Double Redox Research Articles

In Situ Unraveling Surface Reconstruction of Ni‐CoP Nanowire for Excellent Alkaline Water Electrolysis

The surface reconstruction behavior of transition metal phosphides precursors is considered as an important method to prepare efficient oxygen evolution catalysts, but there are still significant challenges in guiding catalyst design at the atomic scale. Here, the CoP nanowire with excellent water splitting performance and stability is used as a catalytic model to study the reconstruction process. Obvious double redox signals and valence evolution behavior of the Co site are observed, corresponding to Co2+/Co3+ and Co3+/Co4+ caused by auto‐oxidation process. Importantly, the in situ Raman spectrum exhibits the vibration signal of Co–OH in the non‐Faradaic potential interval for oxygen evolution reaction, which is considered the initial step in reconstruction process. Density functional theory and ab initio molecular dynamics are used to elucidate this process at the atomic scale: First, OH− exhibits a lower adsorption energy barrier and proton desorption energy barrier at the configuration surface, which proposes the formation of a single oxygen (–O) group. Under a higher –O group coverage, the Co–P bond is destroyed along with the POx groups. Subsequently, lower P vacancy formation energy confirm that the Ni‐CoP configuration can fast transform into a highly active phase. Based on the optimized reconstruction behavior and rate‐limiting barrier, the Ni‐CoP nanowire exhibit an excellent overpotential of 1.59 V at 10 mA cm−2 for overall water splitting, which demonstrates low degradation (2.62%) during the 100 mA cm−2 for 100 h. This work provide systematic insights into the atomic‐level reconstruction mechanism of transition metal phosphides, which benefit further design of water splitting catalysts.

Electron transfer mechanism mediated MOF-derived nanoflowers catalyst for promoting peroxymonosulfate activation and ciprofloxacin degradation

Three MOF-derived nanoparticles were synthesized by manganese doping and calcination of ZIF-67 precursor. The surface physicochemical properties of these materials were compared using SEM, TEM, XRD, FTIR and BET analyses. Among them, cobalt-manganese oxide nanoflowers (CoMn2O4-NFs) exhibited excellent catalytic performance in the degradation of ciprofloxacin (CIP) by activated peroxymonosulfate (PMS), achieving 100 % removal within 30 minutes with a rate constant (kobs) of 0.2960 min−1. The catalytic mechanism was elucidated by quenching experiments, EPR, electrochemical analysis and X-ray photoelectron spectroscopy (XPS). The results show that the non-radical oxidation process was initiated mainly by direct electron transfer and 1O2 (∼80 %), with a small contribution from the radical SO4·- (∼20 %). The nano-confined structure on the surface of CoMn2O4-NFs makes it easy to combine with PMS to form CoMn2O4-NFs/PMS* complexes, which directly capture electrons from CIP to complete the degradation process. The double redox cycle of cobalt-manganese ions and oxygen vacancies on CoMn2O4-NFs could accelerate the electron transfer process. CoMn2O4-NFs maintained high removal efficiency (>99 %) over a wide pH range (3−11), with minimal interference from most environmental anions, demonstrating strong stability and interference resistance. This study provides insights into using metal-based materials for oxidative degradation of organic pollutants via non-radical pathways.

NiC2O4 nanorods embellished NiCo layered double hydroxide nanoflowers with enhanced electrochemical performances for hybrid supercapacitor

Designing and constructing a high performance and multi-component nickel-based material is preferable for efficient energy storage devices. In this study, we reasonably designed a composite material, NiC2O4/NiCo layered double hydroxide (LDH), composed of 1D NiC2O4 nanorods and 3D NiCo-LDH nanoflowers self-assembled from nanosheets via a hydrothermal method. This causes NiCo-LDH nanoflowers to stretch out, increasing the specific surface area (up to 47 m2 g−1), improving contact with the electrolyte and providing abundant active sites, speeding up the transfer of protons. The excellent double redox reactions of NiC2O4 and NiCo-LDH expedite the reaction kinetics and boost electrochemical activities, resulting in high energy densities of 37.6 Wh kg−1 and high power densities of 809.8 W kg−1 for the NiC2O4/NiCo-LDH||AC hybrid supercapacitor devices. Furthermore, DFT calculations indicate NiC2O4/NiCo-LDH enhance the adsorption ability of OH−. And the improved electrochemical performance of NiC2O4/NiCo-LDH is due to partial electrons transfer through the interface.

