Double Electron Transfer Research Articles

Prehydrated Electrons Activated by Continuous Electron Transfer Stemmed from Peracetic Acid Homolysis Mediated by Diamond Surface Defects for Enhanced PFOA Destruction.

Research on the use of peracetic acid (PAA) activated by nonmetal solid catalysts for the removal of dissolved refractory organic compounds has gained attention recently due to its improved efficiency and suitability for advanced water treatment (AWT). Among these catalysts, nanocarbon (NC) stands out as an exceptional example. In the NC-based peroxide AWT studies, the focus on the mechanism involving multimedia coordination on the NC surface (reactive species (RS) path, electron reduction non-RS pathway, and singlet oxygen non-RS path) has been confined to the one-step electron reaction, leaving the mechanisms of multichannel or continuous electron transfer paths unexplored. Moreover, there are very few studies that have identified the nonfree radical pathway initiated by electron transfer within PAA AWT. In this study, the complete decomposition (kobs = 0.1995) and significant defluorination of perfluorooctanoic acid (PFOA, deF% = 72%) through PAA/NC has been confirmed. Through the use of multiple electrochemical monitors and the exploration of current diffusion effects, the process of electron reception and conduction stimulated by PAA activation was examined, leading to the discovery of the dynamic process from the PAA molecule → NC solid surface → target object. The vital role of prehydrated electrons (epre-) before the entry of resolvable electrons into the aqueous phase was also detailed. To the best of our knowledge, this is the first instance of identifying the nonradical mechanism of continuous electron transfer in PAA-based AWT, which deviates from the previously identified mechanisms of singlet oxygen, single-electron, or double-electron single-path transfer. The pathway, along with the strong reducibility of epre- initiated by this pathway, has been proven to be essential in reducing the need for catalysts and chemicals in AWT.

Mesoporous copper-doped δ-MnO2 superstructures to enable high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are competitive alternatives for large-scale energy-storage devices owing to the abundance of zinc and low cost, high theoretical specific capacity, and high safety of these batteries. High-performance and stable cathode materials in AZIBs are the key to storing Zn2+. Manganese-based cathode materials have attracted considerable attention because of their abundance, low toxicity, low cost, and abundant valence states (Mn2+, Mn3+, Mn4+, and Mn7+). However, as a typical cathode material, birnessite-MnO2 (δ-MnO2) has low conductivity and structural instability. The crystal structure may undergo severe distortion, disorder, and structural damage, leading to severe cyclic instability. In addition, its energy-storage mechanism is still unclear, and most of the reported manganese oxide-based materials do not have excellent electrochemical performance. Herein, we propose a copper-doped Cu0.05K0.11Mn0.84O2·0.54H2O (Cu2-KMO) cathode, which exhibits a large interlayer spacing, a stable structure, and accelerated reaction kinetics. This cathode was prepared using a simple hydrothermal method. The AZIB assembled using Cu2-KMO showed high specific capacity (600 mA h g−1 at 0.1 A g−1 after 75 cycles). The dissolution-deposition energy storage mechanism of Cu-KMO in AZIBs with double electron transfer was revealed using ex situ tests. The good electrochemical performance of the Cu2-KMO cathode fabricated by the doping strategy in this study provides ideas for the subsequent preparation of manganese dioxide using other strategies.

Revisiting the Electron Transfer Mechanisms in Ru(III)-Mediated Advanced Oxidation Processes with Peroxyacids and Ferrate(VI).

The potential of Ru(III)-mediated advanced oxidation processes has attracted attention due to the recyclable catalysis, high efficiency at circumneutral pHs, and robust resistance against background anions (e.g., phosphate). However, the reactive species in Ru(III)-peracetic acid (PAA) and Ru(III)-ferrate(VI) (FeO42-) systems have not been rigorously examined and were tentatively attributed to organic radicals (CH3C(O)O•/CH3C(O)OO•) and Fe(IV)/Ru(V), representing single electron transfer (SET) and double electron transfer (DET) mechanisms, respectively. Herein, the reaction mechanisms of both systems were investigated by chemical probes, stoichiometry, and electrochemical analysis, revealing different reaction pathways. The negligible contribution of hydroxyl (HO•) and organic (CH3C(O)O•/CH3C(O)OO•) radicals in the Ru(III)-PAA system clearly indicated a DET reaction via oxygen atom transfer (OAT) that produces Ru(V) as the only reactive species. Further, the Ru(III)-performic acid (PFA) system exhibited a similar OAT oxidation mechanism and efficiency. In contrast, the 1:2 stoichiometry and negligible Fe(IV) formation suggested the SET reaction between Ru(III) and ferrate(VI), generating Ru(IV), Ru(V), and Fe(V) as reactive species for micropollutant abatement. Despite the slower oxidation rate constant (kinetically modeled), Ru(V) could contribute comparably as Fe(V) to oxidation due to its higher steady-state concentration. These reaction mechanisms are distinctly different from the previous studies and provide new mechanistic insights into Ru chemistry and Ru(III)-based AOPs.

