Air-Cathode with 3D Multiphase Electrocatalyst Interface Design for High-Efficiency and Durable Rechargeable Zinc–Air Batteries

The development of rechargeable zinc–air batteries is hindered by the low energy- conversion efficiency and the short cycle life, which are partly due to the unsatisfactory performance of the oxygen electrocatalysts on the air-cathode. The low performance of the catalysts is partially due to the complexity of the gas- involving multiphase interface required for the oxygen cataly sis reactions, and it is often acquired only for a fraction of the loaded catalyst that is in direct contact with the 2D surface of the gas diffus ion layer (GDL). A paradigm is proposed for extending the active region using an enhanced 3D multiphase interface on the cathode, which comprises abundant active sites with optimized hydrophobicity and reliable stability. The oxygen reduction reaction (ORR) or the bifunctional catalyst is embedded into the bulk of the GDL and forms a semihydrophobic catalyst layer (SCL), whereas an auxiliary hydrophilic oxygen evolution reaction (OER) catalyst layer integrated onto the GDL assists to reduce the polarization during the cell charging and improves the cathode durability. An air-cathode comprising the SCL exhibits an overall performance superior to the conventional cathode counterparts including cathodes with metal-based catalysts, due to the enhanced and optimized multiphase interface on the cathode

Low-Loss and Tunable Localized Mid-Infrared Plasmons in Nanocrystals of Highly Degenerate InN

Plasmonic response of free charges confined in nanostructures of plasmonic materials is a powerful means for manipulating the light-material interaction at the nanoscale and hence has influence on various relevant technologies. In particular, plasmonic materials responsive in the mid-infrared range are technologically important as the mid-infrared is home to the vibrational resonance of molecules and also thermal radiation of hot objects. However, the development of the field is practically challenged with the lack of low-loss materials supporting high quality plasmons in this range of the spectrum. Here, we demonstrate that degenerately doped InN nanocrystals (NCs) support tunable and low-loss plasmon resonance spanning the entire midwave infrared range. Modulating free-carrier concentration is achieved by engineering nitrogen-vacancy defects (InN1-x, 0.017 amp;lt; x amp;lt; 0.085) in highly degenerate NCs using a nonequilibrium gas-phase growth process. Despite the significant reduction in the carrier mobility relative to intrinsic InN, the mobility in degenerate InN NCs (amp;gt;60 cm(2)/(V s)) remains considerably higher than the carrier mobility reported for other materials NCs such as doped metal oxides, chalcogenides, and noble metals. These findings demonstrate feasibility of controlled tuning of infrared plasmon resonances in a low-loss material of III-V compounds and open a gateway to further studies of these materials nanostructures for infrared plasmonic applications.Funding Agencies|Knut and Alice Wallenberg Foundation [KAW 14.0276]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (faculty Grant SFO-Mat-LiU) [2009-00971]; EPSRC [EP/M024938/1]</p

MnCo2O4/NiCo2O4/rGO as a Catalyst Based on Binary Transition Metal Oxide for the Methanol Oxidation Reaction

The demands for alternative energy have led researchers to find effective electrocatalysts in fuel cells and increase the efficiency of existing materials. This study presents new nanocatalysts based on two binary transition metal oxides (BTMOs) and their hybrid with reduced graphene oxide for methanol oxidation. Characterization of the introduced three-component composite, including cobalt manganese oxide (MnCo2O4), nickel cobalt oxide (NiCo2O4), and reduced graphene oxide (rGO) in the form of MnCo2O4/NiCo2O4/rGO (MNR), was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray (EDX) analyses. The alcohol oxidation capability of MnCo2O4/NiCo2O4 (MN) and MNR was evaluated in the methanol oxidation reaction (MOR) process. The crucial role of rGO in improving the electrocatalytic properties of catalysts stems from its large active surface area and high electrical conductivity. The alcohol oxidation tests of MN and MNR showed an adequate ability to oxidize methanol. The better performance of MNR was due to the synergistic effect of MnCo2O4/NiCo2O4 and rGO. MN and MNR nanocatalysts, with a maximum current density of 14.58 and 24.76 mA/cm2 and overvoltage of 0.6 and 0.58 V, as well as cyclic stability of 98.3% and 99.7% (at optimal methanol concentration/scan rate of 20 mV/S), respectively, can be promising and inexpensive options in the field of efficient nanocatalysts for use in methanol fuel cell anodes