Structural, DFT and redox activity investigation of 2D silver based MOF for energy storage devices

A new silver(I) 2D MOF (Ag-MOF) was synthesized from 3,4-pyridinedicarboxylic acid (PDCA) by sonication method and characterized by single crystal X-ray diffraction, elemental analysis and FTIR spectroscopy. The material was further utilized for DFT computation and electrochemical performance. Theoretical and practicalresults for Ag-MOF geometrical parameters were found to be in reasonable agreement. Small HOMO-LUMO energy distance of 0.47 eV confirmed that electron transfer was much feasible. Distribution of electron isodensities was elaborated by DFT and FMOs computation. Double redox peaks in CV voltammograms reflected the change in oxidation state. Multiple plateaus in GCD curves showed the pseudo-capacitive behavior. Ag-MOF exhibited 101 Cg−1 specific capacity (Qs), 123 Wh.kg−1 energy density and 12,960 W kg−1 power density at current density of 5 Ag−1. There was a small difference in Rct and Ri which revealed that Ag-MOF had great ability to store energy. Presence of semi-circular arc in the EIS spectrum directly dictates the supercapacitor behavior. The electrode showed 97.5 % cyclic stability after 5000 cycles.

Optimizing Mn in Prussian blue analogs with double redox active sites to induce boosted Zn2+ storage

Prussian Blue analogs (PBAs) are a suitable aqueous zinc-ion batteries (AZIBs) cathode material, but they face issues related to low specific capacity and cycling lifespan due to insufficient active sites and poor ion de-intercalation structural stability. In this study, Mn-Prussian Blue Analog (Mn-PBA) is fabricated using a simple co-precipitation method and the morphology of Mn-PBA is further optimized through artificially manipulating concentration gradients strategy, effectively enhancing the structural stability of Zn2+ de-intercalation. Furthermore, the introduction of Mn established dual Zn2+ active centers in Mn-PBA (Mn-O and Fe(CN)6]4−/[Fe(CN)6]3−), leading to an increased specific capacity. As a proof of concept for AZIBs, the optimized Mn-PBA-3 cathode exhibits a high reversible specific capacity of 143.5 mAh/g and maintains a capacity retention of 88.5 % after 250 cycles at 1 A/g, surpassing commercial MnO2 (30.5 mAh/g after 100 cycles). Mn-PBA-3 also delivers a high capacity of 79.0 mA h g−1 after 2000 cycles of 10 A/g. The mechanism of the Zn2+ double redox reaction of Mn-PBA-3 has been revealed in detail by in situ Raman and a series of ex situ techniques. Under a high operating voltage window of 0–1.9 V, Zn//Mn-PBA-3 demonstrates a capacity of 99.3 mAh/g after 800 cycles (5 A/g) by assembling zinc ion button battery. This work has reference significance for structurally modulated PBAs used in high performance AZIBs.

Indolocarbazole‐Based Small Molecule Cathode‐Active Material Exhibiting Double Redox for High‐Voltage Li‐Organic Batteries

