Charge Carrier Recombination Research Articles

CuMn2O4 anchored on mesoporous yttrium orthovanadate for the visible-light removal of hexavalent chromium ions in water

Recently, there has been significant interest in using one-dimensional nanomaterials for environmental cleanup in water sources, particularly for breaking down and eliminating harmful pollutants. Creating a reusable and effective photocatalyst poses a challenge in addressing semiconductor flaws such as instability and rapid recombination. This work discusses developing a highly responding photocatalyst by introducing varying quantities of CuMn2O4 (CMO) onto the surface of yttrium vanadate (YVO4) nanoparticles using the surfactant sol-gel method. The structures and morphology of these developed nanocomposites were verified using many characterization methods. The findings reveal that CMO is an electron trap within the dual system, which impedes charge carrier recombination and ameliorates photocatalytic performance. Their photocatalytic efficacy was evaluated through the photoreduction of Cr(VI) ions under visible illumination, revealing that adding CMO nanoparticles significantly boosts YVO4's photocatalytic activity. The Cr(VI) photoreduction follows a first-order reaction model. Among the tested photocatalysts, the 2.0 g/L dose of 9.0 % CMO-YVO4 demonstrated the most effective and reusable performance within 45 min. This sustained photocatalytic performance is credited to improved capture of light and effective transfer of charges resulting from the combination of CMO and YVO4.

Fabrication of Z-scheme Fe2O3/g-C3N4 nanocomposite with improved visible light induced photodegradation of pharmaceutical pollutants and photoelectrochemical water oxidation

The photodegradation and photoelectrochemical performance of Fe2O3 catalyst is an encouraging visible-light induced catalyst owing to its less harmfulness, cheap and ecofriendly. However, owing to its quick charge carriers recombination rate and less lifespan of charge carriers obstructs its catalyst application. Therefore, it has been lately established that the construction of heterojunction with other semiconductor might be a possible method to improve its catalytic activity. Herein, a novel Z-scheme Fe2O3/g-C3N4 heterostructure catalyst has been synthesized by a simple hydrothermal technique and studied its photoelectrochemical and photodegradation activity. The addition of g-C3N4 greatly improves the light absorption ability light, reduced charge recombination rate and progress the charge transportation. The composite catalyst exhibited the superior photodegradation performance (97.8 %) of sulfamethoxazole antibiotic remedy within 30 min of visible light illumination. •OH and •O2– radicals show a key role for dye degradation activity, and proposed a possible photodegradation charge carrier transfer mechanism based on a potential band structures of composite catalyst. Furthermore, the prepared catalysts are further used to examine the photoelectrochemical properties for hydrogen generation. The Fe2O3/g-C3N4 nanocomposite photoelectrode exhibited enriched photocurrent density (0.764 mA/cm2) than g-C3N4 (0.271 mA/cm2) and Fe2O3 (0.370 mA/cm2) photoelectrodes, which ∼ 2.8 and ∼2.1 folds greater photocurrent density than pure photoelectrodes. Electrochemical impedance spectroscopy analysis revealed that the composite electrode has minimal charge transfer resistance and greater electron transfer ability. Therefore, the current study presents a facile formation of Z-scheme catalyst and offers a sustainable method to eradicate water impurities and hydrogen generation by renewable solar energy.

Synthesis and characterization of Zn-In-S composites for photocatalytic benzyl alcohol oxidation and nitrobenzene reduction

Photocatalytic transformation of organics is a promising alternative to conventional synthetic methodologies. ZnIn2S4 is active in photocatalytic redox reactions, but its performance is hindered by fast charge carrier recombination, and optimizing its properties through synthesis or modification is complicated. Herein, Zn-In-S based composites were prepared via a facile solvothermal method by varying the ratio of sulfide precursor (TAA) with a fixed Zn/ In molar ratio of 1: 2. The phase composition of the obtained materials depends on the amount of TAA. At lower ratios, composites consisting of crystalline In(OH)3 and unknown ZnxInySz phase were formed. Pure-phase ZnIn2S4 was obtained when the feed molar ratio of zinc and TAA was 1: 6 or higher. The photocatalytic oxidation of benzyl alcohol (BA) and reduction of nitrobenzene (NB) in a coupled system were applied to evaluate the activity of Zn-In-S-based composites. Under visible light irradiation, the ZnxInySz/ In(OH)3 composite (ZIS14) synthesized with a molar ratio of Zn to TAA of 1: 4 exhibited boosted and optimal performance compared to the bare ZnIn2S4 and other samples. After 5 hours of irradiation, the BA conversion and benzaldehyde (BAD) yield were 57 % and 55 %, respectively, and the NB conversion and aniline (AN) yield were 70 % and 35 %, individually, outperforming previous studies under similar experimental conditions. This work not only elucidates the photoredox process of BA and NB in one system, but also has significant implications for understanding the complex hydro/solvothermal processes involved in the fabrication of multicomponent sulfides.

