TiO2 and CoP.

Engineering S-scheme mCN@mPDIP molecular heterojunction with highly efficient interface charge transfer for photocatalytic aerobic oxidation synthesis

The construction of S-scheme heterojunctions, which offers a promising approach for spatially separating photogenerated charge carriers with high redox potentials and multimolecular activation, represents a viable modification strategy in photocatalytic applications. However, the prevalent insufficient contact areas between two components result in low interface charge transfer efficiency, thereby impeding the photocatalytic performance of such heterostructures. Herein, we address this limitation by introducing a unique mCN@mPDIP molecular heterojunction through a pH-triggered molecule self-assembly eutectoid technique, enabling intimate interface contact and promoting highly efficient interfacial charge transfer following an S-scheme mechanism. Consequently, the mCN@mPDIP molecular heterojunction achieves significantly improved charge separation efficiency and higher concentration of active carriers compared to typical bCN-bPDIP bulk heterojunction and nCN/nPDIP nano heterojunction. Combined with the effective sulfide activation on mPDIP sites and O2 activation on mCN sites, the resulting mCN@mPDIP demonstrates outstanding activity in the photocatalytic aerobic oxidation of sulfides into sulfoxides without any redox mediators.

Constructing Metal-Organic Framework Films with Adjustable Electronic Properties on Hematite Photoanode for Boosting Photogenerated Carrier Transport.

Hematite (α-Fe2O3) has become a research hotspot in the field of photoelectrochemical water splitting (PEC-WS), but the low photogenerated carrier separation efficiency limits further application. The electronic structure regulation, such as element doping and organic functional groups with different electrical properties, is applied to alleviate the problems of poor electrical conductivity, interface defects, and band mismatch. Herein, α-Fe2O3 photoanodes are modified to regulate their electric structures and improve photogenerated carrier transport by the bimetallic metal-organic frameworks (MOFs), which are constructed with Fe/Ni and terephthalate (BDC) with 2-substitution of different organic functional groups (─H, ─Br, ─NO2 and ─NH2). The α-Fe2O3 photoanode loaded with FeNi-NH2BDC MOF catalyst exhibits the optimal photocurrent density (2mAcm-2) at 1.23VRHE, which is 2.33 times that of the pure α-Fe2O3 photoanode. The detailed PEC analyses demonstrate that the bimetallic synergistic effect between Fe and Ni can improve the conductivity and inhibit the photogenerated carrier recombination of α-Fe2O3 photoanodes. The ─NH2 group as an electron-donor group can effectively regulate the electron distribution and band structure of α-Fe2O3 photoanodes to prolong the lifetime of photogenerated holes, which facilitates photogenerated carrier transport and further enhances the PEC-WS performance of α-Fe2O3 photoanode.

Systematic investigation on the rational design and optimization of bi-based metal oxide semiconductors in photocatalytic applications

To address the global energy shortage and mitigate greenhouse gas emissions on a massive scale, it is critical to explore novel and efficient photocatalysts for the utilization of renewable resources. Bi-based metal oxide (Bi x MO y ) semiconductors composed of bismuth, transition metal, and oxygen atoms have demonstrated improved photocatalytic activity and product selectivity. The vast number of element combinations available for Bi x MO y materials provides a huge compositional space for the rational design and isolation of promising photocatalysts for specific applications. In this study, we have systematically investigated the electronic and optical properties over Bi2O3 and a series of selected Bi x MO y group materials (BiVO4, BiFeO3, BiCoO3, and BiCrO3) by calculating band structure, basic optical property features, mobility and separation of charge carriers. It is clearly noted that the band gap and band edge position of the Bi x MO y group materials can be tuned in a wide range in comparison to Bi2O3. Similarly, the light response of Bi x MO y also can be broadened from the ultraviolet to the visible light region by adjusting the selection of transition metals. Additionally, the analysis of the effective mass of charge carriers of these materials further confirms their possibility in photocatalytic reaction applications because of the appropriate separation efficiency and mobility of carriers. A selection of experimental investigations on the crystal structure, composition, and optical properties of Bi2O3, BiVO4, and BiFeO3 as well as their catalytic performance in the degradation of methylene blue over was also conducted, which agree well with the theoretical predictions.

Heterojunction functionalized sodium alginate/carboxylated cellulose nanocrystals film enhancing sterilization performance for wound healing

In the realm of natural polysaccharides, hydrogen bonding is a prevalent feature, yet its role in enhancing photocatalytic antimicrobial properties has been underexplored. In this paper, heterojunctions formed by graphene oxide (GO) and ZIF-8 were locked in sodium alginate/ carboxylated cellulose nanocrystals via hydrogen bonding networks, designated as SCGZ. The SCGZ films exhibit superior photocatalytic performance compared to either ZIF-8 or heterojunctions. This enhancement is primarily due to two key factors: firstly, the hydrogen bonding network significantly enhances the transfer of protons and holes, thereby improving the separation efficiency of photo-generated carriers; secondly, the hydrogen bonding between the layers facilitates a more efficient charge transfer, which expedites the movement of electrons from ZIF-8 to GO upon illumination. In vitro studies demonstrated that the SCGZ films possess remarkable antibacterial capabilities, achieving 99.75 % and 99.61 % inhibition rates against S. aureus and E. coli, respectively. In vivo animal experiments have shown that SCGZ films can significantly accelerate the healing process of damaged tissues, with a healing efficiency of up to 90.5 %. This research provides additional insights into the development of natural polysaccharide-based multi‑hydrogen bonded macromolecules with enhanced photocatalytic properties.