Most organic electrode materials (OEMs) for rechargeable batteries employ n‐type redox centers, whose redox potentials are intrinsically limited <3.0 V versus Li+/Li. However, p‐type materials possessing high redox potentials experience low specific capacities because they are capable of only a single redox reaction within the stable electrochemical window of typical electrolytes. Herein, we report 5,11‐diethyl‐5,11‐dihydroindolo[3,2‐b]carbazole (DEICZ) as a novel p‐type OEM, exhibiting stable plateaus at high discharge potentials of 3.44 and 4.09 V versus Li+/Li. Notably, the second redox potential of DEICZ is within the stable electrochemical window. The mechanism of the double redox reaction is investigated using both theoretical calculations and experimental measurements, including density functional theory calculations, ex situ electron spin resonance, and X‐ray photoelectron spectroscopy. Finally, hybridization with single‐walled carbon nanotubes (SWCNT) improves the cycle stability and rate performance of DEICZ owing to the π–π interactions between the SWCNT and co‐planar molecular structure of DEICZ, preventing the dissolution of active materials into the electrolyte. The DEICZ/SWCNT composite electrode maintains 70.4% of its initial specific capacity at 1‐C rate and also exhibits high‐rate capability, even performing well at 100‐C rate. Furthermore, we demonstrate its potential for flexible batteries after applying 1000 bending stresses to the composite electrode.

Unlocking the structure and cation synergistic modulation of Prussian blue analogues with double redox mechanism for improved aqueous nonmetallic ion storage.

Prussian blue analogs (PBAs) exhibit high energy density and a good electrochemical stability window in aqueous non-metallic ion batteries, which is conducive to achieving high energy output and stable operation. Additionally, their synthesis process is simple and environmentally friendly, meeting the demands of sustainable development. However, the poor conductivity, structural stability issues, and inadequate ion diffusion pathways limit their application in batteries. To overcome these challenges, researchers have adopted various optimization strategies: enhancing the conductivity of PBAs by compositing with high-conductivity carbon materials such as graphite, carbon nanotubes, or graphene; optimizing synthesis conditions such as temperature and reaction time to improve the defect and structural water content of PBAs, thereby enhancing their stability and electrochemical performance; employing surface modification techniques, such as conductive polymer encapsulation and acid etching, to improve their electrochemical stability and ion transport performance; and optimizing ion diffusion efficiency and battery kinetics by selecting suitable electrolytes and additives. These comprehensive measures contribute to improving the electrochemical performance of PBAs and promoting the development of their commercial applications. Based on prior research advancements, we introduce a novel synergistic regulation strategy: the creation of multi-redox-active centers to augment the transport capability of non-metallic ions and the optimization of defect structures through the establishment of a metal ion concentration gradient, thereby enhancing both electrochemical stability and performance.

Understanding the Degradation Mechanisms in Lithium Manganese Oxyfluoride Cathodes

The development of next-generation nickel and cobalt-free Li-ion batteries with significantly greater energy density for electric vehicles is largely contingent on the discovery of new cathode materials. A number of novel candidates with a disordered rocksalt crystal structure have recently been reported to exhibit high capacities, offering a highly promising new avenue for cathode research.1–5 However, disordered rocksalt cathode materials generally suffer from voltage and capacity fade over cycling. For example, the Mn-based archetypal oxyfluoride Li2MnO2F shows 254 mAh g-1 discharge capacity in the first cycle but fades to 104 mAh g-1 after 100 cycles. For improving these materials leading to practical devices, it is vital to develop an understanding of the fading mechanisms.Various explanations have been proposed for the gradual deterioration in performance of disordered rocksalt oxide and oxyfluoride cathodes. These include O-loss and surface densification4,6, growth of a CEI layer7, phase segregation6,8. In this study, we examine the main degradation mechanisms in Li2MnO2F over cycling and demonstrate that the capacity and voltage retention can be improved through compositional control, figure below. This understanding points the way to manganese oxyfluorides with better cycling performance. House, R. A. et al. Lithium manganese oxyfluoride as a new cathode material exhibiting oxygen redox. Energy Environ. Sci. 11, 926–932 (2018).Lee, J. et al. Reversible Mn2+/Mn4+ double redox in lithium-excess cathode materials. Nature 556, 185–190 (2018).Yabuuchi, N. et al. Origin of stabilization and destabilization in solid-state redox reaction of oxide ions for lithium-ion batteries. Nat. Commun. 7, 1–10 (2016).Li, L. et al. Fluorination‐Enhanced Surface Stability of Cation‐Disordered Rocksalt Cathodes for Li‐Ion Batteries. Adv. Funct. Mater. 2101888, 2101888 (2021).Chen, R. et al. Disordered lithium-rich oxyfluoride as a stable host for enhanced Li+ intercalation storage. Adv. Energy Mater. 5, (2015).Chen, D., Kan, W. H. & Chen, G. Understanding Performance Degradation in Cation-Disordered Rock-Salt Oxide Cathodes. Adv. Energy Mater. 9, 1–15 (2019).Källquist, I. et al. Degradation Mechanisms in Li2VO2F Li-Rich Disordered Rock-Salt Cathodes. Chem. Mater. 31, 6084–6096 (2019).Chen, D., Ahn, J., Self, E., Nanda, J. & Chen, G. Understanding cation-disordered rocksalt oxyfluoride cathodes. J. Mater. Chem. A 2, 7826–7837 (2021). Figure 1