A highly sensitive fluorescence sensor for tobacco mosaic virus RNA based on DSN cycle and ARGET ATRP double signal amplification

AbstractEarly and sensitive detection of tobacco mosaic virus (TMV) is of great significance for improving crop yield and protecting germplasm resources. Herein, we constructed a novel fluorescence sensor to detect TMV RNA (tRNA) through double strand specific nuclease (DSN) cycle and activator regenerative electron transfer atom transfer radical polymerization (ARGET ATRP) dual signal amplification strategy. The hairpin DNA complementarily paired with tRNA was used as a recognition unit to specifically capture tRNA. By the double‐stranded DNA hydrolyzed with DSN, tRNA is released to open more hairpin DNA, and more complementary DNA (cDNA) is bound to the surface of the magnetic beads (MBs) to achieve the first amplification. After binding with the initiator, the cDNA employed ARGET ATRP to attach more fluorescent signal molecules to the surface of MBs, thus achieving the second signal amplification. Under the optimal experimental conditions, the logarithm of fluorescence intensity versus tRNA concentration showed a good linear relationship in the range of 0.01–100 pM, with a detection limit of 1.03 fM. The limit of detection (LOD) was calculated according to LOD = 3 N/S. Besides, the sensor showed good reproducibility and stability, which present provided new method for early and highly sensitive detection for plant viruses.

Unraveling the Role of Humic Acid in the Oxidation of Phenolic Contaminants by Soluble Manganese Oxo-Anions.

Humic acid (HA) is ubiquitous in natural aquatic environments and effectively accelerates decontamination by permanganate (Mn(VII)). However, the detailed mechanism remains uncertain. Herein, the intrinsic mechanisms of HA's impact on phenolics oxidation by Mn(VII) and its intermediate manganese oxo-anions were systematically studied. Results suggested that HA facilitated the transfer of a single electron from Mn(VII), resulting in the sequential formation of Mn(VI) and Mn(V). The formed Mn(V) was further reduced to Mn(III) through a double electron transfer process by HA. Mn(III) was responsible for the HA-boosted oxidation as the active species attacking pollutants, while Mn(VI) and Mn(V) tended to act as intermediate species due to their own instability. In addition, HA could serve as a stabilizer to form a complex with produced Mn(III) and retard the disproportionation of Mn(III). Notably, manganese oxo-anions did not mineralize HA but essentially changed its composition. According to the results of Fourier-transform ion cyclotron resonance mass spectrometry and the second derivative analysis of Fourier-transform infrared spectroscopy, we found that manganese oxo-anions triggered the decomposition of C-H bonds on HA and subsequently produced oxygen-containing functional groups (i.e., C-O). This study might shed new light on the HA/manganese oxo-anion process.

Electrocatalytically enhanced Cu(II)/peroxymonosulfate (PMS) oxidation: Focus on electrically-induced sustained Cu(II)/Cu(I)/Cu(III) cycling and suppression of singlet oxygen (1O2) production

