Nitrogen-doped porous carbon spheres anchored with Co3O4 nanoparticles as high-performance anode materials for lithium-ion batteries

Non-enzymatic electrochemical sensor based on AuNPs/Cu-N-C composite for efficient nitrite sensing in sausage sample

Nitrogen-doped carbon materials have attracted enormous attention in the detection fields for the high catalytic activity. Herein, Cu-N-C materials were synthesized by template method and used for constructing non-enzymatic electrochemical...

Hydrothermal-template synthesis and electrochemical properties of Co3O4/nitrogen-doped hemisphere-porous graphene composites with 3D heterogeneous structure

Despite the high capacity of Co₃O₄ employed in lithium-ion battery anodes, the reduced conductivity and grievous volume change of Co₃O₄ during long cycling of insertion/extraction of lithium-ions remain a challenge. Herein, an optimized nanocomposite, Co₃O₄/nitrogen-doped hemisphere-porous graphene composite (Co₃O₄/N-HPGC), is synthesized by a facile hydrothermal-template approach with polystyrene (PS) microspheres as a template. The characterization results demonstrate that Co₃O₄ nanoparticles are densely anchored onto graphene layers, nitrogen elements are successfully introduced by carbamide and the nanocomposites maintain the hemispherical porous structure. As an anode material for lithium-ion batteries, the composite material not only maintains a relatively high lithium storage capacity (the first discharge specific capacity can reach 2696 mA h g⁻¹), but also shows significantly improved rate performance (1188 mA h g⁻¹ at 0.1 A g⁻¹, 344 mA h g⁻¹ at 5 A g⁻¹) and enhanced cycling stability (683 mA h g⁻¹ after 500 cycles at 1 A g⁻¹). The enhanced electrochemical properties of Co₃O₄/N-HPGC nanocomposites can be ascribed to the synergistic effects of Co₃O₄ nanoparticles, novel hierarchical structure with hemisphere-pores and nitrogen-containing functional groups of the nanomaterials. Therefore, the developed strategy can be extended as a universal and scalable approach for integrating various metal oxides into graphene-based materials for energy storage and conversion applications.

The Co₃O₄/N-HPGC nanocomposites synthesized by a hydrothermal-template approach with polystyrene microspheres as the template possess excellent electrochemical performance.

Experimental and theoretical investigations of the effect of heteroatom-doped carbon microsphere supports on the stability and storage capacity of nano-Co3O4 conversion anodes for application in lithium-ion batteries

Conversion-type anode materials have been intensely studied for application in Li-ion batteries (LIBs) due to their potentially higher capacities than current graphite-based anodes. This work reports the development of a high-capacity and stable anode from a nanocomposite of N and S co-doped carbon spheres (NSCSs) with Co₃O₄ (NSCS-Co₃O₄). A hydrothermal reaction of saccharose with l-cysteine was carried out, followed by its carbonization. CSs when used as supports for conversion-type materials provide efficient electron/ion transfer channels, enhancing the overall electrochemical performance of the electrodes. Additionally, the heteroatoms doped in a carbon matrix alter the electronic properties, often increasing the reactivity of the carbon surface, and they are reported to be effective for anchoring metal oxide nanoparticles. Consequently, the NSCS-Co₃O₄ nanocomposites developed in this work exhibit enhanced and stable reversible specific capacity over several cycles. Stable cycling behavior was observed at 1 A g^-1 with 1285 mA h g^-1 of specific capacity retained after 350 cycles along with more than 99% of coulombic efficiency. This material shows excellent rate capability with a specific capacity of 745 mA h g^-1 retained even at a high current density of 5 A g^-1. Detailed DFT-based calculations revealed the role of doped supports in controlling the volume expansion upon lithiation.

Structural combination of polar hollow microspheres and hierarchical N-doped carbon nanotubes for high-performance Li-S batteries

Hierarchical structured materials constructed with conductive carbon materials have been extensively studied as S host materials for Li-S batteries. However, their outwardly developed hierarchical structures, which do not contain structures or materials to inhibit polysulfide dissolution, lead to the dissipation of dissolved polysulfides and poor dispersion properties during the slurry-making process, which results in non-uniformity in the cathodes. Herein, an assembly of polar materials (hollow structured SiO2 microspheres) and electrically conductive hierarchical N-doped bamboo-like carbon nanotubes (b-NCNTs) is designed as an efficient S host material for minimizing the dissolution of polysulfides during Li-S battery operations. Highly aligned and packed b-NCNTs are grown in hollow structured SiO2 microspheres. The SiO2 layer coated on the surface of the hollow CoFe2O4 microspheres plays a key role in the synthesis of easily dispersible hierarchical b-NCNTs microspheres (b-NCNTs@SiO2). The S-loaded b-NCNTs@SiO2 electrodes show better cycling stability than S-loaded b-NCNTs electrodes. The polysulfide trapping of the polar SiO2 layer and the well-developed b-NCNTs minimize the dissolution of polysulfides during cycling. In addition, the introduction of electronegative N atoms into the b-NCNTs lattice enhances their polysulfide trapping ability. The S-loaded b-NCNTs@SiO2 electrodes exhibit stable discharge capacities of >771 mA h g-1 over 195 cycles at a current density of 0.5 C and a high reversible capacity of 486 mA h g-1 even at a high current density of 5.0 C.

A Nitrogen-Doped Manganese Oxide Nanoparticles/Porous Carbon Nanosheets Hybrid Material: A High-Performance Anode for Lithium Ion Batteries

A nitrogen-doped MnO nanoparticles/ porous carbon nanosheets (N-MnO/PCS) composite was synthesized by the room-temperature redox reaction between KMnO₄ and PCS followed by a facile carbothermal reduction, and a subsequent coating process of urea onto MnO/PCS and heat treatment. N-MnO nanoparticles with a grain size of about 30 nm are homogenously embedded on the surface of the N-PCS, corresponding to a high loading of 50.09 wt.% in the resulting composite. Benefiting from the enhanced reaction kinetics as well as electrical conductivity and continuous transport pathways of Li⁺ /electron resulting from the N-doping and hybridization of the cross-linked porous carbon substrate, the as-synthesized N-MnO/PCS-1 electrode delivers a large reversible specific capacity (1497.2 mA h g^-1 at 100 mA g^-1 after 160 cycles), outstanding rate capacities (710.6 mA h g^-1 at 1 A g^-1 and 640.1 mA h g^-1 at 2 A g^-1 ) and long-term cycling stability with specific capacity (976 mA h g^-1 at 0.5 A g^-1 after cycling 300 cycles). The simple and green synthesis and electronic properties of this composite mean that it has great potential as a high-capacity anode material for practical application in large-scale energy storage devices.

MnCo2O4 nanoparticles supported on nitrogen and sulfur co-doped mesoporous carbon spheres as efficient electrocatalysts for oxygen catalytic reactions

The development of efficient bifunctional electrocatalysts for the oxygen reduction and oxygen evolution reactions is essential to address the challenge of sluggish reaction kinetics.