Heterostructure Photocatalyst Research Articles

Preparation of MgIn2S4/g-C3N4 for enhanced ranitidine photocatalytic degradation activity via Z-scheme electron transfer

The evidence so far indicates that ranitidine (RAN) contains N-nitrosodimethylamine (NDMA), a strong carcinogen, which is extremely harmful to human health under long-term exposure. Hence, a well-design Z-scheme heterostructure composed of 3D MgIn2S4 micro-flower and 2D g-C3N4 nanosheets was fabricated and used to remove RAN. The optimal photocatalyst (MG-30) exhibited the fastest RAN degradation rate of 0.24685 min−1 within 30 min under visible light, which was 78.1 and 19.8 times higher than those of bare MgIn2S4 and g-C3N4, respectively. Impressively, MG-30 was exceedingly resistant to environmental variations including organic matter, inorganic salts and aqueous substrates. In the meantime, MG-30 boasted the merit such as wide pH range for RAN removal. The excellent results originated from the construction of Z-scheme heterojunctions, which improved the carrier separation efficiency and retained the strong redox ability of MG-30, thereby contributing to the creation of rich active species. Meanwhile, the 3D/2D structure of MgIn2S4/g-C3N4 overrode the limited reflection of visible light. The active species analyses revealed that superoxide radical (·O2−) and hydroxyl radical (·OH) mainly participated in RAN degradation. Furthermore, the possible degradation pathways of RAN and toxicity analysis of intermediates produced were presented. This work emphasizes practical application potential of Z-scheme heterostructure photocatalysts for emerging contaminants degradation in wastewater.

A novel g-C3N4@BiTiO2/NiO ternary heterostructure photocatalysts for effective degradation of tetracycline under light illumination

The effective removal of pharmaceutical contaminants from water sources is a critical environmental concern. In this research, we present an innovative g-C3N4@BiTiO2/NiO heterostructure photocatalyst for enhanced the higher degradation of tetracycline (TC) under visible-light radiation. The heterostructure combines the advantages of graphitic carbon nitride (g-C3N4), bismuth titanate (BiTiO2), and nickel oxide (NiO) to exploit their synergistic effects and enhance photocatalytic performance. The g-C3N4@BiTiO2/NiO heterostructure photocatalyst exhibits improved light absorption capabilities owing to the incorporation of g-C3N4 and BiTiO2, enabling efficient utilization of visible-light radiation. The visible light active the catalytic degradation of tetracycline was evaluated as a model reaction, and the g-C3N4@BiTiO2/NiO ternary heterostructure photocatalyst demonstrated superior performance in the degradation process and the removal efficiency of 91.2% for TC within 50 min under visible-light radiation. The trapping test discovered •O2 radical and •OH radical are the primary active species in the degradation process. Overall, this research contributes to the advancement of photocatalytic technology and offers a sustainable approach to mitigate pharmaceutical pollution in water sources. The novel g-C3N4@BiTiO2/NiO ternary heterostructure photocatalyst holds great potential for practical environmental science and engineering applications.

Minimizing CO2 emissions by photocatalytic CO2 reduction to CH3OH over Li2MnO3/WO3 heterostructures under visible illumination

Photocatalytic CO2 reduction to valuable fuels has proved to be a favourable process to produce renewable energy and reduce CO2 emissions, which mostly depends on designing effective photocatalysts with the rapid separation rate of charge carriers. In this contribution, mesoporous n-n heterojunction Li2MnO3/WO3 nanocomposites were designed via a simplistic sol-gel process for CO2 reduction utilizing visible illumination (λ > 420 nm). XRD and TEM measurements confirmed the synthesized Li2MnO3/WO3 nanocomposite is a monoclinic structure, and its particle size is 25 ± 5 nm. The obtained Li2MnO3/WO3 exhibited narrower bandgap energy (1.74 eV), larger surface area (212 m2g−1), exceedingly visible absorbing, and lower recombination of electron and hole. The yield of CH3OH was determined about 198, 871, 1140, 1550 and 1570 mmolg−1 for bare WO3 and 5%, 10%, 15% and 20% Li2MnO3/WO3 nanocomposites, respectively. These results evidenced that the 15% Li2MnO3/WO3 photocatalyst exhibited the best reduction ability compared to other nanocomposites. The CO2 reduction over 15% Li2MnO3/WO3 photocatalyst achieved a maximal CO2 conversion with the substantially boosted CH3OH, i.e., 1550 mmolg−1 after 9 h, which was enhanced 7.8 folds great than of WO3 NPs. Mesoporous Li2MnO3/WO3 nanocomposites, in comparison with bare WO3 NPs, created more active sites for facilitating CO2 and had a specific electric field to more effectively separate charge carriers. The Li2MnO3/WO3 photocatalyst has superior photostability during the continuous reduction of CO2 for 45 h with no remarkable decrease. The possible direct S-scheme mechanism for electron transfer over Li2MnO3/WO3 photocatalyst with the enhanced CO2 reduction ability was discussed. The present work demonstrates an avenue for building highly effective heterostructure photocatalysts in solar-energy-induced potential applications.

