Spatial Separation Of Carriers Research Articles

Synergistic interfacial engineering of a S-scheme ZnO/In2S3 photocatalyst with S−O covalent bonds: A dual-functional advancement for tetracycline hydrochloride degradation and H2 evolution

Efficient interfacial charge transfer and robust interface interactions are crucial to achieve superior spatial separation of carriers and develop advanced heterogeneous photocatalysts. This study describes the synthesis of a novel S-scheme heterojunction of ZnO/In2S3, with S−O covalent bonds, achieved through a hydrothermal method. The optimized heterojunction shows exceptional photocatalytic activity, achieving a H2 generation rate of 2488 μmol g−1 h−1 and a degradation efficiency of 86 % for tetracycline hydrochloride (TCH) within 2 h. These values surpass those of In2S3 alone by 35 and 1.4 times, respectively. Various techniques, including electron spin resonance, X-ray photoelectron spectroscopy, Kelvin probe force microscopy and density functional theory calculations confirm the S-scheme heterojunction. The establishment of a chemical S−O bond between In2S3 and ZnO facilitates an atomic level interfacial pathway, enabling efficient transportation of interfacial electrons.

In-situ construction of CoS on porous g-C3N4 for fluent charge transfer in photocatalytic hydrogen production

Constructing active sites with optimized surface interface structure on photocatalysts is essential to photocatalytic H2 production. Herein, CoS as a promising cocatalyst is in-situ anchored on the surface porous g-C3N4 (PCN) using a facial solid-state method. The in-situ growth of CoS with small particle size on PCN endows their intimate interfacial contact, which provides a fluent transfer channel of photogenerated carriers. CoS promotes photogenerated electron-hole pairs and reduces the overpotential of H2 evolution. According to the results of Density functional theory (DFT) calculations, benefitting from the difference of work functions between CoS and PCN, photogenerated electrons spontaneously migrate from PCN to CoS, thus resulting in the spatial separation of carriers. Moreover, CoS possesses near-zero ΔGH*, causing the electrons gathered on CoS to be more likely to reduce protons to H2 molecules. The apparent quantum efficiency (AQE) of hydrogen evolution on 2 % CoS/g-C3N4 at λ = 420 nm reaches 35.6 % and the maximum H2-evolving rate reaches as high as 3.27 mmol·h−1·g−1 under the irradiation of natural light. This work provides a facile synthesis method for loading metal sulfide cocatalysts and gains a deeper understanding of the mechanism of CoS acting as active sites for photocatalytic H2 production.

Enhancement of photocatalytic oxidation by water-driven piezoelectricity using MoO3/P(VDF-TrFE) mixed matrix membranes

In this study, novel mixed matrix membranes (MMMs) composed of MoO3/Poly (vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) with distinctive piezo-photocatalytic properties were prepared. The membranes were made from dopes containing a high ratio of MoO3 to P(VDF-TrFE) (2:1 wt%/wt%) through a modified solvent evaporation method. The addition of MoO3 particles significantly impacted the crystallization and self-polarization of the P(VDF-TrFE) matrix, leading to a substantial increase in total crystallinity from 46.4% to 88.9% and a transformation from α to β phase. The flow-induced piezoelectric potential created an internal electric field, enhancing the spatial separation of photogenerated carriers through the piezoelectric effect. Controlled water flow further promoted the spatial separation of carriers. The developed MMMs demonstrated a high Rhodamine B degradation rate, reaching 83.1% within 45 minutes and over 99% within 90 minutes under natural light conditions. The MoO3/P(VDF-TrFE) MMMs exhibit promising piezo-photocatalytic attributes and hold potential for diverse applications due to their unique combination of piezoelectric and photocatalytic properties.

