Photo-generated Charge Research Articles

Fabrication of S‐Scheme GDY‐CuI/ZnWO4 Photocatalyst to Promote Electron Transfer for Enhanced Photocatalytic H2 Evolution

AbstractThe exceptional performance of graphdiyne (GDY) in photocatalysis for hydrogen evolution attracts much attention, but the narrow band gap of GDY complicates the effective realization of the dissociation between photogenerated charges and photogenerated holes. In this study, GDY‐CuI is synthesized by cross‐coupling method, and the wide bandgap ZnWO4 is introduced into it by low‐temperature mixing, which effectively constructed the GDY‐CuI/ZW‐50 double S‐scheme heterojunction. The optimized GDY‐CuI/ZW‐50 catalyst photocatalytic hydrogen evolution performance reached 308.61 µmol after 5 h of visible light irradiation, which is 12.86 and 6.56 times than that of GDY‐CuI and ZnWO4, respectively. The improved efficiency of hydrogen evolution is attributed to the formation of a double S‐scheme heterojunction between GDY, CuI, and ZnWO4 and an internal electric field, which promotes charge transfer, reduces the complexation rate of photogenerated electrons, and enhances the redox capacity of photogenerated charges. A combination of photoelectrochemical analysis, in situ X‐ray photoelectron spectroscopy (In situ XPS), ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT) results revealed the electron transfer mechanism. This work will provide new ideas for the design and preparation of GDY‐based photocatalysts.

Enhanced Photocatalytic Hydrogen Evolution of In2S3 by Decorating In2O3 with Rich Oxygen Vacancies.

The hydrogen (H2) evolution rates of photocatalysts suffer from weak oxidation and reduction ability and low photogenerated charge carrier separation efficiency. Herein, by combining band-gap structure optimization and vacancy modulation through a one-step hydrothermal method, In2O3 containing oxygen vacancy (Ov/In2O3) is simply introduced into In2S3 to promote photocatalytic hydrogen evolution. Specifically, the change in the sulfur source ratio can induce the coexistence of Ov/In2O3 and In2S3 in a high-temperature hydrothermal process. Under light irradiation, In2S3@Ov/In2O3-0.1 nanosheets hold a remarkable average H2 evolution rate up to 4.04 mmol g-1 h-1, which is 32.14, 11.91, and 2.25-fold better than those of pristine In2S3, In2S3@Ov/In2O3-0.02, and In2S3@Ov/In2O3-0.25 nanosheets, respectively. The ultraviolet-visible (UV-vis) diffuse reflectance and photoluminescence (PL) spectra reveal that the formation of Ov/In2O3 in In2S3 optimizes the band-gap structure and accelerates the migration of the photogenerated charge carrier of In2S3@Ov/In2O3-x nanosheets, respectively. Both the enhancement of oxidation and reduction ability and photogenerated charge carrier separation ability are responsible for the remarkable improvement in photocatalytic H2 evolution performance. This work provides a new strategy to prepare a composite of metal sulfide and metal oxide through a one-step hydrothermal method.

Photocatalytic performance and mechanism insights of an S-scheme ZnMn2O4/ZIF-67 heterostructure in photocatalytic CO2 reduction under visible light irradiation

Improved separation among photoelectrons and holes (e−, h+) and regulated electron transport routes are essential to improve photocatalytic performance. This work adopts a convenient but more efficient method to prepare an S-scheme composite photocatalyst integrating narrow band gap semiconductor ZnMn2O4 (ZMO) and zeolitic imidazole framework ZIF-67(Z67) for improved photocatalytic CO2 reduction. The designed photocatalyst ZMO(X)/Z67 showed more visible light harvesting capacity compared to individual ZMO and Z67. The ZMO/Z67 nanocomposite containing 3 % ZMO nanosphere produced 1.91 times higher methanol (48.64 μmolg−1) compared to pure Z67 (25.36 μmolg−1) and 1.42 times higher ethanol (30.32 μmolg−1) compared to pure Z67 (21.28 μmolg−1) after 8 h visible light illumination. The composites' increased photocatalytic performance might be attributed primarily to excellent photogenerated charge separation and transfer via the linked S-scheme heterojunction between ZMO nanospheres and Z67. Various characterization methods are used to explore the structural, morphological, optical, and electrochemical features of produced photocatalysts, and a thorough photocatalytic mechanism is provided. After four recycling, the composite photocatalyst demonstrated good stability and recyclability. This study attributed to a viable method for constructing a direct S-scheme heterojunction for photocatalytic CO2 reduction.

