O2 Nanosheets Research Articles

Rare Earth Doping Engineering Tailoring Advanced Oxygen-Vacancy Co3 O4 with Tunable Structures for High-Efficiency Energy Storage.

Co3 O4 with high theoretical capacitance is a promising electrode material for high-end energy applications, yet the unexcited bulk electrochemical activity, low conductivity, and poor kinetics of Co3 O4 lead to unsatisfactory charge storage capacity. For boosting its energy storage capability, rare earth (RE)-doped Co3 O4 nanostructures with abundant oxygen vacancies are constructed by simple, economical, and universal chemical precipitation. By changing different types of RE (RE=La, Yb, Y, Ce, Er, Ho, Nd, Eu) as dopants, the RE-doped Co3 O4 nanostructures can be well transformed from large nanosheets to coiled tiny nanosheets and finally to ultrafine nanoparticles, meanwhile, their specific surface area, pore distribution, the ratio of Co2+ /Co3+ , oxygen vacancy content, crystalline phase, microstrain parameter, and the capacitance performance are regularly affected. Notably, Eu-doped Co3 O4 nanoparticles with good cycle stability show a maximum specific capacitance of 1021.3Fg-1 (90.78mAhg-1 ) at 2Ag-1 , higher than 388Fg-1 (34.49mAhg-1 ) of pristine Co3 O4 nanosheets. The assembling asymmetric supercapacitor delivers a high energy density of 48.23Whkg-1 at high power density of 1.2kWkg-1 . These findings denote the significance and great potential of RE-doped Co3 O4 in the development of high-efficiency energy storage.

Balancing Activity and Stability in Spinel Cobalt Oxides through Geometrical Sites Occupation towards Efficient Electrocatalytic Oxygen Evolution.

Designing active and stable oxygen evolution reaction (OER) catalysts are vitally important to various energy conversion devices. Herein, we introduce elements Ni and Mn into (Co)tet (Co2 )oct O4 nanosheets (NSs) at fixed geometrical sites, including Mnoct , Nioct , and Nitet , to optimize the initial geometrical structure and modulate the CoCo2 O4 surface from oxygen-excess to oxygen-deficiency. The pristine (Ni,Mn)-(Co)tet (Co2 )oct O4 NSs shows excellent OER activity with an overpotential of 281.6 mV at a current density of 10 mA cm-2 . Moreover, without damaging their initial activity, the activated (Act)-(Ni,Mn)-(Co)tet (Co2 )oct O4 NSs after surface reconstruction exhibit long-term stability of 100 h under 10 mA cm-2 , 50 mA cm-2 , or even 100 mA cm-2 . The optimal balance between electroactivity and stability leads to remarkable OER performances, providing a pivotal guideline for designing ideal electrocatalysts and inspiring more works to focus on the dynamic change of each occupation site component.

Ultrathin In2 O3 Nanosheets toward High Responsivity and Rejection Ratio Visible-Blind UV Photodetection.

Photoelectrochemical-type visible-blind ultraviolet photodetectors (PEC VBUV PDs) have gained ever-growing attention due to their simple fabrication processes, uncomplicated packaging technology, and high sensitivity. However, it is still challenging to achieve high-performance PEC VBUV PDs based on a single material with good spectral selectivity. Here, it is demonstrated that individual ultrathin indium oxide (In2 O3 ) nanosheets (NSs) are suitable for designing high-performance PEC VBUV PDs with high responsivity and UV/visible rejection ratio for the first time. In2 O3 NSs PEC PDs show excellent UV photodetection capability with an ultrahigh photoresponsivity of 172.36mA W-1 and a high specific detectivity of 4.43 × 1011 Jones under 254nm irradiation, which originates from the smaller charge transfer resistance (Rct ) at the In2 O3 NSs/electrolyte interface. The light absorption of In2 O3 NSs takes a blueshift due to the quantum confinement effect, granting good spectral selectivity for visible-blind detection. The UV/visible rejection ratio of In2 O3 NSs PEC PDs is 1567, which is 30 times higher than that of In2 O3 nanoparticles (NPs) and exceeds all recently reported PEC VBUV PDs. Moreover, In2 O3 NSs PEC PDs show good stability and good underwater imaging capability. The results verify that ultrathin In2 O3 NSs have potential in underwater optoelectronic devices.

