MnO2 Nanowires Research Articles

MnO2 Nanowires with Sub-10nm Thick Conjugated Microporous Polymers as Synergistic Triboelectric Materials.

MnO2 nanowires coated with conjugated microporous polymers (CMP) are applied as triboelectric energy harvesting materials. The tribopositive performance of the CMP shells is enhanced with the assistance of MnO2 nanowires (MnO2 NW), likely due to cationic charge transfer from the tribopositive CMP layers to the surface Mn2+ and Mn3+ species of MnO2 NW. This is supported by model studies. The MnO2@CMP-2 with sub-10nm thick CMP layers shows promising triboelectric output voltages up to 576V and a maximum power density of 1.31mWcm-2. Spring-assisted triboelectric nanogenerators fabricated with MnO2@CMP-2/PVP-3 films are used as power supplies to operate electronic devices.

The microwave absorption performance of CF coated with MnO2 nanowires grown by simple hydrothermal method

Microwave absorber can effectively reduce the influence of electromagnetic interference. MnO2 nanowires were deposited on the CF surface by adopting a simple one-step hydrothermal method to fabricate MnO2/CF composites in order to obtain a high-performance microwave absorber. Its microwave absorption (MA) performance and microstructure could be manipulated by adjusting the coating amount. The introduction of MnO2 makes composites possess good MA performance by improving impedance matching. The minimum reflection loss (RLmin) of the MnO2/CF composite is −42.9 dB (1.2 mm, 17.6 GHz), and its effective absorption bandwidth (EAB) reaches 3.84 GHz (1.6 mm). Moreover, its effective absorption band Δƒ (0.5–4 mm thickness) reaches 11.6 GHz. It shows that the MnO2/CF composite could be regarded as an ideal microwave absorber for high frequency.

MnO2 nanowires modified reduced graphene oxide thick film cathode for aqueous zinc-ion prismatic battery

Aqueous zinc-ion batteries are an excellent alternative to lithium-ion batteries that can meet the energy requirements while also being safe and eco-friendly. However, developing a suitable cathode material with good energy density and high-rate capability is challenging. In this study, we developed an aqueous zinc-ion battery with a high surface area MnO2 nanowires modified reduced graphene oxide nanocomposite screen printed interdigitated array electrodes and a distinctive aqueous electrolyte comprising 1 M each of ZnSO4 and Na2SO4, 0.1 M MnSO4, and 0.8 mM sodium dodecyl sulfate. The charge-discharge curves reveal that the cathode material exhibits a high reversible storage capacity of 164 mAh g−1 at a current density of 50 mA g−1. The battery retained 99.59% of its Coulombic efficiency after 300 cycles when cycled at a high current rate of 300 mA g−1. The prismatic battery realized exhibited a calculated energy density of 505.5 Wh kg−1 which is higher than previously reported works. On account of the large energy density and high rate capability coupled with non-toxic components, low cost and facile fabrication method, the Zn||MnO2/rGO battery shows good promise for energy storage application.

Tailoring MnO2 nanowire defects with K-doping for enhanced electrochemical energy storage in aqueous supercapacitors

The fabrication of supercapacitors with outstanding performance is presented with a distinct defect-rich nanostructures. A one-pot, energy-efficient method for synthesizing defective manganese dioxide nanowires doped with potassium (K0.35MnO2) was developed. The introduction of potassium ions at 35 % birnessite resulted in a significant increase in lattice defects and an improvement in conductivity. Addition of KOH induces a phase transition from α-MnO2 to δ-MnO2. These imperfections result in a greater quantity of active sites, which are crucial for the process of energy storage. The K0.35MnO2 structure demonstrates a 405F/g increased capacity at a current density of 1 A/g. The asymmetric supercapacitor (K0.35MnO2/AC) that was manufactured exhibits a capacitance of 106.4F/g when operating at 1 A/g, while maintaining a maximum energy density of 71.5 Wh kg−1 and a power density of 672 W kg−1. Furthermore, 92.7 % of the initial capacitance of the device is retained even after 8,000 cycles at 20 A/g. This study presents novel insights into the production of defective materials for energy storage applications through the utilization of a one-pot process as opposed to the multi-step method. In order to produce high-performance supercapacitors for practical applications, the results indicate that defect engineering is a crucial factor.

