Enhanced Charge Separation Research Articles

Boosted CO2 Photoreduction Performance by CdSe Nanoplatelets via Se Vacancy Engineering.

2D metal-chalcogenide nanoplatelets (NPLs) exhibit promising photocatalysis properties due to their ultrathin morphology, high surface-to-volume ratio, and enhanced in-plane electron transport mobility. However, NPLs, especially cadmium chalcogenides, encounter challenges in CO2 photoreduction due to insufficient solar energy utilization and fast recombination of photogenerated charge carriers. Defect engineering offers a potential solution but often encounters difficulties maintaining structural integrity, mechanical stability, and electrical conductivity. Herein, by taking two monolayers (2ML) CdSe NPLs as a model system, selenium (Se) vacancies confined in atomic layers can enhance charge separation and conductivity. A straightforward approach to create Se vacancies in various monolayers CdSe NPLs (2, 4, and 5ML) has been developed, enabling efficient CO2 photoreduction with a 4-fold increase in CO generation compared to their defect-free counterparts. Significantly, accounting for higher charge density and efficient carrier transport due to Se vacancies, defective 2ML CdSe NPLs (VSe-2ML CdSe) exhibit CO evolution performance up to 2557.5µmol g-¹ h-¹ with no significant decay over 5 h, which is an order of magnitude higher than that of common semiconductor catalysts. This study establishes a practical way to design advanced 2D semiconductor photocatalysts to achieve efficient CO2 photoreduction via defect engineering.

Effective approach for removing antibiotic residues from wastewater using Bi2O3@C3N4 photocatalyst

This study explores the photocatalytic decomposition of antibiotic residues, including tetracycline (TCR) and amoxicillin (AMR), from wastewater using Bi2O3@C3N4 photocatalyst. The characterization findings revealed that Bi2O3@C3N4 exhibited significantly improved light absorption properties and enhanced charge separation efficiency. According to the experimental results, Bi2O3@C3N4 exhibited high degradation efficiencies of 77.6% for TCR and 83.2% for AMR in wastewater samples. It also displayed excellent reusability, with the removal efficiencies of TCR and AMR remaining at 71.3 and 78.8%, respectively, after five cycles. Additionally, the photodegradation of TCR and AMR using Bi2O3@C3N4 is suggested to follow the Z-scheme pathway. The results of this study could be utilized for removing antibiotic pollutants from wastewater, thereby reducing their impact on human health and the environment.

Spontaneous formation of potential cascade enhances charge separation in PM6-Y6 organic photovoltaics.

Mechanisms that enhance charge separation at donor-acceptor interfaces are the key to material design of non-fullerene electron acceptors for high-efficiency organic photovoltaics (OPV). Here, the energetics of charge separation at the PM6-Y6 donor-acceptor interface in the state-of-the-art OPV is analyzed on the basis of quantum mechanics/molecular mechanics calculations. The electron energy level in Y6 becomes lower with increasing distance from the interface with PM6 at which the crystallinity is lower than in the bulk region. Electrostatic interactions from the multipoles of Y6 stabilize the electron in the crystalline region. The PM6-ITIC donor-acceptor interface also exhibits a similar potential cascade owing to the quadruple of ITIC. The potential cascade destabilizes charge transfer states at the PM6-Y6 interface, thereby decreasing the potential barrier for charge separation. Charge delocalization on several molecules via transfer integral further decreases the barrier for charge separation.

A Platinum Complex‐Based Dimerized Electron Acceptor for Efficient Organic Solar Cells

AbstractMetal–organic complexes have demonstrated excellent performance in organic light‐emitting diodes, yet their potential in organic solar cells (OSCs) remains underexplored. In this study, a novel metal–organic complex, Pt‐Y, which features a platinum core connected to Y‐acceptor arms, for application in OSCs is designed and synthesized. The dimerized Pt‐Y acceptor is prepared through straightforward reactions, with the key precursor linking the platinum metal and Y‐acceptors synthesized through Sonogashira coupling. Steady‐state and transient photoluminescence measurements revealed that Pt‐Y exhibits distinct singlet and triplet states with microsecond lifetimes—significantly longer than the nanosecond lifetimes of Y‐acceptors without the metal. Incorporating Pt‐Y as a third component in ternary OSCs has resulted in a remarkable efficiency of 19.2%. Further morphological analysis and transient absorption measurements indicate that the dimerized Pt‐Y displays excellent miscibility with the Y‐acceptor, leading to minimal phase separation and the formation of fibrillar structures. These structures enhance charge separation and transport while reducing charge recombination. This work presents a facile approach to developing metal–organic complexes with exceptional photovoltaic performance in OSCs.

