Sub-5 nm Ultrasmall Metal–Organic Framework Nanocrystals for Highly Efficient Electrochemical Energy Storage

Abstract

Synthesis of ultrasmall metal-organic framework (MOF) nanoparticles has been widely recognized as a promising route to greatly enhance their properties but remains a considerable challenge. Herein, we report one facile and effective spatially confined thermal pulverization strategy to successfully transform bulk Co-MOF particles into sub-5 nm nanocrystals encapsulated within N-doped carbon/graphene (NC/G) by using conducting polymer coated Co-MOFs/graphene oxide as precursors. This strategy involves a feasible mechanism: calcination of Co-MOFs at proper temperature in air induces the partial thermal collapse/distortion of the framework, while the uniform coating of a conducting polymer can significantly improve the decomposition temperature and maintain the component stability of Co-MOFs, thus leading to the pulverization of bulk Co-MOF particles into ultrasmall nanocrystals without oxidation. The pulverization of Co-MOFs significantly increases the contact area between Co-MOFs with electrolyte and shortens the electron and ion transport pathway. Therefore, the sub-5 nm ultrasmall MOF nanocrystals-based composites deliver an ultrahigh reversible capacity (1301 mAh g at 0.1 A g), extraordinary rate performance (494 mAh g at 40 A g), and outstanding cycling stability (98.6% capacity retention at 10 A g after 2000 cycles), which is the best performance achieved in all reported MOF-based anodes for lithium-ion batteries.

Bottom‐Up Fabrication of 1D Cu‐based Conductive Metal–Organic Framework Nanowires as a High‐Rate Anode towards Efficient Lithium Storage

“…[28] More remarkably,t he Cu-CATelectrode, as plottedi n Figure 4f,m anifests ap seudo-capacitive contribution as high as 88.3 %e ven at as mallC Vs weep rate of 0.4 mV s À1 ,v erifying that the Cu-CATN Ws hold enormous promise in LIBs as an high-power anode material, benefiting from its 1D and porous features. [29] As is well established,t he unique 1D NWs always offer numerousa ppealingb enefits (e.g.,r apid electronic/ionic transport, strong tolerance to stress change, shorter ion diffusion length, etc.) fore fficient energy storagec omparedw ith nanoparticles (NPs) and nanosheets (NSs).…”

Metal–Organic Gel‐Derived Multimetal Oxides as Effective Electrocatalysts for the Oxygen Evolution Reaction

“…[15a,b, 34] CoFeNi-O-1 with nanoparticles assembled in an etwork structure morphology (Figure 1b,c)e xhibited the highest capacitance (Figure 5b)a nd the best catalytic activity (Figure 4a), which could be attributed to the specialm orphologyo fC oFeNi-O-1, which can facilitate contact with the substrate molecule and bring about high capacitance through shortening the electron and ion transport pathways. [35] Trivalent Co and Ni in moste lectrocatalysts has been demonstrated as the major active sites in the process of water oxidation, [36] and introducing moderate Fe into Co or Ni oxides can effectively accelerate the OER reactionkineticso wing to Fe being able to stabilizet he key active Or adicali ntermediate with an Fe-induced partial charget ransfer mechanism. [16,37] Doping too much Fe into the Co and Ni oxidesr esultsi nt he low catalytic activity owing to the lower OER activity of Fe-rich phases or too much positivec hargeo nt he catalytic sites, which adversely affects the separation of product from the catalyst.…”

“…In addition, CoFeNi-O-1 shows the largest exchange current density (j 0 )c ompared with the other derivedm etal oxides( Ta bleS5). [35] Trivalent Co and Ni in moste lectrocatalysts has been demonstrated as the major active sites in the process of water oxidation, [36] and introducing moderate Fe into Co or Ni oxides can effectively accelerate the OER reactionkineticso wing to Fe being able to stabilizet he key active Or adicali ntermediate with an Fe-induced partial charget ransfer mechanism. Furthermore, the stability was monitored by chronoamperometrya nd after 1000C Vc ycles (Figure 5d), compared with the initial state, the morphology showedn os ignificant changes ( Figure S12) after finishing the potentiostatic stabilityi nvestigation.…”

Rambutan‐like hollow carbon spheres decorated with vacancy‐rich nickel oxide for energy conversion and storage

“…With the ever‐increasing energy demand and prominent environmental concerns, seeking promising storage, and conversion systems with high efficiency, low cost, robust stability, and environmental friendliness is urgent but challenging . Lithium‐ion batteries (LIBs) and water electrolyzer, deemed to be attractive electrochemical storage and conversion devices, have been extensively studied because they are efficient, stable, and environmentally friendly . However, with the fast development of the electric vehicle industry, the current graphite anode material is not able to satisfy the needs of high energy density and high power density .…”

“…friendly. [5][6][7][8][9][10][11][12] However, with the fast development of the electric vehicle industry, the current graphite anode material is not able to satisfy the needs of high energy density and high power density. 10 Furthermore, oxygen evolution reaction (OER) in water splitting, which involves a four-electron coupled process, suffers from slow kinetics, and large overpotential.…”