Preparation of unique corn-stalk-like MnO₂/CoNi nanowires via in situ epitaxial attachment growth for monitoring environmental pollutant hydrazine

This paper presents the synthesis of a novel corn-stalk-like MnO₂/CoNi oxide composite using an in situ epitaxial attachment growth strategy, in which CoNi oxide nanosheets are anchored onto MnO₂ nanowires. The one-dimensional MnO₂ nanowires, with their large specific surface area, serve as a support to enhance the electronic conductivity of the CoNi oxides. Hexamethylenetetramine (HMTA) is employed as an alkaline linking agent, playing a key role in shaping the CoNi oxide nanosheets and ensuring their successful growth on the MnO₂ nanowires. The MnO₂/CoNi oxide composite-based electrochemical sensor exhibits excellent synergistic and interfacial effects, promoting electron transfer and charge migration. This composite material shows outstanding electrocatalytic performance for hydrazine detection, with a broad linear range (0.48−6106.58 μM), low detection limit (0.286 μM, S/N = 3), and high sensitivity (0.037 μA μM⁻1). Moreover, when tested for hydrazine detection in water samples, the sensor achieved a recovery rate of 95.7–105 %, highlighting its high sensitivity and rapid response in practical applications.

MnO2/rGO bifunctional catalyst and support materials for gel polymer electrolyte based Zn-air batteries

A high-performance and long-lasting, rechargeable Zn-air battery requires a reliable and effective bifunctional catalyst material to facilitate the oxygen reduction and oxygen evolution reactions during the battery operation. Manganese oxide (MnO2) is a promising non-precious perspective due to its multivalency and various polymorphic structures that effectively catalyze oxygen evolution and reduction. In the present work, MnO2 nanowires (NWs) have been integrated with over-reduced graphene oxide (rGO) in various concentrations via a facile hydrothermal route. The synthesized materials, tested in lab-made zinc-air battery devices fabricated using gel polymer electrolyte, exhibit a significant enhancement in the performance and 2–3 times the cycle life compared to the bare MnO2. The ZAB device was tested for galvanostatic charge-discharge technique, and results exhibit a cycle life of 165 h (495 cycles@20 min per cycle) when discharged up to 1.0 V at a current density of 5.2 mA/cm2 and displayed a capacity of 731 mAh/gZn. Reduced graphene oxide acts as a support material that enhances the conductivity and surface area of the active material and also provides active sites for catalysis. This work signifies the importance of the engineering of the catalyst, support material, and additives, as slight changes may result in a significant enhancement in the cycle life.The appropriate composition of catalyst and support material and a compatible gel polymer electrolyte facilitates the fabrication of flexible zinc-air batteries for various applications.

S‐Scheme MnO2/Co3O4 Sugar‐Gourd Nanohybrids with Abundant Oxygen Vacancies for Efficient Visible‐Light‐Driven CO2 Reduction

AbstractConverting CO2 to carbon‐based fuels using solar energy via photocatalysis is a promising approach to boost carbon neutrality. However, the solar‐to‐chemical conversion efficiency is hampered by interconnected multiple factors including insufficient light absorption, low separation efficiency of photogenerated carriers as well as complex and sluggish surface reaction kinetics. Herein, we incorporate MnO2 nanowires and Co3O4 hollow polyhedrons with abundant oxygen vacancies (VO) into MnO2/Co3O4 sugar‐gourd nanohybrids for boosting CO2 photoreduction. The MnO2/Co3O4 nanohybrids not only display strong absorption in the visible–near infrared region, but also facilitate the separation of photogenerated carriers in terms of S‐scheme transfer pathway, supplying abundant electrons for CO2 reduction reaction. Furthermore, the presence of VO enhances the separation efficiency of photogenerated carriers and promotes the chemical adsorption to CO2 molecules. In addition, the interfacial electronic interaction between MnO2 and Co3O4 also contributes to the chemical adsorption and activation to CO2. Owing to the synergy of S‐scheme transfer pathway and VO, the MnO2/Co3O4 hybrids exhibit greatly enhanced photocatalytic activity towards CO2 reduction under the irradiation of visible light in comparison with bare MnO2 and Co3O4, delivering a CO evolution rate of 15.9 umol g−1 h−1 with a 100 % selectivity.