Efficient visible-light-driven removal of persistent antibiotics and synthetic dyes from wastewater using an engineered 2D/2D Bi2MoO6/NiAl-LDH S-scheme heterocatalyst with enhanced interfacial contact.

Highly efficient photocatalysts for degrading persistent antibiotics and synthetic dye pollutants under visible light are crucial for sustainable environmental remediation. In this study, we engineered a novel Bi2MoO6 (BMO)/NiAl-LDH (layered double hydroxide) hybrid catalyst with a unique 2D/2D heterostructure, optimized for the visible-light-driven elimination of ciprofloxacin (CPF) and hazardous synthetic dyes such as rhodamine B and methylene blue. The optimized BMO-30/LDH hybrid demonstrated exceptional photocatalytic performance, achieving nearly complete degradation of CPF and synthetic dyes with high mineralization efficiency, surpassing many previously reported state-of-the-art photocatalysts. This superior activity is primarily attributed to the formation of an S-scheme heterojunction, which enhances charge separation while maintaining strong redox potentials in both components. This mechanism enables the simultaneous generation of reactive O2•- and •OH radicals. The hybrid's enhanced efficiency is further driven by synergistic effects, including strong visible light absorption, a large surface area, and a well-integrated 2D/2D configuration with face-to-face interfacial contact. These structural features maximize charge carrier separation, reduce recombination, and ensure robust photocatalytic activity. Additionally, the hybrid exhibited excellent reusability, retaining over 93% of its initial activity after five cycles. This study introduces a novel approach to engineering advanced 2D/2D heterojunction photocatalysts, highlighting their potential for practical water treatment and environmental remediation applications.

Three-dimensional Au-decorated MoS2/TiO2 nanomaterials gas sensors for efficient NO2 sensing

The quest for a proficient charge transport layer that enhances charge separation in multiple heterojunction composites remains a perpetual endeavor within the realm of NO2 gas sensors, aimed at attaining heightened sensitivity and response efficiency. Herein, based on the foundation of MoS2/TiO2 binary composite structure, Au-doped MoS2/TiO2 ternary composite structures with different doping content of Au were prepared via a simple hydrothermal synthesis process. The results indicate that the Au-MoS2/TiO2 ternary composite structure exhibits the highest sensitivity to NO2 gas at 500 ppm concentration at 50 °C under 4 mW/cm2 red LED illumination condition, with a response of 510 %, compared to the optimal response of 191 % for the binary composite structure materials. This work proposes the functionalization of MoS2/TiO2 heterojunction with Au, extending beyond the conventional noble metal decoration, and the potential utilization of the multiple heterojunctions for gas sensors.

PH-Triggered Phase Transitions, Coexposure of (001) and (110) Facets, and Oxygen Vacancies in BiOCl Photocatalysts.

Bismuth oxychloride (BiOCl) is known for its unique layered microstructure, which plays a pivotal role in enhancing its photocatalytic properties. This study introduces a novel strategy for controlling the phase composition, facet orientation, and oxygen vacancy formation in BiOCl through precise pH adjustment during the synthesis. By employing a hydrothermal method, we systematically varied the pH to produce distinct BiOCl phases and conducted detailed structural and photocatalytic analyses. Remarkably, BiOCl synthesized at pH = 7 demonstrated superior photocatalytic activity on rhodamine B (RhB) degradation, which can be attributed to the coexposure of the (001) and (110) facets, as well as an increased concentration of oxygen vacancies. Density functional theory study also revealed that a high concentration of oxygen vacancies leads to enhanced charge separation, which is beneficial for photocatalytic activity. These results indicate that optimizing the pH during synthesis is a viable approach to enhancing the photocatalytic efficiency of BiOCl, offering significant potential for advanced applications in environmental remediation and solar energy conversion.

Enhanced Photoelectrocatalytic Performance of ZnO Nanowires for Green Hydrogen Production and Organic Pollutant Degradation.