Surface diffusion induced degradation enhancement and zero-order kinetics in edge-connected MoS2/Au/TiO2 Z-scheme photocatalytic system

Heterostructured photocatalysts have demonstrated great potential in the photodegradation of organic pollutants, while the surfaces & interfaces of their multiple structural components play critical roles in determining their photocatalytic mechanisms and kinetics. Here, we fabricate an edge-connected MoS2/Au/TiO2 photocatalytic system via a selective photodeposition method and utilize a surface-diffusion mechanism to maximize the synergistic effects among the components. The resultant photocatalytic system behaves as a Z-scheme with well spatially separated redox reaction sites. The optimal catalyst 10 % MS/Au/T exhibited a pseudo 1st-order rate constant of 0.0145 min−1 within 120 min, which is seven times more than that of pristine TiO2. The edge-deposited MoS2 in the nanocomposite serves as a reservoir to adsorb and then transport the pollutant molecules rapidly to TiO2 surface for oxidation. Such a pre-concentration effect, as well as the Z-scheme charge transfer mechanism, has enhanced the overall degradation efficiency, and induced the occurrence of zero-order degradation kinetics. The charge transfer behaviors, the diffusion-enhancement mechanism, zero-order kinetics, and the order transition are then thoroughly studied against the MoS2 mass loading. 10 % MS/Au/T showed the highest values of zero and first-order constants, which were 0.073 ppm/min and 0.011 min−1, respectively. A diffusion-enhanced model is developed and validated to explain the experimental observations. This work provides meaningful insights into degradation enhancement and kinetic analysis for heterostructured photocatalytic systems.

Construction of graphitic carbon nitride coupled TiO2 heterostructured composite for enhanced photocatalytic performance towards organic pollutant degradation

The g-C3N4/TiO2 heterostructure photocatalysts (PCs) were successfully synthesized in a facile way. Powder XRD, FT-IR, XPS, SEM, HR-TEM, and UV–Vis spectra were used for structural, morphological, and optical characterization. The photocatalytic action of the as-synthesized GTO2 catalyst samples was examined via methylene blue (MB) dye and the degradation efficiency under light exposure was 80.8 % in 160 min. The outcomes exhibited that the photocatalytic MB dye degradation confirmed pseudo-first-order kinetic fitting, and the kinetic constant of GTO2 was 5.04 folds higher than those of GCN and 3.21 folds higher than those of TiO2, respectively. The enhanced photocatalytic activity of GTO2 PCs was due to the heterostructure formation on the TiO2/g-C3N4 interface. Formation of efficient GTO2 heterostructure PCs resulted in the suppression of photo-produced electron–hole (e-/h+) pair recombination rate and the increase of its charge separation respectively. The superoxide radical anions (•O2–) and hydroxyl radicals (•OH) played a prominent role in the photocatalytic MB dye degradation process by efficient GTO2 PCs.

In-situ self-assembled flower-like ZnIn2S4/CdIn2S4 composites with enhanced interfacial charge transfer and photocatalytic degradation of atrazine

In heterostructure photocatalysts, interface charge transfer is a crucial step in the photocatalytic process, so it is crucial to construct photocatalysts with high interface charge transfer efficiency. Here we report an in-situ self-assembled flower-like ZnIn2S4/CdIn2S4 (ZCIS) composites with excellent catalytic performance for atrazine (ATZ) degradation. The ZCIS-4 composite could degrade 99.82% of ATZ within 40 min, which showed 1.42 and 1.91 times better than blank ZnIn2S4 and CdIn2S4, respectively. The excellent catalytic performance is attributed to the built-in electric field in the in-situ self-assembled composite photocatalyst, which accelerates the rapid transfer of interfacial charges and the rapid separation of photogenerated electron hole pairs. The toxicity assessment shown that some intermediates exhibited decreased toxicities; however, the toxicities were still significant. Active radical capture experiments and electron spin resonance characterization demonstrated that h+, O2− were the main active free radicals. Differential charge density simulation calculations verified that interface photogenerated electrons were transported from CIS to the ZIS surface.

