CoO nanomaterials with diverse morphologies were usually synthesized in liquid phase accompanied by the template or surfactant under harsh conditions, which further restricted their practical application. Herein, we reported an extremely simple and practical solid-state chemical method to synthesize CoO-octahedrons, -plates, and -rods. Among these, the shape control of CoO-octahedrons and CoO-plates involve variation of the amount of reactant, and the formation of CoO-rods with {110} facet can be achieved by replacing the reactant. The formation of the CoO nanomaterials with different morphologies originated from the different microenvironments of reaction and the structure of reactants. The catalytic activity of CoO samples for CO oxidation was evaluated in normal feed gas. The as-prepared CoO-rods exposed {110} facet exhibited superior catalytic activity for CO oxidation, which can be attributed to more oxygen defects on CoO-rods surface. Additionally, CoO-rods exhibited excellent durablility (without pretreatment) in normal feed gas, even in the presence of moisture, comparable or better than that reported in the literature. The practical and environmental friendly solvent-free strategy provided a new promising route for large-scale preparation of (metal) oxide with remarkable CO oxidation performance for practical application.
Achieving full utilization of active sites and optimization of the electronic structure of metal centers is the key to improving the intrinsic activity of single-atom catalysts (SACs) but still remains a challenge to date. Herein, a versatile molten saltassisted pyrolysis strategy was developed to construct ultrathin, porous carbon nanosheets supported Co SACs. Molten salts are capable of inducing the formation of a Co singleatom and porous graphene-like carbon, which facilitates full exposure of the active center and simultaneously endows the Co SACs with abundant defective Co-N 4 configurations. The reported Co SACs deliver an excellent bifunctional activity and good stability for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Moreover, metal-air batteries (MABs) assembled with the Co SACs as air electrode also deliver excellent performance with high power densities of 160 mW•cm −2 , large capacities of 760 mAh•g −1 , and superior long-term charge/discharge stability, outperforming those of commercial Pt/C+RuO 2 . DFT theoretical calculation results show that the defects in the second coordination shell (CS) of Co SACs promote desorption of the OH* intermediate for the ORR and facilitate deprotonation of OH* for the OER, which can serve as the favorable active site for oxygen bifunctional catalysts. Our work provides an efficient strategy for the preparation of SACs with fully exposed active centers and optimized electronic structures.
Ultra-large-scale synthesis of iron
oxide nanoparticles (875 g)
has been achieved in a single reaction via a facile solution-based
dehydration process. The obtained nanoparticles capped with hydrophobic
oleic acid ligands are magnetite with the average size of 5 nm. The
synthesized samples exhibit a higher catalytic activity toward the
direct coal liquefaction (DCL) than the commercial Fe3O4 powders. The conversion, oil yield, and liquefaction degree
with the synthesized Fe3O4 nanoparticles are
89.6, 65.1, and 77.3%, respectively. The excellent catalytic performance
of the synthesized Fe3O4 nanoparticles can be
attributed to their extremely small size and high dispersity. This
facile approach to prepare highly active nanocatalyst for the DCL
will be applicable for future industrial processes.
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