Recombination Of Electron-hole Pairs Research Articles

Modification of bismuth-rich to synthesize floral spherical Z-type heterojunction CoAl2O4/Bi4O5Br2 photocatalysts for photocatalytic degradation of tetracycline: DFT calculations, toxicity assessment

Strategies were employed to boost responsiveness to visible light to augment the elimination of water-borne organic contaminants and mitigate the recombination of electron-hole pairs. Herein, a floral spherical CoAl2O4/Bi4O5Br2 Z-scheme heterojunction was effectively produced through in-situ construction, followed by an evaluation of its photocatalytic activity against tetracycline hydrochloride. The best-prepared photocatalyst CoAl2O4/Bi4O5Br2 showed good photodegradation performance (91.5%) under visible light. In addition, it exhibits good removal efficiency for other antibiotics and dyes, and the prepared catalyst demonstrates favorable stability. The accomplishment of fabricating the CoAl2O4/Bi4O5Br2 heterojunction, along with the photogenerated carrier relay mechanism conforming to a Z-scheme process, was substantiated through a variety of analytical techniques and DFT calculations. Within the engineered Z-scheme heterojunction of CoAl2O4/Bi4O5Br2, an intrinsic electric field facilitates the direct shuttling of photo-induced charges from Bi4O5Br2's conduction band to CoAl2O4's valence band. Simultaneously, this electric field formation serves to diminish the recombination rate of electrons and holes. Finally, possible degradation pathways were proposed, and the intermediates were evaluated for toxicity. The results indicate that the construction of CoAl2O4/Bi4O5Br2 heterojunction is a feasible pathway for the effective degradation of antibiotics.

Improving visible light-driven CO2 conversion to high calorific fuels over sustainable highly crystalline and holey sulphur doped graphitic carbon nitrides

The effectiveness of CO2 reduction through g-C3N4 (CN) is considerably hindered by poor visible light absorption and the high rate of recombination of electron-hole (e−/h+) pairs. An effective method for increasing CO2 photoreduction efficiency is to incorporate non-metal components into the CN to modify its electronic properties and enhance its performance. This research presents the findings of our inquiry into sulfur-doped graphitic carbon nitrides (S–CN) for CO2 reduction through visible light. The XPS study reveals that the substitution of nitrogen atoms in the heptazine ring by sulfur (S) doping significantly influences the electronic configuration of CN, while the UV–visible absorbance spectra reveals that the CN band gap value 2.64 eV has reduced to 2.50 eV after S doping. Therefore, S–CN exhibits exceptional visible-light absorption, separation and migration of photoexcited e−/h+, corroborated by photoluminescence and transient photocurrent response experiments. Besides, S–CN demonstrated remarkable CO2 reduction capabilities without any cocatalyst or sacrificial agent, achieving CO/CH4 formation rates of 25/3 μmolg−1h−1, outperforming traditional CN. Our research highlights the relevance of impeding the e−/h+ recombination process to boost solar energy conversion output, suggesting potential for productive solar fuel generation using g-C3N4.

High efficiency photocatalytic hydrogen evolution by black phosphorus quantum dots decorated 1D g-C3N4 nanotubes

Bare g-C3N4 (CN) encounters substantial charge recombination with strong fluorescence, which is detrimental to the photocatalytic reactions. In this work, g-C3N4 is curved into nanotubes then combined with black phosphorus quantum dots (BPQDs). The BPQDs decorated tubular CN (BPTCN) exhibits a stable and high photocatalytic hydrogen evolution rate of 507.51 μmolh−1g−1 under visible irradiation, which is four times higher than that of pure TCN. The apparent quantum yield (AQY) at 420 nm of BPTCN reaches 2.58%. The excellent photocatalytic ability of the BPTCN is attributed the suppressed recombination of electron-hole pair and improved carrier transport efficiency, which are introduced by the 1D tubular structure and the band alignment of the BPTCN heterojunction.