Improving Li percolation and redox reversibility of Li-rich disordered rocksalt cathode with Mn2+/4+ double redox via inactive d0 Nb5+ substitution

Disordered rocksalt (DRX) cathodes are promising for next-generation lithium-ion batteries due to its high discharge capacity. Benefiting from the high degree of freedom in compositional design, cationic multi-electron redox is realized through the stabilization of d0 transition metals (TMs), and irreversible oxygen loss is alleviated by increased TM capacity contribution. However, such materials reported so far are almost weakly crystalline (fluorine)oxides prepared by mechanochemical methods. Herein, we prepare highly crystalline Mn(II)-based DRX oxides Li1.15Mn0.275Ti0.575O2 (LMTO), and Li1.23Mn0.275Ti0.255Nb0.24O2 (LMTNO) with partial d0 Ti4+ replaced by d0 Nb5+. Increased lattice spacings of LMTNO are confirmed due to the larger ionic radius of Nb5+, which is conducive to Li+ diffusion. In combination with bond-valence sum method and electrochemical impedance spectroscopy, lower Li+ percolation energy and better rate performance of LMTNO are demonstrated kinetically. Density functional calculations reveal that d0 Nb5+ is superior to d0 Ti4+ for the stabilization of Mn-O bonds, and relieves MnO6 octahedral distortion to alleviate the Jahn-Teller effect. In-situ X-ray diffraction indicates that the structural evolution and redox reaction are more reversible in LMTNO during the electrochemical process. This work understands the effect of d0 TMs on the electrochemical performance of DRX cathodes and provides new insights into multi-electron redox.

The enhancement effect of Cu modification on N2 selectivity of V0.5/Pt0.04/TiO2 catalyst for selective catalytic oxidation of NH3

BackgroundCurrently selective catalytic oxidation (SCO) is considered as an effective approach to remove slipped ammonia from exhaust gas of NH3-fuel engines. But it is still challenging to achieve high NH3 conversion and N2 selectivity simultaneously. MethodsCu was introduced to modify V0.5/Pt0.04/TiO2 catalysts and the effects of Cu addition step and amounts on NH3 removal performance of the composite catalysts were investigated. Significant findingsCompared to V0.5/Pt0.04/TiO2 catalyst, Cu0.5V0.5/Pt0.04/TiO2 catalyst exhibited a similar NH3 conversion rate but a much better N2 selectivity. When reaction temperature was higher than 225 °C, a complete NH3 removal could be achieved for Cu0.5V0.5/Pt0.04/TiO2 catalyst, while N2 selectivity was higher than 80 % in a wide temperature range of 225–375 °C. The introduction of Cu resulted in the formation of CuVOx species with strong catalytic oxidation activity due to double redox couples of V5+/V4+ and Cu2+/Cu1+. There was a synergistic effect between CuVOx species and Pt species, which significantly facilitated i-SCR reactions, thus improving N2 selectivity. As main intermediates, -NH2 species actively participated in NH3-SCO reactions over Cu0.5V0.5/Pt0.04/TiO2 catalyst.

Sandwich-type electrochemical immunosensor based on CuFe2O4-Pd for cardiac troponin I detection.