Research on the Thickness and Microstructure of Plate-like TiO2 by the Nanosheet-Seeding Growth Technique

The nanosheet-seeding growth (NSG) technique is an interesting synthesis method for preparing two-dimensional (2D) materials by employing ultrathin nanosheets as templates. In this work, the synthesis of 2D TiO2 nanoplates using Ti0.87O2 nanosheets via the NSG process is thoroughly studied to achieve a better understanding of this process. The influence of various synthesis conditions on the morphology and phase composition has been carefully examined. The study of synthesis time reveals that the TiO2 grows in the Stranski–Krastanov mode on the templates and the growth follows second-order kinetics. It is also found that the concentration of precursors and the synthesis time are the effective parameters in controlling the thickness of TiO2 nanoplates. The phase of the sample changes from anatase TiO2 to NH4TiOF3 and the morphology changes from flake to disk with the increase in the precursor concentration. The synthesis temperature has a large influence on the morphology and thickness of the sample but has little effect on the phase composition. However, the synthesis temperature changes the color of the sample, and a high temperature enlarges the light absorption range of the sample.

Active bimetallic Fe–O–Co sites built on 2D trimetallic complex spinel oxides for industrially oxygen evolution electrocatalyst

Fabrication of active and durable non-noble metal heterogeneous electrocatalysts to settle the relatively slow kinetic process and poor stability during the oxygen evolution reaction (OER) process is of great significance. Herein, we fabricate in-situ 2D Fe-based trimetallic complex spinel oxide nanosheets (FeCoNi)O4 via a polyethylene glycol-barbituric acid deep eutectic solvent-assisted route. Multiple analytical characterizations illustrate a deep understanding of the structure and composition of (FeCoNi)O4, disclosing Fe, Co, and Ni ions occupy both tetrahedrally and octahedrally coordinated positions. Meanwhile, the synergistic actions of preparing multiple-cations substitution and constructing oxygen vacancy activate covalent Fe–O–Co bonds in (FeCoNi)O4. Due to the active bimetallic Fe–O–Co sites, enhanced electronic conductivity and unique structure stability, the synthesized 2D (FeCoNi)O4 nanosheets exhibit excellent OER performance with relatively low overpotential (421 mV for 1000 mA/cm2) and long-term stability (720 mA/cm2 for 6 h) in alkaline media, which is much better than that of Fe-based bi/monometallic spinel oxides. In-situ Raman spectra and quasi-in-situ X-ray photoelectron spectroscopy results depict that O-bridged Fe–O–Co bimetallic sites promote the formation of μ(O–O) intermediates and undergo the direct O2 evolution route, thus accelerating OER.

Improved oxygen evolution reaction performance in Co0.4Mn0.6O2 nanosheets through Triple-doping (Cu, P, N) strategy and its application to Zn-air battery

In this work, we successfully synthesized bimetallic transition oxides into two-dimensional nanosheets, which expose all the catalytic sites on the surface. Then, Cu, N, and P elements were rationally doped inside the as prepared Co0.4Mn0.6O2 nanosheets to activate the Co/Mn catalytic sites. It is found that the resulting N/P-Cu0.1Co0.3Mn0.6O2/CNTs composites show an overpotential η10 of 290 mV for OER, much lower than the value measured using the original Co0.4Mn0.6O2/CNTs (463 mV). Meanwhile, N/P-Cu0.1Co0.3Mn0.6O2/CNTs also show decent performance with a half potential (E1/2) of 0.82 V vs RHE for ORR, i.e., a 702 mV voltage difference for OER and ORR, much lower than other transition metal oxide catalysts. By using N/P-Cu0.1Co0.3Mn0.6O2/CNTs as a cathodic catalyst for ZAB, we measured superior performance, with a peak power density of 108.1 mW cm−2 and stable operation for over 200 h at 10 mA cm−2, better than IrO2-Pt/C-based ZAB.

The novel LiMn1.8Al0.2O4 nanosheets for high energy and power density supercapacitor cathode applications

The novel LiMn1.8Al0.2O4 nanosheets for high energy and power density supercapacitor cathode applications

Multilayer films of exfoliated 2D oxide nanosheets by electrospray deposition

The potential of the electrospray deposition technique as new method to make nanosheet-based multilayer films is evaluated. Densely packed nanosheet-based films with thicknesses of 1–20 nm with rms roughnesses of 2.1–2.4 nm were fabricated on samples of 1 cm2 size with a growth rate of 0.5 nm/min. Electrosprayed Ti0.87O2 nanosheet films were successfully used as oriented growth templates for 40 nm perovskite SrRuO3 thin films grown by pulsed laser deposition. The electrospray method provides a fast and easy alternative to the more commonly used Langmuir–Blodgett (LB) deposition method for nanosheet films.

Crystal Surface Engineering Induced Active Hexagonal Co2 P-V2 O3 for Highly Stable Lithium-Sulfur Batteries.

