Showing papers by "Yong Wang published in 2020"

Multi-metal–Organic Frameworks and Their Derived Materials for Li/Na-Ion Batteries

Abstract: Lithium-ion and sodium-ion batteries are widely regarded as green energy storage power devices to support the development of modern electronic and information technology systems. Therefore, the design of advanced cathode and anode materials with higher energy and power densities is crucial to satisfy the increasing demand for next-generation high-performance batteries. To address this, researchers have explored metal–organic frameworks that possess extremely large surface areas, uniform ordered pores and controllable functional groups for application in the fields of energy storage, adsorption, catalysis, separation, etc. In addition, multi-metal–organic frameworks (MMOFs) and their derivatives have also been reported to provide better tunability to allow for the control of size, porosity, structure and composition, resulting in enhanced electronic and ion conductivities and richer redox chemistries at desirable potentials. Moreover, the synergistic effects between two or more metal components in MMOFs and their derivatives can accommodate large volume expansions during stepwise Li-/Na-ion insertion and extraction processes to allow for the improvement of structural stability in electrodes as well as enhanced cyclability. Based on all of this, this review will discuss and summarize the most recent progress in the synthesis, electrochemical performance and design of MMOFs and their derivatives. In addition, future trends and prospects in the development of MMOF-based materials and their application as high-performance Li/Na storage electrode materials are presented. Recent advances in multi-metal–organic frameworks and their derived materials for applications in lithium-/sodium-ion batteries are summarized and critically discussed.

A rational synthesis of single-atom iron–nitrogen electrocatalysts for highly efficient oxygen reduction reaction

Abstract: Developing low-cost nonprecious catalysts to replace Pt-based material is of great significance and importance for high-performance energy devices. Designing highly efficient, stable, and economic oxygen reaction electrocatalysts with atomically-dispersed metal–N–C active sites through an effective strategy is highly desired for the oxygen reduction reaction (ORR). Currently, the preparation of monoatomic catalysts with high loading and high activity, and the assurance of active sites fully exposed and participating in the reaction is challenging. Herein, atomically-dispersed Fe sites anchored to a porous carbon (Fe-SA/PC) hybrid synthesized via a facile dual-confinement route is reported. The experimental and theoretical simulations reveal that edge oxygen dopants facilitate the micropore trapping of the organic iron complex and the formation of isolated Fe atoms by subsequent pyrolysis. The optimized Fe-SA/PC catalyst exhibits outstanding electrocatalytic activity toward the ORR with a half-wave potential of 0.91 V, which is superior to most of the reported single-atom catalysts. DFT calculations proved that Fe–Nx sites with carbon defects can synergistically reduce the reaction barriers as compared to the intact Fe–Nx atomic configuration. This work provides a promising strategy for the design and construction of a series of high performance single-atom catalysts.

Integrating Mixed Metallic Selenides/Nitrogen-Doped Carbon Heterostructures in One-Dimensional Carbon Fibers for Efficient Oxygen Reduction Electrocatalysis

Abstract: Developing electrocatalysts for oxygen reduction reaction (ORR) with superior catalytic activity, long-period stability, and low price is extremely desirable but full of challenges. Hybrid nitrogen-doped carbon nanofibers encapsulated with mixed metallic selenides of ZnSe and CoSe₂ (assigned as Co₁–ₓZnₓSe, x represents the molar ratio of Zn/Co) nanoparticles are successfully prepared and denoted as Co₁–ₓZnₓSe@NCF-y (y represents the carbonization temperature). By controlling the ratio of Zn to Co and the carbonization temperature, the obtained Co₀.₆₂Zn₀.₃₈Se@NCF-800 fibers with a large specific surface area (385 m² g–¹) and a high content of nitrogen species (8.39 wt %) exhibit outstanding ORR electrocatalytic activity with a half-wave potential of 0.83 V (vs reversible hydrogen electrode, RHE), a limiting current density of 5.05 mA cm–², an excellent catalytic stability, and methanol tolerance. The superior ORR catalytic performances can be first explained by the hierarchical nanoparticles-in-fiber structure, which helps suppress the particle agglomeration, increase the structural stability, and promote the mass/electron transportation. The mixed metallic selenides are also believed to facilitate the electronic conductivity through redistribution of electrons from the metallic selenides to the nitrogen-doped carbon layers. Meanwhile, the highly nitrogen-doped carbon layers act as supports for metallic selenides to exhibit good electrocatalytic performances and electrochemical stability.

Carbonyl Functional Group Modified Metal–Organic Coordination Polymer with Improved Lithium-Storage Performance

Abstract: Exploration of the structures and architectural design of crystalline porous metal–organic coordination polymer (MOCP) materials with boosted active lithium-storage functional groups is still an ur...