Electron Paramagnetic Resonance Experiments Research Articles

Magnetically separable Z-scheme ZnFe2O4/MoS2 photocatalyst for boosting photo-Fenton degradation activity by a hole-mediated mechanism

The development of high-efficiency and robust photocatalysts is imperative and challenging in advanced oxidation processes (AOPs). Herein, magnetically separable ZnFe2O4/MoS2 photocatalyst was prepared by a simple hydrothermal method. The degradation characteristics of several organic pollutants (rhodamine B (RhB), methyl orange, methylene blue, and antibiotic tetracycline) were investigated with/without the addition of H2O2 under visible light irradiation. It is found that the synergistic effect of Z-scheme ZnFe2O4/MoS2 photocatalyst and photo-fenton-like reaction promotes the decomposition of H2O2, accelerates the separation efficiency of photogenerated electrons and holes, and thus improves the photocatalytic activity. The RhB photo-degradation of the constructed Z-scheme ZnFe2O4/MoS2 (96.3%) photocatalyst in the absence of H2O2 for 100min is better than that of MoS2 (74.8%) and ZnFe2O4 (6.2%), with a rate constant of 0.0332min-1. The slight amount of H2O2 boosts the photocatalytic performance significantly. Its degradation rate is 98.6% within 8min with the rate constant of 0.396min-1, 12 times higher than that of ZnFe2O4/MoS2 photocatalyst without H2O2. The magnetic separation, recycling stability and neutral solution process are also confirmed in ZnFe2O4/MoS2 system, indicating the enormous potential of this photocatalyst in environmental remediation and waste water treatment. The hole-mediated oxidation mechanism has been proposed instead of conventional active radicals of •OH based on the free radicals capture and electron spin resonance experiments. MoS2 plays a crucial role in facilitating the H2O2 decomposition and realizing the conversion circulation from Fe3+ to Fe2+ by the redox cycling as a co-catalyst. This study provides insights into the photocatalytic mechanism of Z-scheme photo-Fenton heterojunction photocatalysts, conducive to the development of high-efficient and stable photocatalysts in AOPs.

Frequency multiplexing enables parallel multi-sample EPR

Electron paramagnetic resonance (EPR) spectroscopy stands out as a powerful analytical technique with extensive applications in the fields of biology, chemistry, physics, and material sciences. It proves invaluable for investigating the molecular structure and reaction mechanisms of substances containing unpaired electrons, such as metal complexes, organic and inorganic radicals, and intermediate states in chemical reactions. However, despite their remarkable capabilities, EPR systems face significant limitations in terms of sample throughput, as current commercial systems only target the analysis of one sample at a time. Here we introduce a novel scheme for conducting ultra-high frequency continuous-wave EPR (CW EPR) targeting the EPR spectroscopy of multiple microliter volume samples in parallel. Our proof-of-principle prototype involves two decoupled detection cells equipped with high qualty factor Q=104\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q=104$$\\end{document} solenoidal coils tuned to 488 and 589 MHz, ensuring a significant frequency gap for effective radio frequency (RF) decoupling between the channels. To further enhance electromagnetic decoupling, an orthogonal alignment of the coils was adopted. The paper further presents an innovative radiofrequency circuit concept that utilizes a single physical RF channel to simultaneously conduct parallel EPR on up to eight cells. Parallel EPR experiments on two BDPA samples, each with a sample volume of 18.3 μL, registered signal-to-noise ratios of 255 and 252 for the two EPR measurement cells, with no observable coupling. The showcased prototype, built using cost-effective commercially available fabrication technology, is readily scalable and represents an initial step with promising potential for advancing sample screening with high-throughput parallel EPR.