Decoherence ensures convergence of non-adiabatic molecular dynamics with number of states.

Non-adiabatic (NA) molecular dynamics (MD) is a powerful approach for studying far-from-equilibrium quantum dynamics in photophysical and photochemical systems. Most NA-MD methods are developed and tested with few-state models, and their validity with complex systems involving many states is not well studied. By modeling intraband equilibration and interband recombination of charge carriers in MoS2, we investigate the convergence of three popular NA-MD algorithms, fewest switches surface hopping (FSSH), global flux surface hopping (GFSH), and decoherence induced surface hopping (DISH) with the number of states. Only the standard DISH algorithm converges with the number of states and produces Boltzmann equilibrium. Unitary propagation of the wave function in FSSH and GFSH violates the Boltzmann distribution, leads to internal inconsistency between time-dependent Schrödinger equation state populations and trajectory counts, and produces non-convergent results. Introducing decoherence in FSSH and GFSH by collapsing the wave function fixes these problems. The simplified version of DISH that omits projecting out the occupied state and is applicable to few-state systems also causes problems when the number of states is increased. We discuss the algorithmic application of wave function collapse and Boltzmann detailed balance and provide detailed FSSH, GFSH, and DISH flow charts. The use of convergent NA-MD methods is highly important for modeling complicated quantum processes involving multiple states. Our findings provide the basis for investigating quantum dynamics in realistic complex systems.

Photocatalytic β-O-4 bond cleavage in lignin models and native lignin through CdS integration on titanium oxide photocatalyst under visible light irradiation

Converting lignin, a key sustainable biopolymer, into valuable oxygen-containing compounds is a significant challenge. To address such a challenge, photocatalytic self-transfer hydrogenolysis strategy is employed utilizing a CdS(x%)/TiO2 heterojunction photocatalyst, with minimal CdS loading on TiO2. The CdS(3 %)/TiO2 catalyst, under blue light, dehydrogenates HCα–OH groups, transferring hydrogen to Cβ–O bonds, cleaving β-O-4 ether bonds in lignin model compounds yielding over 95 % phenols and acetophenones. It utilizes glyceryl moieties as a hydrogen source, yielding ∼ 24 % of diverse lignin monomer derivatives from teak lignin. Improved charge separation in the CdS(3 %)/TiO2 catalyst is revealed by electrochemical and spectral analyses and exhibits delayed charge carrier recombination. Scavenging studies confirm a type II charge transfer mechanism and support visible-light-driven lignin fragmentation. The present photocatalytic process offers a promising, cost-effective approach for converting lignin into valuable aromatic compounds, advancing renewable biomass-derived chemicals.

Microwave-assisted rapid synthesis of ZnO multipod-BiOBr heterojunction on recycled PET plastic waste for photocatalytic degradation of oily wastewater