Purposeful control of the highly active crystal planes is an effective strategy to improve the nanocrystalline catalytic activity. Therefore, Co2 P nanocrystals with high exposure of (211) lattice plane loaded at 2D hexagonal V2 O3 nanosheets (H-Co2 P-V2 O3 ) are designed via the control of morphology. After optimization, this H-Co2 P-V2 O3 boosts the redox kinetics of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSBs), which is due to the increase of the Co-active sites by exposing more (211) lattice planes of Co2 P, and the high adsorption and catalysis characteristic of H-Co2 P-V2 O3 for the conversion of LiPSs into LSBs. In the case of modification separator by H-Co2 P-V2 O3 composite, the battery achieves an outstanding reversibility of 876.9 mAh g-1 over 500 cycles at 1 C, a superior rate property of 611.5 mAh g-1 at 8 C, and a long-term cycling performance with a low attenuation of 0.04% per cycle over 1000 cycles at 4 C for LSBs. Impressively, a remarkable areal capacity of 12.38 mAh cm-2 is retained under the high sulfur loading of 14.5mg cm-2 after 100 cycles. It is believed that the crystal surface engineering provides guidance to further improve the electrochemical performance of the LSB field.

Hydrophobization Engineering of the Air-Cathode Catalyst for Improved Oxygen Diffusion towards Efficient Zinc-Air Batteries.

Poor oxygen diffusion at multiphase interfaces in an air cathode suppresses the energy densities of zinc-air batteries (ZABs). Developing effective strategies to tackle the issue is of great significance for overcoming the performance bottleneck. Herein, inspired by the bionics of diving flies, a polytetrafluoroethylene layer was coated on the surfaces of Co3 O4 nanosheets (NSs) grown on carbon cloth (CC) to create a hydrophobic surface to enable the formation of more three-phase reaction interfaces and promoted oxygen diffusion, rendering the hydrophobic-Co3 O4 NSs/CC electrode a higher limiting current density (214 mA cm-2 at 0.3 V) than that (10 mA cm-2 ) of untreated-Co3 O4 NSs/CC electrode. Consequently, the assembled ZAB employing hydrophobic-Co3 O4 NSs/CC cathode acquired a higher power density (171 mW cm-2 ) than that (102 mW cm-2 ) utilizing untreated-Co3 O4 NSs/CC cathode, proving the enhanced interfacial reaction kinetics on air cathode benefiting from the hydrophobization engineering.

Dielectric Spectroscopy and Electric Modulus Analyses of Ti0.8O2 Nanosheets‒Ag Nanoparticles‒Cellulose Filter Paper Composites

We employ dielectric spectroscopy and the complex electric modulus formalism to characterize electrical properties of the Ti0.8O2 nanosheets‒Ag nanoparticles‒cellulose filter paper composites, intended for use as a triboelectric nanogenerator. The addition of these fillers (5–17 atom% Ti and 1–6 atom% Ag) increases both the dielectric permittivity and AC conductivity while typically keeping the low loss tangent. The observed exponent to the frequency-dependent universal power law indicates the three-dimensional (3D) hopping mechanism in the composited films, contrasting with the 1D- or 2D-conduction in the ceramics. The electrical responses are also distinct from those of sole nanosheets, indicating some filler-matrix interactions. Electric modulus analyses indicate that the Ti0.8O2 nanosheets act as a charge generation/reservoir, while the Ag nanoparticles generate long-range conduction paths. The relaxation time increases with the dielectric nanosheets content but decreases with metallic nanoparticle content. In addition, these co-fillers decrease the dielectric heating but increases the refractive index of the films. The simple analyses reported herein could be applied to other composites, providing a better understanding on the role of diverse functional co-fillers.

Triple-Doping (Cu, P, N) for the Activation of Catalytic Sites in Co0.4mn0.6o2 Nanosheets for Zn-Air Battery Applications

Triple-Doping (Cu, P, N) for the Activation of Catalytic Sites in Co0.4mn0.6o2 Nanosheets for Zn-Air Battery Applications

Interface-Induced Electrocatalytic Enhancement of CO2 -to-Formate Conversion on Heterostructured Bismuth-Based Catalysts.