Controlling the Energy-Level Alignment of Silicon Carbide Nanocrystals by Combining Surface Chemistry with Quantum Confinement

This work was supported by the Marie Curie Initial Training Network (RAPID-ITN, Grant 606889) and by EPSRC (Grants EP/K022237/1 and EP/M024938/1). A.U.H. and S.A. are thankful for the financial support from RAPID-ITN and Ulster University’s Vice Chancellor scholarships, respectively.The knowledge of band edges in nanocrystals (NCs) and quantum-confined systems is important for band alignment in technologically significant applications such as water purification, decomposition of organic compounds, water splitting, and solar cells. While the band energy diagram of bulk silicon carbides (SiCs) has been studied extensively for decades, very little is known about its evolution in SiC NCs. Moreover, the interplay between quantum confinement and surface chemistry gives rise to unusual electronic properties and remains barely understood. Here, we report for the first time the complete band energy diagram of SiC NCs synthesized such that they span the regime from strong to intermediate to weak quantum confinement. The absolute positions of the highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbitals show clear size dependence. While the HOMO level follows the expected behavior for quantum-confined electronic states, the LUMO energy shifts below the bulk conduction band minimum, which cannot be explained by a simple quantum confinement caused by the size effect. We show that this effect is a result of the interplay between quantum confinement and the formation of surface states due to partial and site-selective oxygen passivation.Publisher PDFPeer reviewe

Microplasma Processed Ultrathin Boron Nitride Nanosheets for Polymer Nanocomposites with Enhanced Thermal Transport Performance

This Research Article reports on the enhancement of the thermal transport properties of nanocomposite materials containing hexagonal boron nitride in poly(vinyl alcohol) through room-temperature atmospheric pressure direct-current microplasma processing. Results show that the microplasma treatment leads to exfoliation of the hexagonal boron nitride in isopropyl alcohol, reducing the number of stacks from amp;gt;30 to a few or single layers. The thermal diffusivity of the resulting nanocomposites reaches 8.5 mm(2) s(-1) times greater than blank poly(vinyl alcohol) and twice that of nanocomposites containing nonplasma treated boron nitride nanosheets. From TEM analysis, we observe much less aggregation Of the nanosheets after plasma processing along with indications of an amorphous carbon interfacial layer, which may contribute to stable dispersion of boron nitride nanosheets in the resulting plasma treated colloids.Funding Agencies|National Natural Science Foundation of China [51203135, 51173174]; Invest NI PoC award [325]; COST Action [TD1208]; Engineering &amp; Physical Sciences Research Council (EPSRC) [EP/M024938/1, EP/K022237/1]</p

Ultra-small photoluminescent silicon-carbide nanocrystals by atmospheric-pressure plasmas

Highly size-controllable synthesis of free-standing perfectly crystalline silicon carbide nanocrystals has been achieved for the first time through a plasma-based bottom-up process. This low-cost, scalable, ligand-free atmospheric pressure technique allows fabrication of ultra-small (down to 1.5 nm) nanocrystals with very low level of surface contamination, leading to fundamental insights into optical properties of the nanocrystals. This is also confirmed by their exceptional photoluminescence emission yield enhanced by more than 5 times by reducing the nanocrystals sizes in the range of 1-5 nm, which is attributed to quantum confinement in ultra-small nanocrystals. This method is potentially scalable and readily extendable to a wide range of other classes of materials. Moreover, this ligand-free process can produce colloidal nanocrystals by direct deposition into liquid, onto biological materials or onto the substrate of choice to form nanocrystal films. Our simple but efficient approach based on non-equilibrium plasma environment is a response to the need of most efficient bottom-up processes in nanosynthesis and nanotechnology.Funding Agencies|Royal Society International Exchange Scheme [IE120884]; Leverhulme International Network [IN-2012-136]; EPSRC [EP/K022237/1, EP/M024938/1]; EU-FP7 [606889]; University of Ulster Vice-Chancellor Studentship; EU [606889]; CSIRO; Australian Research Council; School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology</p

Evaluation of a New Resampling Scheme for f Monte Carlo Methods

A new class of methods for reducing the number of particles in delta-f Monte Carlo simulations is presented. The reduction of particles is necessary when there is a continuous growth of the number of particles during the simulation. The method is based on resampling the particles distribution in local partitions of the phase-space. The resampling is accomplished by replacing particles with fewer numbers of new particles in each partition while ensuring that the moments of distribution are conserved. It’s demonstrated that the method well preserves the distribution function