Exploring the influence of Ag nanocube size on surface plasmon resonance assisted photocatalytic H2-production of optimized Ag loaded TiO2

Ag nanocubes decorated plasmonic TiO2 were synthesized by polyol method as a potential photocatalyst for photocatalytic hydrogen evolution. In this work, the Ag loading concentration on TiO2 was optimized for enhanced photocatalytic hydrogen evolution. Among different Ag loading, 1 wt% showed the highest hydrogen production capacity under solar irradiation due to elevated photon absorption in the presence of plasmonic Ag. Further, the influence of surface plasmon resonance of Ag nanocubes on TiO2 was also studied by tuning the Ag particle size and evaluating the photocatalytic hydrogen production under optimized Ag loading. The size of the Ag nanoparticles was varied using different molecular weight (Mw) PVPs as the size-directing agent. TEM analyses of the samples confirmed the formation of Ag nanocubes of various sizes in accordance with the PVPs used. Ag nanocube with a size of 15.98 nm showed the highest SPR effect, which enables higher photon absorption and could generate high photogenerated charge carriers for better photocatalytic reactions. The photocatalytic hydrogen production capacity of the above samples was evaluated under solar irradiation, and the sample with an Ag nanocube size of 15.98 nm showed a yield of 4258.40 μmol g-1 in 4 h, which is 12-fold higher than its pristine counterpart. This work illustrated the effect of Ag nanocube size for effective SPR and the transportation of this high energy towards host TiO2 for enhanced photocatalytic performance.

Advancing photocatalytic activity through a green route: Bismuth ferrite@molybdenum trioxide heterostructure for sustainable water treatment

Photocatalysis has become increasingly pervasive in the chemical industry, profoundly impacting operational costs. However, an ideal photocatalyst must possess characteristics such as excellent reactivity, high selectivity, prolonged stability, low toxicity, and cost-effectiveness. Moreover, it should facilitate the efficient separation of photo-generated charge carriers, thereby minimizing recombination rates. In pursuit of advancing photocatalytic activity for sustainable water treatment, this investigation focused on synthesizing a groundbreaking photocatalyst, the Bismuth Ferrite@Molybdenum trioxide heterostructure, using an eco-friendly green chemistry technique with pomegranate extract. This approach aligns with the goal of environmental sustainability and represents a novel contribution to the field. Employing a comprehensive approach, advanced characterization techniques such as XRD, SEM, FT-IR, and UV–Vis were applied to analyze the material's structural, morphological, and optical properties. According to the characterization results, the heterostructure demonstrates superior photocatalytic efficiency, heightened crystallinity, and reduced recombination rates during dye degradation for water treatment compared to both individual photocatalysts. Notably, the composite catalyst exhibits a synergistic impact, outperforming individual BiFeO3 and MoO3 photocatalysts. SEM observations confirm the successful integration of rod-like MoO3 and cylindrical BiFeO3 morphologies, highlighting the strategic combination achieved through the green chemistry route. Furthermore, UV–Vis spectroscopy reveals key optical parameters, emphasizing a narrow bandgap energy of 2.74 eV with a high refractive index of 2.43 eV. The exceptional efficacy of the heterostructure in degrading dyes within the visible spectrum, surpassing expectations within a 4-hour timeframe, highlights its efficiency and precision. Remarkably, achieved degradation rates for Rhodamine B dye (98 %), Methyl Blue (96 %), and Methyl Orange dye (95 %) highlights the promising role of proposed photocatalytic system in effectively addressing water pollutant challenges.