Design and construction of SnIn4S8/Cd0.5Zn0.5S heterostructure photocatalyst for efficient Cr(VI) reduction

The development of highly competent and economical photocatalysts for competent erasure of heavy metal pollutants in water is of momentous import but still a significant challenge. Herein, 3D/0D SnIn4S8/Cd0.5Zn0.5S heterostructure photocatalyst was resoundingly fabricated through integrating Cd0.5Zn0.5S nanoparticles on the surface of SnIn4S8 microsphere via a simple solvothermal method and applied to high efficiency photoreduction Cr(VI). The fabricated SnIn4S8/Cd0.5Zn0.5S with optimized composition ratio achieves the exceptional reduction Cr(VI) property and the photoreduction efficiency of 20 % SnIn4S8/Cd0.5Zn0.5S can reach 91.1 % within 30 min visible light illumination. The prominent photocatalytic efficiency comes from the intimate contact of heterostructure interface, which effectively expedites the separation and migration of carrier and inhibits the photocorrosion of photocatalyst. This work provides a promising photocatalyst for water environment remediation, and promotes the exploration of heterostructure photocatalyst for wastewater purification.

N,P co-doped carbon quantum dots bridge g-C3N4 and SnO2: Accelerating charge transport in S-scheme heterojunction for enhanced photocatalytic hydrogen production

The preparation of photocatalysts with efficient electron-hole separation efficiency is the key to achieving sustainable utilization of solar energy. Herein, a three-phase composite of N,P co-doped carbon dots (NPCDs), SnO2 nanowires, and g-C3N4 nanotubes (CNNT) is synthesized, forming an S-scheme SnO2/NPCDs/CNNT heterojunction. The construction of S-scheme heterojunction not only improves the reduction ability due to band bending, but also promotes the separation of carriers. The conductive NPCDs are located between SnO2 and CNNT and formed as a unique charge transfer channel that accelerates carriers transfer between S-scheme heterojunction interfaces. Additionally, NPCDs serves as electron acceptors to receive electrons from the conduction band of CNNT, thereby further facilitating the carrier separation. This synergistically boosts the photocatalytic hydrogen production activity of SnO2/NPCDs/CNNT three-phase catalysts, leading to a high H2 yield (10.73 mmol·g−1·h−1) and outstanding cyclic stability. This study offers a strategy for designing heterostructure photocatalysts that enhanced charge separation through interface engineering.

Construction of novel g-C3N4/β-FeOOH Z-Scheme heterostructure photocatalyst modified with carbon quantum dots for efficient degradation of RhB

The degradation of organic pollutants using semiconductor photocatalysts is a new ecological approach, but the currently available photocatalysts are not very efficient. Herein, in order to obtain efficient visible-light photocatalysts, g-C3N4/β-FeOOH-modified carbon quantum dots (CDs) composite photocatalysts with Z-Scheme charge transfer mechanism were successfully synthesized. The phase composition and morphology of the composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrophotometry (FT-IR), and X-ray photoelectron spectroscopy (XPS) techniques. Due to the upconversion effect of the CDs, the optical response range of the composite was effectively widened, and the optical utilization rate was improved. The Z-Scheme heterostructure not only improves the light trapping ability, significantly inhibits charge-carrier complexation, and realizes the spatial separation of redox sites, but also ensures that the photocatalyst maintains a suitable valence-conductivity band position and maintains the strong redox reactivity. In addition, CDs have the unique characteristics of electronic storage and transfer, which effectively enhance the quantum separation efficiency of the composite. The photocatalytic efficiency was measured by degrading rhodamine B (RhB) under visible light. The degradation performance was the best when the weight ratio of CDs was 6%, and the RhB solution degradation rate reached 100 % in 60 min. The unique structure and reliable mechanism provide a way for the development of advanced photocatalyst.