Numerous azo dyes are discharged into industrial wastewater annually, posing significant threats to ecology and human health. In this study, an applied electric field was implemented in a trace copper-activated peroxymonosulfate system (EC/Cu(II)/PMS), achieving high removal efficiency (95.40 %) of Congo red (CR). The electron-donating effect of the cathode greatly enhanced the redox cycling of Cu(II)/Cu(I). Almost complete activation of PMS occurred during the entire reaction with an electrical consumption of merely 0.85 kWh/m3. Using electron paramagnetic resonance (EPR), quenching experiments, and chemical probes, the reactive substance that dominate CR removal, including Cu(III), sulfate radical (SO4•−), hydroxyl radical (HO∙), and singlet oxygen (1O2), were investigated. Cu(III) was identified as the main reactive substance, contributing over 90 %, and was primarily formed through double electron transfer of Cu(I). HO∙ can emerge as a secondary oxide of Cu(III). SO4•− originated mainly from the electroactivation of PMS. It was noted that 1O2 can be physically quenched by water, and thus 1O2 was considered as a side reaction product of PMS. Applying an electric field lowered the overall production of 1O2 and markedly mitigated the inefficient consumption of PMS. Moreover, the degradation pathways proposed for CR, based on mass spectrometry analysis, were in agreement with the predictions made by density functional theory (DFT). The toxicological characteristics of both CR and its intermediates were comprehensively analyzed as well. The study presents a straightforward and efficient strategy for PMS activation with versatile application potential for dye wastewater treatment.

Sustainable cycling and mechanism of Co(II)/Co(IV)/Co(III) with S(IV) highly triggered by Co(IV) in E/Co(II)/S(IV) for enhanced removal of reactive brilliant red X-3B

The massive discharge and inadequate treatment of dye wastewater have led to the extensive accumulation of azo dyes in natural water bodies, which is a severe threat to human health. In this study, a novel homogeneous electrochemical system, denoted E/Co(II)/S(IV), was developed by the incorporation of an electric field and cobalt/sulfite. Notably, the decontamination efficiency of the E/Co(II)/S(IV) system for reactive brilliant red X-3B (X-3B) was 95.14 % within 10 min, which was accomplished by utilizing only a trace amount of Co(II). The entire process exhibited an exceptionally low energy consumption of only 0.331 kWh/m3. Single-factor experiments were conducted to explore the influence of various operational parameters and water matrix components on the system decontamination efficiency. By combining the chelator EDTA and chemical probe PMSO, the presence of Co(III) and Co(IV) was detected. The results showed that Co(IV) mainly triggered the chain reaction. The activation products of S(IV), including SO3•−, SO4•−, SO5•− and HO∙, played a dominant role in the degradation of X-3B, with SO4•− having the most substantial contribution. Under anodic oxidation, Co(II) underwent double-electron transfer, leading to the conversion of Co(II) into Co(IV). Subsequently, Co(IV) activated S(IV) via a single-electron transfer mechanism, initiating a free radical chain reaction. During the reaction, Co(IV) transformed into Co(III) and Co(II), thus achieving the Co(II)/Co(IV)/Co(III) cycle. The generation of oxygen as a result of the electrochemical process offers a viable solution for addressing the issue of hypoxia stemming from the rapid activation of S(IV). The active sites in the X-3B molecule were elucidated through density functional theory predictions, and three degradation pathways for X-3B were identified via mass spectrometry analysis. The toxicological characteristics of both X-3B and its degradation products were comprehensively assessed using toxicity estimation software tool and algal culture experiments. This research offers valuable insights into the refinement of cobalt/sulfite systems and introduces innovative concepts for electrochemical applications, which have broad-reaching implications for dye wastewater purification.

Halide-Coupled Double Electron Transfer with Electron-Rich Diboranes.

The ditriflato-diborane B2 (μ-hpp)2 (OTf)2 (hpp=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) acts as a stable surrogate of the elusive dication [B2 (hpp)2 ]2+ , being both electrophilic (vacant boron p orbitals) and nucleophilic (filled B-B bond orbital). This combination of seemingly contrasting behaviors could be used to develop a metallomimetic diborane chemistry, with Lewis σ-basic and π-acidic substrates being bound and reduced at the diborane. Here, we report on a novel reaction type within this general theme, in which double electron transfer from the diboron unit to the boron-bound organic substrate is coupled with halide transfer in the other direction. Novel diborylated dienamines are synthesized in this way. The scope of this unprecedented reaction motif and the reaction pathways are elucidated.

