Preparation of Ferromagnetic Co3O4 Nanoparticles by Wet Chemical Synthesis Method

Cobalt oxide nanoparticles (Co3O4) were synthesized by wet chemical method using cobalt sulfate as precursor and ethylene glycol as surfactant. Their physico-chemical properties were characterized by high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and vibration sampling magnetometer (VSM) analyses. The crystal structure of samples after annealing was done by XRD analysis. XRD measurement exhibited the structure of Co3O4 nanocrystals for annealed samples.  The TEM results showed the cobalt oxide nanoparticles with good uniformity. The SEM images revealed that the size of nanoparicles increased in the range of 20-50 nm with increasing annealing temperature. The magnetic results indicated a good coercive field and saturation magnetism around 452 G and 18 emu/g, respectively.                                                                                 &nbsp

Borohydride Reduction of Cobalt Oxide (Co3O4) Nanoparticles

Recently, magnetic nanomaterials have been used in a wide range of applications such as medicine and electronics. In this research, rod-like shaped cobalt oxide magnetic nanoparticles (Co3O4) were synthesized by a simple co-precipitation method using cobalt chloride as a precursor and sodium borohydride (NaBH4) as reducing agent. Their structural and surface morphological properties were characterized by high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and vibration sampling magnetometer with (VSM). XRD measurement exhibited the structure of Co3O4 nanocrystals for annealed samples. The TEM results showed the cobalt oxide nanoparticles with good uniformity in the range size of 10-40 nm. The SEM images revealed that the particles changed from spherical shape to rod-like shape with increasing temperature. Magnetic measurements showed the coercive field of around 84.5G and saturation magnetization of annealed of around 9.83 emu/g

Synthesis of nano-sized ceria (CeO2) particles via a cerium hydroxy carbonate precursor and the effect of reaction temperature on particle morphology

Cerium oxide (CeO2) or ceria has been shown to be an interesting support material for noble metals in catalysts designed for emission control, mainly due to its oxygen storage capacity. Ceria nanoparticles were prepared by precipitation method. The precursor materials used in this research were cerium nitrate hexahydrate (as a basic material), potassium carbonate and potassium hydroxide (as precipitants). The morphological properties were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-Vis spectrophotometer. XRD results showed face centered cubic CeO2 nanoparticles for annealed nanoparticles at 1000°C. SEM measurement showed that by increasing the calcinations temperature from 200 to 600°C, the crystallite size decreased from 90 to 28 nm. The SEM results showed that the size of the CeO2 nanoparticles decreased with increasing temperature. The particle size of CeO2 was around 25 nm as estimated by XRD technique and direct HRTEM observation. SEM and TEM studies showed that the morphology of the prepared powder was sphere-like with a narrow size distribution. The sharp peaks in FTIR spectrum determined the purity of CeO2 nanoparticles and absorbance peak of UV-Vis spectrum showed the small band gap energy of 3.26 ev

Oxygen redox chemistry in lithium-rich cathode materials for Li-ion batteries: Understanding from atomic structure to nano-engineering

Lithium-rich oxide compounds have been recognized as promising cathode materials for high performance Li-ion batteries, owing to their high specific capacity. However, it remains a great challenge to achieve the fully reversible anionic redox reactions to realize high capacity, high stability, and low voltage hysteresis for lithium-rich cathode materials. Therefore, it is critically important to comprehensively understand and control the anionic redox chemistry of lithium-rich cathode materials, including atomic structure design, and nano-scale materials engineering technologies. Herein, we summarize the recent research progress of lithium-rich cathode materials with a focus on redox chemistry. Particularly, we highlight the oxygen-based redox reactions in lithium-rich metal oxides, with critical views of designing next generation oxygen redox lithium cathode materials. Furthermore, we purposed the most promising strategies for improving the performances of lithium-rich cathode materials with a technology-spectrum from the atomic scale to nano-scale

Surface and structure engineering of MXenes for rechargeable batteries beyond lithium

With the rapid growth in renewable energy, researchers worldwide are trying to expand energy storage technologies. The development of beyond-lithium battery technologies has accelerated in recent years, amid concerns regarding the sustainability of battery materials. However, the absence of suitable high-performance materials has hampered the development of the next-generation battery systems. MXenes, a family of 2D transition metal carbides and/or nitrides, have drawn significant attention recently for electrochemical energy storage, owing to their unique physical and chemical properties. The extraordinary electronic conductivity, compositional diversity, expandable crystal structure, superior hydrophilicity, and rich surface chemistries make MXenes promising materials for electrode and other components in rechargeable batteries. This report especially focuses on the recent MXene applications as novel electrode materials and functional separator modifiers in rechargeable batteries beyond lithium. In particular, we highlight the recent advances of surface and structure engineering strategies for improving the electrochemical performance of the MXene-based materials, including surface termination modifications, heteroatom doping strategies, surface coating, interlayer space changes, nanostructure engineering, and heterostructures and secondary materials engineering. Finally, perspectives for building future sustainable rechargeable batteries with MXenes and MXene-based composite materials are presented based upon material design and a fundamental understanding of the reaction mechanisms

Boosting the Electrochemical Performance of Lithium-Rich Cathodes by Oxygen Vacancy Engineering

The challenges of voltage decay and irreversible oxygen release for lithium-rich layered oxide cathode materials have hindered their commercial application despite their high energy density and low cost. Herein, a facile post-annealing strategy is developed to pre-introduce oxygen vacancies (OVs) into Li1.2Mn0.457Ni0.229Co0.114O2 cathode materials. The induced OVs modify the local Mn coordination environments, enhance structural stability, and suppress oxygen release. The modified cathode exhibits a discharge capacity of 224.1 mAh g−1 at 0.1 C after 100 cycles with 97.7 % capacity retention. Even at 2 C, excellent capacity retention of 93.3 % after 300 cycles can be achieved. In situ and ex situ X-ray diffraction are used to elucidate the reaction mechanisms and crystal structure during cycling tests. Ex situ X-ray photoelectron spectroscopy confirmed the suppressed oxygen release, enhanced oxygen vacancies and reduced cathode-electrolyte interfacial layer after cycling for the post-annealed cathode. Our results show that the presence of oxygen vacancies through thermal expansion diminishes the phase transitions in cathode materials during the heating process. These findings contribute to developing next-generation Li-ion batteries (LIBs) by oxygen vacancy engineering for new cathode materials with improved electrochemical performances