In-situ growing of MIL88A(Fe)@active faceted Cu2O core-shell heterostructure for super photocatalytic performance and catalytic reduction of toxic nitrophenol compounds

Herein, well-constructed 2D active (110) and (111) faceted Cu2O nanosheets are in-situ grown on the surface of spindle MIL-88A to form a novel porous MIL88A (Fe)@active faceted Cu2O core-shell heterostructure via a facile solvothermal method. The fabricated heterostructure is optimized to be a promising catalyst for the catalytic reduction of various nitrophenol compounds such as P-nitrophenol and 2,4-dinitrophenols, as well as the removal of methylene blue dye (MB). The optimal M88@Cu2O-2 heterostructure demonstrated an outstanding catalytic performance for reducing nitrophenols, reaching 96.7 % for P-nitrophenol and 96.1 % for 2.4-dinitrophenol. It also achieved excellent photocatalytic activity for MB dye, reaching 95 % through 30 min, compared to 64 % and 72 % for Cu2O and MIL-88A, with rate constants (k) reaching 0.1, 0.038, and 0.04 min−1, respectively. The surprising photocatalytic performance of the prepared structure could be attributed to the following aspects: (i) the growth of the active (111) and (110) facets Cu2O on the surface of MIL-88A, which could provide various surface energies, reactivates, and crystallographic arrangements, all of which impact the photocatalytic efficiency of the designed M88@Cu2O-2 heterostructure, (ii) the construction of an efficient heterojunction between active faceted Cu2O and MIL88A, which resists the recombination of e- and h+, improving the migration and separation of charge carriers, and (iii) the core-shell construction could provide more electron transport channels to significantly enhance the suppression of electron-hole pair recombination in the photocatalytic process. Besides that, the M88@Cu2O-2 core-shell has great photo-electrochemical performance, reaching 17.68 μA/cm2 for the photocurrent test and 73 mA/cm2 for the LSV test when exposed to visible light. Our study will provide a new vision for developing more hierarchical core/shell MOF-based heterostructures with outstanding multifunctional performance for future industrial practice.

Chiral Inorganic Polar BaTiO3/BaCO3 Nanohybrids with Spin Selection for Asymmetric Photocatalysis.

Chirality-dependent photocatalysis is an emerging domain that leverages unique chiral light-matter interactions for enabling asymmetric catalysis driven by spin polarization induced by circularly polarized light selection. Herein, we synthesize chiral inorganic polar BaTiO3/BaCO3 nanohybrids for asymmetric photocatalysis via a hydrothermal method employing chiral glucose as a structural inducer. When excited by opposite circularly polarized light, the same material exhibits significant asymmetric catalysis, while enantiomers present an opposite polarization preference. More importantly, the preferred circularly polarized light undergoes reversal with reversal of the CD signal. Systematic experimental results demonstrate that more photogenerated carriers are generated in chiral semiconductors under suitable circularly polarized light irradiation, including more spin-polarized electrons, which inhibits the recombination of electron-hole pairs and promotes the activation of oxygen molecules into reactive oxygen species, thus inducing this asymmetric photocatalytic feature. This study provides valuable insights for the development of highly efficient polarization-sensitive chiral perovskite nanostructures as promising candidates for next-generation, multifunctional chiral device applications.

Exploring Pt-Impregnated CdS/TiO2 Heterostructures for CO2 Photoreduction.

This work focuses on the production of methane through the photocatalytic reduction of carbon dioxide using Pt-doped CdS/TiO2 heterostructures. The photocatalysts were prepared using P25 commercial titania and CdS synthesized through a solvothermal methodology, followed by the impregnation of Pt onto the surface to enhance the physicochemical properties of the resulting photocatalysts. The pure and heterostructure-based materials were characterized using X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy (UV-Vis), ultraviolet photoelectron spectroscopy (UPS), and photoluminescence spectroscopy (PL). The obtained results show the successful synthesis of the heterostructure impregnated with Pt. Moreover, the observed key role of CdS and Pt nanoparticles in the final semiconductor is to reduce the electron-hole pair recombination rate by acting as an electron sink, which slows down the recombination process and increases the photocatalyst efficiency. Thus, Pt-doped CdS/TiO2 heterostructures with the best observed composition presents better catalytic activity than P25 titania with methane production values being 460 and 397 µmol CH4/g·h, respectively.

