Unconventional grain growth suppression in oxygen-rich metal oxide nanoribbons.
Ontology highlight
ABSTRACT:
SUBMITTER: Han HJ
PROVIDER: S-EPMC8500517 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Chemically interfacing the inert basal plane of graphene with other materials has limited the development of graphene-based catalysts, composite materials, and devices. Here, we overcome this limitation by chemically activating epitaxial graphene on SiC(0001) using atomic oxygen. Atomic oxygen produces epoxide groups on graphene, which act as reactive nucleation sites for zinc oxide nanoparticle growth using the atomic layer deposition precursor diethyl zinc. In particular, exposure of epoxidized graphene to diethyl zinc abstracts oxygen, creating mobile species that diffuse on the surface to form metal oxide clusters. This mechanism is corroborated with a combination of scanning probe microscopy, Raman spectroscopy, and density functional theory and can likely be generalized to a wide variety of related surface reactions on graphene.
| S-EPMC3883755 | biostudies-literature
Project description:Amorphous oxide semiconductor (AOS)-based Schottky diodes have been utilized for selectors in crossbar array memories to improve cell-to-cell uniformity with a low-temperature process. However, thermal instability at interfaces between the AOSs and metal electrodes can be a critical issue for the implementation of reliable Schottky diodes. Under post-fabrication annealing, an excessive redox reaction at the ohmic interface can affect the bulk region of the AOSs, inducing an electrical breakdown of the device. Additionally, structural relaxation (SR) of the AOSs can increase the doping concentration at the Schottky interface, which results in a degradation of the rectifying performance. Here, we improved the thermal stability at AOS/metal interfaces by regulating the oxygen vacancy (VO) concentration at both sides of the contact. For a stable quasi-ohmic contact, a Cu-Mn alloy was introduced instead of a single component reactive metal. As Mn only takes up O in amorphous In-Ga-Zn-O (a-IGZO), excessive VO generation in bulk region of a-IGZO can be prevented. At the Schottky interfaces, the barrier characteristics were not degraded by thermal annealing as the Ga concentration in a-IGZO increased. Ga not only reduces the inherent VO concentration but also retards SR, thereby suppressing tunneling conduction and enhancing the thermal stability of devices.
| S-EPMC6536494 | biostudies-literature
Project description:Silicon nanoribbons (Si NRs) with a thickness of about 30 nm and a width up to a few micrometers were synthesized. Systematic observations indicate that Si NRs evolve via the following sequences: the growth of basal nanowires assisted with a Pt catalyst by a vapor-liquid-solid (VLS) mechanism, followed by the formation of saw-like edges on the basal nanowires and the planar filling of those edges by a vapor-solid (VS) mechanism. Si NRs have twins along the longitudinal < 110 > growth of the basal nanowires that also extend in < 112 > direction to edge of NRs. These twins appear to drive the lateral growth by a reentrant twin mechanism. These twins also create a mirror-like crystallographic configuration in the anisotropic surface energy state and appear to further drive lateral saw-like edge growth in the < 112 > direction. These outcomes indicate that the Si NRs are grown by a combination of the two mechanisms of a Pt-catalyst-assisted VLS mechanism for longitudinal growth and a twin-assisted VS mechanism for lateral growth.
| S-EPMC3211989 | biostudies-literature
Project description:Lithium-rich nickel-manganese-cobalt (LirNMC) layered material is a promising cathode for lithium-ion batteries thanks to its large energy density enabled by coexisting cation and anion redox activities. It however suffers from a voltage decay upon cycling, urging for an in-depth understanding of the particle-level structure and chemical complexity. In this work, we investigate the Li1.2Ni0.13Mn0.54Co0.13O2 particles morphologically, compositionally, and chemically in three-dimensions. While the composition is generally uniform throughout the particle, the charging induces a strong depth dependency in transition metal valence. Such a valence stratification phenomenon is attributed to the nature of oxygen redox which is very likely mostly associated with Mn. The depth-dependent chemistry could be modulated by the particles' core-multi-shell morphology, suggesting a structural-chemical interplay. These findings highlight the possibility of introducing a chemical gradient to address the oxygen-loss-induced voltage fade in LirNMC layered materials.
| S-EPMC7733467 | biostudies-literature
Project description:Sub-5?nm cobalt oxide nanoparticles are produced in a flowing water system by pulsed laser fragmentation in liquid (PLFL). Particle fragmentation from 8?nm to 4?nm occurs and is attributed to the oxidation process in water where oxidative species are present and the local temperature is rapidly elevated under laser irradiation. Significantly higher surface area, crystal phase transformation, and formation of structural defects (Co2+ defects and oxygen vacancies) through the PLFL process are evidenced by detailed structural characterizations by nitrogen physisorption, electron microscopy, synchrotron X-ray diffraction, and X-ray photoelectron spectroscopy. When employed as electrocatalysts for the oxygen evolution reaction under alkaline conditions, the fragmented cobalt oxides exhibit superior catalytic activity over pristine and nanocast cobalt oxides, delivering a current density of 10?mA?cm-2 at 369?mV and a Tafel slope of 46?mV?dec-1 , which is attributed to a larger exposed active surface area, the formation of defects, and an increased charge transfer rate. The study provides an effective approach to engineering cobalt oxide nanostructures in a flowing water system, which shows great potential for sustainable production of active cobalt catalysts.