Unraveling the degradation of levofloxacin using highly efficient β-cyclodextrin-modified copper ferrite through peroxymonosulfate activation: Mechanistic performance and degradation pathways

In this study, a highly magnetic β-cyclodextrin-modified copper ferrite (CuFe2O4@β-CD) catalyst was developed utilizing a hydrothermal method, which was subsequently utilized to degrade Levofloxacin (LEV) antibiotic in aqueous solution via heterogeneous activation of peroxymonosulfate (PMS). The findings demonstrated that the 98.87 % degradation of LEV was achieved with CuFe2O4@β-CD/PMS, much higher than that of pure CuFe2O4/PMS (87.78 %) within a 24-minute time frame under optimal parameters ([CuFe2O4@β-CD] = 0.4 g/L, [PMS] = 0.4 mM, [LEV] = 25 mg/L, pH = 6), and CuFe2O4@β-CD/PMS was present. The rate constant of CuFe2O4@β-CD/PMS (0.1608 min−1) was much greater than that of the CuFe2O4/PMS system (0.0822 min−1). The increased availability of active sites for PMS activation may be credited to the larger surface area (189.42 m2/g) of the CuFe2O4@β-CD catalyst in comparison to the pristine CuFe2O4 (87.76 m2/g), which facilitated the improved degradation of LEV. Additionally, the impact of various reaction parameters and intervening anions on the degradation of LEV was investigated. The emergence of free radicals (SO4•−, •OH, and 1O2) was corroborated via electron paramagnetic resonance and scavenging experiments. On the basis of recognizing reaction intermediates, a hypothetical degradation mechanism for LEV was developed. PMS activation was caused by the transformation of Cu+/Cu2+ and Fe3+/Fe2+ pairs, which was accomplished via radical and non-radical pathways. Also, CuFe2O4@β-CD demonstrated exceptional stability and retained its catalytic activity after five concurrent cycles. In conclusion, the CuFe2O4@β-CD catalyst demonstrated encouraging potential in the context of purifying LEV-contaminated water.

Fabrication of porous biochar supported Bi2MoO6 photocatalyst for efficient degradation of ciprofloxacin in seawater under visible light irradiation: Mechanistic investigation and intermediates analysis

Efficient separation of photocarriers is a critical approach for advancing high-performance photocatalyst systems to effectively remove environmental contaminants. In this investigation, a hydrothermal technique was employed to synthesize composites of Bi2MoO6 and porous biochar derived from banana peels (BPB). The samples underwent various characterization methods to assess their composition, morphology, and photoelectrochemical properties. The BPB/Bi2MoO6 composite exhibited a synergistic adsorption and photocatalytic impact in eliminating the antibiotic ciprofloxacin (CIP) from pure water and seawater. The optimized BPB/Bi2MoO6 sample displayed a significant degradation efficiency of 98.7 % for CIP after 90 min of visible-light exposure in pure water. In artificial seawater, the degradation efficiency for CIP remained high at 93.6 %, which was 12.2 times greater than that of pure Bi2MoO6. The study also explored the impact of various factors such as catalyst dosage, solution pH, and pollutant concentration on the photocatalytic performance of BPB/Bi2MoO6. Moreover, the catalyst exhibited enhanced efficiency in the adsorption-photocatalytic degradation of CIP within a continuous flow reaction system. The enhanced photocatalytic performance was attributed to the composite's exceptional adsorption capacity, enhanced response to visible light, and efficient separation of photoinduced electron-hole pairs. Furthermore, the BPB/Bi2MoO6 photocatalyst displayed good stability and recyclability over five consecutive photodegradation cycles. Radical trapping and electron spin resonance (ESR) experiments verified that the degradation of CIP was mainly driven by •OH and h+ radicals. A thorough investigation employing density functional theory (DFT), radical trapping and ESR tests, and liquid chromatography mass spectrometry (LC-MS) was conducted to elucidate the degradation mechanism and pathways. Furthermore, toxicity assessment software was utilized to illustrate the progressive reduction in toxicity of the intermediate products. In conclusion, this study provides valuable insights into the role of biochar in enhancing the photocatalytic degradation of pollutants and offers guidance for the future development of environmentally friendly photocatalysts.