Seeding Layer Effect on the Microstructure of Hydrothermally Grown α‐Manganese Dioxide Nanowires on Three‐Dimensional Graphene Foam

AbstractHydrothermal synthesis is a straightforward approach for producing high‐yield manganese dioxide (MnO2) nanostructures with efficient morphological control at low temperatures. This study investigates the microstructural dependency of hydrothermally grown α‐MnO2 nanowires (NWs) on pre‐treatment conditions on the substrate surface. Within this scope, α‐MnO2 NWs were synthesized on chemical vapor deposition (CVD)‐based graphene foam (GF) substrates pre‐treated via potassium permanganate (KMnO4) solution as a seeding layer with different concentrations (0.025, 0.050, 0.075, 0.1 M). A direct α‐MnO2 NWs growth (without pre‐treatment) was also performed on GF by hydrothermal method. The seeding layer effect on the NWs growth was elaborated to comprehend the process‐structure correlations by characterizing the resultant graphene foam/α‐MnO2 nanowires (GF/α‐MnO2 NWs) nanocomposites through Scanning Electron Microscopy (SEM), Raman Spectroscopy, X‐Ray Diffraction (XRD), and X‐Ray Photoelectron Spectroscopy (XPS). SEM, XRD, and Raman Spectroscopy revealed the successful acquisition of highly crystalline α‐MnO2 in one‐dimensional nanowire morphology on the high‐quality GF. Moreover, XPS results confirmed that all nanocomposites comprise α‐MnO2 and graphene without chemical degradation. Consequently, slight changes in solution concentration of seeding layers caused a noticeable alteration in the nanowire's structure, which could ensure effective control of nanocomposite properties without sacrificing the high purity of each component.

Robust porous artificial layers with boosted lithiophilicity and Li+ diffusion for dendrite-free Li metal anodes

Li has been considered to the most prospective anode for Li batteries because of the lowest redox potential and high theoretical capacity. However, the practical application is hindered by uncontrolled dendrite growth. Herein, a robust porous PVDF/MnO2 (RP-PVDF/MnO2) artificial layer is introduced on Li to form RP-PVDF/MnO2@Li anodes. The porous structure can accelerate Li+ transfer kinetics, while the excellent lithiophilicity of the MnO2 guides the uniform Li nucleation. Meanwhile, the robust RP-PVDF/MnO2 films assembled by the PVDF and ultralong MnO2 nanowires deliver a high Young's modulus of 303 MPa, enabling the mechanical integrity of the artificial layers. As a result, the RP-PVDF/MnO2@Li symmetric half-cells demonstrate remarkable stability up to 3200 h at 10 mAh cm−2 and 10 mA cm−2. The RP-PVDF/MnO2@Li||LiFePO4 (LFP) full-cells maintain 83.5 % capacity retention after 1600 cycles at 2C. Even under harsh cycling condition with a LFP loading of 21.0 mg cm−2, electrolyte/capacity (E/C) of 9.0 g Ah−1 and negative/positive (N/P) of 3.0, the RP-PVDF/MnO2@Li||LFP full-cells can deliver 85.4 % capacity retention after 140 cycles. This work illustrates superiority of robust lithiophilic artificial layers with boosted Li+ transfer kinetics for advanced metal batteries.

Study on the Performance of Aniline Electrodeposited on MnO2 Nanowire as an Anode for Sodium-Ion Batteries.