Heterojunctions based on ZnO multipod and BiOBr were developed on the floating recycled polyethylene terephthalate (PET) and they were used to investigate the photocatalytic degradation of hexane in water emulsion. Characterizations of the synthesized ZnO-BiOBr-PET photocatalysts was performed using XRD, FESEM, EDX, BET/BJH, FTIR, UV-Vis DRS, PL, WCA, and CV analyses. The FESEM results demonstrated that ZnO multipods have been synthesized during the very short time of microwave heating that effectively hosted the highly dispersed BiOBr nanoplates, particularly in the 15 %ZnO-5 %BiOBr-80 %PET sample. The BET/BJH analysis revealed the low surface areas for the synthesized samples, however, the sample with the highest ZnO multipod loading (15 %ZnO-5 %BiOBr-80 %PET) exhibited slightly enhanced surface area due to the highly dispersed BiOBr over the ZnO multipods. The fabricated samples displayed hydrophobicity and liquid marble like behaviour due to the presence of PET, while the variations in the percentages of ZnO and BiOBr strongly influenced the water contact angle. The formation of heterojunction between ZnO multipod and BiOBr was confirmed which lead to a shift in the visible light region, increased the light harvesting, and also reduced the charge carrier recombination in the composite sample of 15 %ZnO-5 %BiOBr-80 %PET. The ZnO-BiOBr-PET photocatalysts were tested for the photocatalytic degradation of hexane in a water emulsion and results indicated that 15 %ZnO-5 %BiOBr-80 %PET could degrade 92.1 % of initial hexane, retaining its performance over four successive runs with only an 11.7 % decrease in activity. Scavenger tests revealed that, in addition to hydroxyl radicals, superoxide also played a significant role in the photocatalytic degradation of hexane. This obervations indicate the efficient capturing and utilizing of O2 by this LMP even in non-oxygenated conditions.

Engineering of g-C3N4 for Photocatalytic Hydrogen Production: A Review.

Graphitic carbon nitride (g-C3N4)-based photocatalysts have garnered significant interest as a promising photocatalyst for hydrogen generation under visible light, to address energy and environmental challenges owing to their favorable electronic structure, affordability, and stability. In spite of that, issues such as high charge carrier recombination rates and low quantum efficiency impede its broader application. To overcome these limitations, structural and morphological modification of the g-C3N4-based photocatalysts is a novel frontline to improve the photocatalytic performance. Therefore, we briefly summarize the current preparation methods of g-C3N4. Importantly, this review highlights recent advancements in crafting high-performance g-C3N4-based photocatalysts, focusing on strategies like elemental doping, nanostructure design, bandgap engineering, and heterostructure construction. Notably, sophisticated doping techniques have propelled hydrogen production rates to a 104-fold increase. Ingenious nanostructure designs have expanded the surface area by a factor of 26, concurrently extending the fluorescence lifetime of charge carriers by 50%. Moreover, the strategic assembly of heterojunctions has not only elevated charge carrier separation efficiency but also preserved formidable redox properties, culminating in a dramatic hundredfold surge in hydrogen generation performance. This work provides a reliable and brief overview of the controlled modification engineering of g-C3N4-based photocatalyst systems, paving the way for more efficient hydrogen production.

The cooperative p-n heterojunction and Schottky junction in Au-decorated hierarchical CuS@SnS2 hollow cubes for boosted charge transport and CO2 photoreduction

During the photocatalytic CO2 reduction process, fast charge transport, abundant active sites, and high visible light utilization in photocatalysts are key to achieving excellent CO2 conversion efficiency. In this work, we have designed and prepared hierarchical CuS@SnS2p-n heterostructure hollow cubes for photocatalytic CO2 reduction. First, a monolayer of CuS was in situ generated on the pre-prepared Cu2O cubes to construct core–shell Cu2O@CuS cubes by sulfidation of Cu2O cubes. The following etching process led to the formation of CuS hollow cubes. Finally, the hierarchical CuS@SnS2p-n heterostructure hollow cubes were obtained by growing SnS2 nanosheets on the CuS hollow cubes. The prepared CuS@SnS2p-n heterostructure hollow cubes showed an improved photocatalytic CO2 reduction activity compared with the bare CuS and SnS2 control samples. The p-n heterojunction formed between SnS2 and CuS as well as its hollow structure enhanced the charge carrier separation efficiency and the light absorption capacity of the hybrid catalyst. Furthermore, after the decoration of Au nanoparticles, the formed Schottky junction further discouraged the charge carrier recombination. Thus, the cooperative p-n heterojunction and Schottky junction greatly facilitated photocatalytic CO2 reduction, and exhibiting the maximum CO and CH4 yields of 140.1 and 77.5 μmol g−1 h−1, respectively. This work presents an efficient design of high-performance catalysts for photocatalytic CO2 reduction.