Frustrated Radical Pair‐Initiated Hydrodehalogenation of Alkyl and Aryl Halides Under Visible Light

AbstractHere we employed Al(C6F5)3/Mes3P frustrated radical pair (FRP) to catalyze hydrodehalogenation reaction. Through the initiation of the FRP, stannane radicals were generated to facilitate the halogen‐atom transfer (XAT) process and proceed the hydrodehalogenation of a wide range of alkyl and aryl halides under visible light at room temperature. Electron paramagnetic resonance (EPR) experiment, radical clock reaction coupled with control experiments provide solid evidence to support the radical mechanism. Moreover, this strategy can be applied to the synthesis of pharmaceutical compounds, such as indoles and quinolines as well as the deuterated compounds.

Novel insights into ferrate (VI) activation by Mn-modified sludge biochar for sulfamethoxazole degradation: Dominance of hydroxyl group and Mn-O bond in the non-radical pathway

Ferrate (Fe (VI)), as a versatile oxidizer, has been widely employed for water treatment. However, the rapid self-decomposition of Fe (VI) diminishes its practical application efficiency. In this study, a novel Mn-modified sludge biochar (MSBC) was synthesized for the first time to activate Fe (VI) and generate highly reactive Fe (IV)/Fe (V) for the rapid removal of sulfamethoxazole (SMX). The results showed that MSBC (0.10 g/L) effectively activated Fe (VI) (100 μM), and 87.39 % of SMX (10 μM) and 40.26 % of total organic carbon (TOC) were removed within 10 min. Notably, raising the solution pH (e.g., from 6.0 to 11.0) would result in decreasing the reactivity of Fe (VI) and a lower removal efficiency of SMX. The quenching, electron paramagnetic resonance and probe experiments suggested that •O2– and high-valent iron species (Fe (V)/Fe (IV)) were identified as the major contributions to the removal of SMX. The detailed activation sites of MSBC were –OH and Mn-O, as corroborated by density functional theory (DFT) calculation and characterization. These activation sites facilitated activation of Fe (VI) through efficient electron transfer. The Fukui index indicated that the N, S, and O atom of SMX were the primary attacked sites. Subsequently, five potential degradation pathways were proposed, with the cleavage of the S-N bond being the predominant one. The toxicity of these products was examined using ECOSAR program, revealing that main products showed low toxicity or non-toxicity. The Cl-, SO42-, and NO3– had negligible effect on SMX degradation, although excessive concentrations of HCO3– and humic acid (HA) showed slightly inhibition. Additionally, the Fe (VI)/MSBC system also effectively removed 87.34 % of sulfadiazine (SDZ) and 93.91 % of sulfamethoxypyridazine (SMP). Overall, this study offered a practical and cost-effective approach for the activation of Fe (VI) and provided new insights to the degradation mechanism.

Selective Transition Enhancement in a g-Engineered Diradical.

A diradical with engineered g-asymmetry was synthesized by grafting a nitroxide radical onto the [Y(Pc)2]⋅ radical platform. Various spectroscopic techniques and computational studies revealed that the electronic structures of the two spin systems remained minimally affected within the diradical system. Fluid-solution Electron Paramagnetic Resonance (EPR) experiments revealed a weak exchange coupling with |J| ~ 0.014 cm-1, subsequently rationalized by CAS-SCF calculations. Frozen solution continuous-wave (CW) EPR experiments showed a complicated and power-dependent spectrum that eluded analysis using the point-dipole model. Pulse EPR manipulations with varying microwave powers, or under varying magnetic fields, demonstrated that different resonances could be selectively enhanced or suppressed, based on their different tipping angles. In particular, Field-Swept Echo-Detected (FSED) spectra revealed absorptions of MW power-dependent intensities, while Field-Swept Spin Nutation (FSSN) experiments revealed two distinct Rabi frequencies. This study introduces a methodology to synthesize and characterize g-asymmetric two-spin systems, of interest in the implementation of spin-based CNOT gates.