Manganese dioxide is an ideal anode for sodium-ion batteries due to its rich crystal shapes. However, its low conductivity, low reversible discharge capacity, slow diffusion kinetics, and poor cyclic stability limit its potential for industrial application. The design of manganese dioxide (MnO2) with various morphologies, such as nanowires, nanorods, and nanoflowers, has proven effective in enhancing its electrochemical performance. Stacking nanowire structures is of interest as they increase the open space by forming an interconnected network, thus facilitating favorable diffusion pathways for sodium ions. Concurrently, the substantial increase in the electrolyte contact area efficiently mitigates the strain induced by the volume expansion associated with the repetitive migration and insertion of sodium ions. Based on previous research, this work presents the structural design of flexible MnO2/polyaniline (MnO2/PANI) nanowires assembled on carbon cloth (CC), an innovation in MnO2 modification. Compared to conventional MnO2 nanowires, the MnO2/PANI nanowires exhibit enhanced structural stability and improved dynamic performance, thereby marking a significant advancement in their material properties. This MnO2/PANI composite exhibits a rate capacity of approximately 200 mA h g-1 after 60 cycles at a current density of 0.1 A g-1, and maintains a rate capacity of 182 mA h g-1 even after 200 cycles under the same current density. This study not only provides new insights into the underlying mechanisms governing energy storage in MnO2/PANI nanowires but also paves the way for their further development and optimization as anodes for sodium-ion batteries, thereby opening up fresh avenues for research and application.

Realizing highly conductive “polymer in salt” electrolytes through Li-ion-highway for room temperature all-solid-state Li-S batteries

“Polymer in salt” electrolytes (PISEs) have great application prospects because of their higher ionic conductivity than conventional solid polymer electrolytes (SPEs) at room temperature. However, it is still a challenge to realize both high ionic conduction and mechanical properties for PISEs. Here we address the issue by comprising interconnected ultra-long MnO2 nanowires modified with (3-Aminopropyl)trimethoxysilane (AMW) in PAN-LiTFSI-based PISEs. The presence of AMW reinforces the mechanical properties and aids Li-ion migration between ionic aggregates through a “hand-to-hand” mode. The resulting electrolyte (PIS-AMW) exhibits a high tensile strength of 2.77 MPa, ionic conductivity of 4.44 × 10−4 S cm−1 and Li-ion transference number of 0.61 at 25 °C. Li symmetric cells assembled with PIS-AMW demonstrate satisfactory cycling stability for up to 600 h. All-solid-state lithium‑sulfur batteries assembled with this electrolyte exhibit a capacity of 643 mAh g−1 at 0.05C and 25 °C after 80 cycles. The strategy effectively resolves the dilemma between long-range ionic conduction and mechanical properties in PISEs, which have potential applications in high-energy-density solid-state batteries.

Improved near-resonant two photon absorption of α-MnO2 nanowires surface functionalized reduced graphene oxide sheets

The versatile study of graphene derivatives has resurgence of interest on understanding its nonlinear optical response at different nanoscales. Nanostructured manganese dioxide: reduced graphene oxide (MnO2: rGO) hybrids were synthesized by reduction method by varying the content of rGO (5, 10, 15 & 20 wt%). X-ray Photoelectron Spectroscopy studies confirmed the surface functionalization of MnO2 on rGO. Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Tunnelling Electron Microscopy (HRTEM) witness that with respect to the content of rGO, the morphology of MnO2 varies radically from clusters to nanorods to nanowires over the surface of rGO sheets. Ground state absorption spectra of the hybrids have absorption edge at 268 nm corresponding to combined metal oxide charge transfer between rGO (π-π* transition of CC and n-π transition of C-O bonds) and MnO2 (d-d transition). Moreover, hierarchical MnO2 nanowire network resided on 2D rGO sheets involves broad absorption at the visible spectral domain due to polaron transition as well the localization of π- π* transited electrons that facilitates the probability of occurrence of excited state absorption. Intensity dependent open aperture Z-scan technique of the prepared hybrids using Q-switched Nd: YAG 532 nm nanopulsed laser reveals unusual transitions and enhanced nonlinear absorption. MnO2:(5 wt%) rGO shows saturable absorption (SA) at low intensity and changeover dynamically to reverse saturable absorption (RSA) at higher intensity. MnO2:(10 & 15 wt%) rGO exposes coupled nonlinear absorption (SA + RSA) owing to the combined effect of graphene (π-states) and MnO2 (σ-states). MnO2:(20 wt%) rGO exhibits a stronger RSA ascribed to sequential two photon absorption. The third-order nonlinear absorption coefficient and limiting threshold of MnO2: rGO (20 wt%) are 4.04 ×10-10 m/W and 0.84 ×1012 W/m2, which shows five-fold increase compared to bare rGO and MnO2. The obtained results propose that the optical nonlinearity of MnO2 nanowires surface functionalized rGO sheets can significantly be tuned to meet the requirements for fabricating laser safety devices.