High‐performance Photoelectrochemical Hydrogen Production Using Asymmetric Quantum Dots

AbstractSolar‐driven photoelectrochemical (PEC) reactions using colloidal quantum dots (QDs) as photoabsorbers have shown great potential for the production of clean fuels. However, the low H2 evolution rate, consistent with low values of photocurrent density, and their limited operational stability are still the main obstacles. To address these challenges, the heterostructure engineering of asymmetric capsule‐shaped CdSe/CdxZn1‐xSe QDs with broad absorption and efficient charge extraction compared to pure‐shell QDs is reported. By engineering the shell composition from pure ZnSe shells into CdxZn1‐xSe gradient shells, the electron transfer rate increased from 4.0 × 107 s−1 to 32.7 × 107 s−1. Moreover, the capsule‐shaped architecture enables more efficient spatial carrier separation, yielding a saturated current density of average of 25.4 mA cm−2 under AM 1.5 G one sun illumination. This value is the highest ever observed for QDs‐based devices and comparable to the best‐known Si‐based devices, perovskite‐based devices, and metal oxide‐based devices. Furthermore, PEC devices based on heterostructured QDs maintained 96% of the initial current density after 2 h and 82% after 10 h under continuous illumination, respectively. The results represent a breakthrough in hydrogen production using heterostructured asymmetric QDs.

Long-Lived and Bright Biexcitons in Quantum Dots with Parabolic Band Potentials.

Multiple exciton physics in semiconductor nanocrystals play an important role in optoelectronic devices. This work investigates radially alloyed CdZnSe/CdS nanocrystals with suppressed Auger recombination due to the spatial separation of carriers, which also underpins their performance in optical gain and scintillation experiments. Due to suppressed Auger recombination, the biexciton lifetime is greater than 10 ns, much longer than most nanocrystals. The samples show optical gain, amplified spontaneous emission, and lasing at thresholds <2 excitons per particle. They also show broad gain bandwidth (>500 meV) encompassing 4 amplified spontaneous emission bands. Similarly enabled by slowed multiple exciton relaxation, the samples display strong performance in scintillating films under X-ray illumination. The CdZnSe/CdS samples have fast radioluminescence rise (<80 ps) and decay times (<5 ns), light yields up to 6700 photons·MeV-1, and the demonstrated capacity for incorporation into large area films for scintillation imaging.

Gradient tungsten-doped Bi3TiNbO9 ferroelectric photocatalysts with additional built-in electric field for efficient overall water splitting

Bi3TiNbO9, a layered ferroelectric photocatalyst, exhibits great potential for overall water splitting through efficient intralayer separation of photogenerated carriers motivated by a depolarization field along the in-plane a-axis. However, the poor interlayer transport of carriers along the out-of-plane c-axis, caused by the significant potential barrier between layers, leads to a high probability of carrier recombination and consequently results in low photocatalytic activity. Here, we have developed an efficient photocatalyst consisting of Bi3TiNbO9 nanosheets with a gradient tungsten (W) doping along the c-axis. This results in the generation of an additional electric field along the c-axis and simultaneously enhances the magnitude of depolarization field within the layers along the a-axis due to strengthened structural distortion. The combination of the built-in field along the c-axis and polarization along the a-axis can effectively facilitate the anisotropic migration of photogenerated electrons and holes to the basal {001} surface and lateral {110} surface of the nanosheets, respectively, enabling desirable spatial separation of carriers. Hence, the W-doped Bi3TiNbO9 ferroelectric photocatalyst with Rh/Cr2O3 cocatalyst achieves an efficient and durable overall water splitting feature, thereby providing an effective pathway for designing excellent layered ferroelectric photocatalysts.