A sandwich-type electrochemical immunosensor was designed by highly efficient catalytic cycle amplification strategy of CuFe2O4-Pd for sensitive detection of cardiac troponin I. CuFe2O4 with coupled variable valence metal elements exhibited favorable catalytic performance through bidirectional cycling of Fe2+/Fe3+ and Cu+/Cu2+ redox pairs. More importantly, Cu+ acted as the intermediate product of the catalytic reaction, promoted the regeneration of Fe2+ and ensured the continuous recycling occurrence of the double redox pairs, and significantly amplified the current signal response. Pd nanoparticles (Pd NPs) loaded on the surface of amino-functionalized CuFe2O4 (CuFe2O4-NH2) served as electrochemical mediators to capture labeled antibodies (Ab2), and also as co-catalysts of CuFe2O4 to further enhance the catalytic efficiency, thusimproving the sensitivity of the electrochemical immunosensor. Under the optimal experimental conditions, the linear range was 0.001 ~ 100ng/mL, and the detection limit was 1.91fg/mL. The electrochemical immunosensor has excellent analytical performance, giving a new impetus for the sensitive detection of cTnI.

3D printing of customized MnO2 cathode for aqueous zinc-ion batteries

In order to overcome the problems of inferior cycling stability and slow ion diffusion of MnO2 cathode in aqueous zinc-ion battery, a high-accuracy customized 3D printed MnO2 cathode was prepared via direct ink writing. The rheological test showed that the printing ink indicated shear-thinning behavior with the storage modulus platform value over 105 Pa. The SEM images displayed that the customized mesh—layer structure was well maintained after 100 cycles. The 3D structure with excellent mechanical strength could effectively alleviate the internal stress and provide a greater specific surface area. The specific capacity of the 3D printing cathode was three times higher than that of the 2D one at 50 mA/g after 110 stable cycles. The energy storage mechanism of the reversible Mn2+/Mn4+ double redox for 3D printing battery was also studied through a variety of ex-situ experiments.

Voltage-dependent formation of cathode–electrolyte interphase with independent metallic layer in LiNi0.8Mn0.1Co0.1O2 cathode for high-energy density lithium-ion batteries

Layered LiNi0.8Mn0.1Co0.1O2 (NMC811) has emerged as the promising cathode material for next generation lithium-ion batteries owing to its high capacity. The double redox reaction between Ni2+/Ni3+ and Ni3+/Ni4+ is the major source of the large capacity, but it often leads to the formation of an unstable cathode–electrolyte interphase (CEI) layer. Herein, the correct nature of the CEI layer for the NMC811 battery has been studied with a particular attention to the voltage dependency (4.3 V vs. 4.7 V). A CEI metallic layer consisting of transition metal (TM) composites (i.e. 54.9MnOx, 54.9MnF3, 58.7NiO, 58.7NiF3, 58.9CoOx, and 58.9CoF3) has been long considered as a part of inorganic layer. However, the present study found that the metallic layer can be present as an independent CEI layer depending on the cut-off voltages. To further understand the nature of the CEI formation with the cathode material, a density-functional theory was conducted. The Fermi level with respect to the redox couples of the TMs/oxygen orbitals and their covalency not only affect the cathode stability but also modulate the CEI property. It is also proposed that the covalency of TM(3d)-O(2p) is the key factor that determines the localization of the TM metallic layer.

Ir(IV) and Ir(III) in situ transition promotes ROS generation for eradicating multidrug-resistant bacterial infection.

Whether reactive oxygen species are a consequence or a cause of antibacterial activity is not fully known. A glutathione (GSH)-mediated oxidative defense mechanism is an important factor against bacterial infection. Reactive oxygen species (ROS) storm-mediated bacterial death by depleting GSH is also considered an effective strategy. Therefore, we designed and synthesized hybrid iridium ruthenium oxide nanozymes (IrRuOx NPs), where IrRuOx NPs alternately consume GSH through double redox electron pair auto-valent cycles, while an IrRuOx NP-mediated Fenton-like reaction occurs to realize an ROS storm, which in turn mediates lipid peroxidation to promote bacterial death. The results showed that IrRuOx NPs can effectively inhibit and kill Gram-positive and Gram-negative bacteria in vitro, and can be used as broad-spectrum antibiotics. Importantly, the wound and sepsis models of MRSA infection confirmed the efficient antibacterial activity of IrRuOx NPs in vivo. Accordingly, this study provides a new idea for metal oxide hybrid nanoenzymes and their biological functions.