Interfacial chemical bond regulating the electronic coupling of ZnIn2S4−x-WO3−x for enhancing the photocatalytic pollutions degradation coupled with hydrogen evolution

Constructing Z-scheme heterostructure photocatalysts with a staggered band structure holds great potential to realize synergistic oxidation and reduction reactions. However, the Z-scheme heterostructure with interfacial vacancies significantly disturbs the behaviors of charge transfer and remains a challenging as well as urgent issue to exploit. Here, the ultrathin ZnIn2S4−x-WO3−x Z-scheme heterostructure (ZW) was synthesized via a facile in situ hydrothermal strategy. Experimental results and DFT calculations unveiled that the dual vacancies induced the formation of interfacial bonds. Importantly, the interfacial bonds tremendously modulate the electronic structure of heterostructure for enlarging the built-in electric field and reducing the aggregation effect of charge in the interface vacancies, which contributed to promoting charge transfer through the interface as well as exciton dissociation. Ultimately, the optimized ZW-4 exhibited an exceptional photocatalytic hydrogen evolution performance of 737.75 μmol g−1 h−1 and a pollution degradation rate greater than 99.99% without using any cocatalyst under visible light irradiation. Our work offers a deep insight into the ideal charge migration paths in highly efficient Z-scheme heterojunctions with vacancies.

Defect and Donor Manipulated Highly Efficient Electron-Hole Separation in a 3D Nanoporous Schottky Heterojunction.

Given the rapid recombination of photogenerated charge carriers and photocorrosion, transition metal sulfide photocatalysts usually suffer from modest photocatalytic performance. Herein, S-vacancy-rich ZnIn2S4 (VS-ZIS) nanosheets are integrated on 3D bicontinuous nitrogen-doped nanoporous graphene (N-npG), forming 3D heterostructures with well-fitted geometric configuration (VS-ZIS/N-npG) for highly efficient photocatalytic hydrogen production. The VS-ZIS/N-npG presents ultrafast interfacial photogenerated electrons captured by the S vacancies in VS-ZIS and holes neutralization behaviors by the extra free electrons in N-npG during photocatalysis, which are demonstrated by in situ XPS, femtosecond transient absorption (fs-TA) spectroscopy, and transient-state surface photovoltage (TS-SPV) spectra. The simulated interfacial charge rearrangement behaviors from DFT calculations also verify the separation tendency of photogenerated charge carriers. Thus, the optimized VS-ZIS/N-npG 3D hierarchical heterojunction with 1.0 wt % N-npG exhibits a comparably high hydrogen generation rate of 4222.4 μmol g-1 h-1, which is 5.6-fold higher than the bare VS-ZIS and 12.7-fold higher than the ZIS without S vacancies. This work sheds light on the rational design of photogenerated carrier transfer paths to facilitate charge separation and provides further hints for the design of hierarchical heterostructure photocatalysts.

In-situ synthesis and enhanced photocatalytic nitrogen fixation property of novel NiS/g-C3N4 heterostructure photocatalysts with nitrogen vacancy

Rapid recombination of the photo-generated charge carriers leads to the poor photocatalytic nitrogen fixation property of pristine graphite-like carbon nitride (g-C3N4). To enhance the photocatalytic performance of g-C3N4, nickel sulfide (NiS) nanoparticles were anchored onto the surface of g-C3N4 by using the in-situ decomposition-thermal polymerization method in this work. The incorporation of NiS cocatalyst expanded the absorption range, enhanced the efficiency of separating photo-generated charge carriers, reduced the band gap from 2.78 eV to 2.47 eV, increased the specific surface area 7.1 m2·g−1 to 19.5 m2·g−1, and enlarged the photo-current density, which can inhibit the recombination of photo-generated charge carriers. Furthermore, the emergence of the nitrogen vacancy occurred during the in-situ synthetic process as a result of the thermal decomposition of thioacetamide hydrolysate, thereby leading to an enhancement in the photocatalytic nitrogen fixation efficiency. The results of the nitrogen fixation experiment demonstrated that 13 % NiS/g-C3N4 exhibited the highest activity, with a photocatalytic nitrogen fixation rate of 8.15 mg/L. This rate is 7.6 times greater than that of pure g-C3N4, which can be attributed to several factors, including a higher separation rate of photogenerated electrons, a larger specific surface area, a wider range of responsiveness to visible light, and the presence of the nitrogen vacancy.