Pb-N Chemically Anchors CsPbBr3 on 1D Porous Tubular g-C3N4 for Enhanced Photocatalytic CO2 Reduction.

Halide perovskite CsPbBr3 (CPB) quantum dots (QDs) are considered as a promising candidate for solar-driven CO2 conversion for their unique optoelectronic properties and suitable band structure. However, the CO2 conversion efficiency of pristine CsPbBr3 quantum dots is severely limited due to their rapid electron-hole pair recombination and insufficient active sites. In this study, by immobilizing CPB QDs onto one-dimensional (1D) porous tubular g-C3N4 (TCN), an effective 0D/1D CPB@TCN heterojunction photocatalyst for CO2 reduction is fabricated. Density functional theory (DFT) calculations combined with experimental studies demonstrate that CPB QDs are uniformly anchored on the surface of TCN through Pb-N chemical bonding, resulting in efficient separation and transfer of photogenerated carriers in CPB@TCN photocatalysts. The resultant CPB@TCN photocatalysts exhibit significantly enhanced photocatalytic activity for CO2 reduction with the highest conversion rate of 22.62 μmol·g-1·h-1, which is 5.33-times higher than that of pristine CPB QDs. This work unveils the interfacial bonding mechanism of CPB@TCN heterojunction through Pb-N chemical bond, which provides new insights for the development perovskite-based heterojunction photocatalysts.

Synthesis of TiO2-ZnO n-n Heterojunction with Excellent Visible Light-Driven Photodegradation of Tetracycline.

Zinc oxide-based photocatalysts with non-toxicity and low cost are promising candidates for the degradation of tetracycline. Despite the great success achieved in constructing n-n-type ZnO-based heterojunctions for the degradation of tetracycline under full-spectrum conditions, it is still challenging to realize rapid and efficient degradation of tetracycline under visible light using n-n-type ZnO-based heterojunctions, as they are constrained by the quick recombination of electron-hole pairs in ZnO. Here, we report highly efficient and stable n-n-type ZnO-TiO2 heterojunctions under visible light conditions, with a degradation efficiency reaching 97% at 1 h under visible light, which is 1.2 times higher than that of pure zinc oxide, enabled by constructing an n-n-type heterojunction between ZnO and TiO2 to form a built-in electric field. The photocatalytic degradation mechanism of n-n TiO2-ZnO to tetracycline is also proposed in detail. The demonstration of efficient and stable heterojunction-type ZnO photocatalysts under visible light is an important step toward commercialization and opens up new opportunities beyond conventional ZnO technologies, such as composite ZnO catalysts.

A comparative study for optimizing photocatalytic activity of TiO2-based composites with ZrO2, ZnO, Ta2O5, SnO, Fe2O3, and CuO additives

Despite the widespread use of titanium dioxide (TiO2) in photocatalytic applications, its inherent limitations, such as low efficiency under visible light and rapid recombination of electron-hole pairs, hinder its effectiveness in environmental remediation. This study presents a comparative investigation of TiO2-based composites, including TiO2/ZrO2, ZnO, Ta2O3, SnO, Fe2O3, and CuO, aiming to assess their potential for enhancing photocatalytic applications. Photocatalysis holds promise in environmental remediation, water purification, and energy conversion, with TiO2 being a prominent photocatalyst. To improve efficiency and broaden applicability, various metal oxide composites have been explored. Composites were synthesized and characterized using techniques such as XRD, SEM, TEM, and zeta potential analysis to evaluate their structural and morphological properties. Photocatalytic performance was assessed by degrading herbicide Imazapyr under UV illumination. Results revealed that, the photo-activity of all prepared composites were more effective than the photo-activity of commercial hombikat UV-100. The photonic-efficiency is arranged according to the order TiO2/CuO > TiO2/SnO > TiO2/ZnO > TiO2/Ta2O3 > TiO2/ZrO2 > TiO2/Fe2O3 > Hombikat TiO2-UV100. All composites exhibited superior performance, attributed to enhanced light absorption and charge separation. The study underscores the potential of these composites for environmental remediation and energy conservation, offering valuable insights for the development of advanced photocatalysts.