Constructing dual electron transfer channels to accelerate CO2 photoreduction guided by machine learning and first-principles calculation

Designing dual electron transfer channels to achieve efficient carrier separation and understanding the corresponding mechanisms for CO2 photoreduction is of great significance. However, it is still challenging to find desirable model to achieve optimal photocatalytic performance. Herein, first-principles calculations and machine learning were combined to predict an optimized microstructure with dual electron transfer channels. The results indicate that the construction of BiOBr-Bi-g-C3N4 heterojunction has optimal free energy (|ΔG|) for H2O dissociation and CO2 reduction. Besides, the double electron transfer channels and excellent Bi active site can localize the photoexcited carriers at the interlayers rather than randomly distributing. These localized carriers generate intriguing superposition states at a particular timescale that optimize the multi-electronic reaction kinetics pathway of CO2 reduction, resulting in a 4.7 and 3.1 fold increase compared to pristine Bi-BiOBr and Bi-g-C3N4 with single electron transfer pathway. Machine learning was further used to optimize the experimental parameters, and the photocatalytic mechanism was verified by combining first-principles calculation with comprehensive experimental characterizations. This work provides experimental and theoretical references for the accurate prediction, rational design and ingenious fabrication of high-performance photocatalytic materials.

Selective oxidation of histamine H2-Receptor antagonists by peracetic Acid: Kinetics and mechanism

Peracetic acid (PAA) is an emerging substitutive oxidant to chlorine disinfectants owing to the low generation of harmful by-products. Herein, we report PAA-induced oxidation of histamine H2-receptor antagonists (HRAs) via non-radical participation for the first time. Results showed that PAA can selectively oxidize HRAs with high reactivity to ranitidine (RNTD), nizatidine (NZTD), cimetidine (CMTD), and famotidine (FMTD), but low reactivity to roxatidine (RXTD). PAA-induced HRAs oxidation followed the second-order kinetic reaction, the apparent second-order reaction rate constants (k2, app) of RNTD, FMTD, CMTD and NZTD were 18.78 ± (2.4), 37.22 ± (6.1), 36.53 ± (7.8), 30.04 ± (2.4) M−1•s−1, respectively. The value of k2, app decreased as pH increased. Scavenging experiments indicated that PAA-induced HRAs oxidation proceeded via a non-radical process. The theoretical calculation and product analysis further reveal that the reaction involves the double-electron transfer from thioether sulfur in HRAs to peroxide bond. HRAs oxidation by PAA was not affected by water matrices (Cl-, HCO3–, HA), which has good applicability in surface water (SW) and wastewater (WW). Toxicity assessment indicated ecotoxicity of oxidation products was much lower than that of HRAs. This work provided a facile and emerging technology to eliminate the HRAs and their toxicity in the wastewater.

Intramolecular Through-Space Double-Electron Transfer Between A Pair of Redox-Active Guanidine Units Aligned by Dithiolate Bridges.

Using unconventional synthesis protocols, two redox-active triguanidine units are connected by a dithiolate bridge, aligning the two redox-active units in close proximity. The reduced, neutral and the tetracationic redox states with two dicationic triguanidine units are isolated and fully characterized. Then, the dicationic redox states are prepared by mixing the neutral and tetracationic molecules. At low temperatures, the dications are diamagnetic (singlet ground state) with two different triguanidine units (neutral and dicationic). At room temperature, the triplet state with two radical monocationic triguanidine units is populated. At low temperature (210 K), chemical exchange by intramolecular through-space electron-transfer between the two triguanidine units is evidenced by EXSY NMR spectroscopy. Intramolecular through-space transfer of two electrons from the neutral to the dicationic triguanidine unit is accompanied by migration of the counterions in opposite direction. The rate of double-electron transfer critically depends on the bridge. No electron-transfer is measured in the absence of a bridge (in a mixture of one dicationic and one neutral triguanidine), and relatively slow electron transfer if the bridge does not allow the two triguanidine units to approach each other close enough. The results give detailed, quantitative insight into the factors that influence intramolecular through-space double-electron-transfer processes.

Evaluation of the radical scavenging potency and mechanism of natural phenolamides: A DFT study

Phenolamides have received increasing interest owing to their diverse pharmacological activities and health benefits. However, the structure–antioxidant activity relationship and underlying mechanism are still largely unclear. Herein, thermodynamic and kinetic calculations based on density functional theory (DFT) were carried out to clarify the antioxidant effects and mechanisms of four aromatic monoamines conjugated phenolamides (AMCPs). The results show that solvent effect plays a crucial role in modulating the action mechanisms for the studied phenolamides. In non-polar media, the studied AMCPs prefer to trap radicals via the formal hydrogen atom transfer (fHAT) mechanism, while in polar solvents the radical-scavenging reaction proceeds via mixed mechanisms with sequential proton loss electron transfer (SPLET), sequential proton loss hydrogen atom transfer (SPLHAT) and sequential double proton loss electron transfer (SdPLET) depending on the pH of environments. 4-OH in A-ring was found to be the preferred site to trap radical for CoTrp and CaTrp, while 5′–OH in C-ring for CoSer and FeSer. Moreover, the representative compound CaTrp was predicted to has excellent HOO scavenging potency (koverall = 3.15 × 108 M−1 s−1) in water at physiological pH, stronger than the two well-known antioxidants Trolox and ascorbic acid, and thus deserves to further utilization as nutraceutical or pharmaceutical candidates.