Piezo-photocatalytic synergetic for H2O2 generation via dual-pathway over Z-scheme ZIF-L/g-C3N4 heterojunction

The constructed ZIF-L/g-C3N4 piezo-photocatalytic system showed exceptional H2O2 production yield. It was primarily attributable to the matched Z-scheme band alignments and the forceful piezoelectric field formed between g-C3N4 and ZIF-L, which was favor of reducing the energy barrier of electron excitation and directional transferring of photo-generated charge carriers. Meanwhile, the composition between ZIF-L and g-C3N4 can alter the H2O2 generation mechanism from single-pathway to dual-pathway. Thus, this mutual promotion significantly elevated the catalytic H2O2 production rate to 1.45 mmol g−1 h−1 without any contaminative scavenger. The catalytically produced H2O2 solution can be used to achieve ultrafast degradation of organic pollutants with 100% efficiency through homogeneous Fenton reaction within tens of seconds. The mediating multi-roles of natural organic matter (NOM) in regulating the H2O2 production were systematically investigated. Finite-element-method (FEM) simulations and density functional theory (DFT) calculations conjointly revealed the constructed piezo-photocatalytic system not only markedly accelerated separation of charge carriers, but also facilitated the activation of vital intermediates (O2*, OOH* and *OH) for H2O2 synthesis, which were the rate-determining steps for oxygen reduction reaction (ORR) and water oxidation reaction (WOR). This study will provoke the rational design of MOFs-based dual-pathway materials for piezo-photocatalytic H2O2 generation and follow-up applications.

Construction of carbon and nitride double vacancy defects on ultrathin porous g-C3N4 nanosheets assisted by freeze-drying for enhanced photocatalysis

Graphitic carbon nitride based photocatalysts have been found extensive application in the degradation of antibiotics and organic pollutants. However, the insufficient of surface active sites and the low efficiency of photogenerated charge carriers separation hinder the development. Herein, ultrathin porous polymer carbon nitride nanosheets (PCNS-F) with carbon and nitride double vacancy defects were successfully fabricated. The facile freeze-drying step, following solvent-thermal treatment and preceding the thermal etching process, stands as a critical step for triggering vacancy generation and adjusting the carbon/nitride ratio. The optimized PCNS-F photocatalyst exhibits an ultrathin structure featuring a substantial abundance of defects in a porous state, resulting in exceptional structural characteristics (183.3 m² g-1, 0.84 cm³ g-1). Surface defect sites increase, and the efficient separation and transfer of photo-generated charge carriers are promoted with the introduction of a suitable vacancy density. PCNS-F demonstrated outstanding photocatalytic degradation performances for tetracycline (81.7 %) and methylene blue (97.7 %) under visible light irradiation for 2 h, which are 10 and 7.2 times higher than those of bulk g-C3N4. The active species of ∙O2- was confirmed to play a major role in the photodegradation process. This work provides a mild approach for engineering carbon and nitride double vacancy defects on g-C3N4 nanosheets, accompanied by tuning carbon/nitride ratio, to effectively eliminate pollutants and cleanse the environment.’

Low-coordinated Fe–N3 sites in carbon nitride for efficient photo-Fenton wastewater treatment

Single-atom coordinated host catalyst offers a promising strategy for photo-Fenton induced wastewater treatment due to the tunable photophysical/chemical properties. However, designing efficient atomically dispersed single-atom catalysts with highly reactive unsaturated coordination remains a challenge. Herein, we designed the low-coordinated Fe–N3 site in carbon nitride (FeCN), which showed excellent degradation efficiency for 4-CP declined to 90.1 % in Tap water and 88.2 % in Dalian Lake within 1h. X-ray absorption near-edge spectroscopy (XANES) demonstrated the monoatomic Fe was anchored to CN via the low-coordinated Fe–N3 structure. Density Functional Theory (DFT) and photoelectric characterizations demonstrated that the Fe–N3 site could facilitate the photo-generated charge migration to the Fe–N3 site due to the asymmetric electron distribution of Fe–N3 site and the Fe_d orbitals occupying the conduction band positions. Besides, project density of states (PDOS) illustrated the strong electronic interaction between the Fe–N3 site and OH*, which confirmed the Fe–N3 site facilitated the activation of H2O2 and further accelerated the performance of photo-Fenton wastewater treatment. This study can provide insights into the design of highly active low-coordination single-atom catalysts and the Fenton-like mechanisms.