Enhanced electroreduction of low-concentration nitrate using a Cu-Pd bimetallic cathode system: Performance evaluation, mechanism analysis, and potential applications

Copper (Cu) is a widely recognized cathode for the electrochemical reduction of nitrate (NO3-). Nevertheless, its practical applications are currently restricted due to limited activity and selectivity, particularly at low NO3- concentrations. Herein, a Cu-Pd bimetallic cathode system was designed for NO3- reduction reaction with low NO3- concentrations (≤40 mg-N L−1). In this system, a Cu nanowire array cathode was utilized for NO3- reduction, while a Pd/C particle cathode was employed for NO2- reduction with H2 generated in situ from a polypyrrole electrode. Due to the improved mass transfer and active sites derived from Pd/C particle cathode, along with the synergistic effects of NO3- reduction and NO2- reduction, the constructed Cu-Pd bimetallic cathode system achieved a 7.32-fold increase in NO3– removal rate and a 1.70-fold increase in NH4+ selectivity compared to the traditional Cu cathode. This performance surpassed that of many other state-of-the-art Cu-based cathodes under similar conditions. Moreover, the Cu-Pd bimetallic cathode system displayed high reusability, and extremely low Cu and Pd leaching. Additionally, it showed strong resistance to environmental factors and can adapt to a wide pH range (3−9) and various NO3- concentrations (10–40 mg-N L−1). The electron spin resonance and scavenger experiments confirmed that both direct electron transfer and indirect reduction by atomic H* were involved in the NO3- removal process, with indirect reduction playing a more significant role. Overall, our findings guide the design of superior catalytic systems for NO3- removal to enhance the activity and selectivity of NO3- reduction for efficient water purification.

Boosting bulk photocharge separation and transfer in heterojunctions for antibiotics removal: Enhanced internal electric field and interfacial electric field

The electric fields created by semiconductor heterojunctions often only separated photogenerated charges at component interface, not sufficiently inhibiting carriers’ recombination in their bulk phases. Herein, we introduced the enhanced bulk internal electric field into BixOyIz/g-C3N4 heterojunction, constructing a dual electric field structure through in-situ precipitation and calcination to boost photocharge separation and transfer at both the interface and the bulk. The interfacial electric field created by heterojunction boosted the photocharge separation, and the enhanced internal electric field resulting from iodine reduction improved the bulk charge dynamics of BixOyIz. The dual electric field endowed BixOyIz/g-C3N4 with high photocatalytic activity and broad application potential. Specifically, the photocatalytic reaction rate constants of BixOyIz/g-C3N4 calcined at 460 °C for tetracycline removal reached 0.024 min−1, which was 3.42 times higher than that of BiOI/g-C3N4. The electron paramagnetic resonance (EPR) and scavenging experiments proved that ·O2− was the predominant active species in oxidizing tetracycline. The experiments on simulated real water showed that BixOyIz/g-C3N4 has a broad range of pH applicability, strong resistance to anionic interference, and good cycling performance. This work provided new insights for inhibiting bulk phase photocharge recombination of individual components in heterojunctions.

Promoting charge separation in CuInS2/CeO2 photocatalysts by an S-scheme heterojunction for enhanced photocatalytic H2 production

Low charge separation efficiency significantly hampers the performance of photocatalytic hydrogen production. Constructing heterojunctions emerges as a crucial strategy to enhance photocatalytic activity by improving charge separation. An S-scheme heterojunction not only effectively separates the photogenerated charge in composite photocatalysts but also preserves optimal redox capabilities. This study presents the first report of CuInS2/CeO2 (CIS/CeO2) and demonstrates how charge separation within CIS/CeO2 to enhance photocatalytic hydrogen production through the construction of an S-scheme heterojunction. The UV–visible-driven hydrogen production rate of CIS/CeO2 is 4.6 and 9.4 times higher than that of CIS and CeO2 alone, respectively. The improved photocatalytic performance primarily stems from enhanced charge separation promoted by the S-scheme heterojunction. The charge transfer pathway was confirmed as an S-scheme mechanism through a combination of band structure experiments, density functional theory (DFT) calculations on work function, internal electric field, and charge differential density distribution, alongside electron paramagnetic resonance (EPR) experiments. Multiple perspectives were employed to elucidate the reasons behind facilitating efficient charge separation. This research provides valuable insights for advancing photocatalytic performance.