Origin of Cycle Performance in the Ag2O/TiO2 Heterostructure Photocatalyst.

In recent years, many studies on photocatalysis focused on improving efficiency. However, the cycle performance is also an important index for industrialization. Here, an Ag2O/TiO2 heterostructure photocatalyst is prepared for continuous photodegradation of methylene blue (MB) under visible light, and the samples after the first and fifth round reactions are recycled to study the microstructure evolution of the photocatalyst. The results show that the performance is obviously improved in the second round and remains stable in the following reaction round. Due to the charge transfer, Ag2O/TiO2 gradually changes to Ag2O@Ag-TiO2-x during the photocatalytic reaction. The resulting localized surface plasmon resonance effect and the change of the interface structure greatly increase the number of carriers and prolong the lifetime of carriers. Such variations of microstructures and photoelectric properties of the samples due to the charge transfer and redox reaction on the surface of the photocatalyst dominate the cycle performance.

Interfacial Charge Transfer Effects of MoS2/α-Fe2O3 Nano-Heterojunction and Efficient Photocatalytic Hydrogen Evolution under Visible-Light Irradiation.

Researchers have made efforts to develop high-productivity photocatalysts for photocatalytic hydrogen production to reduce the problem of a lack of energy. Bulk semiconductor photocatalysts mainly endure particular limitations, such as low visible light application, a quick recombination rate of electron-hole pairs, and poor photocatalytic efficiency. The major challenge is to improve solar-light-driven heterostructure photocatalysts that are highly active and stable under the photocatalytic system. In this study, the proposed nano-heterojunction exhibits a great capacity for hydrogen production (871.2 μmol g-1 h-1), which is over 8.1-fold and 12.3-fold higher than that of the bare MoS2 and bare α-Fe2O3 samples, respectively. It is demonstrated that the MoS2/α-Fe2O3 heterojunction gives rise to an enhanced visible light response and accelerated photoinduced charge carrier separation. This work provides an improved visible light absorption efficiency and a narrowed energy band gap, and presents a "highway" for electron-hole pairs to promote transfer and inhibit the combination of photoinduced charge carriers for the utilization of nano-heterojunction photocatalysts in the field of hydrogen production.

Double S‐Scheme Polydopamine/TiO2/Chlorophyll as Stable and Efficient Green Photoelectrocatalyst

AbstractInspired by natural photosynthesis, a new green catalyst with better photocatalytic properties was obtained. Nanostructured TiO2, a cheap cost natural Chlorophyll‐a as an electron promotor and a mussel‐inspired polydopamine (PD) bio adhesive were synergistically combined in the double S‐scheme hybrid photocatalysts The role of PD as a bridging molecule between the pigments of Chl and TiO2 was clearly demonstrated by improved charge transfer and recombination rate. Methylorange as a probe molecule was used to test the stability and efficiency of the new photocatalyst. This challenging approach on obtaining new green bioinspired catalysts avoiding critical raw materials is in line with the new vision on catalysts. The results of this study show the effectiveness and stability of the new photocatalyst. Based on the combined effect of PD functionalization and Chl sensitization, the NT/PD‐Chl heterostructure photocatalyst had the best photo(electro)catalytic performance for MO degradation which was shown to be 97.74 % after 180 min.

Bi-metal-organic framework-derived S-scheme InP/CuO-C heterostructure for robust photocatalytic degradation of ciprofloxacin in a microfluidic photoreactor