Optical valley separation in two-dimensional semimetals with tilted Dirac cones

Quasiparticles emerging in crystalline materials can possess a binary flavor known as the valley quantum number which can be used as a basis to encode information in an emerging class of valleytronic devices. Here we show that two-dimensional semimetals with tilted Dirac cones in the electronic band structure exhibit spatial separation of carriers belonging to different valleys under illumination. In stark contrast to gapped Dirac materials this optovalleytronic phenomenon occurs in systems with intact inversion and time-reversal symmetry that host gapless Dirac cones in the band structure, thereby retaining the exceptional graphene-like transport properties. We thus demonstrate that optical valley separation is possible at arbitrarily low photon frequencies including the deep infrared and terahertz regimes with full gate tunability via Pauli blocking. As a specific example of our theory, we predict tunable valley separation in the proposed two-dimensional tilted Dirac cone semimetal 8-Pmmn borophene for incident infrared photons at room temperature. This work highlights the potential of two-dimensional tilted Dirac cone materials as a platform for tunable broadband optovalleytronic applications.

Intralayer spatial carrier separation capability for visible light driven photocatalytic properties of SnGe2N4-layered nanostructure: A first-principles study

Recently, semiconductor photocatalysts for green hydrogen (H2) fuel require two-dimensional (2D) material with semiconducting direct bandgap and enhanced visible light absorptions. In this study, the first-principles calculation of the 2D layered nanostructure of SnGe2N4 is presented for photocatalysis applications, which has a direct bandgap of 1.73 eV/2.64 eV (Perdew–Burke–Ernzerhof/Heyd–Scuseria–Ernzerhof with generalized gradient approximation) with enhanced optical absorptions. The structure is checked to confirm the chemical formidability and dynamical steadiness by formation energy calculations and phonon dispersions. To attain the tunability of electronic and optical properties, biaxial strains, together with tensile and compressive strains, are incorporated, and it is found that compressive strain widens the bandgap, whereas tensile strain causes bandgap reduction. Biaxial strains also improve the optical absorption and the highest absorption coefficient is obtained at ∼1.47 ⨯ 105 cm−1 for 6% compressive strain, comparable to conventional perovskite materials. However, in the visible spectrum, the highest absorption coefficient is obtained for 6% tensile strain. The calculated photocatalytic band edges suggest that this material has sufficient kinetic overpotential for photo redox at compressive strains in both pH = 7 and pH = 0. In addition, the spatial carrier separation is achieved due to having a large intralayer effective potential deviation of ∼6.96 eV, as well as intralayer spatial atomic group contribution in the valance band maximum and conduction band minimum. Conclusively, the analysis in this study can be a theoretical background of this layered nanostructure as a potent photocatalyst for water splitting.

Tunable electronic and optical properties of GeC/PtO2 vdW hetero-bilayer using first-principles study

The detailed optical and electronic characteristics of 2D GeC and 2D PtO2 under biaxial strains and electric fields across the plane are studied systematically using the density functional theory (DFT) based first-principles framework. The six different stacking patterns of the stacked van der Waals (vdW) GeC/PtO2 hetero-bilayers were DFT screened, and HBL 4 and HBL 5 are found both dynamically stable and energetically favorable, evident from the non-zero phonon frequency and negative binding energy from phonon dispersion and binding energy calculations, respectively. The bandgap of 2D GeC and 2D PtO2 is found to be ∼2.08 eV (direct) and ∼1.63 eV (indirect), while the bandgaps in vdW HBL 4 (HBL 5) are found to be 0.51 eV (0.49 eV). Biaxial strain lowered the bandgap by ∼11.13 (∼1.81) times at 6% compressive (tensile) biaxial strain in HBL 4 (HBL 5). Semiconductor-to-metal switching is found in both HBLs at ±0.6 V/Å of the cross-plane electric field. All the HBLs show type-II band-alignment, evident from the difference in charge density and projected density of state contour, indicating spatial carrier separation capability. The peak of the optical absorption coefficient is found to be ∼3.1 × 105 cm−1 at 310 nm for both HBL 4 and HBL 5, which is comparable to high-absorbing perovskite material. Moreover, the optical absorption is sensitive to the biaxial strains and electric fields, and increased visible band optical absorption is found for tensile strains in both HBLs. These exceptional findings and engineered bandgap in GeC/PtO2 vdW HBL indicate the promising application of this material in 2D advanced nanoelectronics.