Short-Wave Infrared Light-Emitting Diodes Using Colloidal CuInS2 Quantum Dots with ZnI2 Dual-Passivation.

Short-wave infrared (SWIR) light-emitting diodes (LEDs) have emerged as promising technologies for diverse applications such as optical communication, biomedical imaging, surveillance, and machine vision. Colloidal quantum dots (QDs) are particularly attractive for SWIR LEDs due to their solution processability, compatibility with flexible substrates, and tunable absorption and luminescence. However, the presence of toxic elements or precious metals in most SWIR-emitting QDs poses health, environmental, and cost challenges. In this context, CuInS2 (CIS) QDs are known for low toxicity, cost-effective fabrication, and SWIR-light emitting capability. However, CIS QDs have not yet been directly utilized to fabricate SWIR LEDs to date, which is due to low particle stability, inefficient charge carrier recombination, and significantly blue-shifted luminescence after integrating into LED devices. To address challenges, we propose a dual-passivation strategy using ZnI2 as a chemical additive to enhance both the optical property of plain CIS QDs and charge carrier recombination upon LED device implementation. The resulting CIS-QD-based LEDs exhibit a stable SWIR electroluminescence (EL) peak (over 1000 nm) with a high EL radiance and a record external quantum efficiency in the SWIR region. Our study represents a significant step forward in SWIR-QLED technology, offering a pathway for the development of high-performance, low-cost, and nontoxic SWIR light sources.

Synergistic combination of Mn/Fe bimetal-doped carbon nitride and peroxymonosulfate for efficient photocatalytic degradation of antibiotics

The widespread of antibiotics has resulted in potential threats to the aquatic environment and human health. The visible light-assisted peroxymonosulfate (PMS) activation method is considered to be an effective way to remove antibiotics in wastewater. In this study, Mn/Fe bimetal doped graphitic carbon nitride (MnFe-CN-x) was first synthesized for PMS activation under visible light towards tetracycline (TC) removal. The optimized MnFe-CN-50 possessed the excellent photocatalytic activity, PMS activation performance and photo-Fenton-like synergistic effect. In the photo-Fenton-like system, TC (20 mg L−1) was degraded by 99 % in 50 min and the kinetic constant was 0.074 min−1. The high dispersion of Mn and Fe in carbon nitride inhibited the recombination of charge carriers in MnFe-CN-x, increased its photocurrent density and charge mobility, effectively optimized the electronic structure, and promoted the generation of 1O2. Based on the analytical results of predictive toxicity evaluation software (TEST), it was confirmed that MnFe-CN-x could effectively reduce the environmental risks associated with antibiotic contamination. This study provided new insights into synthesizing bimetal-doped graphitic carbon nitride and the use of synergistic effects of photocatalysis and PMS activation to remove organic pollutants from wastewater.

Optimizing charge transport and band-offset in silicon heterojunction solar cells: impact of TiO2 contact deposition temperature

Carrier selective contacts are a primary requirement for fabricating silicon heterojunction solar cells (SHSCs). TiO2 is a prominent carrier selective contact in SHSCs owing to its excellent optoelectronic features such as suitable band offset, work function, and cost-effectiveness. Herein, we fabricated simple SHSCs in an Al/TiO2/p-Si/Ti/Au device configuration. Ultrathin 3 nm TiO2 layers were deposited onto a p-type silicon substrate using the atomic layer deposition method. The deposition temperature of TiO2 layers varied from 100 °C to 250 °C. X-ray photoelectron spectroscopic studies suggest that deposition temperature highly affects the chemical states of TiO2 and reduces the formation of defective state densities at the Fermi energy. The optical band gap values of TiO2 layers are also altered from 3.13 eV to 3.27 eV when the deposition temperature increases. The work function tuning from −5.13 eV to −4.83 eV has also been observed in TiO2 layers, suggesting the variation in Fermi level tuning, which arises due to changes in carrier concentrations at higher temperatures. Several device parameters, such as ideality factor, trap density, reverse saturation current density, barrier height, etc, have been quantified to comprehend the effects of deposition temperature on photovoltaic device performance. The results suggest that the deposition temperature significantly influences the charge transport and device performance. At an optimum temperature, a significant reduction in charge carrier recombination and trap state density has been observed, which helps to improve power conversion efficiency.