With growing environmental concerns and the need for sustainable energy, multifunctional materials that can simultaneously address water treatment and clean energy production are in high demand. In this study, we developed a cost-effective method to synthesize zinc oxide (ZnO) nanowires via the anodic oxidation of zinc foil. By carefully controlling the anodization time, we optimized the Zn/ZnO-5 min electrode to achieve impressive dual-function performance in terms of effective photoelectrocatalysis for water splitting and waste water treatment. The electrode exhibited a high photocurrent density of 1.18 mA/cm2 at 1.23 V vs. RHE and achieved a solar-to-hydrogen conversion efficiency of 0.55%. A key factor behind this performance is the presence of surface defects, such as oxygen vacancies (OVs), which enhanced charge separation and boosted electron transport. In tests for waste water treatment, the Zn/ZnO-5 min electrode demonstrated the highly efficient degradation of methylene blue (MB) dye, with a reaction rate constant of 0.4211 min-1 when exposed to light and a 1.0 V applied voltage significantly faster than using light or voltage alone. Electrochemical analyses, including impedance spectroscopy and voltammetry, further confirmed the superior charge transfer properties of the electrode under illumination, making it an excellent candidate for both energy conversion and pollutant removal. This study highlights the potential of using simple anodic oxidation to produce scalable and efficient ZnO-based photocatalysts. The dual-function capability of this material could pave the way for large-scale applications in renewable hydrogen production and advanced waste water treatment, offering a promising solution to some of today's most pressing environmental and energy challenges.

Reversing Surface Charge for Highly‐Active Organic Photovoltaic Catalysts

AbstractOrganic photovoltaic materials typically exhibit low charge separation and transfer efficiency and severe exciton/carrier recombination due to high exciton binding energy and short exciton diffusion lengths, limiting the enhancement of photocatalytic hydrogen evolution performance. Here, we introduce a surface charge reversal strategy to regulate the charge character of organic photovoltaic catalyst (OPC). Compared to OPC nanoparticles (NPs) stabilized by an anionic surfactant ((−) NPs), NPs stabilized by a cationic surfactant ((+) NPs) exhibit a raised Fermi level, larger surface band bending and Schottky barrier, thereby enhancing charge separation and transfer efficiency while suppressing charge carrier recombination. As a result, (+) NPs demonstrate better photocatalytic performance than (−) NPs, independent of the chemical structure of OPCs and surfactant molecules. Under the illumination of AM1.5G, 100 mW cm−2, the PM6: 2FBP‐4F NPs stabilized by cationic surfactant (dodecyltrimethylammonium bromide, DTAB) exhibit much higher photocatalytic activity for hydrogen evolution (up to 946.1±15.76 mmol h−1 g−1) than that of PM6: 2FBP‐4F NPs stabilized by anionic surfactant, among the best results reported so far for photocatalytic hydrogen evolution under simulated sunlight.

Improving the Photocatalytic Performance of TiO2 Coating via the Dual Incorporation of MoO2 and V2O5 by Plasma Electrolytic Oxidation

In this study, the photocatalytic activity of TiO₂ coatings on pure titanium was significantly enhanced through the dual incorporation of MoO₂ and V₂O₅ particles. This enhancement was achieved by performing a series of plasma electrolytic oxidation (PEO) treatments in an alkaline-phosphate electrolyte, where Na₂MoO₄ and V₂O₅ nanoparticles were added either individually or in combination. The PEO process was carried out at a current density of 100 mA/cm² for 5 minutes. The results revealed notable changes in the surface morphology of the TiO₂ coatings, with increased porosity and pore size observed upon the addition of MoO₄ ions, while the incorporation of V₂O₅ nanoparticles led to a slight reduction in pore size. Interestingly, the simultaneous addition of both MoO₂ and V₂O₅ resulted in a porous structure with medium pore size and porosity, which proved optimal for photocatalytic applications. The compositional analysis confirmed the successful incorporation of MoO₂ and V₂O₅ into the TiO₂ matrix via electrochemical decomposition and electrophoresis mechanisms. Photocatalytic performance was evaluated through the degradation of methylene blue (MB) under visible light. The results demonstrated that the combined incorporation of MoO₂ and V₂O₅ significantly improved the degradation efficiency compared to TiO₂ coatings prepared without these additives. Notably, the TiO₂ coating with both additives achieved 99.9 % degradation of MB within 80 minutes, indicating enhanced charge separation and photocatalytic efficiency. This study highlights the potential of dual additive incorporation to improve the functional properties of TiO₂ coatings, making them suitable for advanced environmental and industrial applications.