Activation of peroxymonosulfate (PMS) by rGO supported Co3O4 catalyst for iohexol degradation

Sulphate radical (SO4·-) -based advanced oxidation process (SR-AOP) is a promising sewage treatment technology. Reduced graphene oxide (rGO) supported Co3O4 composites were synthesized by a hydrothermal method for the degradation of iohexol (IOH) in the rGO/Co3O4/peroxymonosulfate (PMS) system. Experimental results show that rGO/Co3O4 possessed much better PMS activated ability than pure GO or Co3O4, which is ascribed to the summation of rGO and Co3O4. The efficiency of rGO/Co3O4 composite, single GO and Co3O4 nanocrystals for the degradation of IOH were 98.7%, 15.8% and 79.8% at 15min, and their corresponding reaction rate constants (kapp) were 0.21min-1, 0.0077min-1 and 0.080min-1, respectively. The results of active species capture experiment and electron paramagnetic resonance (EPR) experiment, showed that singlet oxygen is the main active species, which is non-radical degradation. rGO is conducive to the electron conduction of Co3O4, thus improving the efficiency of PMS activation. The system is simple and efficient, which is an effective technology to remove IOH.

Tailored anthraquinone-based covalent organic frameworks boosted atrazine degradation through peroxymonosulfate activation driven by visible light

Atrazine (ATZ), a wildly used s-triazine herbicide to avoid grassy insects and weeds, causes biological and environmental issues due to its prolonged existence and various toxic properties. Peroxymonosulfate (PMS) photoactivation-based advanced oxidation processes (AOPs) meet the challenges of sustainable energy and environmental concerns, and thus are promising challenging for ATZ degradation. However, preparing photocatalysts to realize efficient ATZ degradation remains challenging. Here, we prepared the highly efficient visible-light photocatalyst with abundant anthraquinone groups, i.e. TpDQ-COF, which was employed to activate PMS for fast and efficient ATZ degradation. ATZ degradation in the TpDQ-COF/PMS system reached 0.127 min−1 under visible light (VL), which is ca. 17.9 times that of TpDA-COF without anthraquinone. It implies that anthraquinone units served as pivotal active sites for facilitating photoelectron separation and migration, which triggered ROS generation towards highly effective ATZ degradation. In addition, the radical-quenching and Electron Paramagnetic Resonance (EPR) experiments proved that •OH, •SO4- and 1O2 played pivotal roles in ATZ degradation under TpDQ-COF/PMS/VL system. The ATZ degradation pathways included dealkylation, dechlorination-hydroxylation, alkylic-hydroxylation, and alkylic-oxidation, which were confirmed by intermediates and density functional theory (DFT) analysis. Overall, TpDQ-COF showcased its excellent practical utility in the removal of organic pollutants in contaminated water.

Regulation of d-band center of TiO2 through fluoride doping for enhancing photocatalytic H2O2 production activity