The presence of antibiotics in the environment raises significant environmental concerns due to their adverse impact on organisms and the potential transmission of drug-resistant genes. Heterostructure photocatalysts have emerged as a promising remedy for this issue. This study introduces an innovative approach that employs an In/Cu-organic framework (bimetallic-MOF) as a sacrificial precursor for crafting a carbon-supported InP/CuO heterostructure with adjustable band-matching properties. Through comprehensive analyses encompassing structural, morphological, optical, electrochemical, and density functional theory calculations, compelling evidence is presented for the cubic carbon layer housing zinc-blende InP and monoclinic CuO. Furthermore, the existence of an S-scheme charges transfer pathway between InP and CuO is strongly substantiated, significantly enhancing spatial charge separation. The engineered InP/CuO S-scheme nanoheterostructure exhibits exceptional performance and stability under visible light exposure within a custom-designed spiral microfluidic photoreactor (SMPR), achieving an impressive 81.70% degradation of ciprofloxacin – a commonly found antibiotic in wastewater – in just 15 min. The findings from photoelectrochemical and spectroscopic analyses reveal that the InP/CuO S-scheme heterostructure, derived from the bi-MOF, in conjunction with the SMPR, not only exhibits a robust response to visible light, improved carrier mobility, and effective charge separation and transfer, but also enhances mass and photon transfer. Within the S-scheme heterostructure, the process of charge transfer centers on the creation of reactive oxygen species, specifically OH and O2–, on InP and CuO surfaces, correspondingly. These species function as oxidation and reduction photocatalysts, respectively, exerting a pivotal influence in augmenting the overall performance. The findings make substantial contributions towards creating effective and sustainable solutions for mitigating environmental contamination, emphasizing the crucial role of advanced material design and microfluidic reactor engineering in the realm of photocatalysis.

Unraveling the synergy of interface engineering α-MnO2/Bi2WO6 heterostructures and defective active sites for superdurable photocatalysis: Mechanistic insights into charge separation/transfer

The construction of visible-light-driven hybrid heterostructure photocatalysts is of great significance for environmental remediation, although the utilization of strong visible-light response photocatalysts with high efficiency and stability remains a major challenge. On the other hand, defect engineering is an excellent way to introduce metal cation vacancies in materials, thereby ensuing in highly enhanced catalytic performance. Inspired by this, we effectively constructed a built-in interface α-MnO2/Bi2WO6 heterostructure with abundant intimate interfaces and defective Mn3+/Mn4+ active sites for photocatalytic tetracycline hydrochloride (TC-HCl), hexavalent chromium Cr6+ reduction, and Escherichia coli (E. coli) inactivation. The experimental results, such as the active species test and X-ray photoelectron spectroscopy, indicated that the defective sites Mn3+/Mn4+, surface oxygen vacancies, and Bi(3+x)+ boosted the visible light absorption, and highly enhanced the photoinduced charge separation/transfer. Furthermore, experimental and DFT calculations reveal the high charge density at the built-in interface heterostructure and the Z-scheme charge transfer mechanism during the photocatalytic process. The results further reveal that O2− and 1O2 are the main reactive active species contributing to the photocatalytic reaction. The exceptional TC-HCl decomposition activity of the α-MnO2/Bi2WO6 heterostructure (97.56%, 2.31, and 2.04 times higher than bulk), enhanced reaction kinetics (Kapp = 0.041 min−1, 6.4, and 5.2 times higher than bulk), removal rate of 80.3%, Cr6+ reduction to Cr3+ (98.56%, Kapp = 0.0599 min−1), and almost 100% bacterial inactivation compared to bulk α-MnO2 (42.22%) and Bi2WO6 (47.76%), were mainly due to the enhanced charge separation/transfer at the built-in interface and high charge density. This study opens new horizons for constructing Z-scheme MnO-based interface heterostructures with abundant defect sites for exceptional photocatalytic applications.

Designing of covalent organic framework/2D g-C3N4 heterostructure using a simple method for enhanced photocatalytic hydrogen production

Designing heterostructure photocatalysts is a promising approach for developing highly efficient photocatalysts for hydrogen energy production. In this work, we synthesized a series of a covalent organic framework (COF)/g-C3N4 (CN) heterojunction photocatalysts, denoted as x % COF/CN (in which x indicates the weight % of COF and x = 5, 10, 20, 30, 40, 50, 90, 95, 100), for hydrogen production. The COF, which is a key component of the photocatalyst, was prepared by assembling benzothiadiazole (BT) and pyrene (Py) derivatives as building blocks. Integrating COF rods into the two-dimensional (2D) layered g-C3N4 structure significantly improved photocatalytic H2 production. The hybrid system (30 % COF/CN) displayed an outstanding hydrogen evolution rate (HER) of 27540 ± 805 μmol g−1h−1, outperforming most known COFs and g-C3N4-based photocatalysts, besides exhibiting stable photocatalytic performance. Moreover, the apparent quantum yield (AQY) was 15.5 ± 0.8 % at 420 nm. Experimental techniques and density functional theory (DFT) calculations demonstrated that the 30 % COF/CN heterostructure has broad visible-light absorption, adequate band energy levels, and the best chemical reactivity descriptors compared to the individual components, resulting in effective carrier separation and excellent performance. Our findings offer a valuable strategy for developing highly efficient and stable heterojunction photocatalysts for visible-light‐driven H2 evolution.

