The Graphene Supported CoO Nanoparticles as an Advanced Catalyst for Aerobic Oxidation of Cyclohexane

Transition metals are commonly employed as catalysts for oxidation of cyclohexane. However, the harsh reaction conditions and the low efficiency hinder their further application. In this work, to further improve...

In Situ Formation of Surface-Induced Oxygen Vacancies in Co9S8/CoO/NC as a Bifunctional Electrocatalyst for Improved Oxygen and Hydrogen Evolution Reactions

Creating oxygen vacancies and introducing heterostructures are two widely used strategies in Co-based oxides for their efficient electrocatalytic performance, yet both strategies have rarely been used together to design a bifunctional electrocatalyst for an efficient overall water splitting. Herein, we propose a facile strategy to synthesize oxygen-defect-rich Co9S8/CoO hetero-nanoparticles with a nitrogen-doped carbon shell (ODR-Co9S8/CoO/NC) through the in situ conversion of heterojunction along with surface-induced oxygen vacancies, simply via annealing the precursor Co3S4/Co(OH)2/ZIF-67. The as-prepared ODR-Co9S8/CoO/NC shows excellent bifunctional catalytic activities, featuring a low overpotential of 217 mV at 10 mA cm−2 in the oxygen evolution reaction (OER) and 160 mV at 10 mA cm−2 in the hydrogen evolution reaction (HER). This performance excellency is attributed to unique heterostructure and oxygen defects in Co9S8/CoO nanoparticles, the current work is expected to offer new insights to the design of cost-effective, noble-metal-free electrocatalysts.

Impact, Hardness and Fracture Morphology of Aluminium Alloy (Al-Si) filled Cobalt Oxide Nanoparticles at Various Stir Casting Temperatures

The automotive and aviation fields require engineering materials that can save and optimise fuel consumption. Unique characteristics of lightweight, higher strength to weight ratio, good corrosion resistance, and good castability are indispensable for castable metal such as Silicon Aluminium (Al-Si). The mechanical properties of Al-Si could be further improved through the addition of Cobalt Oxide (CoO) nanoparticles during the casting process. The importance and purpose of this study were to determine the impact toughness, hardness and fracture morphology of Al-Si metal alloy filled with 0.015 wt.% CoO nanofiller at the various melting temperature of 750 °C, 800 °C and 850 °C. The stir casting method was utilised considering the most appropriate method for mixing nanoparticles powder into the Al-Si matrix. Three test specimens were prepared for each temperature variation. Impact testing using the Charpy method (ASTM E23-56 T) and hardness testing using Rockwell Superficial HR15T and fracture morphology obtained from impact testing fractures were performed accordingly. The impact test results showed that the Al-Si added with 0.015% CoO at 800 °C of melting temperature possessed the highest impact toughness value of 25.111 x 10-3 Joule mm-2 than the other variations. The hardness test results showed that Al-Si added 0.015% CoO with a melting temperature of 850 °C had the highest hardness value of 79.52 HR15T. The fracture morphology of the impact test in all specimens shows uniform brittle fracture characteristics. It is found that the melting temperature during the stir-casting process of Al-Si has played a significant role in influencing the resulted properties of Al-Si filled CoO nanoparticles metal matrix composites. The selection of an accurate melting temperature for the stir casting process will affect the resulted properties of produced metal composites.

Crystalline and magnetic properties of CoO nanoparticles locally investigated by using radioactive indium tracer

We herein report a comprehensive investigation on the magnetic, structural, and electric properties of CoO nanoparticles with different sizes by local inspection through hyperfine interactions measured in a wide range of temperatures (10-670 K) by using radioactive 111In( 111Cd) tracers with the perturbed angular correlations (PAC) technique. Small cobalt oxide nanoparticles with 6.5 nm have been prepared by the wet chemical route, which has shown essential to incorporate radioactivity tracers during nucleation and grown syntheses. Nanocrystalline samples with 22 nm size were obtained by thermal treatments under low pressure of helium at 670 K. The hyperfine data were correlated with X-ray diffraction (XRD), ZFC-FC magnetic measurements and transmission electron microscopy (TEM) to describe the structure, magnetic properties, size, and shape of samples. An analysis of the temperature evolution of hyperfine parameters revealed that the structural distortion and the magnetic disorder in the core and on the surface layer play an important role in the magnetic behavior of CoO nanoparticles.

Development of an Efficient Bi-Functional Catalyst made of a Novel Hybrid Material for Rechargeable Zn-Air Battery

One-pot synthesis of mesoporous hybrid material consisting of Mn-Co/CoO nanoparticles encapsulated in an N-doped graphene shell decorated with Mo2C nanoparticles (Mo2C-NC@Mn-Co/CoO) was reported. The Mn and Mo components synergistically refined the graphitized carbons due to the interactions with N and C atoms while promoting the stability of the Co/CoO nanoparticles. These components exhibited a beneficial effect on the dispersion of the active metal/metal oxide nanoparticles and the formation of a mesoporous structure under high-temperature conditions, which together led to optimized oxygen adsorption/desorption capabilities as well as mass transport properties. The hybrid material showed high bifunctional performance for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), as well as promising catalytic properties as the air electrode in a zinc-air battery, featuring superior long-term cycle stability comparable to that of Pt-C/RuO2 materials.