| S-EPMC7028056 | biostudies-literature
Project description:Identification of catalytic sites for oxygen reduction and evolution reactions (ORR/OER) is critical to rationally develop highly efficient bifunctional carbon-based metal-free electrocatalyst. Here, a unique defect-rich N-doped ultranarrow graphene nanoribbon with a high aspect ratio that exhibits excellent ORR/OER bifunctional activities and impressive long-term cycling stability in Zn-air batteries is successfully fabricated. Density functional theory calculations indicates that the topological defects (e.g., pentagons and heptagons) cooperated with pyridinic-N dopants on the edges are more favorable to electrocatalytic activity toward ORR and OER. This work provides a new design principle for carbon-based electrocatalytic nanomaterials.
| S-EPMC6299708 | biostudies-literature
Project description:Electrochemical deposition is a facile strategy to prepare functional materials but suffers from limitation in thin films and uncontrollable interface engineering. Here we report a universal electrosynthesis of metal hydroxides/oxides on varied substrates via reduction of oxyacid anions. On graphitic substrates, we find that the insertion of nitrate ion in graphene layers significantly enhances the electrodeposit-support interface, resulting in high mass loading and super hydrophilic/aerophobic properties. For the electrocatalytic oxygen evolution reaction, the nanocrystalline cerium dioxide and amorphous nickel hydroxide co-electrodeposited on graphite exhibits low overpotential (177?mV@10?mA?cm-2) and sustains long-term durability (over 300?h) at a large current density of 1000?mA?cm-2. In situ Raman and operando X-ray diffraction unravel that the integration of cerium promotes the formation of electrocatalytically active gamma-phase nickel oxyhydroxide with exposed (003) facets. Therefore, combining anion intercalation with cathodic electrodeposition allows building robust electrodes with high electrochemical performance.
| S-EPMC6006371 | biostudies-literature
Project description:The development of a universal activity descriptor like the d-band model for transition metal catalysts is of great importance to catalyst design. However, due to the complicated electronic structures of metal oxides, the correlation of the binding energies of reaction intermediates (*OH, *O, and *OOH) in the oxygen evolution reaction (OER) with experimentally controllable properties of metal oxides has not been well established. Here we demonstrate that excess electrons are the essential factor that governs the binding properties of intermediates on the surfaces of reducible metal oxides. We propose that the number of excess electrons (NEE) is an essential activity descriptor toward the OER activities of these oxides, which perfectly reproduces the volcano curve plotted using the descriptor ΔG O - ΔG OH, so that tuning NEE can effectively tailor the OER activities of reducible metal oxide based catalysts. Guided by this descriptor, we predict a novel non-precious catalyst with an overpotential of 0.54 eV, which could be a potential alternative to current Ru or Ir based catalysts.
| S-EPMC6430015 | biostudies-literature
Project description:A major challenge in the field of water electrolysis is the scarcity of oxygen-evolving catalysts that are inexpensive, highly corrosion-resistant, suitable for large-scale applications and able to oxidize water at high current densities and low overpotentials. Most unsupported, non-precious metals oxygen-evolution catalysts require at least ~350 mV overpotential to oxidize water with a current density of 10 mA/cm2 in 1 M alkaline solution. Here we report on a robust nanostructured porous NiFe-based oxygen evolution catalyst made by selective alloy corrosion. In 1 M KOH, our material exhibits a catalytic activity towards water oxidation of 500 mA/cm2 at 360 mV overpotential and is stable for over eleven days. This exceptional performance is attributed to three factors. First, the small size of the ligaments and pores in our mesoporous catalyst (~10 nm) results in a high BET surface area (43 m2/g) and therefore a high density of oxygen-evolution catalytic sites per unit mass. Second, the open porosity facilitates effective mass transfer at the catalyst/electrolyte interface. Third and finally, the high bulk electrical conductivity of the mesoporous catalyst allows for effective current flow through the electrocatalyst, making it possible to use thick films with a high density of active sites and ~3×104 cm2 of catalytic area per cm2 of electrode area. Our mesoporous catalyst is thus attractive for alkaline electrolyzers where water-based solutions are decomposed into hydrogen and oxygen as the only products, driven either conventionally or by photovoltaics.
| S-EPMC6456064 | biostudies-literature
Project description:The lithium-air battery has great potential of achieving specific energy density comparable to that of gasoline. Several lithium oxide phases involved in the charge-discharge process greatly affect the overall performance of lithium-air batteries. One of the key issues is linked to the environmental oxygen-rich conditions during battery cycling. Here, the theoretical prediction and experimental confirmation of new stable oxygen-rich lithium oxides under high pressure conditions are reported. Three new high pressure oxide phases that form at high temperature and pressure are identified: Li2O3, LiO2, and LiO4. The LiO2 and LiO4 consist of a lithium layer sandwiched by an oxygen ring structure inherited from high pressure ?-O8 phase, while Li2O3 inherits the local arrangements from ambient LiO2 and Li2O2 phases. These novel lithium oxides beyond the ambient Li2O, Li2O2, and LiO2 phases show great potential in improving battery design and performance in large battery applications under extreme conditions.
| S-EPMC5604394 | biostudies-literature