Contrasting Ultra-Low Frequency Raman and Infrared Modes in Emerging Metal Halides for Photovoltaics.

Lattice dynamics are critical to photovoltaic material performance, governing dynamic disorder, hot-carrier cooling, charge-carrier recombination, and transport. Soft metal-halide perovskites exhibit particularly intriguing dynamics, with Raman spectra exhibiting an unusually broad low-frequency response whose origin is still much debated. Here, we utilize ultra-low frequency Raman and infrared terahertz time-domain spectroscopies to provide a systematic examination of the vibrational response for a wide range of metal-halide semiconductors: FAPbI3, MAPbI x Br3-x , CsPbBr3, PbI2, Cs2AgBiBr6, Cu2AgBiI6, and AgI. We rule out extrinsic defects, octahedral tilting, cation lone pairs, and "liquid-like" Boson peaks as causes of the debated central Raman peak. Instead, we propose that the central Raman response results from an interplay of the significant broadening of Raman-active, low-energy phonon modes that are strongly amplified by a population component from Bose-Einstein statistics toward low frequency. These findings elucidate the complexities of light interactions with low-energy lattice vibrations in soft metal-halide semiconductors emerging for photovoltaic applications.

(Invited) Probing the Influence of the Dielectric Environment on Charge Carrier Dynamics in Semiconducting Polymers

Pi-conjugated semiconducting polymers have garnered attention for a variety of electronic and optoelectronic applications, such as field-effect transistors, thermoelectric generators, and photovoltaic devices. In these systems, the charge carrier dynamics are primarily governed by the properties of the polaron and the polymer microstructure. More recently, there has been growing interest in the suitability of these polymer for electrochemical transistors and (photo)electrochemical applications, where the understanding is further complicated by the presence of ions and solvent molecules, as well as the dynamic transport of these species into the semiconducting polymer. Here, we will employ steady-state and transient spectroscopic techniques to probe the influence of charge carrier doping, as well as the extrinsic and local dielectric environments, on charge carrier generation, transport, and recombination in prototypical semiconducting polymer(s). Incorporation of electrochemical techniques enables in-situ spectroscopic measurements that mimic operando conditions. Our observations will provide a better understanding of the factors that control the carrier dynamics in these compositionally complex systems and will have implications for their viability and optimization for (photo)electrochemical applications.

(Invited) Probing Spin Selective Surface Chemistry with Circularly Polarized XUV Light

Controlling spin states of surface reaction intermediates is an important but often overlooked parameter to designing semiconductor photocatalysts to mimic nature’s best photosynthetic complexes. Extreme Ultraviolet Reflection-Absorption (XUV-RA) spectroscopy enables direct observation of surface electron dynamics by combining element, oxidation, and spin state resolution, with surface sensitivity and ultrafast time resolution. While absorption of linearly polarized XUV light can probe the local oxidation and spin states of individual elements, it is insensitive to absolute spin alignment. To enable the study of spin-selective electron dynamics at interfaces, we have recently implemented ultrafast XUV Magnetic Circular Dichroism (XUV-MCD). Employing XUV-MCD in a reflection geometry, we are now studying the ultrafast surface electron dynamics that give rise to spin polarized photocurrents in magnetic and chiral semiconductors. As an example, yttrium iron garnet (Y3Fe5O12, YIG) is a ferrimagnetic oxide with a visible band gap, consisting of two sub-lattices based on octahedrally and tetrahedrally coordinated Fe(III) centers. Ultrafast XUV measurements show that electron-phonon coupling and polaron formation rates differ significantly between octahedral and tetrahedral centers leading to very different charge carrier recombination kinetics. Circular measurements show that this difference in recombination rate gives rise to long-lived, spin-polarized charge accumulation at the YIG surface that drives spin selective water oxidation. This new ability to observe real-time spin polarization at surfaces promises to provide key design parameters for semiconductor photocatalysts capable of spin selective surface chemistry.