The Effect of Cu(II) Nanoparticle Decoration on the Electron Relaxations and Gaseous Photocatalytic Oxidations of Nanocrystalline TiO2

A photocatalytic effect arises from the electron relaxation of semiconductors. Directing the electron relaxation toward photocatalytic reactions is the focus of photocatalytic studies. Co-catalyst decoration is a main way to modulate the electron relaxation, and the Cu(II) nanoparticles have been widely studied as an important co-catalyst. However, the detailed mechanism is still not well known. The current study is devoted to investigating the effect of the Cu(II) nanoparticle decoration on the electron relaxations for TiO2 through in situ photochromism and photoconductances, based on which the relation to the photocatalytic properties was discussed. The result shows that the Cu(II)/Cu(0) redox couple assists the double electron transfer from TiO2 to O2, while the Cu(I)/Cu(0) redox couple assists the single electron transfer to O2. Although the Cu(II) decoration changes the mechanism and increases the rate of the electron relaxations, the electron relaxation does not occur via the Cu redox couple assistance. It was found that the electron relaxation kinetics depends on the reduced Cu species, which can be greatly increased when the Cu(II) was reduced to Cu(0). It is also revealed that the electron relaxation corresponds to the electron transfer from TiO2 to O2, but it does not occur through the Cu redox couple assistance. The result also shows that the increase in the electron relaxation is mainly directed toward the recombination rather than photocatalytic reactions. The present research gains some insights on the role of the co-catalysts in the electron relaxations and its relation to photocatalysis; this should be meaningful for designing novel photocatalytic materials.

Mechanistic insight into the free radical scavenging and xanthine oxidase (XO) inhibitor potent of monoacetylphloroglucinols (MAPGs)

Three novel antioxidant candidates based on phenolic polyketide, monoacetylphloroglucinol (MAPG), a natural antibiotic compound produced by plant growth-promoting rhizobacteria (PGPR), Pseudomonas fluorescens F113 have been proposed. Initially, a green and highly efficient route to the synthesis of MAPG and its two analogues from phloroglucinol (PG) has been developed. Afterward, their rational mechanism of antioxidant activity has been investigated based on thermodynamic descriptors involved in the double (/) radical trapping processes. These calculations have been performed using the systematic density functional theory (DFT) method at the B3LYP/Def2-SVP level of theory in the gas phase and aqueous solution. Our findings reveal that the double formal hydrogen atom transfer (df-HAT) mechanism is preferred in the gas phase, while the double sequential proton loss electron transfer (dSPLET) mechanism is preferred in aqueous solution for all MAPGs. The 6–OH group represents the most favorable site for trapping radical species for all MAPGs, which is supported by the pKa values obtained from DFT calculations. The role of acyl substituents on the PG ring has been comprehensively discussed. The presence of acyl substituents has a strong influence on the thermodynamic parameters of the phenolic O–H bond in PG. These results are supported by frontier molecular orbitals (FMOs) analysis, where the addition of acyl substituents increases the chemical reactivity of MAPGs significantly. Based on molecular docking and molecular dynamic simulations (MDs), MAPGs are also predicted to be promising candidates for xanthine oxidase (XO) inhibition. Highlights The antioxidant activity of the three synthesized monoacetylphloroglucinols (MAPGs) has been investigated using the density functional theory (DFT) method. Acyl substituents increase the chemical reactivity and antioxidant activity of MAPGs. Double formal hydrogen atom transfer (df-HAT) is the preferred mechanism in the gas phase. Double sequential proton loss electron transfer (dSPLET) seems to be more favored in aqueous solution. MAPGs are expected to be promising xanthine oxidase (XO) inhibitors.