Development of engineered Zn-MOF/g-C3N4 based photoelectrochemical system for real-time sensors and removal of naproxen in wastewater

Naproxen-contaminated water may lead to the accumulation of the drug in aquatic organisms and can pose high risks to an aquatic environment and human beings. Therefore, this work aimed to develop photoelectrochemical sensing and degradation of naproxen (NPX) using zinc-metal organic framework /graphitic carbon nitride thin film-based fluorine-doped tin oxide (Zn-MOF/g-C3N4/FTO) as anode material for the sensing and degradation of naproxen (NPX). The surface morphology, structure, surface property, surface area, optical property, photocurrent, and charge transfer kinetics abilities were studied using different techniques. The nanocomposites showed a superior photocurrent response (0.815 mA cm-2) compared to the original g-C3N4 (0.328 mA cm-2). The photo-anode made of Zn-MOF@g-C3N4/FTO displayed the highest photocurrent value, indicating that the alignment of the two semiconductor bands prevented the quick recombination of electron-hole pairs. Owing to these attractive features, the Zn-MOF/g-C3N4/FTO electrode was applied for photoelectrochemical detection of NPX using chronoamperometry. Interestingly, the nanocomposites-based FTO ascribed a lower detection limit (2.3 ng l-1) with a wide linear range concentration of NPX (0.5 to 200 µg l-1). Additionally, the analytical assessment of repeatability and reproducibility demonstrated robust performance, with commendable relative standard deviations (RSD%) of 2.54 % and 2.40 %, respectively. On the other hand, a remarkable degradation efficiency of 97.52 % was attained when employing a bias potential of 0.1 V during a 2 h photoelectrocatalytic oxidation of NPX. The degradation process was primarily driven by the active participation of holes and hydroxyl radicals in ring opening and subsequent cleavage of by-products. The notable effectiveness of this degradation can be attributed to the combined and synergistic effects of both electrochemical and photocatalytic degradation techniques. The current state demonstrates its effectiveness in the photoelectrochemical sensing and removal of NPX using MOF/g-C3N4 nanocomposites-based electrode materials in wastewater.

Enhancing photocatalytic performance of covalent organic frameworks via ionic polarization

Covalent organic frameworks have emerged as a thriving family in the realm of photocatalysis recently, yet with concerns about their high exciton dissociation energy and sluggish charge transfer. Herein, a strategy to enhance the built-in electric field of series β-keto-enamine-based covalent organic frameworks by ionic polarization method is proposed. The ionic polarization is achieved through a distinctive post-synthetic quaternization reaction which can endow the covalent organic frameworks with separated charge centers comprising cationic skeleton and iodide counter-anions. The stronger built-in electric field generated between their cationic framework and iodide anions promotes charge transfer and exciton dissociation efficiency. Moreover, the introduced iodide anions not only serve as reaction centers with lowered H* formation energy barrier, but also act as electron extractant suppressing the recombination of electron-hole pairs. Therefore, the photocatalytic performance of the covalent organic frameworks shows notable improvement, among which the CH3I-TpPa-1 can deliver an high H2 production rate up to 9.21 mmol g−1 h−1 without any co-catalysts, representing a 42-fold increase compared to TpPa-1, being comparable to or possibly exceeding the current covalent organic framework photocatalysts with the addition of Pt co-catalysts.