Electrochemical CO2 reduction reaction (CO2 RR) is a promising approach to convert CO2 to carbon-neutral fuels using external electric powers. Here, the Bi2 S3 -Bi2 O3 nanosheets possessing substantial interface being exposed between the connection of Bi2 S3 and Bi2 O3 are prepared and subsequently demonstrate to improve CO2 RR performance. The electrocatalyst shows formate Faradaic efficiency (FE) of over 90% in a wide potential window. A high partial current density of about 200mA cm-2 at -1.1V and an ultralow onset potential with formate FE of 90% are achieved in a flow cell. The excellent electrocatalytic activity is attributed to the fast-interfacial charge transfer induced by the electronic interaction at the interface, the increased number of active sites, and the improved CO2 adsorption ability. These collectively contribute to the faster reaction kinetics and improved selectivity and consequently, guarantee the superb CO2 RR performance. This study provides an appealing strategy for the rational design of electrocatalysts to enhance catalytic performance by improving the charge transfer ability through constructing a functional heterostructure, which enables interface engineering toward more efficient CO2 RR.

Fluorine Doping Induced Crystal Space Change and Performance Improvement of Single Crystalline LiNi0.6Co0.2Mn0.2O2 Layered Cathode Materials

AbstractThe Li−Ni−Co−Mn−O layered cathode materials are promising for the advanced lithium‐ion batteries due to their moderate cost and high specific capacity. However, the low electronic conductivity and poor stability at high currents need to be overcome to meet the ever‐growing demands. In this work, single crystal hexagonal nanosheets of LiNi0.6Co0.2Mn0.2O2 are synthesized by the hydrothermal process, which are further controllably doped with fluorine to improve the lithium storage performance. The fluorine doping can not only improve the layered structure, but also increase the lattice oxygen content, to promote the lithium‐ion migration and crystal structure stability of the layered LiNi0.6Co0.2Mn0.2O2. Optimized fluorine doping leads to excellent capacity and cyclic stability of the single crystal LiNi0.6Co0.2Mn0.2O2 nanosheets with an original capacity of 168.3 mAh g−1, and an excellent capacity retention rate of 94.5 % at 1.0 C over 100 cycles, which are superior to the control samples and hold potential for the lithium‐ion battery applications.

Full Solar-Spectrum-Driven Antibacterial Therapy over Hierarchical Sn3 O4 /PDINH with Enhanced Photocatalytic Activity.

Antibacterial photocatalytic therapy (APCT) is considered to be a potential treatment for administrating antibiotic-resistant bacteria. However, due to the low photocatalytic efficiency and weak ability to capture bacteria, it is not practically applied. In this work, an organic-metal oxide hybrid semiconductor heterostructure is fabricated for the photocatalytic generation of reactive oxygen species (ROS) to kill the drug-resistant bacteria. The organic semiconductor, perylene diimide (PDI), can self-assemble on Sn3 O4 nanosheets to form a "hook-and-loop" sticky surface that can capture bacteria, via large numbers of hydrogen bonding and π-π stacking interactions, which are not possible in inorganic semiconductors. This easy-to-fabricate hybrid semiconductor also possesses improved photocatalytic activity, which is owing to the formation of heterostructure that achieves full-spectrum absorption, and the reduction of the photocarrier recombination rate to produce more reactive oxygen species. It has a good promoting effect on the wounds of mice infected by Staphylococcus aureus. This work shows new ideas for fabricating smart full-spectrum inorganic-organic hybrid adhesive heterostructure photocatalysts for antibacterial photocatalytic therapy.

Ion Irradiation Inducing Oxygen Vacancy-Rich NiO/NiFe2 O4 Heterostructure for Enhanced Electrocatalytic Water Splitting.

Oxygen evolution reaction (OER) is an obstacle to the electrocatalytic water splitting due to its unique four-proton-and-electron-transfer reaction process. Many methods, such as engineering heterostructure and introducing oxygen vacancy, have been used to improve the catalytic performance of electrocatalysts for OER. Herein, the above two kinds of regulation are simultaneously realized in a catalyst by using unique ion irradiation technology. A nanosheet structured NiO/NiFe2 O4 heterostructure with rich oxygen vacancies converted from nickel-iron layered double hydroxides by Ar+ ions irradiation shows significant enhancement in both OER and hydrogen evolution reaction performance. Density functional theory (DFT) calculations reveal that the construction of NiO/NiFe2 O4 can optimize the free energy of O* to OOH* process during OER reaction. The oxygen vacancy-rich NiO/NiFe2 O4 nanosheets have an overpotential of 279mV at 10mA cm-2 and a low Tafel slope of 42mV dec-1 . Moreover, this NiO/NiFe2 O4 electrode shows an excellent long-term stability at 100mA cm-2 for 450 h. The synergetic effects between NiO and NiFe2 O4 make NiO/NiFe2 O4 heterostructure have high conductivity and fast charge transfer, abundant active sites, and high catalytic reactivity, contributing to its excellent performance.

Solution-Processed Two-Dimensional Metal Oxide Anticorrosion Nanocoating.