Dual sulfur defect engineering of Z-scheme heterojunction on Ag-CdS1-x@ZnIn2S4-x hollow core-shell for ultra-efficient selective photocatalytic H2O2 production

Photocatalytic production of hydrogen peroxide (H2O2) using sunlight as an energy source, water and molecular oxygen as feedstock is considered as a green and sustainable promising strategy to solve the energy and environmental crisis. Despite significant improvements in photocatalyst design tuning, however, the relatively low photocatalytic H2O2 productivity is still far from satisfactory. Herein, we developed a multi-metal composite sulfide (Ag-CdS1-x@ZnIn2S4-x) with double S vacancies and hollow core–shell Z-type heterojunction structure for H2O2 generation by a simple hydrothermal method. The unique hollow structure improves the utilization of light source. The existence of Z-type heterojunction promotes the spatial separation of carriers, and the core–shell structure increases the interface area and active sites. Under visible light irradiation, Ag-CdS1-x@ZnIn2S4-x had a high hydrogen peroxide yield of 1183.7 μmol h−1 g−1, which was 6 times that of CdS. The electron transfer number (n = 1.53) obtained from the Koutecky-Levuch plot and DFT calculation confirm that the presence of dual disulfide vacancies provides good selectivity of 2e- O2 reduction to H2O2. This work provides new insights into the regulation of highly selective two-electron photocatalytic H2O2 production, and also provides new ideas for the design and development of highly active energy conversion photocatalysts.

Hollow Spherical Pd/CdS/NiS with Carrier Spatial Separation for Photocatalytic Hydrogen Generation.

Inspired by the unique properties of the three-dimensional hollow nanostructures in the field of photocatalysis, as well as the combination of co-catalyst, porous hollow spherical Pd/CdS/NiS photocatalysts are prepared by stepwise synthesis. The results show that the Schottky junction between Pd and CdS accelerates the transport of photogenerated electrons, while a p-n junction between NiS and CdS traps the photogenerated holes. As co-catalysts, the Pd nanoparticles and the NiS are loaded inside and outside the hollow CdS shell layer, respectively, which combines with the particular characteristic of the hollow structure, resulting in a spatial carrier separation effect. Under the synergy of the dual co-catalyst loading and hollow structure, the Pd/CdS/NiS has favorable stability. Its H2 production under visible light is significantly increased to 3804.6 μmol/g/h, representing 33.4 times more than that of pure CdS. The apparent quantum efficiency is 0.24% at 420 nm. A feasible bridge for the development of efficient photocatalysts is offered by this work.

Oxygen Vacancies-Rich S-Cheme BiOBr/CdS Heterojunction with Synergetic Effect for Highly Efficient Light Emitting Diode-Driven Pollutants Degradation.

Recently, the use of semiconductor-based photocatalytic technology as an effective way to mitigate the environmental crisis attracted considerable interest. Here, the S-scheme BiOBr/CdS heterojunction with abundant oxygen vacancies (Vo-BiOBr/CdS) was prepared by the solvothermal method using ethylene glycol as a solvent. The photocatalytic activity of the heterojunction was investigated by degrading rhodamine B (RhB) and methylene blue (MB) under 5 W light-emitting diode (LED) light. Notably, the degradation rate of RhB and MB reached 97% and 93% in 60 min, respectively, which were better than that of BiOBr, CdS, and BiOBr/CdS. It was due to the construction of the heterojunction and the introduction of Vo, which facilitated the spatial separation of carriers and enhanced the visible-light harvest. The radical trapping experiment suggested that superoxide radicals (·O2-) acted as the main active species. Based on valence balance spectra, Mott-Schottky(M-S) spectra, and DFT theoretical calculations, the photocatalytic mechanism of the S-scheme heterojunction was proposed. This research provides a novel strategy for designing efficient photocatalysts by constructing S-scheme heterojunctions and introducing oxygen vacancies for solving environmental pollution.