A spiral-windable, free-standing, durable membrane constructed with ultralong hydrogel@MnO2 nanowires for oil/water separation under harsh environment

An ideal membrane for oil/water separation at industrial scale is expected to possess the combined merits of excellent separation performance, sound mechanical flexibility, and high durability under harsh environments. In response to these challenging requirements, we came up with a new concept to design the membrane constructed with ultralong hydrogel-functionalized MnO2 nanowires. The super-oleophobic nanowires form highly open and tight pore structures within the membrane, which endows its high permeation flux (2800 L h−1 m−2 bar−1), high oil/water separation efficiency (>99 %) and low fouling tendency for separating emulsified oil from water. Furthermore, the brittleness problem of MnO2 materials is collectively resolved due to the high aspect ratio and surface functionalization of the hydrogel-functionalized MnO2 nanowires. This results in the new membrane with extraordinary mechanical flexibility and potential for spiral-wound membrane modules, which are highly desired in industrial applications due to a lower footprint and lower capital cost. The new membrane also demonstrates high durability under harsh environments with non-neutral pH values or high salinities. Given its facile synthesis process and inexpensive materials, this spiral-windable and durable membrane with high separation performance has the great potential to be applied at industrial scale for oily wastewater treatment under harsh environments.

High mass loading potassium ion stabilized manganese dioxide nanowire forests for rechargeable Zn batteries

Manganese dioxide (MnO2) represents an ideal cathode material for rechargeable aqueous Zn batteries due to its high theoretical capacity (308 mAh g−1), suitable potential (1.4 V vs. Zn2+/Zn), natural abundance, and negligible toxicity. However, the capacity and rate capability of MnO2 deteriorate significantly in thick electrodes owing to its low electrical and ionic conductivities. Herein, we report the design of high mass loading potassium ion stabilized α-MnO2 (K0.133MnO2) nanowire forests on carbon cloth through a seed-assisted hydrothermal method for Zn batteries. The vertically aligned K0.133MnO2 nanowire forests with uninterrupted charge transport afford a high area capacity of 3.54 mAh cm−2 and a capacity retention of 79.2% over 1000 cycles in aqueous electrolyte. Moreover, the high area capacity and cyclability can be readily transferred to quasi-solid-state devices.

Achieving a smooth “adsorption-diffusion-conversion” of polysulfides enabled by MnO2-ZnS p-n heterojunction for Li-S battery

The commercial application of lithium-sulfur batteries is primarily impeded by the constant shuttling of soluble polysulfides and sluggish redox kinetics. Nowadays, the discovery of the heterojunction, which combines materials with diverse properties, offers a new perspective for overcoming these obstacles. Herein, a functional coating separator for the lithium-sulfur battery is designed using a MnO2-ZnS p-n heterojunction with a spontaneous built-in electric field (BIEF). The MnO2 nanowire provides suitable adsorption capacity for polysulfides, while the abundant reactive sites brought by ZnS ensure efficient conversion. Moreover, the BIEF significantly facilitates the migration of electrons and polysulfides at the MnO2-ZnS interface, enabling a smooth “adsorption-diffusion-conversion” reaction mechanism. By serving as both the adsorption module and catalytic sites, this BIEF allows batteries utilizing separators modified with MnO2-ZnS heterojunction to achieve an impressive initial capacity of 1511.1 mAh g−1 at 0.1C and maintain a capacity decay rate of merely 0.048% per cycle at 2.0C after 1000 cycles. Even when increasing sulfur loading to 9.4 mg cm−2 in lean electrolyte (5.4 μL mg−1), the battery still exhibits an ultrahigh areal capacity of 6.0 mAh cm−2 after 100 cycles.