Efficient photocatalytic selective oxidation of 5-hydroxymethylfurfural on Bi24O29Br10(WO4)2solid solution via enhanced charge separation

The photocatalytic oxidation of biomass-derived structural units such as 5-hydroxymethylfurfural is a promising reaction for obtaining valuable chemicals and effectively storing solar radiation for long periods. In this work, we...

Vacancy-engineered bismuth vanadate for photoelectrocatalytic glycerol oxidation with simultaneous hydrogen production

A defect-engineered BiVO4 catalyst with oxygen vacancies on an SnO2 skeleton enhances charge separation, light absorption, and glycerol activation, enabling efficient DHA production under neutral PEC conditions for sustainable biomass valorization.

Cryo‐Electrochemical Deposition of Gold Single Atoms on G‐C3N4 for Photoelectrochemical Water Reduction

AbstractThe pursuit of sustainable energy has intensified the exploration of hydrogen as a clean energy carrier, with photoelectrocatalytic water reduction emerging as a green approach to harness solar energy. Graphitic carbon nitride (g‐C3N4), recognized for its stability and non‐toxicity, presents limitations in photoconversion efficiency due to rapid electron‐hole recombination and narrow light absorption range. To address these challenges, herein, a cryo‐electrochemical deposition strategy is introduced to synthesize g‐C3N4 loaded with gold single‐atom catalysts (Au1), enhancing charge separation and light absorption. The atomic dispersion of Au1 on g‐C3N4 significantly elevates photoelectrocatalytic hydrogen production, achieving a record yield rate on the Au1(14.5%)/g‐C3N4 sample. Density functional theory (DFT) calculations and comprehensive characterizations reveal the role of Au1 in modulating the electronic structure and improving charge carrier dynamics. The findings underscore the potential of single‐atom catalysis in advancing photoelectrocatalytic water reduction systems for solar energy conversion and clean energy production.

A review of photoelectrochemical water oxidation using hematite photoanode

Background: The sun, as an abundant and renewable energy source, provides a sustainable alternative to fossil fuels, which contribute significantly to CO₂ emissions and global warming. With CO₂ emissions surpassing 35 billion tons in 2023, the need for clean energy solutions has become increasingly urgent. Solar energy utilization includes photoelectrochemical (PEC) water splitting, where hematite is widely recognized as an efficient photoanode material due to its availability, stability, and favorable band gap for visible light absorption. However, hematite faces challenges such as poor conductivity, surface recombination, and slow oxygen evolution reaction (OER) kinetics, which limit its performance. Methods: This review examines various strategies to enhance hematite photoanode performance for PEC water splitting. The study explores three key approaches: (1) using three-dimensional conductive substrates with high surface area to facilitate heterojunction formation, (2) doping with tetravalent metal ions (e.g., Ti⁴⁺) to improve conductivity and charge carrier density, and (3) integrating Bi₂WO₆ with hematite to enhance charge separation and photoelectrochemical efficiency. The hydrothermal method was applied for hematite fabrication due to its feasibility, cost-effectiveness, and scalability. Findings: The analysis highlights the effectiveness of each strategy in overcoming hematite’s inherent limitations. The use of 3D conductive substrates improves electron transport and surface reaction sites, while Ti⁴⁺ doping enhances charge carrier density and conductivity. Conclusion: Hematite remains a promising photoanode material for PEC water splitting, but its limitations must be addressed to maximize efficiency. The combination of 3D conductive substrates, metal ion doping, and Bi₂WO₆ integration has shown potential in improving hematite’s photoelectrochemical performance. Novelty/Originality of this article: This review provides a comprehensive analysis of hematite performance enhancement strategies, focusing on the synergistic effects of 3D conductive substrates, Ti⁴⁺ doping, and Bi₂WO₆ integration.

Advanced MASnI3 and PTAA-Integrated ZnO2 Perovskite Composite: Optimizing Stability and Charge Dynamics for Next-Gen Photobatteries.