Synergy of Z-scheme heterostructure with interfacial S−O bonding in In2S3/BiOBr for efficient tetracycline hydrochloride degradation and Cr(VI) reduction

High-efficiency interfacial charge transfer is the key to achieve better spatial carrier separation, and thus to develop advanced heterogeneous photocatalysts for environmental remediation. However, It still remains a great challenge to design and exploit the effective charge transfer scheme. Herein, a novel Z-scheme In2S3/BiOBr with S−O covalent bonding was prepared by hydrothermal and subsequent thermal annealing methods. The obtained photocatalysts were systematically characterized and used for tetracycline hydrochloride degradation and Cr(VI) reduction in aqueous solution. As a result, the optimized In2S3/BiOBr heterostructure (IS/BOB-39) exhibited superior photocatalytic activities for tetracycline hydrochloride degradation and Cr(VI) reduction under simulated solar light irradiation compared with individual materials. The Z-scheme transfer mechanism was corroborated by trapping experiments, ESR and XPS analysis, which provided an effective transfer pathway for spatial separation of carriers. Moreover, the formation of chemical S−O bond between In2S3 and BiOBr, which acted as a specific bridge to expediently transmit interfacial electrons, showed a synergistic effect with Z-scheme transfer model on the significantly enhanced photocatalytic performance. In addition, the In2S3/BiOBr heterojunction presented excellent cycle stability, resulting from the tight heterointerface. This work provides a promising approach to design and fabricate high effect Z-scheme heterojunction in wastewater treatment.

Insight into the Crystal Facet Effect of {101} and {100} Facets of CeVO4 in the Photochemical Property and Photocatalysis.

To investigate the photochemical property of specific crystal facets, two well-defined CeVO4 dodecahedrons with exposed {101} and {100} facets are prepared, which have distinguishing appearances and unequal {101}/{100} area ratios (A{101}/A{100}), i.e., compressed dodecahedra (CeVO4 CD, A{101}/A{100} ≈ 1) and elongated dodecahedra (CeVO4 ED, A{101}/A{100} ≈ 0.3). During the visible-light-irradiated process, the {101} and {100} facets are certified to selectively deposit photogenerated holes (h+) and electrons (e-), thus exhibiting the photooxidability and photoreducibility, respectively. Meanwhile, a surface heterojunction could form at the adjacent facet interface and facilitate the spatial separation of carriers. Benefiting from the large exposure extent of the {101} facet and the rational A{101}/A{100} (∼1), the CeVO4 CD shows a superior photocatalytic performance for the degradation of tetracycline to the CeVO4 ED. Finally, simulation calculations reveal that the energy deviations of the valence band (VB) and conduction band (CB) between CeVO4{101} and CeVO4{100} impel the photogenerated h+ and e- to transfer in opposite directions, resulting in the facet-dependent photoactivity of the CeVO4 dodecahedron.

Highly efficient photocatalytic degradation of norfloxacin via Bi2Sn2O7/PDIH Z-scheme heterojunction: Influence and mechanism

The severe pollution caused by antibiotics has prompted considerable concerns in recent decades. In this study, the Bi2Sn2O7/PDIH Z-scheme heterojunction photocatalyst was synthesized and highly photocatalytic activity on norfloxacin was obtained. The degradation of norfloxacin reached 98.71% in 90 min under visible light. The apparent rate constant of norfloxacin (0.4 903 min−1) was 3.65 and 20 times that of PDIH and the Bi2Sn2O7. Meanwhile, XPS, electrochemical, Photoluminescence spectroscopy and electron paramagnetic resonance results showed that Z-scheme charge-transfer process facilitated the spatial carrier separation and preserve redox capability. Furthermore, the degradation intermediates of norfloxacin and their toxicities were evaluated. Finally, in the view of the survey about the impact of different water matrices, it was found that the Bi2Sn2O7/PDIH maintained high efficiency in raw natural water. This work enriched inorganic/organic heterojunction engineering for PDIH, and provided the enormous potential for combining the Bi2Sn2O7 with PDIH to address the antibiotic pollution issues in the actual water treatment.