In-situ cation-exchange deposited Ag2S/In4SnS8 of Z-type heterojunction coupled with DNA recycling amplification for photoelectrochemical biosensing

Herein, a novel photoelectrochemical (PEC) biosensor was developed utilizing an in situ cation-exchange method to deposit a high-performance Ag2S/In4SnS8, a Z-type heterojunction with co-shared S atoms, as a signal indicator and using DNA recycling amplification for the sensitive and accurate detection of miRNA-141. The photosensitive Ag2S deposited on the In4SnS8 surface not only facilitated the rapid generation of photoelectrons but also formed a Z-type heterojunction with In4SnS8, effectively inhibiting electron-hole pair recombination. This resulted in a considerable improvement in the photoelectric conversion efficiency of Ag2S/In4SnS8, yielding an ∼ 120-fold increase in photocurrent compared to that of In4SnS8 under 660-nm visible-light irradiation. Furthermore, the arborescent DNA structure formed by hybrid chain reaction (HCR) enhanced the steric effect, thereby reducing the PEC response. Importantly, numerous quenchers MnPP competed for light absorption and captured photogenerated electrons in the valence bands of In4SnS8 and Ag2S, reducing electron transfer to the electrode and further considerably reducing the photocurrent. This enabled the sensitive detection of miRNA-141 across a concentration range from 10 amol·L−1 to 100 pmol·L−1, with a limit of detection as low as 3.3 amol·L−1 (S/N = 3). The proposed biosensor exhibits excellent stability and is expected to be applied for detecting clinically relevant disease markers.

Pt loaded CoFe2O4-based nanoparticles for breast cancer treatment with chemodynamic therapy and sonodynamic therapy

Breast cancer is one of the most widespread cancers worldwide in the female population. However, the side effects and toxicity of chemotherapy and radiotherapy are the obstacles to the treatment of breast cancer. Therefore, we developed a Pt loaded CoFe2O4-based nanoparticles (CF@Pt) for breast cancer treatment with chemodynamic therapy (CDT) and sonodynamic therapy (SDT). The Co2+/Co3+ and Fe2+/Fe3+ gave CF@Pt peroxidase-like activity and catalase activity to gain ·OH and O2 in the tumor microenvironment (TME) for CDT. Furthermore, the separation of electron-hole pairs of CF@Pt transferred the O2 into 1O2 in the presence of ultrasound (US) for SDT. The high level of O2 generated by CDT would produce more 1O2 by SDT that promoted the CDT efficiency. Moreover, the addition of Pt limited the recombination of electron-hole pairs and reduced the energy gap to enhance SDT/CDT combination therapy. In addition, CF@Pt could be engulfed by MDA-MB-231 cells and induced the apoptosis while it had good biocompatibility and blood compatibility. This design provided a novel application on the treatment of breast cancer.

Understanding the effect of co-doped N,Pd/TiO2 dopants on the efficiency and product selectivity of the photocatalytic CO2 reduction

Carbon dioxide photoreduction using solar energy has emerged as a promising strategy to address challenges related to climate change. TiO2 is the most used catalyst, due to its excellent properties regarding reagents adsorption, light absorption, and electron-hole pair recombination rate. Supercritical synthesis allows fine-tuning of its physicochemical and photocatalytic properties by simple changes in the synthesis conditions. In this work, this technique has been used to increase the TiO2 photocatalytic activity and selectivity to methane by doping it with metal (Pd) and non-metal elements (N). Regarding the mono-doped catalysts, it has been observed that nitrogen-doped TiO2 (0.1 wt%) exhibits an improved visible light sensitization, while the palladium-doped material (1–3 wt%) leads the selectivity towards low chain fuel hydrocarbons and provides active sites for CO2 reduction. These characteristics are further improved in the TiO2-based photocatalysts co-doped with N and Pd. Specifically, band gaps of N,Pd co-doped TiO2 are 0.4–0.6 eV lower, and photogenerated charges in the co-doped catalysts are separated more efficiently due to their lower resistance to charge transfer. In the case of the co-doped photocatalysts the CO2 conversion rates are 40 % larger than mono-doped TiO2, this increase being mainly due to CH4 production, which reaches a selectivity of 60 %.

A Dual-Active Covalent Triazine Framework Film for Efficient Visible-Light-Driven Hydrogen Peroxide Production.