Interface engineered cascade-type electronic structure of 2D/0D/2D CdS–CdCO3/SnO2 quantum dots/g-C3N4 nanocomposite for boosting solar-driven photocatalysis

A rational design of heterojunctions with high-quality contacts is essential for efficiently separating photogenerated charge carries and boosting the solar-driven harvesting capability. Herein, we fabricated a novel heterojunction of SnO2 quantum dots–anchored CdS–CdCO3 with g-C3N4 nanosheets as a superior photocatalyst. SnO2 quantum dots (SQDs) with positively charged surfaces were tightly anchored on the negatively charged surface of CdS nanosheets (NSs). The resulting CdS@SnO2 was finally decorated with g-C3N4 NSs, and a new crystalline phase of CdS–CdCO3 was formed during the hydrothermal decoration process, g-C3N4 decorated CdS–CdCO3@SnO2 (CdS–CdCO3@SnO2@g-C3N4). The as-synthesized photocatalysts were evaluated for the degradation of methyl orange dye under solar light conditions. The CdS–CdCO3@SnO2@g-C3N4 exhibited 7.7-fold and 2.3-fold enhancements in photocatalytic activities in comparison to those of the bare CdS and CdS@SnO2 NSs, respectively. The optimal performance of CdS–CdCO3@SnO2@g-C3N4 is primarily attributed to the cascade-type conduction band alignments between 2D/0D/2D heterojunctions, which can harvest maximum solar light and effectively separate photoexcited charge carriers. This work provides a new inspiration for the rational design of 2D/0D/2D heterojunction photocatalyst for green energy generation and environmental remediation applications.

Photo-rechargeable asymmetric supercapacitors based on nickel–cobalt sulfide on titania as novel photo-active electrodes

Photo-supercapacitors (PSCs), which are environmentally benign devices for direct conversion and storage of solar energy into electricity, have a high potential for eliminating the requirement for grid electricity for a sustainable future. In this research, nickel sulfide (NS), cobalt sulfide (CS) and nickel cobalt sulfide (NCS) deposited on TiO2 nanotubes (TNT) have been prepared as novel photoactive electrodes for photorechargeable supercapacitors. X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), High-resolution transmission electron microscopy (HRTEM), Energy-dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Ultraviolet–visible spectroscopy (UV–Vis) were used to characterize the phase, morphology, elemental composition, oxidation states and optical properties of the films produced. Based on the photoelectrochemical measurements, the NCS@TNT-1 samples showed higher capability to produce and separate photogenerated charges compared to bare TNTs, NS@TNT and CS@TNT. The highest capacity of up to 471.6 mF/cm2 (at 0.7 mA/cm2) was shown by the NCS@TNT-1 electrode, which is about 11 times higher than that of bare TNTs (44 mF/cm2). In addition, the specific capacitance of the NCS@TNT-1 electrode (as the best sample) increased approximately twofold, reaching 955.6 mF/cm2 upon light illumination. Three photochargeable asymmetric supercapacitors were fabricated with NCS@TNT as the electrode and PVA-KOH as the electrolyte and separator. The specific capacitance of the fabricated supercapacitor increased by 1.57 times when illuminated by light. The device showed outstanding stability over 10,000 galvanostatic charge and discharge cycles with a capacity retention of 87 % and 94 % in the dark and under light conditions, respectively. More importantly, the illumination resulted in an extended discharge time.

A self-standing dual-electric field synergistic Janus nanofibre piezoelectric photocatalyst with degradation of antibiotics: Performances, DFT calculation and mechanism unveiling

A self-standing dual-electric field synergistic [TiO2/polyvinylidene fluoride (PVDF)]//[g-C3N4 tube/PVDF] Janus nanofibres (named as [TP]//[CTP]JNs) S-scheme heterostructure piezoelectric photocatalyst is designed and constructed via conjugative electrospinning. Dual-fields of built-in electric fields supplied by S-scheme heterostructure and piezoelectric field formed by PVDF jointly boost separation and transfer of photo-induced charges. As a case study, piezoelectric photocatalytic efficiency of [TP]//[CTP]JNs for tetracycline hydrochloride (TCH) under ultrasonic united with simulated sunlight illumination is 93.35% (40 min), which is 1.39 times of the photocatalytic efficiency (light illumination only) and 5.32 times of piezoelectric catalytic efficiency (applying ultrasonic only), proving the advantages of the synergistic effect of piezoelectric catalysis and photocatalysis on contaminant degradation. The dynamic behaviors of photocatalysis and photo-generated charges are deeply revealed through fs-TA and TRPL decay spectra, and the degradation pathways of antibiotics are reasonably speculated by combining LCMS spectra with Fukui index. By the degradation ability, COMSOL simulation and DFT calculation, the structural advantage of Janus nanofibers is fully verified, and S-scheme charge transfer mechanism is confirmed by combining a series of sound ample experiments with theoretical calculations. Additionally, the construction mechanism of Janus nanofibers is proposed, and corresponding construction technique is established.