Molecularly thin two-dimensional (2D) nanomaterials are attractive building blocks for constructing anticorrosion nanocoatings as an ultimate pursuit in the metal-related industry. However, the nanocoating of prefocused graphene is far from industrial demands due to its high cost, low scalability, and insufficient quality. We propose all requirements to realize rational anticorrosion nanocoating of metal oxide nanosheets. The proof-of-concept study with Ti0.87O2 and Ca2Nb3O10 nanosheets demonstrates that the 10 and 20 nm thick coatings fabricated by a facile layer-by-layer (LbL) self-assembly on stainless steel (SUS) give perfect inhibition efficiency (IE) values of 99.92% and 99.89%, respectively. A driving test with a nanosheet-coated car-baffle demonstrated suitable corrosion resistance and mechanical and thermal robustness for industrial applications. The revealed and controlled thermal oxidation mechanisms are critical toward high-temperature application of the 2D oxide anticorrosion nanocoating. The advantages of nanosheet coating and extensible materials design will open a solid but exciting route to anticorrosion nanotechnology.

Titania Nanosheet Generates Peroxynitrite-Dependent S-Nitrosylation and Enhances p53 Function in Lung Cancer Cells.

Metal nanomaterials can enhance the efficacy of current cancer therapies. Here, we show that Ti0.8O2 nanosheets cause cytotoxicity in several lung cancer cells but not in normal cells. The nanosheet-treated cells showed certain apoptosis characteristics. Protein analysis further indicated the activation of the p53-dependent death mechanism. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses revealed the cellular uptake of the nanosheets and the induction of cell morphological change. The nanosheets also exhibited a substantial apoptosis effect on drug-resistant metastatic primary lung cancer cells, and it was found that the potency of the nanosheets was dramatically higher than standard drugs. Ti0.8O2 nanosheets induce apoptosis through a molecular mechanism involving peroxynitrite (ONOO−) generation. As peroxynitrite is known to be a potent inducer of S-nitrosylation, we further found that the nanosheets mediated the S-nitrosylation of p53 at C182, resulting in higher protein-protein complex stability, and this was likely to induce the surrounding residues, located in the interface region, to bind more strongly to each other. Molecular dynamics analysis revealed that S-nitrosylation stabilized the p53 dimer with a of <−1.5 kcal/mol. These results provide novel insight on the apoptosis induction effect of the nanosheets via a molecular mechanism involving S-nitrosylation of the p53 protein, emphasizing the mechanism of action of nanomaterials for cancer therapy.

Defect-Rich High-Entropy Oxide Nanosheets for Efficient 5-Hydroxymethylfurfural Electrooxidation.

High-entropy oxides (HEOs), a new concept of entropy stabilization, exhibit unique structures and fascinating properties, and are thus important class of materials with significant technological potential. However, the conventional high-temperature synthesis techniques tend to afford micron-scale HEOs with low surface area, and the catalytic activity of available HEOs is still far from satisfactory because of their limited exposed active sites and poor intrinsic activity. Here we report a low-temperature plasma strategy for preparing defect-rich HEOs nanosheets with high surface area, and for the first time employ them for 5-hydroxymethylfurfural (HMF) electrooxidation. Owing to the nanosheets structure, abundant oxygen vacancies, and high surface area, the quinary (FeCrCoNiCu)3 O4 nanosheets deliver improved activity for HMF oxidation with lower onset potential and faster kinetics, outperforming that of HEOs prepared by high-temperature method. Our method opens new opportunities for synthesizing nanostructured HEOs with great potential applications.

Atomic-scale regulation of anionic and cationic migration in alkali metal batteries

The regulation of anions and cations at the atomic scale is of great significance in membrane-based separation technologies. Ionic transport regulation techniques could also play a crucial role in developing high-performance alkali metal batteries such as alkali metal-sulfur and alkali metal-selenium batteries, which suffer from the non-uniform transport of alkali metal ions (e.g., Li+ or Na+) and detrimental shuttling effect of polysulfide/polyselenide anions. These drawbacks could cause unfavourable growth of alkali metal depositions at the metal electrode and irreversible consumption of cathode active materials, leading to capacity decay and short cycling life. Herein, we propose the use of a polypropylene separator coated with negatively charged Ti0.87O2 nanosheets with Ti atomic vacancies to tackle these issues. In particular, we demonstrate that the electrostatic interactions between the negatively charged Ti0.87O2 nanosheets and polysulfide/polyselenide anions reduce the shuttling effect. Moreover, the Ti0.87O2-coated separator regulates the migration of alkali ions ensuring a homogeneous ion flux and the Ti vacancies, acting as sub-nanometric pores, promote fast alkali-ion diffusion.