Facile Synthesis of Ag-Doped Urchin-like MnO2 on Carbon Cloth for Supercapacitors.

Based on MnO2/carbon cloth (CC) composite materials, an Ag-doped MnO2 nanowire, self-assembled, urchin-like structure was synthesized in situ on the surface of CC using a simple method, and a novel and efficient flexible electrode material for supercapacitors was developed. The morphology, structure, elemental distribution, and pore distribution of the material were analyzed using SEM, TEM, XRD, XPS, and BET. The electrochemical performance was tested using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). In the three-electrode system, GCD testing showed that the specific capacitance of the material reached 520.8 F/g at 0.5 A/g. After 2000 cycles at a current density of 1 A/g, the capacitance retention rate was 90.6%, demonstrating its enormous potential in the application of supercapacitor electrode materials.

An integrated electrocatalytic membrane reactor and nanofiltration system for highly efficient removal of arsenic (III) from water

Arsenic (As) contamination in drinking water and groundwater has become as a major environmental concern due to extremely strong toxicity of As. Herein, a facile, efficient and energy-saving integrated membrane process via coupling the electrocatalytic membrane reactor (ECMR) and nanofiltration (NF) membrane is developed for the arsenic removal from As(III)-contained water. The ECMR, constructed with the one-dimensional (1D) MnO2 nanowires (NWs) loaded in the flat carbon membrane as anode, exhibits superior catalytic activity for the electro-oxidation of As(III). The maximum conversion rate of As(III) to As(V) achieves 96.0 % in the ECMR. The NF membrane is employed to filter the resultant permeate from ECMR. The concentration of As(V) after NF treatment is reduced to below 10 μg L−1 (99.5 % removal rate of As(V)) even if the As(III) concentration in the feed solution of ECMR is up to 2000 μg L−1, under a reaction temperature of 20 °C, a current density of 0.4 mA cm−2, a residence time of 10 min, an electrolyte Na2SO4 concentration of 15 g L−1 reaction conditions. The energy consumption of the whole integrated process was only 0.00211 kWh/μgAs. The superior catalytic performance of ECMR with 1D MnO2 NWs can be attributed to large electrochemical active surface area, 1D nanostructure with highly exposed (310) plane of 1D MnO2 NWs as well as strong interaction of oxide with the carbon membrane surface and the porous structure.

Efficiency and synergy of MnO2@LDO for arsenic and fluoride simultaneous sorption from water

High levels of groundwater containing both arsenic and fluorine are prevalent, resulting in serious health problems when consumed as drinking water. This co-pollution phenomenon is widespread and requires urgent attention. The multiple forms of arsenic and arsenic–fluorine co-contamination pose a significant challenge to efficiently co-remove both substances. This research utilized a green and stable synthesis approach to create MgLaFe layered double oxide (LDO) heterostructures, which were anchored on α-MnO2 nanowires. The materials comprise magnesium and lanthanum elements with a powerful attraction toward fluoride ions; elemental iron, which can establish stable compounds with arsenate; and MnO2, which can effectively oxidize arsenous acid, thereby enabling efficient co-removal of arsenic and fluorine. The efficient oxidation process of the MnO2 nanowire and the prompt ion adsorption process of the LDO work together synergistically. The adsorption performance was assessed through isotherms and kinetic fitting. Chemisorption was found to be the process for As(Ⅲ), As(V), and F− adsorption, with As(Ⅲ) going through monolayer adsorption on the surface of MnO2 nanowires, while As(V) and F− were mainly adsorbed by multilayer process on LDO. The maximum adsorption capacities were 111.76, 230.51, and 765.10 mg/g for As(Ⅲ), As(V), and F−, respectively. The x-ray photo-electronic spectroscopy analysis provided further elucidation on the adsorption mechanism of the MnO2@LDO heterostructure, detailing each component's role in the process. The results confirm the successful construction of the heterostructure and the efficient coupling of oxidation and adsorption.