Boosting photothermal-assisted photocatalytic H2 production over black g-C3N4 nanosheet photocatalyst via incorporation with carbon dots

Although photocatalytic H2 production based on semiconductor materials has a wide potential application, it still facing challenges such as slow reaction kinetics or complex synthesis processes. To meet these challenges, the carbon dots loaded black g-C3N4 (CN-B-CDs) was synthesized by simple calcination method to achieve efficient photothermal-assisted photocatalytic H2 production. Photothermal imaging experiments confirmed the photothermal effect of CN-B and CDs as dual heat sources to increase the temperature of the composite system, thus improving the effective separation of photo-generated charges. In addition, multiple photocatalytic H2 production tests exhibited that CN-B-CDs photocatalysts not only have strong stability but also can accommodate a variety of complex water bodies, which displayed the potential for industrial application. This study combined the photothermal effect and the mechanism by which the CDs promote the charge transfer to design a new photocatalytic H2 production system and provided a new scheme for achieving efficient photothermal-assisted photocatalytic H2 production using carbon-based materials.

Regulating Sulfur Redox Kinetics by Coupling Photocatalysis for High-Performance Photo-Assisted Lithium-Sulfur Batteries.

Challenges such as shuttle effect have hindered the commercialization of lithium-sulfur batteries (LSBs), despite their potential as high-energy-density storage devices. To address these issues, we explore the integration of solar energy into LSBs, creating a photo-assisted lithium-sulfur battery (PA-LSB). The PA-LSB provides a novel and sustainable solution by coupling the photocatalytic effect to accelerate sulfur redox reactions. Herein, a perovskite quantum dot-loaded MOF material serves as a cathode for the PA-LSB, creating built-in electric fields at the micro-interface to extend the lifetime of photo-generated charge carriers. The band structure of the composite material aligns well with the electrochemical reaction potential of lithium-sulfur, enabling precise regulation of polysulfides in the cathode of the PA-LSB system. This is attributed to the selective catalysis of the liquid-solid reaction stage in the lithium-sulfur electrochemical process by photocatalysis. These contribute to the outstanding performance of PA-LSBs, particularly demonstrating a remarkably high reversible capacity of 679 mAh g-1 at 5 C, maintaining stable cycling for 1500 cycles with the capacity decay rate of 0.022 % per cycle. Additionally, the photo-charging capability of the PA-LSB holds the potential to compensate for non-electric energy losses during the energy storage process, contributing to the development of lossless energy storage devices.

Enhancing the Activity of a Carbon Nitride Photocatalyst by Constructing a Triazine-Heptazine Homojunction.

Establishing homojunctions at the molecular level between different but physicochemically similar phases belonging to the same family of materials is an effective approach to promoting the photocatalytic activity of polymeric carbon nitride (CN) materials. Here, we prepared a CN material with a uniform distribution of homojunctions by combining two synthetic strategies: supramolecular assemblies as the precursor and molten salt as the medium. We designed porous CN rods with triazine-heptazine homojunctions (THCNs) using a melem supramolecular aggregate (Me) and melamine as the precursors and a KCl/LiBr salt mixture as the liquid reaction medium. The triazine/heptazine ratio is controlled by varying the relative amounts of the chosen precursors, and the molten salt treatment enhances the structural order of the interplanar packing units for the THCN skeleton, leading to rapid charge migration. The resulting built-in electric field induced by the triazine-heptazine homojunction enhances photogenerated charge separation; the optimal THCN catalyst exhibits an excellent H2 evolution rate via photocatalytic water splitting, which is ∼24 times as high as that of reference bulk CN, with long-term stability.