To advance off-grid energy solutions, developing flexible photobatteries capable of direct light charging is essential. This study presents an innovative photobattery architecture that incorporates zinc oxide (ZnO2) as an electron-transporting and hole-blocking layer, combined with a hybrid methylammonium tin iodide composite with poly-triarylamine (MASnI3/PTAA) for light absorption and hole transport. PTAA facilitates efficient hole transport to the anode, thereby enhancing charge separation and reducing recombination losses. The MASnI3 perovskite serves as an effective sunlight absorber, generating charge carriers. ZnO2, known for its high chemical stability and rapid electron mobility, effectively blocks holes and ensures swift electron flow to the cathode, which optimizes the overall charge transfer dynamics. This refined structure achieves a photoconversion efficiency enhancement of up to 0.53% and retains approximately 98% of its capacity after 700 cycles. The optimized MASnI3/PTAA/ZnO2 photobattery demonstrates a 3-fold reduction in light charging time, positioning it as a strong candidate for practical, light-rechargeable energy storage applications.

Highly Efficient and Stable Potassium‐Doped g‐C3N4/Zn0.5Cd0.5S Quantum Dot Heterojunction Photocatalyst for Hydrogen Evolution

ABSTRACTThe advancement of efficient and robust photocatalysts for water splitting is pivotal for the sustainable production of clean hydrogen energy. This study introduces a novel photocatalyst, synthesized by integrating 0D Zn0.5Cd0.5S quantum dots (ZCS QDs) onto 2D K+‐doped graphitic carbon nitride (K‐CN) microribbons, via an in‐situ hydrothermal growth method. A comprehensive characterization was performed to assess the optical characteristics, structural attributes, and charge transfer efficacy of the prepared photocatalysts. Our findings reveal that the incorporation of K+ ions effectively modulates the bandgap and valence band positions of g‐C3N4, facilitating an optimal energy level alignment with ZCS QDs. Moreover, the integration of ZCS QDs improves the photon capture ability and concurrently diminishes the recombination rate of photogenerated charge carriers. The optimized ZCS 51%/K‐CN photocatalyst demonstrates a promising simulated sunlight‐driven hydrogen production rate of 9.606 mmol·h−1·g−1, surpassing that of pristine ZCS QDs by nearly three times, without the need for noble metal co‐catalysts. Most notably, the photocatalyst maintains its hydrogen evolution performance consistently over five photocatalytic cycles, underscoring its stability. The remarkable photocatalytic activity is primarily ascribed to the formation of a type‐II heterojunction between K‐CN and ZCS QDs, which enhances charge separation and transfer. This research represents a significant step forward in the design of heterojunction photocatalysts by merging QDs with g‐C3N4, offering a highly effective and durable solution for photocatalytic hydrogen production.

Manipulating p-π Resonance through Methoxy Group Engineering in Covalent Organic Frameworks for an Efficient Photocatalytic Hydrogen Evolution.

Kinetic factors frequently emerge as the primary constraints in photocatalysis, exerting a critical influence on the efficacy of polymeric photocatalysts. The diverse conjugation systems within covalent organic frameworks (COFs) can significantly impact photon absorption, energy level structures, charge separation and migration kinetics. Consequently, these limitations often manifest as unsatisfactory kinetic behavior, which adversely affects the photocatalytic activity of COFs. To address these challenges, we propose a methoxy (-OMe) molecular engineering strategy designed to enhance charge carrier kinetics and mitigate mass transfer resistance. Through strategic modulation of the position and quantity of -OMe units, we can effectively manipulate the p-π conjugation, thereby enhancing charge separation and migration. Moreover, COFs enriched with -OMe moieties exhibit enhanced mass transfer dynamics due to the hydrophilic nature of methoxy groups, which facilitate the diffusion of reactants and products within the porous structure. This approach is hypothesized to drive an efficient photocatalytic hydrogen evolution reaction.

Reversing Surface Charge for Highly-Active Organic Photovoltaic Catalysts.