Achieving Inkjet‐Printed 2D Tin Iodide Perovskites: Excitonic and Electro‐Optical Properties

AbstractCurrently, there is a great demand for non‐toxic lead‐free halide perovskites as active materials for solar cells, light‐emitting diodes and other optoelectronic devices. Although an essential progress has been made using tin(II) halide perovskites, still greater efforts are needed to improve their stability and manufacture films and devices under a scalable technology. The first goal of the work is to achieve suitable physical properties of 2D Sn(II) polycrystalline perovskite films obtained by the industrially scalable inkjet printing deposition technique. In the present work, inks of 2D tin(II) halide perovskite 2‐thiopheneethylammonium tin(II) iodide, TEA2SnI4, have been successfully formulated in DMF (toxic) and DMSO (non‐toxic) solutions and using appropriate additives (SnF2 and reducing agents) for improving the stability of the inks and the resulting films. Room‐ and low‐temperature excitonic photoluminescence (PL), charge carrier recombination dynamics and µ‐PL is used to explain the observed two excitonic bands, which are associated to the bulk and edges of perovskite grains nanoplatelet‐like composing the polycrystalline films. Promising electro‐optical properties are also obtained in the TEA2SnI4 films inkjet‐printed from DMSO formulations onto ITO‐interdigitated electrodes, such as low dark currents, ≈10 – 20 nA at 10 V of bias voltage, and high responsivities ≈1–20 A/W.

Enhanced bifunctional photocatalytic CO2 reduction and H2 evolution utilizing Cu-doped ZnIn2S4 nanosheets via cation exchange reaction

In this study, Cu-doped ZnIn2S4 nanosheets were synthesized through cation exchange reactions to enhance the dual-functional photocatalytic processes of CO2 reduction and hydrogen evolution. The optimized Cu doping levels in Cu-ZIS samples significantly improved the photocatalytic performance, resulting in enhanced H2-evolution rates and increased selectivity in CO2 reduction, particularly in the production of C2H4 and CO. Characterization techniques confirmed the successful integration of Cu into the ZIS lattice, thereby improving charge transfer and separation within the material. Mechanistic studies indicated that Cu doping enhanced light absorption, charge transfer efficiency, and introduced shallow energy levels, consequently reducing charge carrier recombination and improving overall catalytic performance. These findings highlight the substantial potential of Cu-doped ZnIn2S4 nanosheets for sustainable dual-functional applications in solar energy conversion.

Charge carrier recombination studies of Tm-doped CsPbBr3 by temperature-dependent PL and TR-PL

In this work, we investigated the photophysics of Tm-doped CsPbBr3 by photoluminescence (PL) and time-resolved photoluminescence (TR-PL) across the temperature range of 20–300 K. The trivalent state of Tm ions in CsPbBr3 was demonstrated clearly by using X-ray absorption spectroscopy. Three emission peaks of Tm-doped CsPbBr3 were identified as the Tm3+1G4 → 3H6 transition, band gap emission, and near band edge (NBE) defect state. The role of energy transfer between Tm3+ ions and CsPbBr3 perovskite is suggested to make the dominant peak vary between band gap emission and NBE defect states above 150 K. Notably, below 100 K, PL peak intensities increased significantly because of the 2D localization of excitons, as evidenced by the linear increase in radiative lifetime obtained from temperature-dependent TR-PL. Power-dependent PL measurements confirmed the excitonic nature of recombination. In addition, analysis of streak images from time-gated TR-PL spectra at 20 K and 180 K further confirmed the NBE defect state of Tm-doped CsPbBr3. This work will open new avenues in the understanding of transient spectra by using improved characterization abilities, which in turn can assist in identifying emission mechanisms.

Bi-functional NiFe2O4/SrTiO3 S-scheme heterojunction for eminent performance photocatalytic treatment of sewage effluent and electrochemical hydrazine determination