BiVO4-based heterojunction nanophotocatalysts for water splitting and organic pollutant degradation: a comprehensive review of photocatalytic innovation

Abstract The novel semiconductor photocatalytic material bismuth vanadate (BiVO4) is gaining significant attention in research due to its unique characteristics, which include a low band gap, good responsiveness to visible light, and non-toxic nature. However, intrinsic constraints such as poor photogenerated charge transfer, slow water oxidation kinetics, and fast electron–hole pair recombination limit the photocatalytic activity of BiVO4. Building heterojunctions has shown to be an effective strategy for enhancing charge separation and impeding electron–hole pair recombination over the last few decades. This review covers the state-of-the-art developments in heterojunction nanomaterials based on BiVO4 for photocatalysis. It explores heterojunction design, clarifies reaction mechanisms, and highlights the current developments in applications including photocatalytic water splitting and organic matter degradation. Finally, it offers a preview of the development paths and opportunities for BiVO4-based heterojunction nanomaterials in the future. This comprehensive assessment of BiVO4-based heterojunctions provides insightful knowledge to researchers in materials science, chemistry, and environmental engineering that will drive advances and breakthroughs in these important fields.

Oxygen-deficient WO3 for stable visible-light photocatalytic degradation of acetaldehyde within a wide humidity range

Indoor VOCs pollution has attracted broad attention for its harm to mankind’s health recent years. Photocatalytic degradation of indoor VOCs holds great prospects in addressing these health concerns in daily life. However, traditional photocatalysts have a large recombination rate of charge carriers and a decrease of the photocatalytic degradation efficiency under high relative humidity. Herein, uniform tungsten oxide nanoparticles with enriched oxygen vacancies (WO3-U) were synthesized by a direct annealing method with urea addition, which exhibited superior performance in the visible-light photocatalysis. The reaction rate constant value of photocatalytic acetaldehyde degradation over WO3-U catalyst was above 3 times higher than that of pristine WO3 sample. More importantly, the WO3-U catalyst maintained stable and excellent photocatalytic performance at relative humidity range of 25–100 %. Except for the enhanced photogenerated charges separation, abundant oxygen vacancies could effectively accelerate O2 activation to generate •O2−, which accounted mainly for the initial conversion of acetaldehyde. Then the subsequent transformation of •O2− into •OH to promoted the final mineralization of acetaldehyde. In addition, the presence of oxygen vacancies also facilitated H2O dissociation to form surface hydroxyl groups, which increased the adsorption of acetaldehyde, resulting in the consistent photocatalytic performance of WO3-U catalyst within a wide humidity range. This work provides guidelines to design visible-light responsive photocatalysts with efficient activity at high humidity conditions for indoor VOCs degradation.

One-pot microwave synthesize bandgap tunable g-C3N4 for highly efficient photocatalytic H2O2 production

Graphitic carbon nitride (g-C3N4) faces limitations in photocatalytic application due to its limited light response and high recombination rate of photo-generated charge carriers. Herein, we synthesized a K, P co-doped g-C3N4 (KPCN) with cyano defects via microwave-assisted heating of the mixture of KH2PO4 and melamine in just 7 min. The KPCN exhibits a reduced bandgap of 2.37 eV and introduces a mid-gap of 1.77 eV, which broadens light absorption to the visible-near-infrared (vis-NIR) spectrum with light absorption to 867 nm. Impressively, the co-doped K and P adjust the interlayer and in-plane electron distribution of g-C3N4, enhancing charge separation and transfer. The KPCN exhibits a remarkable improvement in H2O2 yield of 7.74 mM g−1 h−1, demonstrating superior catalytic activity compared to microwave pure g-C3N4 (MCN, 5.1 times) and bulk g-C3N4 (BCN, 19.2 times). The results indicate that the K, P co-doped g-C3N4 synthesized rapidly and efficiently by microwave method has relatively stable and considerable photocatalytic activity, which has great potential application in the industrial production of H2O2.

Constructing a CeFeO3/LaFeO3/ZnIn2S4 double Z-scheme heterojunction for photocatalytic atrazine degradation under visible light irradiation