Theoretical study on the free radical scavenging potency and mechanism of natural coumestans: Roles of substituent, noncovalent interaction and solvent

The free radical scavenging potency and mechanisms of seven representative natural coumestans were systematically evaluated using density functional theory (DFT) approach. Thermodynamic feasibility of different mechanisms was assessed by various physio-chemical descriptors involved in the double (2H+/2e‒) radical-trapping processes. Energy diagram and related transition state structures of the reaction between wedelolactone (WEL) and hydroperoxyl radical were constructed to further uncover the radical-trapping details. Results showed that the studied coumestans prefer to scavenge radicals via formal hydrogen atom transfer (fHAT) mechanism in the gas phase and non-polar environment, whereas sequential proton loss electron transfer (SPLET) is favored in polar media. Moreover, the feasibility of second fHAT and SPLET processes was also revealed. Sequential double proton loss double electron transfer (SdPLdET) mechanism represents the preferred pathway in aqueous solution at physiological pH. Our findings highlight the essential role of ortho-dihydroxyl group, noncovalent interaction and solvents on radical-trapping potency. 4′-OH in D-ring was found to be the most favorable site to trap radical for most of the studied coumestans, whereas 3-OH in A-ring for lucernol (LUN).

Exploration of double Z-type ternary composite long-afterglow/graphitic carbon nitride@metal–organic framework for photocatalytic degradation of methylene blue

Methylene blue (MB) is a very widely used cationic dye for color cotton and silk products. The harmful MB has a complex aromatic structure that is difficult to be degraded in natural aqueous. In this study for the first time, a novel double Z-type ternary composite long-afterglow/graphitic carbon nitride@metal–organic framework (SrAl2O4:Eu2+,Dy3+/g-C3N4@NH2-UiO-66, SGN) has been synthesized by solvothermal method, and was used as a new photocatalyst for removal of MB. The photocatalytic performance of the composited photocatalyst SGN was largely improved compared to that of the non-composite. After 30 min of photocatalysis, the degradation ratio of SGN was 5.86, 4.04 and 10 times more efficient than that of long-afterglow (SAO), g-C3N4 and NH2-UiO-66, respectively. The high photocatalytic activity of the SGN could be ascribed to the double Z-type electron transfer mechanism. More importantly, due to the luminescence of SAO, the degradation ratio of ternary SGN can reach about 50 % after 5 h in the dark. Superoxide anion (·O2–) was verified to be the main active substance in the photocatalytic process by quenching experiments and electron spin resonance (ESR) spectra analysis. The total organic matter contents (TOC) and partial degradation products were measured, which confirmed that some MB was mineralized into H2O and CO2, and some was degraded into smaller molecules. Moreover, the excellent stability and recyclability of this catalyst were also investigated. Here, a new promising material with high degradation performance for water pollution treatment is presented.

Nd2Sn2O7/Bi2Sn2O7/Ag3PO4 double Z-type heterojunction for antibiotic photodegradation under visible light irradiation: Mechanism, optimization and pathways

A novel visible light response Nd2Sn2O7/Bi2Sn2O7/Ag3PO4 (NSO/BSO/APO) composite photocatalyst with double Z-type heterojunction was successfully synthesized by a one-pot hydrothermal-precipitation method. The addition ratios of Nd2Sn2O7(NSO) and Ag3PO4(APO) during composite photocatalyst preparation were optimized, and the photocatalytic reaction conditions included tetracycline hydrochloride (TC) concentration, catalyst dosage, and initial pH of the solution were screened. The maximum degradation rate of 15 mg/L TC (pH = 8) reached 97.10% exposed to visible light in 120 min by NSO/BSO/APO-30 photocatalyst (dosage: 0.4 g/L), its kinetic constant is about 9.78 times that pure Bi2Sn2O7 (BSO). The morphology, composition, and optical properties of the catalysts were characterized. The f-f transition of Nd3+ in NSO improves the absorption ability of the catalyst to visible light. In addition, h+, O2− and OH participated in the photodegradation of TC in NSO/BSO/APO-30 system. The fitting of the Mott-Schottky curve and Tauc-plot curves confirmed the rationality of the double Z-type electron transfer mechanism. The EIS and PL tests show that the NSO/BSO/APO-30 composite catalyst had the lowest charge transfer resistance and the lowest carrier recombination rate. In addition, three possible degradation pathways of TC during the photodegradation by NSO/BSO/APO-30 were analyzed by High-resolution mass spectrometry (APCI-MS).