Titanium dioxide (TiO2) has received extensive attention for photocatalytic hydrogen peroxide (H2O2) production, with the d-band center related to the adsorption performance, which affects the photocatalytic reaction process. Herein, an ingenious strategy to lower the antibonding-orbital occupancy in the Ti 3d orbital by fluoride ion (F−) doping is proposed, with density functional theory calculations predicting that F-doping into TiO2 induces a non-uniform charge distribution and enables an upshift of the d-band center in F/TiO2. This manipulation provides accessible active centers with favorable d-band energy levels, which can improve the charge-transfer behavior, strengthen the interaction between the adsorbed oxygen and the photocatalyst, and reduce the adsorption energy of oxygen, eventually promoting the photocatalytic H2O2 production rate. The experimental results further confirm that a lower antibonding-orbital occupancy can intensify the adsorption of atomic oxygen at the Ti sites. Electron paramagnetic resonance experiment reveals that the presence of F− ions in the lattice induces the formation of Ti3+ centers that localize the extra electron needed for charge compensation. Femtosecond transient absorption (fs-TA) spectroscopy suggests that photogenerated electrons are transferred from the conduction band of F/TiO2 to the Ti3+ surface states and surface F− ions, expediting the separation of electrons and holes. Consequently, with F− doping in TiO2, the photocatalytic H2O2 production yields improved from 277 to 467 μmol·g−1·h−1, with ethanol as a sacrificial reagent. This study provides a new strategy for regulating the d-band center to optimize the adsorption strength between the photocatalyst and oxygen atoms and achieve enhanced photocatalytic H2O2 production performance.

In situ construction of Ti3+ self-doped TiO2/Ti3C2 Schottky heterojunctions for highly selective photo-Fenton-like degradation of organic pollutants: Surface/interface effect and mechanism insight

The efficient activation of H2O2 in heterogeneous Fenton-like systems is important for the degradation of organic pollutants. Herein, a Ti3C2 MXene catalyst prepared by a simple HF etching method was used to activate H2O2. Ti3+ self-doped TiO2/Ti3C2 MXene (Ti3+-TiO2/Ti3C2) Schottky heterojunctions were in situ constructed in the photo-Fenton-like system. Owing to the Ti3+-TiO2/Ti3C2 Schottky heterojunctions, abundant multivalence titanium species, and strong surface negative charges, the Ti3C2 catalyst exhibited outstanding photo-Fenton-like performances towards the degradation of cationic organic dyes (methylene blue, rhodamine B, basic fuchsin) in a wide pH range of 3.04–10.02. Radical trapping and electron paramagnetic resonance experiments revealed that surface-bound hydroxyl radicals (OH), superoxide radicals (O2−), and photogenerated holes (h+) were the dominant species in the Ti3C2/H2O2/Visible-light system. Density functional theory calculations confirmed that TiO2/Ti3C2 Schottky heterojunctions not only promoted the separation of photogenerated carriers, but also facilitated the desorption of hydroxyl groups (–OH) from the decomposition of H2O2, thereby increasing the yield of reactive species (OH, O2−, and h+).

Sulfonamides as N-Centered Radical Precursors for C-N Coupling Reactions To Generate Amidines.

Nitrogen-centered radicals (NCRs) are valuable intermediates for the construction of C-N bonds. Traditional methods for the generation of NCRs employ toxic radical initiators, transition metal catalysts, photocatalysts, or organometallic reagents. Herein, we report a novel strategy for the generation of NCRs toward the construction of C-N bonds under transition-metal-free conditions. Thus, super-electron-donor (SED) 2-azaallyl anions undergo single-electron transfer (SET) with sulfonamides, forming aminyl radicals (R2N•, R = alkyl) and culminating in the generation of amidines bearing various functional groups (33 examples, up to 96% yield). Broad substrate scope and gram-scale telescoped preparation demonstrate the practicality of this method. Radical clock and electron paramagnetic resonance (EPR) experiments support the proposed radical coupling pathway between the generated N-centered radical and the C-centered 2-azaallyl radical.