The limited light absorption range and rapid recombination of interfacial charges were deemed to be the main restriction of the photocatalysts for atrazine (ATZ) degradation, and the construction of Z-scheme heterojunction was an effective strategy. Herein, a CeFeO3/LaFeO3/ZnIn2S4 (CFO/LFO/ZIS) double Z-scheme ternary heterojunction photocatalyst was fabricated by the in-situ precipitation and hydrothermal method. The photocatalytic ATZ degradation efficiency of optimized heterojunction reached 52% within 175 min under visible light irradiation, which was 3.1, 3.7 and 1.7 times higher than that of CFO, LFO and ZIS, respectively. The enhanced photocatalytic activity was due to the excellent light capture capacity and improved photogenerated charge separation in CFO/LFO/ZIS double Z-scheme heterojunction photocatalyst. Meanwhile, some environmental factors on the influence of photocatalytic ATZ degradation performance were systematically investigated. Quenching experiments confirmed that ·OH, h+ and 1O2 were the main active species during the photocatalytic ATZ degradation process. The possible photogenerated charge separation route was proposed via the analysis of the IEF effects between CFO, LFO and ZIS. Finaly, the possible ATZ degradation pathway was deduced by LC-MS measurement and toxicity assessment of the intermediates were also evaluated by the Toxicity Estimation Software Tool (TEST). This work not only provided a potential magnetic recyclable ferrate based double Z-scheme heterojunction photocatalyst for enhancing photogenerated charge separation and light absorption, but also evaluated the intermediate toxicity and related environmental factors on the activity of photocatalyst, which was facilitating the practical application for the degradation of ATZ.

Dual Channel H2O2 Photosynthesis in Pure Water over S-Scheme Heterojunction Cs3PMo12/CC Boosted by Proton and Electron Reservoirs.

Dual channel photo-driven H2O2 production in pure water on small-scale on-site setups is a promising strategy to provide low-concentrated H2O2 whenever needed. This process suffers, however, strongly from the fast recombination of photo-generated charge carriers and the sluggish oxidation process. Here, insoluble Keggin-type cesium phosphomolybdate Cs3PMo12O40 (abbreviated to Cs3PMo12) is introduced to carbonized cellulose (CC) to construct S-scheme heterojunction Cs3PMo12/CC. Dual channel H2O2 photosynthesis from both H2O oxidation and O2 reduction in pure water has been thus achieved with the production rate of 20.1mmolL-1gcat. -1h-1, apparent quantum yield (AQY) of 2.1% and solar-to-chemical conversion (SCC) efficiency of 0.050%. H2O2 accumulative concentration reaches 4.9mmol L-1. This high photocatalytic activity is guaranteed by unique features of Cs3PMo12/CC, namely, S-scheme heterojunction, electron reservoir, and proton reservoir. The former two enhance the separation of photo-generated charge carriers, while the latter speeds up the torpid oxidation process. In situ experiments reveal that H2O2 is formed via successive single-electron transfer in both channels. In real practice, exposing the reaction system under natural sunlight outdoors successfully results in 0.24mmol L-1 H2O2. This work provides a key practical strategy for designing photocatalysts in modulating redox half-reactions in photosynthesis.

Enhanced Light Absorption and Photo-Generated Charge Separation Efficiency for Boosting Photocatalytic H2 Evolution through TiO2 Quantum Dots with N-Doping and Concomitant Oxygen Vacancy.

Low-range light absorption and rapid recombination of photo-generated charge carriers have prevented the occurrence of effective and applicable photocatalysis for decades. Quantum dots (QDs) offer a solution due to their size-controlled photon properties and charge separation capabilities. Herein, well-dispersed interstitial nitrogen-doped TiO2 QDs with stable oxygen vacancies (N-TiO2-x-VO) are fabricated by using a low-temperature, annealing-assisted hydrothermal method. Remarkably, electrostatic repulsion prevented aggregation arising from negative charges accumulated in situ on the surface of N-TiO2-x-VO, enabling complete solar spectrum utilization (200-800 nm) with a 2.5 eV bandgap. Enhanced UV-vis photocatalytic H2 evolution rate (HER) reached2757µmol g-1 h-1, 41.6 times higher than commercial TiO2 (66µmol g-1 h-1). Strikingly, under visible light, HER rate was 189µmol g-1 h-1. Experimental and simulated studies of mechanisms reveal that VO can serve as an electron reservoir of photo-generated charge carriers on N-doped active sites, and consequently, enhance the separation rate of exciton pairs. Moreover, the negative free energy (-0.35 V) indicates more favorable thermodynamics for HER as compared with bulk TiO2 (0.66 V). This research work paves a new way of developing efficient photocatalytic strategies of HER that are applicable in the sustainable carbon-zero energy supply.