Photocatalytic hydrogen peroxide production from water and oxygen offers a clean and sustainable alternative to the conventional energy-intensive anthraquinone oxidation method. Compared to powdered covalent triazine frameworks (CTFs), the film morphology of CTFs provides better connectivity in 2D, yielding several advantages: more efficient connections between active sites, reduced electron-hole pair recombination, increased resistance to superoxide radical induced corrosion, and decreased light scattering. Leveraging these benefits, it has incorporated dual active sites for both the oxygen reduction reaction (ORR) and the water oxidation reaction (WOR) into a CTF film system. This dual-active CTF film demonstrated an exceptional hydrogen peroxide production rate of 19460µmolh⁻¹m⁻2 after 1h and 17830µmolh⁻¹m⁻2 after 5h under visible light irradiation (≥420nm) without the need for sacrificial agents.

Designed of dual direct band gap graphdiyne/Co2VO4 S-scheme heterojunction: Enhance the bonding stability of Co active sites to promote photocatalytic hydrogen evolution

The selection of direct band gap semiconductors with high-efficiency electron transitions and the rational adjustment of the d-band center of transition metal atoms can effectively enhance photocatalytic hydrogen evolution. Based on this premise, the double direct band gap graphdiyne/Co2VO4 S-scheme heterojunction was designed via an immersion method. DFT calculation, in-situ XPS and EPR analysis not only provided support for the formation of graphdiyne /Co2VO4 S-scheme heterojunction but also demonstrated that Co maybe served as the most efficient active site for hydrogen evolution. Furthermore, the design of S-scheme heterojunction effectively prolongs the carrier lifetime of the photocatalyst, resolves the deficiency in high electron-hole pair recombination rate of direct band gap semiconductors, and maintains its efficient electronic transition. PDOS analysis revealed that the interaction between graphdiyne and Co2VO4 at the microscopic interface tends to modulate the d-band center of cobalt atoms, resulting in a decrease in electron occupation on antibonding orbitals and consequently enhancing bonding stability at Co active sites. Moreover, introducing graphdiyne effectively increases electron state density near the Fermi level of Co2VO4, facilitating rapid migration of photogenerated charges. This study provides valuable insights into the regulating d-band centers of transition metal and the development of double direct band-gap S- scheme heterojunctions.

Efficient photodegradation of acid orange 7 in water using a facile ultrasound-assisted microwave-combustion synthesized Ag-ZnAl2-xFexO4 solid-solution photocatalyst

This study explores the development of Ag-ZnAl2-xFexO4 solid-solution photocatalysts for Acid Orange 7 (AO7) degradation under visible light irradiation. The microwave auto-combustion method was employed to synthesize these photocatalysts, allowing for the investigation of the influence of Fe substitution (x) on their properties and performance. Characterization techniques revealed a trade-off between Fe content, surface area, pore size, and light absorption capacity. The Ag-ZnAlFeO4 variant achieved an optimal balance, demonstrating exceptional photocatalytic activity for AO7 degradation. This optimized photocatalyst achieved a removal efficiency of 99.3 % under neutral pH conditions, highlighting its effectiveness and potential for practical applications. Interestingly, the mineralization efficiency of AO7 reached 85.2 % after 160 minutes of reaction time. Kinetic studies supported the superior performance of Ag-ZnAlFeO4, attributing its success to its favorable morphology, high surface area, strong light absorption, and minimal electron-hole pair recombination. The proposed degradation mechanism involves light absorption, generation of electron-hole pairs, and their subsequent reactions with water and oxygen molecules to degrade AO7. This work establishes Ag-ZnAl2-xFexO4, particularly Ag-ZnAlFeO4, as a promising visible-light photocatalyst for the efficient degradation of organic pollutants.