Devising of materials that afforded dual applicability in decontamination and pollutant detection were still a towering challenge owing to the increasing flux of discharge toxic contaminants over the years. Herein, the NiFe2O4 nanoparticles-loaded on cube-like SrTiO3 (NiFe2O4/SrTiO3) composite was fabricated by a two-step hydrothermal approach providing remarkable photocatalytic treatment and electrochemical sensing of noxious pollutants in wastewater. The material traits of the fabricated composite were scrutinized by myriad characterization approaches. The NiFe2O4/SrTiO3 hybrid material demonstrated high surface area of 19.81 m2/g, adequate band gap energy of 2.75 eV, and prominent photoluminescence characteristics. In the presence of visible light, the NiFe2O4/SrTiO3 exhibited profound photocatalysis capability to eliminate sewage effluent-bearing chlortetracycline hydrochloride (CTCH) with 88.6% COD removal in 120 min, outperforming other pure materials. Meanwhile, the toxicity examination of effluent, the possible degradation pathway of CTCH and the proposed photocatalysis mechanism were also divulged. More importantly, the glassy carbon electrode was modified with synergized NiFe2O4/SrTiO3 (NiFe2O4/SrTiO3−GCE) was adopted for the precise quantification of Hydrazine (Hz). The NiFe2O4/SrTiO3−GCE obeyed first-order response for the Hz detection within the range of 1–10 mM: cyclic voltametric: limit of detection (LOD) of 0.119 μM with sensitivity of 18.9 μA μM−1 cm−2, and linear sweep voltametric: LOD of 0.222 μM with a sensitivity of 12.05 μA μM−1 cm−2. The stability and interference of modified electrode were also inspected. This work furnished valuable insights to yield a composite with the prominent S-scheme heterojunction system for quenching of charge carrier recombination and consequently contributing to the future realization into the domains of environmental clean-up and toxic chemical detection.

Slowing hot carriers cooling dynamics via perovskite morphology manipulating enable high-performance perovskite solar cells

Slowing hot carriers (HCs) cooling of lead halide perovskites exhibits great promise for achieving highly efficient perovskite solar cells (PSCs). However, the effect of the quality of perovskite on PSCs performance has not been well studied. Herein, we fabricated high-quality perovskite films by employing an organic small molecule, tris(pentafluorophenyl)borane (TFB) as an additive material. It was found that the perovskite films with TFB become smoother and pinhole-free morphology with increased grain size and reduced trap-state density. More importantly, ultrafast transient absorption spectroscopy results reveal that the high-quality TFB-doped perovskite films can significantly slow down HCs cooling process compared with pristine perovskite film, which is beneficial for prolonging the lifetime of carriers and reducing the charge carrier recombination in the device. Accordingly, the power conversion efficiency (PCE) of CsFAMA-based PSCs doping with TFB is enhanced to 22.56% from the control device (20.22%). Compared with 21.79% efficiency for the control device, a high PCE of 24.09% is obtained in FA-based PSCs treated with TFB. Besides, the unencapsulated TFB-doped device retains 91% of its initial value after storing for 1900 h under ambient conditions (∼45% humidity). These findings provide some insights for understanding HCs’ dynamics for constructing highly efficient PSCs.

Novel Ag@NH2-UiO-66(Zr) photocatalyst with controllable charge transfer pathways for efficient Cr(VI) remediation

Rational fabrication of core-shell photocatalysts to hamper the charge recombination is extraordinarily essential to enhance photocatalytic activity. In this work, core-shell Ag@NH2-UiO-66 (Ag@NU) Schottky heterojunctions with low Ag content (1 wt%) were constructed by a two-step solvothermal method and adopted for Cr(VI) reduction under LED light. Typically, the one with the Ag: NH2-UiO-66 mass ratio (1 : 100) led to 100% Cr(VI) removal within 1 h, superior to bare NH2-UiO-66 and Ag/NH2-UiO-66 (Ag was directly decorated on NH2-UiO-66 surface). The enhanced photocatalytic activity was related to the migration of the electrons on the CB of NH2-UiO-66 to Ag NPs through a Schottky barrier, and thus the undesired charge carriers recombination was avoided. This result was also evidenced by Density functional theory (DFT) calculations. The computational simulations indicate that the introduction of Ag effectively narrowed the band gap of NH2-UiO-66, facilitating the transfer of photo-generated electrons, expanding the light absorption area, and significantly enhancing photocatalytic efficiency. Most importantly, such a core-shell structure can inhibit the formation of •O2−, letting the direct Cr(VI) reduction by photo-excited e−. In addition, this structure can also protect Ag from being oxidized by O2. Ten cyclic tests evidenced the Ag@NU had excellent chemical and structural stability. This research offers a novel strategy for regulating the Cr(VI) reduction by establishing core-shell photocatalytic materials.