Simple and fast synthesis of BiOBr/[Bi6O5(OH)3](NO3)5·3H2O composites for efficient photocatalytic degradation of RhB under visible light

In this study, a heterostructure photocatalyst consisting of Bi6O5(OH)3](NO3)5·3H2O (was denoted as BiOOHN) and BiOBr was fabricated via a simple and economic co-precipitation method. In this method, the amount of Br in the composition was controlled by changing the volume of hydrobromic acid (HBr) during the manufacturing process. The photocatalytic performance of the prepared samples by photodegradation of rhodamine B (RhB) solution under visible light radiation was investigated and the optimum amount of HBr was obtained. The results showed that BiOBr/BiOOHN composite has higher photocatalytic efficiency compared to pure BiOOHN and BiOBr, so that almost 100 % of RhB solution was degraded in the presence of BiOBr/BiOOHN composite photocatalyst during 100 min, while this value was equal to 0 % and 21 % for pure BiOOHN and BiOBr, respectively. Results indicated that the BiOOHN band gap is in the ultraviolet region (3.45 eV) and not possible to activate this sample to generate electron-hole pairs under visible radiation. While the energy gap of the samples synthesized in the presence of HBr was around 2.90 eV, which enables the activation of these compounds under visible radiation to generate electron-hole pairs for photocatalytic reactions. Therefore, the weak BiOOHN photocatalytic performance is attributed to the its wide band gap energy in comparison with other samples. Also, the better performance of composite samples compared to pure BiOBr is owing to the formation of a heterostructure between BiOOHN and BiOBr. It leads to better separation of electron-hole pairs at the interface of two semiconductors and hinders their recombination, which improves photocatalytic performance. Also, a mechanism for the photocatalytic reactions of RhB degradation was proposed based on experimental data and the experiment of trapping active species. According to this mechanism, the holes and free hydroxyl radicals (•OH) play a key role in the photocatalytic degradation reactions of RhB.

Efficient Photocatalytic CO2 Reduction with High Selectivity for Ethanol by Synergistically Coupled MXene-Ceria and the Charge Carrier Dynamics.

The primary factors that govern the selectivity and efficacy of CO2 photoreduction are the degree of activation of CO2 on the active surface sites of photocatalysts and charge separation/transfer kinetics. In this context, the rational synthesis of heterostructured MXene-coupled CeO2-based photocatalysts with different loading concentrations of Ti3C2MXene via a one-step hydrothermal approach has been undertaken. These photocatalysts exhibit a shift in X-ray diffraction peaks to higher 2θ values and changes in stretching vibrations of 5 wt % Ti3C2MXene/CeO2(5-TC/Ce) that indicate interaction between Ti3C2MXene and CeO2. Moreover, XPS analysis confirms the presence of the Ce3+/Ce4+ states. A sharp band at 2335 cm-1 observed during the CO2 photoreduction process corresponds to bidentate b-CO32-, which facilitates the adsorption of CO2 at the surface of the catalyst as revealed by the TPD analysis. Furthermore, the Schryvers test and NMR analysis were undertaken to confirm the formaldehyde intermediate formation during CO2 photoreduction to C2H5OH. The decrease in emission intensity, reduced lifetimes (2.68 ns), and lower interfacial resistance, as revealed by PL, TR-PL, and EIS analysis, imply an efficient charge separation and charge transfer in the case of the Ti3C2MXene/CeO2 heterojunction. The decrease in the intensity of peaks in the EPR spectrum in the case of 5-TC/Ce further confirms efficient charge transfer kinetics across the interface. The optimized 5-TC/Ce shows CO2 reduction with a drastically enhanced yield of ethanol on the order of 6127 μmol g-1 at 5 h with 98% selectivity and 7.54% apparent quantum efficiency, which is 6-fold higher than that of ethanol produced by bare CeO2. Herein, CeO2 that acts as a redox couple (Ce3+/Ce4+) when coupled with MXene having a metallic nature that reduces the electron transfer resistance is in unison, enabling an enhanced mobilization of electrons. Thereby, the synergistic coupling of Ti3C2MXene with CeO2 leads to an efficient photoreduction of CO2 under visible light illumination.