π-d Electron-Coupled PBDIT/CdS Heterostructure Enables Hole Extraction for Efficient Photocatalytic Hydrogen Production.

Construction of heterostructures is one of the most promising strategies for designing photocatalysts for highly efficient solar hydrogen (H2) production because the introduction of an electron-donating counterpart contributes to more effective photon absorption, while the heterostructures benefit spatial carrier separation. However, the hole-transfer rate is usually 2-3 orders of magnitude slower than that of the electron-transfer rate within the heterostructures, ensuing serious charge recombination. Here, we find the energy band offset-driven charge-transfer behavior in a donor-acceptor (D-A)-conjugated polymer/CdS organic/inorganic heterostructure and realize hole-transfer improvement in cooperation with a further hole removal motif of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. The photocatalytic H2 production activity is increased by nearly 2 orders of magnitude with the apparent quantum yield hitting ca. 80% at 450 nm without co-catalysts. Ultrafast transient absorption together with surface photovoltage characterizations consolidates the hole extraction mechanism. The intimate bond formed at the interface between the polymer and the inorganic semiconductor acts as an interpenetrating network at the nanoscale level, thus providing a charge-transfer freeway for boosting charge separation.

Interface engineering of ZnO/In2O3 Z-scheme heterojunction with yolk-shell structure for efficient photocatalytic hydrogen evolution

Photocatalytic activities based on charge transfer and separation at interfaces can be effectively promoted by matching chemical Z-scheme heterojunctions and electronic structures. However, the fabrication of morphology-controlled heterojunctions has been a challenge to many researchers. Herein, hollow spheres ZnO/In2O3 was constructed via hydrothermal strategy by fine-tuning the concentration of metal nitrate precursors, and special yolk-shell morphology was generated by the symmetrical Ostwald ripening process. The fabricated Z-Scheme heterojunction exhibited characteristic multi-channel charge transfer properties, which favors the spatial separation of carriers. The ZnO/In2O3 hollow spheres increased the utilization of light source, and the yolk-shell structure increased the interface area and the active sites. Benefiting from the synergistic effect, the ZnO/In2O3 exhibited excellent photocatalytic activities for H2 production, which was comparatively 26.7 times that obtained using ZnO nanoparticles. From calculations based on DFT, the Z-scheme photogenerated charge transfer mechanism was proposed. The proposed mechanism was verified by analyzing the chemical properties (surface) and the •O2− and •OH free radical concentrations before and after the photoreaction. The mechanism presented the ZnO/In2O3 with strong capabilities for H2 production and elucidated the improved photocatalytic performances. This work creates an innovative route for constructing Z-scheme photocatalytic systems with great photocatalytic activities for H2 production.

Study of Two-Dimensional Janus WXY (X≠Y= S, Se, and Te) Trilayer Homostructures for Photovoltaic Applications Using DFT Screening of Different Stacking Patterns.