Novel noble-metal-free NiCo2O4/CdIn2S4 S-scheme heterojunction photocatalyst with redox center for highly efficient photocatalytic H2 evolution

The exploration of efficient and noble-metal-free photocatalysts for photocatalytic H2 production is still a hot topic. Herein, a novel NiCo2O4/CdIn2S4 S-scheme heterojunction composites were successfully synthesized. Morphology characterization manifests that CdIn2S4 nanoparticles are tightly bound to the rod NiCo2O4 to form S-scheme heterojunction. Besides, X-ray photoelectron spectroscopy (XPS) results verify the existence of co-existing cobalt and nickel ions with multivalent state, which could provide H2 evolution active site and form redox centers. The S-scheme heterojunction and redox centers prompt the transfer of photogenerated e− from CdIn2S4 to NiCo2O4 for improving carrier separation efficiency, which is confirmed by a series of electrochemical experiments and photoluminescence (PL). The specific surface area and transmission electron microscope (TEM) results show that NiCo2O4 possesses a high specific surface area and porous structure, which could provide more active sites and facilitate H2O adsorption for further reduction reaction. The optimal NiCo2O4/CdIn2S4 composites possess maximum H2 evolution rate of 624 μmol·g−1·h−1, which is about 3.2 times than CdIn2S4-1 %Pt (198 μmol·g−1·h−1). After three cycles, the activity of NiCo2O4/CdIn2S4 shows no significant weaken. Moreover, the possible H2 evolution mechanism of NiCo2O4/CdIn2S4 S-scheme heterojunction composites is discussed. This research offers an idea for bimetallic oxide (NiCo2O4 etc.) modified sulfide to improve photocatalytic hydrogen production.

Regulating band structure, charge transfer and separation, oxygen adsorption and activation by surface ion modification.

As a most promising environmental technology, the substantial enhancement of photocatalytic efficiency is still a big challenge for practical applications. In this work, the surface of Bi2O2CO3 (BOC) nanotubes are modified by Cl and I. The as-obtained samples at different hydrothermal temperatures (T) are designated as T-X-BOC (X = Cl, I). X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS) prove that Cl and I merely chemically adsorb on the BOC surface, rather than dope into the crystal lattice. The surface modification of Cl and I slightly increases light absorption range, while significantly promotes the photoelectron migration from bulk to the surface that greatly enhances the carrier separation efficiency. Density functional theory (DFT) calculations further prove that surface Cl and I have adjusted band structure and surface charge distribution. Besides, the surface Cl and I favor the O2 adsorption and trap the surface photoelectrons, thus promoting the formation of •O2-; while the surface Cl and I impede the surface adsorption of H2O, thus refraining the generation of •OH. In the degradation of rhodamine B (RhB), holes and •O2- radicals play the crucial role. Under ultraviolet light irradiation (λ < 420nm) for 45min, the RhB degradation ratios over 150-Cl-BOC (94%) and 150-I-BOC (85%) are 4.2 and 3.7 times higher than that of original BOC (18%), respectively. This work demonstrates that the simple surface halogenation modification greatly improves the photocatalytic activity.

Z-scheme γ-Fe2O3/g-C3N4 in Photo-Fenton reaction for oxytetracycline degradation: Mechanism study and DFT calculation

With the urbanization and industrialization of the world, the pollution of water due to the misuse of antibiotics is increasing. In this study, a Z-scheme γ-Fe2O3/g-C3N4 composite photocatalyst was prepared, and the removal efficiency of oxytetracycline (OTC) reached 85.7% within 60 min under the Photo-Fenton reaction system higher than that of g-C3N4 and γ-Fe2O3. The composite has great anti-interference capability and sustainability, and the recyclability was demonstrated using hysteresis return lines data. The photoelectrochemical characterization was analyzed to investigate the effect of the building of Z-scheme heterojunction on the photogenerated carrier separation efficiency. The charge behavior of heterojunction interfaces was probed in conjunction with DFT calculations, and differential charge maps were used to visualize charge distributions to analyze possible charge transfer pathways. In addition, the active substances in the system were identified by ESR data and capture experiments. The results showed that ·OH was the dominant active substance for OTC degradation. Meanwhile, LC-MS data combined with Fukui function calculations led to the derivation of a possible degradation pathway dominated by ·OH. This research provides a reference for subsequent studies of non-homogeneous Photo-Fenton systems and offers a viable option for mitigating OTC pollution in water bodies.