Disentangling the Unusual Magnetic Anisotropy of the Near‐Room‐Temperature Ferromagnet Fe4GeTe2

AbstractIn the quest for 2D conducting materials with high ferromagnetic ordering temperature the new family of the layered FenGeTe2 compounds, especially the near‐room‐temperature ferromagnet Fe4GeTe2, receives a significant attention. Fe4GeTe2 features a peculiar spin reorientation transition at TSR ≈ 110 K suggesting a non‐trivial temperature evolution of the magnetic anisotropy (MA)—one of the main contributors to the stabilization of the magnetic order in the low‐dimensional systems. An electron spin resonance (ESR) spectroscopic study reported here provides quantitative insights into the unusual magnetic anisotropy of Fe4GeTe2. At high temperatures the total MA is mostly given by the demagnetization effect with a small contribution of the counteracting intrinsic magnetic anisotropy of an easy‐axis type, whose growth below a characteristic temperature Tshape ≈ 150 K renders the sample seemingly isotropic at TSR. Below one further temperature Td ≈ 50 K the intrinsic MA becomes even more complex. Importantly, all the characteristic temperatures found in the ESR experiment match those observed in transport measurements, suggesting an inherent coupling between magnetic and electronic degrees of freedom in Fe4GeTe2. This finding together with the observed signatures of the intrinsic two‐dimensionality should facilitate optimization routes for the use of Fe4GeTe2 in the magneto‐electronic devices, potentially even in the monolayer limit.

Efficient photocatalytic reduction of Cr(VI) and degradation of tetracycline by Bi2Se3@ZnIn2S4 binary heterostructures enriched with sulfur vacancies: Mechanism and mineralization analysis

Constructing a sulfur-vacancy-enriched heterostructure offers advantages in enhancing photocatalytic performance due to the synergy between the vacancy’s electron-trapping and the internal electric field (IEF) features. In this study, a series of IEF-modulated type-I heterostructures containing sulfur vacancies-rich ZnIn2S4 (SV-ZIS) and Bi2Se3 (BSe) was rationally developed by hydrothermal and reduction methods. The optimized BSe@SV-ZIS catalyst shows an outstanding photocatalytic Cr(VI) reduction and tetracycline degradation rates, which are ∼ 2.1 and ∼ 1.5 times higher than that of pure SV-ZIS and BSe, respectively. Notably, the enhanced catalytic performance of binary samples could be linked to efficient absorption of the full spectrum of light, heterojunction formation and larger contact area to enhance the charge carriers movement at their interface and exceptional photo-stability. By assisting DRS, VB-XPS, and UPS analyses, details of the energy band position, charge carriers transport route, and preliminary photocatalytic mechanism were systematically explored. Furthermore, radical scavenging and electron paramagnetic resonance experiments were conducted to provide evidence of the participation of the reactive species during photocatalysis over BSe@SV-ZIS. Kinetic analysis revealed that the rate of photocatalytic process adheres to the Langmuir–Hinshelwood kinetic model. These results demonstrated that the heterostructuring approach holds significant potential as an effective avenue for developing photocatalysts that can harness both visible and NIR light, offering promising solutions to contemporary challenges in the realms of environmental decontamination and energy.

Photocatalytic reduction of Cr(VI) by AgIn5S8/ZnIn2S4 heterojunction under visible light: Experimental and density functional theory study

Ternary metal sulfides have excellent light absorption properties, but their high recombination rate of photo generated carriers limits their practical application. To address this problem, this work constructed a novel nanoflower−like AgIn5S8/ZnIn2S4 heterojunction and explored its removal performance for Cr(VI) in water. AgIn5S8 was prepared by the solvothermal method, whereas ZnIn2S4 and AgIn5S8/ZnIn2S4 heterojunction was synthesized via the hydrothermal method. The morphological characteristics of AgIn5S8/ZnIn2S4 heterojunction showed that the AgIn5S8 particles uniformly distributed on the surface of ZnIn2S4 with a flower like structure. The obtained 10% AgIn5S8/ZnIn2S4 exhibited a higher specific surface area (75.07 m2/g) than AgIn5S8 (20.91 m2/g) and ZnIn2S4 (58.30 m2/g), with the maximum Cr(VI) removal efficiency of 88.5% at an initial concentration of 20 mg/L. The photocatalytic reduction of Cr(VI) by AgIn5S8/ZnIn2S4 conformed to the pseudo-first-order kinetic model. The superoxide radicals (·O2−) and photogenerated electrons (e−) were identified as the major active substances for Cr(VI) photoreduction according to the electron paramagnetic resonance (EPR) and free radical trapping experiments. The Mott−Schottky analysis demonstrated that the band structures of AgIn5S8 and ZnIn2S4 were compatible. Density functional theory (DFT) calculations showed that AgIn5S8/ZnIn2S4 heterojunction enhanced the separation efficiency of photogenerated carriers through an internal electric field (IEF). These results demonstrate that type–II AgIn5S8/ZnIn2S4 heterojunctions have the potential for effective removal of Cr(VI) in wastewater under visible light irradiation.