Threshold Calibration of Redox Conditions in Lacustrine Fine-Grained Sedimentary Rocks Based on the Internal Cross-Calibration of Multiple Redox Proxies: A Case Study of the Upper Triassic Chang 8–Chang 7 Members in the Southern Ordos Basin, China

Redox conditions of lacustrine strata assessed by redox proxies with unified thresholds were conflicted in the Ordos Basin. The internal cross-calibration approach of multiple redox proxies, based on the enrichment sequence model of authigenic redox-sensitive element (RSE) governed by redox potential, has recently been proposed to calibrate redox thresholds in marine depositional systems. However, this assessment model often induces an overlapped threshold between anoxic–ferruginous and anoxic–euxinic conditions. Except for the redox potential, the enrichment of RSE is also controlled by its host phase. Thus, we introduced the enrichment degree and occurrence state model controlled by the host phase content into this approach to identify anoxic–euxinic conditions by an enrichment threshold of Mo (or U). Based on this method including double redox assessment models, we calibrated the thresholds of various redox conditions of the Chang 8–Chang 7 Members in the southern Ordos Basin. Subsequently, the effectiveness of previous bi-element proxies, the evolution of redox conditions, and their influencing factors were analyzed based on the calibrated thresholds. Results show that this method is applicable in the lacustrine strata. The cross plot of DOPT (degree of pyritization based on the total Fe and S content) (or SEF)–MoEF (or UEF) (enrichment factor) is suggested for calibrating thresholds of different redox conditions. Previous bi-element proxies are not suggested to be used again. There is a positive redox evolution sequence from oxic–suboxic (suboxidized) to anoxic–euxinic conditions in Chang 8–Chang 7 Members. Hydrothermal activity and paleoproductivity play different roles in the formation of redox conditions.

Sn-Doping in a Sb2Se3 Conversion-cum-Alloying Material Renders Efficient Sodium-Ion Electrochemical Performance: Facile Kinetics Achieved by Active Metal Doping

Conversion-cum-alloying anode materials have particularly been sought after as promising high-capacity Na+ anode materials owing to a double redox alkali-ion uptake offered by them. The addition of electrochemically nonactive conducting additives to enhance the sluggish kinetics of the conversion/deconversion step although instrumental in enhancing the kinetics ends up in a considerable decline in electrochemical capacity. Herein, we demonstrate an alternative strategy of doping an ultra-active Sn element in the well-known conversion-cum-alloying Na+ battery anode, Sb2Se3. The Sn-doped Sb2Se3 phase, Sn0.2Sb1.8Se3, besides depicting an enhanced capacity (reversible capacity of 520 mA h g–1) and cyclic stability, delivered an excellently improved rate performance (360 mA h g–1 at a current of 500 mA g–1) in comparison to pristine Sb2Se3 which delivers a capacity of 45 mA h g–1 at the same current density. Electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) lend support to improved kinetics of the conversion/deconversion process. The enhanced kinetics reflects in larger anodic peak currents (147 mA g–1 for Sn0.2Sb1.8Se3 against 32 mA g–1 for Sb2Se3) in CV plots and reduced charge-transfer resistance (RCT of 350 Ω for Sn0.2Sb1.8Se3 against 670 Ω for Sb2Se3) in EIS measurements. The electrochemical galvanostatic intermittent titration technique reveals a 3-order-magnitude increase in the diffusion coefficients (2.02 × 10–14–6.6 × 10–11 cm2 s–1) in the Sn0.2Sb1.8Se3 in comparison to pristine Sb2Se3 (2.5 × 10–17–4.2 × 10–14 cm2 s–1).