Based on the first-principles density functional theory, Janus WXY (X ≠ Y = S, Se, and Te) trilayer homostructures for different stacking patterns are studied in this work to analyze their appropriateness in fabricating photovoltaic (PV) devices. A total of fifteen trilayer homostructures are proposed, corresponding to the suitable five stacking patterns, such as AAA, AA′A, ABA, AB′A, and A′BA′ for each Janus WXY (X ≠ Y = S, Se, and Te) material. Structural and energetic parameters for all the fifteen structures are evaluated and compared to find energetically stable structures, and dynamic stability is confirmed by phonon dispersion curves. All these configurations being homostructure, lattice mismatch is found to be very low (∼0.05%), unlike heterostructure, making them feasible for optoelectronics and PV applications. WSSe AAA, WSSe AA′A, and WSeTe AA′A are dynamically stable along with negative binding energy and show type-II band alignment, enabling effective spatial carrier separation of photogenerated carriers. The optical properties of dynamically stable WSSe AAA and WSSe AA′A structures are also calculated, and the absorption coefficients at the visible light region are found to be ∼3.5 × 105 cm–1, which is comparable to the perovskite material absorption coefficient. Moreover, we have compared the optical characteristics of dynamically stable WSSe AAA and WSSe AA′A structures with their monolayer structures to realize the significance of stacking trilayer structures. Electrical properties such as mobility and conductivity for dynamically stable WSSe AAA and WSSe AA′A structures are evaluated to suggest them as a probable efficient material in PV technology.

Alkali-mediated dissolution-recrystallization strategy for in situ construction of a BiVO4/Bi25VO40 heterojunction with promoted interfacial charge transfer: Formation mechanism and photocatalytic tetracycline degradation studies

Constructing a heterojunction between semiconductors with identical elements constitutes an intimate contact that can greatly accelerate the charge carrier transfer and separation. Herein, a novel BiVO4/Bi25VO40 heterojunction was designed by the in situ conversion of pre-prepared BiVO4 in alkaline conditions. We investigated the formation process of BiVO4/Bi25VO40 heterojunctions by XRD structural refinement, Raman spectra, morphology characterization, and density functional theory calculations, and found that heterojunction formation occurred through a dissolution–recrystallization process, in which monoclinic BiVO4 decahedrons were first etched by alkali solution on the preferential {0 1 0} face and then transformed into cubic Bi25VO40. By adjusting the alkali treatment conditions, the phase composition of the heterojunction can be precisely modulated with BiVO4 decreasing and Bi25VO40 increasing in content as the synthesis time was extended. Benefiting from the in situ conversion strategy and matched band structure, the intimate type II heterojunction with close interfacial contact was formed between BiVO4 and Bi25VO40, leading to facilitated charge transfer with spatial separation of carriers and significantly enhanced photocatalytic performance in the probe reaction of tetracycline (TC) degradation. The active species responsible for TC removal were explored by radical trapping tests and ESR spectra, and the photodegradation pathways were proposed on the basis of HPLC-MS. This work provides deeper insight on the rational design of highly efficient semiconductor photocatalysts by precise regulation of the crystal growth process for solar energy conversion.

Synergistic Effect of the Sulfur Vacancy and Schottky Heterojunction on Photocatalytic Uranium Immobilization: The Thermodynamics and Kinetics.

Not only a critical matter in the nuclear fuel cycle but uranium is also a global contaminant with both radioactive and chemical toxicity. Reducing soluble hexavalent uranium [U(VI)] to relatively nonimmigrated tetravalent uranium [U(IV)] by photocatalytic technologies is recognized as a highly promising strategy for avoiding environmental pollution and re-extracting uranium resources from nuclear wastewater. Herein, we have designed a heterojunction photocatalyst constructed from the carbon aerogels (CA) and the CdS nanoflowers with an S-vacancy (CA@CdS-SV). With the S-vacancy and heterojunction being synergized, the U(VI) removal rate exceeded 97% in 40 min without the addition of any sacrificial agents. As impacted by the synergistic effects of the S-vacancy and heterojunction, thermodynamics and kinetics revealed that photogenerated electrons were first captured via shallow traps generated by vacancies on CdS-SV and then transferred to the CA surfaces through the heterojunction to realize the spatial separation of carriers, thereby achieving a satisfactory performance. This work is considered to underpin the improvement of U(VI) immobilization by exploiting the synergistic effect of vacancy engineering and the Schottky heterojunction from the perspective of thermodynamics and kinetics.