Dual p-n Z-scheme heterostructure boosted superior photoreduction CO2 to CO, CH4 and C2H4 in In2S3/MnO2/BiOCl photocatalyst

The creation of a Z-scheme heterojunction is a sophisticated strategy to enhance photocatalytic efficiency. In our study, we synthesized an In2S3/MnO2/BiOCl dual Z-scheme heterostructure by growing BiOCl nanoplates on the sheets of In2S3 nanoflowers, situated on the surface of MnO2 nanowires. This synthesis involved a combination of hydrothermal and solution combustion methods. Experiments and density functional theory (DFT) calculations demonstrated that the In2S3/MnO2/BiOCl composite exhibited notable photo reduction performance and photocatalytic stability. This was attributed to the pivotal roles of BiOCl and MnO2 in the composite, acting as auxiliaries to enhance the electronic structure and facilitate the adsorption/activation capacity of CO2 and H2O. The yield rates of CO, CH4, and C2H4 over In2S3/MnO2/BiOCl as the catalyst were 3.94, 5.5, and 3.64 times higher than those of pure In2S3, respectively. Photoelectrochemical analysis revealed that the dual Z-scheme heterostructure, with its oxygen vacancies and large surface area, enhanced CO2 absorption and active sites on the nanoflower/nanowire intersurfaces. Consequently, the dual Z-scheme charge transfer pathway provided efficient channels for boosting electron transfer and charge separation, resulting in high C2H4, CH4, and CO yields of formed and exihibits an promising photoreduction rate of CO2 to CO (51.2 µmol/g.h), CH4 (42.4 µmol/g.h) and C2H4 (63.2 µmol/g.h), respectively. DFT, in situ Diffuse reflectance infrared fourier transform spectroscopy, and temperature-programmed desorption tests were employed to verify the intermediates pathway. The study proposed a potential photocatalytic mechanism based on these findings.

Self-supporting oxygen vacancy-rich α-MnO2 nanowire/few-layer graphite/SWNT bundle composite film for high-performance flexible aqueous zinc-ion battery cathode

The increasing demand for flexible and wearable electronic devices has led to widespread interest in flexible electrochemical energy storage devices. However, the transformation of the battery structure from conventional to flexible presents a great challenge to the battery design. Herein, we developed a facile method for the preparation of a self-supporting composite film consisting of oxygen-vacancy rich MnO2 nanowires (NWs), few-layer graphite nanosheets (FLGs), and single-walled carbon nanotube (SWNT) bundles as the cathode of flexible zinc-ion batteries. This ternary interwoven interconnection 3D structure enhances the electrochemical performance of the battery and realizes fast charge transfer; oxygen vacancies in the MnO2 NWs caused by heat treatment (300 °C in Ar) allow for rapid intercalation and diffusion of Zn2+. The interwoven FLGs and SWNT bundles improve the electrical conductivity, and the robust interactions between the two carbon nanomaterials and the MnO2 NWs effectively make the composite film with excellent mechanical properties. This self-supporting flexible electrode exhibits a high specific capacity of 374 mAh/g at 0.4 A/g, maintains a Coulombic efficiency of ∼ 100 % after 1600 cycles at 2 A/g, and has a high energy density of 651.5 Wh kg−1 at 65.2 W kg−1. Moreover, the flexible zinc ion batteries assembled with the electrode demonstrate good mechanical properties and a high reversible specific capacity of 343 mAh/g after 75 bending cycles. Based on these findings, we believe that this composite film holds great promise as a cathode material in flexible energy storage applications.