Probing Lithium Storage Mechanism of MoO₂ Nanoflowers with Rich Oxygen-Vacancy Grown on Graphene Sheets

The search for new electrode materials is of paramount importance for the practical apply of lithium-ion batteries (LIBs). Herein, flower-like MoO₂ microislands consist of MoO₂ nanorods grown on both sides of graphene sheets were synthesized via a solvo-thermal method, followed by a simple thermal treatment in argon. Our EXAFS and ESR data suggest there oxygen-vacancies in MoO₂ of the FMMGS hybrids. Besides, by tunning the ratio of glucose and CTAB, samples with different oxygen-vacancies content were synthesized. When used as anode materials for lithium-ion batteries, the oxygen-vacancy-rich FMMGS hybrids exhibited obviously higher capacity, rate capability than any nonvacancy samples. Importantly, synchrotron-radiation-based X-ray absorption near-edge structure (XANES), extended X-ray absorption fine-structure (EXAFS) and ex situ X-ray diffraction (ex situ XRD) were employed to elucidate the Li-ion insertion and extraction processes in the MoO₂ electrode. Our data clearly revealed that Li₂MoO₄ was generated during the Li uptake/removal process, which can be attributed to the existence of abundant oxygen vacancies in MoO₂ microislands. This provides us a useful insight for better understanding of dynamic cycling behavior in various Mo-based electrodes

A Ternary Alloy Substrate to Synthesize Monolayer Graphene with Liquid Carbon Precursor

Here we demonstrate a ternary Cu₂NiZn alloy substrate for controllably synthesizing monolayer graphene using a liquid carbon precursor cyclohexane <i>via</i> a facile CVD route. In contrast with elemental metal or bimetal substrates, the alloy-induced synergistic effects that provide an ideal metallic platform for much easier dehydrogenation of hydrocarbon molecules, more reasonable strength of adsorption energy of carbon monomer on surface and lower formation energies of carbon chains, largely renders the success growth of monolayer graphene with higher electrical mobility and lower defects. The growth mechanism is systemically investigated by our DFT calculations. This study provides a selective route for realizing high-quality graphene monolayer <i>via</i> a scalable synthetic method by using economic liquid carbon supplies and multialloy metal substrates