Organic photovoltaic materials typically exhibit low charge separation and transfer efficiency and severe exciton/carrier recombination due to high exciton binding energy and short exciton diffusion lengths, limiting the enhancement of photocatalytic hydrogen evolution performance. Here, we introduce a surface charge reversal strategy to regulate charge characters of organic photovoltaic catalyst (OPC). Compared to OPC nanoparticles (NPs) stabilized by anionic surfactant ((-) NPs), NPs stabilized by cationic surfactant ((+) NPs) exhibit a raised Fermi level, larger surface band bending and Schottky barrier, thereby enhancing charge separation and transfer efficiency while suppressing charge carrier recombination. As result, (+) NPs demonstrate better photocatalytic performance than (-) NPs, independent of the chemical structure of OPCs and surfactant molecules. Under illumination of AM1.5G, 100 mW cm-2, the PM6: 2FBP-4F NPs stabilized by cationic surfactant (dodecyltrimethylammonium bromide, DTAB) exhibit much higher photocatalytic activity for hydrogen evolution (up to 946.1±15.76 mmol h-1 g-1) than that of PM6: 2FBP-4F NPs stabilized by anionic surfactant, among the best results reported so far for photocatalytic hydrogen evolution under simulated sunlight.

Dual-functional Cu2O/g-C3N4 heterojunctions: a high-performance SERS sensor and photocatalytic self-cleaning system for water pollution detection and remediation

This study introduces a multifunctional device based on Cu2O/g-C3N4 monitoring and purification p–n heterojunctions (MPHs), seamlessly integrating surface-enhanced Raman scattering (SERS) detection with photocatalytic degradation capabilities. The SERS and photocatalytic performances of the Cu2O in various morphologies, g-C3N4 nanosheets (NSs) and Cu2O/g-C3N4 MPHs with different g-C3N4 mass ratios were systematically evaluated, with a particular emphasis on the Cu2O/g-C3N4-0.2 MPH, where g-C3N4 constituted 20% of the total mass. Multiple optical and electrochemical tests revealed that the Cu2O/g-C3N4-0.2 MPH effectively enhances charge separation and reduces charge transfer resistance. The Cu2O/g-C3N4-0.2 SERS sensor exhibited a relative standard deviation (RSD) below 15% and achieved an enhancement factor (EF) of 2.43 × 106 for 4-ATP detection, demonstrating its high sensitivity and consistency. Additionally, it demonstrated a 98.3% degradation efficiency for methyl orange (MO) under visible light within 90 min. Remarkably, even after 216 days, its photocatalytic efficiency remained at 93.7%, and it retained an 84.0% efficiency after four cycles. XRD and SEM analyses before and after cycling, as well as after 216 days, confirmed the structural and morphological stability of the composite, demonstrating its cyclic and long-term stability. The excellent performance of the Cu2O/g-C3N4 MPH is attributed to its Z-type mechanism, as verified by radical trapping experiments. The evaluation of the self-cleaning performance of the Cu2O/g-C3N4-0.2 SERS sensor demonstrated that its Z-scheme structure not only provides excellent self-cleaning capability but also enables the detection of both individual and mixed pollutants, while significantly enhancing the SERS signal response through an effective charge transfer enhancement mechanism.

Nano‐Space Confinement Crystal Growth Boosted Hole Extraction in Carbon‐Based CsPbI3 Perovskite Solar Cells

AbstractCarbon‐based CsPbI3 perovskite solar cells (C‐PSCs) have shown a great promising due to its excellent chemical stability. However, the low hole selectivity and inefficient charge separation at the perovskite/carbon interface suppress their photovoltaic performance. Introducing a low‐dimensional (LD) perovskite structure is anticipated to address the issue but the randomly grown LD perovskite crystals would considerably increase the surface roughness, which not only weakens interface contact for inhibiting hole extraction but also increases the charge transporting length in LD perovskite. Herein, COMSOL Multiphysics simulation is first explored to establish the relation of the LD perovskite structure with the device performance, which suggests that a p‐type and thin LD perovskite capping layer with high coverage is favorable for device performance. To verify the simulation results, a nano‐space confinement (NSC) strategy is proposed to inhibit the vertical growth of 2D Cs2PbI2Cl2 perovskite plates for promoting in‐plane growth, during which a polymethyl methacrylate (PMMA) layer is pre‐covered on the Cs2PbI2Cl2 nuclear before their growth. Consequently, a well‐covered p‐type Cs2PbI2Cl2 capping layer is deposited on n‐type CsPbI3 perovskite layer, which significantly increases the hole selectivity and enhances charge separation for promoting the efficiency of C‐PSCs to 18.23% with an ultra‐high VOC of 1.161 V.