Nitric oxide-mediated regulation of mitochondrial protective autophagy for enhanced chemodynamic therapy based on mesoporous Mo-doped Cu9S5 nanozymes

The depletion of reactive oxygen species (ROS) by glutathione (GSH) and oxidative stress induced protective autophagy severely impaired the therapeutic effect of chemodynamic therapy (CDT). Therefore, how to construct a CDT treatment nanosystem with high yield and full utilization of ROS in tumor site is the main issue of CDT. Herein, a multifunctional cascade bioreactor based on mesoporous Mo-doped Cu9S5 (m-MCS) nanozymes loaded with L-Arginine (LA), abbreviated as m-MCS@LA, is constructed for realizing enhanced CDT promoted by ultrasound (US) triggered gas therapy. The m-MCS based on the catalytic performance of multivalent metal ions, which were served as nanozymes, exhibit enhanced Fenton-like and glutathione (GSH) peroxidase-like activities in comparison to Cu9S5 nanoparticles without Mo-doping. Once placed in tumor microenvironment (TME), the existence of redox couples (Cu+/Cu2+ and Mo4+/Mo6+) in m-MCS enabled it to react with hydrogen peroxide (H2O2) to generate ·OH for achieving CDT effect via Fenton-like reaction. Meanwhile, m-MCS could consume overexpressed GSH in tumor microenvironment (TME) to alleviate antioxidant capability for enhancing CDT effect. Moreover, m-MCS with mesoporous structure could be employed as the carrier to load natural nitric oxide (NO) donor LA. US as the excitation source with high tissue penetration can trigger m-MCS@LA to produce NO. As the gas transmitter with physiological functions, NO could play dual roles to kill cancer cells through gas therapy directly, and enhance CDT effect by inhibiting protective autophagy simultaneously. As a result, this US-triggered and NO-mediated synergetic cancer chemodynamic/gas therapy based on m-MCS@LA NPs can effectively eliminate primary tumor and achieved tumor-specific treatment, which provide a possible strategy for developing more effective CDT in future practical applications. Statement of SignificanceThe depletion of reactive oxygen species (ROS) by glutathione (GSH) and oxidative stress induced protective autophagy severely impaired the therapeutic effect of chemodynamic therapy (CDT). Herein, a multifunctional cascade bioreactor based on mesoporous Mo-doped Cu9S5 (m-MCS) nanozymes loaded with L-Arginine (m-MCS@LA) is constructed for realizing enhanced CDT promoted by ultrasound (US) triggered gas therapy. The m-MCS with double redox couples presents the enhanced enzyme-like activities to perform cascade reactions for reducing GSH and generating ROS. LA loaded by m-MCS can produce NO triggered by US to inhibit the mitochondria protective autophagy for reactivating mitochondria involved apoptosis pathway. The US-triggered and NO-mediated CDT based on m-MCS@LA can effectively eliminate primary tumor through the high yield and full utilization of ROS.

(Digital Presentation) Recent Development of the Cobalt Free and Lithium Rich Manganese Based Disordered Rocksalt Oxyfluorides As a Cathode Material for Lithium Ion Batteries