ZIF-8/balsa wood derived N-doped porous carbon as self-supporting electro-Fenton cathode for efficient antibiotics degradation

Efficient electrochemical advanced oxidation processes (EAOPs) based on carbon catalysts are highly promising candidates for green environmental remediation technologies. Wood derived N-doped porous carbon (WNPC) was prepared the balsa wood with in-situ growth of zeolitic imidazolate framework-8 (ZIF-8) was used as precursor. WNPC acted as self-supporting electric Fenton cathode with high yield and selectivity (96 %) of in-situ H2O2 generation, which effectively avoided the use binder for powder material. Owing to abundant N-doping and oxygen functional groups, the H2O2 yield of WNPC was three times that of balsa wood derived carbon (WC) in electro-Fenton system. The graphite-N promoted the electron transfer, while the pyridinic-N could enhance the selectivity of the 2e-ORR for H2O2 generation. Furthermore, the specific surface area of WNPC was 10 times of WC, with improved hydrophilicity and accelerated electron transfer. The removal efficiency of tetracycline hydrochloride (TC) achieved 91 % within 120 min in electro-Fenton system with WNPC and Fe2+, which was much higher than that with WC (63 %). Free radical scavenging and electron paramagnetic resonance experiments confirmed that ·OH and O2–· were the main active substances for TC degradation in electro-Fenton system. In addition, WNPC has good stability, reusability, and comparable degradation performance of various organic pollutants, and also had efficient degradation performance with actual water. This research proposed a novel strategy to construct efficient electro-Fenton catalyst with wood as precursor, which provides an advancing electrocatalytic methods to achieve efficient and environmentally conscious water purification.

Multicolor lignin-derived carbon quantum dots: Controllable synthesis and photocatalytic applications

The cost-effective, high-performance fabrication of multicolor carbon quantum dots (CQDs) from biomass is critical to its prospective application. Lignin, with its phenylpropane structural unit and abundant functional groups, is a reliable precursor for the formation of high-quality CQDs. Here, CQDs from renewable lignin were successfully prepared via a two-step method, and controllable preparation of CQDs to emit blue, green, yellow, and red fluorescence was achieved by adjusting the N-containing acid dopant. The investigated fluorescence mechanism revealed that the energy bandgap of the lignin-derived CQDs decreased and the emission wavelength redshifted as the graphitization degree and number of C=O surface groups increased. The light absorption region of the Bi7O9I3 photocatalysts modified with blue CQDs to red CQDs gradually broadened in the redshifted direction. In particular, compared with pure Bi7O9I3 (70.9%), the red CQDs-modified Bi7O9I3 (RCQD/BOI) can remove 94.7% of antibiotics within 60 min of light irradiation. The superior photocatalytic activity of RCQD/BOI is attributed to the established internal electric field that accelerates charge transfer and effectively separates the photogenerated e+-h+ inside Bi7O9I3. Furthermore, through radical capture, electron paramagnetic resonance (EPR) experiments validated the photocatalytic mechanism of RCQD/BOI and revealed that h+, O2− and OH are key reactants in the photocatalytic degradation process. This promising and sustainable approach for the synthesis of multicolor lignin-derived CQDs opens the avenue of high-value utilization of biomass resources, green production of CQDs nanomaterials, and efficient development of CQDs-based photocatalysts for wastewater treatment.