Enhanced antibiotic degradation using rGO composites under visible light photocatalysis

A robust reduced graphene oxide (rGO), polyaniline (PANI) with calcium (Ca) and magnesium (Mg) bimetallic nanocomposite was successfully prepared using an in-situ chemical facial reducing method and named rGO@PANI-Ca:Mg. Various spectroscopic techniques, including XRD, SEM, TEM, XPS, and supplementary methods, were utilized to characterize the catalyst phase, microstructure, and optical attributes. The composite's photocatalytic efficiency was assessed by degrading antibiotics such as ciprofloxacin (CP) and tetracycline (TC) using calcium peroxide (CaO2) under visible light irradiation. The rGO@PANI-Ca:Mg composite demonstrates superior degradation efficiency for CP, 45 %, and for TC, 70 %, achieving a correlation coefficient R² of 0.94 and 0.991 respectively. This performance surpasses that of pristine GO, rGO, and rGO@PANI. The heightened photocatalytic activity is ascribed to forming a heterojunction, effectively mitigating electron-hole pair recombination. The incorporation of CaO2 promotes the generation of additional active reactive oxygen species (ROS), particularly OH·, ·O2−, e-, h+, as verified by radical scavenging experiments, indicating an enhancement in the degradation and a potential mechanism is also suggested. The degradation rate of TC, CP, and real wastewater (RW) is about 71 %, 45 %, and 40.98 %, respectively. The composite demonstrates stability and reusability for up to three catalytic cycles. Our experiments also showed that when bacteria were treated with a 2 mg catalyst, the minimum inhibitory concentration (MIC) was determined to be at a 10−3 dilution. This MIC value represents the lowest concentration at which the catalyst effectively inhibited bacterial growth, as evidenced by clear inhibition zones.

Design and Preparation of Heterostructured Cu2O/TiO2 Materials for Photocatalytic Applications.

The extensive use of fossil fuels has sped up the global development of the world economy and is accompanied by significant problems, such as energy shortages and environmental pollution. Solar energy, an inexhaustible and clean energy resource, has emerged as a promising sustainable alternative. Light irradiation can be transformed into electrical/chemical energy, which can be used to remove pollutants or transform contaminants into high-value-added chemicals through photocatalytic reactions. Therefore, photocatalysis is a promising strategy to overcome the increasing energy and environmental problems. As is well-known, photocatalysts are key components of photocatalytic systems. Among the widely investigated photocatalysts, titanium dioxide (TiO2) has attracted great attention owing to its excellent light-driven redox capability and photochemical stability. However, its poor solar light response and rapid recombination of electron-hole pairs limit its photocatalytic applications. Therefore, strategies to enhance the photocatalytic activity of TiO2 by narrowing its bandgap and inhibiting the recombination of charges have been widely accepted. Constructing heterojunctions with other components, including cuprous oxide (Cu2O), has especially narrowed the bandgap, providing a promising means of solving the present challenges. This paper reviews the advances in research on heterostructured Cu2O/TiO2 photocatalysts, such as their synthesis methods, mechanisms for the enhancement of photocatalytic performance, and their applications in hydrogen production, CO2 reduction, selective synthesis, and the degradation of pollutants. The mechanism of charge separation and transfer through the Cu2O/TiO2 heterojunctions and the inherent factors that lead to the enhancement of photocatalytic performance are extensively discussed. Additionally, the current challenges in and future perspectives on the use of heterostructured Cu2O/TiO2 photocatalysts are also highlighted.

Co-Fe Prussian blue Analogues encapsulated graphdiyne nanosheets formed type-II heterojunction for photocatalytic H2 evolution

The energy crisis and environmental pollution are becoming more and more serious, and photocatalytic hydrogen evolution technology can alleviate the above phenomena. In this paper, the type-II heterojunction was successfully constructed with CoFe-PBA/GDY and applied in photocatalytic hydrogen evolution. Density functional theory (DFT) calculations and in-situ XPS analysis were used to infer a potential mechanism for the formation of photocatalytic hydrogen. It was shown that the construction of type-II heterojunction induced the transfer of photogenerated electrons from CoFe-PBA to GDY, and suppressed the recombination of photogenerated electrons and holes in CoFe-PBA/GDY. The highest photocatalytic hydrogen evolution activity of CoFe-PBA/GDY-15 is among them, 71.24 μmol of hydrogen are precipitated in just 4h, 14.07 times that of GDY (5.06 μmol) and 14.97 times that of CoFe-PBA (4.76 μmol). This work provides a new way for constructing type-II heterojunction based on GDY to improve photocatalytic hydrogen evolution.