Recently, new types of cation disordered rocksalt (DRS) have been reported which show good reversibility. In our study we combined the strategy of using high-valent cations with partial substitution of fluorine for oxygen anions in disordered rocksalt-structure phase to achieve optimal Mn2+/Mn4+ double-redox reaction in the composition system Li2MnxTi1-xO2F (1/3 ≤ x ≤ 1). we synthesized 4 different compositions (Li2MnIIIO2F, Li2MnII 1/3MnIII 1/3TiIV 1/3O2F, Li2MnII 1/2TiIV 1/2O2F and Li2MnII 1/3TiIII 1/3TiIV 1/3O2F). Two of them were synthesized for the first time, Li2MnII 1/3MnIII 1/3TiIV 1/3O2F and Li2Mn II 1/3TiIII 1/3TiIV 1/3O2F. By studying the electrochemical properties of different compounds we found that Ti+4 in the structure keeps Mn at the second state of charge, thus enabling a double redox reaction of Mn2+/Mn4+. By investigating the electrochemical properties of all samples we found that the sample with the composition Li2Mn2/3Ti1/3O2F showed the best electrochemical properties with initial high discharge capacity of 227 mAh g-1 in the voltage window of 1.5-4.3 V and 82% of capacity retentionafter 100 cycles. However, fluorination might lead to several issues such as synthesis limitation, lithium diffusion issues due to preferable strong Li-F bonds, etc. thus, two more different samples based on the Li2Mn2/3Ti1/3O2F composition were synthesized and their properties were investigated (Li1.5MnII 1/3MnIII 1/3TiIV 1/3O2F0.5 and Li1.25MnII 1/3MnIII 1/3TiIV 1/3O2F0.25) in order to find the proper amount of fluorine in the structure which promises the electrochemical behavior. In the following the effect of fluorine on lithium diffusion was investigated by ex-situ Raman studies. These studies shed light on the diffusion pathways of lithium ions during charge and discharge process. The structural characteristics are examined using X-ray diffraction patterns, Rietveld refinement, energy-dispersive X-ray spectroscopy and scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The oxidation states and charge transfer mechanism are also studied further using extended X-ray absorption fine structure and X-ray photoelectron spectroscopy in which the results approve the double redox mechanism of Mn2+/Mn4+ in agreement with Mn-Ti structural charge compensation. The findings pave the way for designing high capacity electrode materials with multi-electron redox reactions.

Achieving reversible Mn2+/Mn4+ double redox couple through anionic substitution in a P2-type layered oxide cathode

P2-type Mn-based layered oxides have emerged as promising cathode materials for sodium-ion batteries (SIBs) due to their high theoretical capacity. However, the incorporation of Mn3+ cations induce severe Jahn-Teller (J-T) effect, which seriously distorts the localized lattice structure and results in insufficient battery performance. Herein, we successfully introduce reversible Mn2+/Mn4+ double redox couple into P2-type Na0.6Mg0.3Mn0.7O2 cathode with suppressed J-T effect through F anion doping strategy. The comprehensive results clearly suggest that F-substitution with an appropriate amount enlarges the interlayer spacing and reduces the band gap, resulting in accelerated charge transfer kinetics. In addition, the strong interaction between Mn and F suppresses the Mn2+ dissolution at discharged states and promotes the reversible conversion from Mn2+ to Mn4+ at charged states, leading to ameliorated J-T effect and enhanced electrochemical performance. Moreover, the oxygen redox reaction is also enhanced through F anion doping strategy. Our present study provides an effective avenue to address the J-T effect by introducing reversible Mn2+/Mn4+ double redox couple in Mn-based oxides, which is expected to revive this cathode family toward practical applications of SIBs.

Ti3C2@WSe2 as photoelectractive materials coupling with recombinase polymerase amplification for nucleic acid detection

The photoelectrochemical biosensor based on double redox cycle amplification technology coupled with Tungsten diselenide and MXene-modified electrode was developed. Signal amplification technology is a commonly used method to improve the sensitivity. In this article, in the double redox cycle amplification method, p-aminophenol is used as the signal molecule, and squaric acid acts as a redox indicator. Tris(2-carboxyethyl) phosphine is an excellent reducing agent, which greatly improves the photoelectric response. Tungsten diselenide and MXene are used as photosensitive materials. In the presence of model target, respiratory syncytial virus RNA, the recombinase polymerase amplification process occurred because there is amplification template, so that the signal molecule p-aminophenol will be produced, leading to redox cycle was carried out, and the photocurrent signal is improved. In the absence of syncytial virus RNA, the photocurrent signal is low. The detection range of the biosensor is from 0.2 fM to 80 fM, and the detection limit reaches 30 aM for respiratory syncytial virus RNA. The method of introducing redox cycle amplification and Tungsten diselenide, MXene into photoelectrochemical biosensing provides a new idea for future biological analysis and has application potential.