A new sodium ion preintercalated and oxygen vacancy-enriched vanadyl phosphate cathode for aqueous zinc-ion batteries

At present, layered vanadium–oxygen structures have attracted wide attention for multivalent metal ion storage, especially in aqueous zinc-ion batteries (AZIBs), due to the attractive layered structure and large specific capacity based on V5+/V3+ double electron transfer. However, in addition to a large specific capacity, a high output voltage is necessary to achieve a high specific energy density. Vanadium oxide and vanadate usually feature low working voltages, serious structural degradation and limited practical. To alleviate these problems, some cathode modification strategies have been proposed that improve the operating voltage, structural stability and diffusion kinetics of multivalent metal ions. In this paper, vanadyl phosphate (Nay(VO1−x)3(PO4)2) nanosheets preintercalated with sodium ions and modified with oxygen vacancies were prepared via a facile one-step liquid phase treatment. The Nay(VO1−x)3(PO4)2 nanosheet cathode for AZIBs delivered a high specific capacity of 75.3 mAh g−1 at 0.1 A g−1 and retained 27.5 mAh g−1 after 4000 cycles at 2 A g−1. Subsequently, the as-prepared Nay(VO1−x)3(PO4)2 nanosheets were physically and electrochemically characterized, and a possible mechanism of Zn2+ insertion/extraction and structural decomposition was proposed based on ex situ XRD and XPS characterizations. Our work provides a simple method for simultaneously introducing sodium ion preintercalation and oxygen vacancies into vanadyl phosphate structures, and provides some insights into the zinc storage mechanism.

A novel visible-light-induced double Z-scheme photocatalytic system: NH2-UiO-66/BiOBr/Bi2S3 for degradation of tetracycline hydrochloride and rhodamine B

The unique properties of MOFs make them the best candidates for catalytic and photocatalytic applications. In this research, the NH2-UiO-66 material was prepared by solvothermal method, and different content of NH2-UiO-66 was added before the composite growth of Bi2S3 and BiOBr nanomaterials to obtain the NH2-UiO-66/BiOBr/Bi2S3 ternary composite material. In order to investigate the relationship between the structure and properties of the catalyst, XRD, FT-IR, SEM, HRTEM, UV–vis DRS, XPS and other characterization technologies were used to analyze the structure, morphology, optical properties of the samples, showing that NH2-UiO-66/BiOBr/Bi2S3 have been successfully synthesized. Their photocatalytic performance was evaluated based on the photocatalytic degradation of tetracycline hydrochloride and rhodamine B under visible light. The results show that 2% NH2-UiO-66/BiOBr/Bi2S3 has better photocatalytic activity than other materials. Moreover, NH2-UiO-66/BiOBr/Bi2S3 also demonstrated good photocatalytic reusability and stability. The formation of Bi2S3 and BiOBr heterojunctions and the introduction of NH2-UiO-66 with more active sites increase the carrier performance and separation efficiency. Then the valence band and conduction band values of the semiconductor material are calculated through the M-S curve, combined with the forbidden bandwidth deduced by UV–vis DRS and the experimental results of radical trapping, a double Z-type electron transfer mechanism suitable for this system is inferred. Finally, taking RhB as an example, the degradation path of dye pollutants was studied.

Bromine–Graphite Intercalation Enabled Two-Electron Transfer for a Bromine-Based Flow Battery

Br2/Br− is a promising redox couple in flow batteries because of its high potential, solubility, and low cost. However, the reaction between Br− and Br2 only involves a single-electron transfer process, which limits its energy density. Herein, a novel two-electron transfer reaction based on Br−/Br+ was studied and realized through Br+ intercalation into graphite to form a bromine–graphite intercalation compound (Br–GIC). Compared with the pristine Br−/Br2 redox pair, the redox potential of Br intercalation/deintercalation in graphite is 0.5 V higher, which has the potential to substantially increase the energy density. Different from Br2/Br− in the electrolyte, the diffusion rate of Br intercalation in graphite decreases with increasing charge state because of the decreasing intercalation sites in graphite, and the integrity of the graphite structure is important for the intercalation reaction. As a result, the battery can continuously run for more than 300 cycles with a Coulombic efficiency exceeding 97% and an energy efficiency of approximately 80% at 30 mA/cm2, and the energy density increases by 65% compared with Br−/Br2. Combined with double-electron transfer and a highly reversible electrochemical process, the Br intercalation redox couple demonstrates very promising prospects for stationary energy storage.