Microwave Hydrothermal Synthesis of Ni-based Metal–Organic Frameworks and Their Derived Yolk–Shell NiO for Li-Ion Storage and Supported Ammonia Borane for Hydrogen Desorption

Abstract

This paper reports fast microwave hydrothermal synthesis of Ni-based metal−organic frameworks (Ni-MOFs) and their derived yolk−shell NiO structures by direct calcination in air. The molar ratio of the Ni ion to the benzene-1,3,5-tricarboxylic acid (H 3 BTC) ligand has important influence on the NiO morphologies and their electrochemical performances. The obtained yolk−shell NiO microsphere displays a large reversible capacity of 1060 mAh g −1 at a small current density of 0.2 A g −1 and a good high-rate capability when evaluated as an anode for rechargeable lithium-ion batteries. Moreover, the facilitated hydrogen release from ammonia borane (AB) at a lower temperature and the depressed release of undesired volatile byproducts are also observed in the Ni-MOFs supported AB.There is a increasing demand to make efficient use of energy and to find renewable and clean energy sources that can substitute for fossil fuels. 1,2 Energy storage, an important intermediate step toward versatile, clean, and efficient energy applications, has received worldwide concern both in academia and industry. 3−7 Among various candidates of energy storage systems, lithium-ion batteries (LIB) and fuel cells have received considerable attention owing to their high energy densities and environmental benignity. 8−16 LIB, one of the most important rechargeable batteries, have been widely used due to their high energy density and long cycle life. 10,17,18 Metal oxides such as NiO have long been extensively investigated as a potential electrode material for LIBs because of their 2−3 times higher theoretical capacities than commercial graphite electrodes. 19−42 However, their cycling performances and high-rate capabilities are still not satisfactory due to the large volume change associated with lithium insertion and extraction and poor electrical conductivity. 32−38,40−42 Hydrogen is one of the most promising candidates to replace nonrenewable fuel sources because it can react with oxygen to generate electricity with high energy density without byproducts. 43−45 Thus, hydrogen has been regarded as a suitable energy carrier for energy production from primary sources. Advanced materials are highly desired that can store a large amount of hydrogen at mild conditions (common temperature and relatively low pressure) along with a fast release kinetics. 46 Over the past decade, ammonia borane (NH 3 BH 3 , AB) has received much attention as a solid-state hydrogen storage medium because of its satisfactory stability, relatively low molecular mass, and remarkably high energy density. 47−50 However, its practical application is greatly limited by the poor kinetics of hydrogen generation below 85°C and the release of impurities that are detrimental to fuel cells.Metal−organic frameworks (MOFs) are porous materials synthesized by assembling metal ions with organic bridging ligands. 51,52 The metal ions in the MOFs can be thermally transformed into metal oxides, and the C and other elements are oxidized into gas molecules after calcining the MOFs in air at e...

Bimetal-Organic-Framework Derivation of Ball-Cactus-Like Ni-Sn-P@C-CNT as Long-Cycle Anode for Lithium Ion Battery

“…However, the commercial graphite anode exhibits a low theoretical capacity of only 372 mA h g −1 . To address this issue, numerous investigations have been made to explore and design new anode materials with high capacity and long cycle life, such as Si, Sn, transitional metal oxides and sulfides . Among many classes of alternative anode materials, metal phosphides seem to be a new potential to replace graphite due to their low polarization, minor electrode volume expansion, and high gravimetric capacity based on either intercalation or conversion reactions .…”

Functionalized Graphene Quantum Dot Modification of Yolk–Shell NiO Microspheres for Superior Lithium Storage

“…The strong peak centered at ≈0.44 V in the cathodic scan is arising from the reductive reaction from NiO to Ni, the generation of amorphous Li 2 O together with a solid electrolyte interface (SEI) layer. While in the anodic scan, the peak at ≈2.21 V can be assigned to the formation of NiO . Figure b demonstrates the discharge/charge curves of NiO/GQDsCOOH electrode at 0.1 A g −1 .…”

“…Substantial efforts have been made to address these issues, among which two commonly effective strategies are designing of NiO to possess special morphology with structural merits or compositing it with external supports. In the former case, NiO is preferably designed in the form of nanostructures such as nanorod, nanofiber, nanotube, nanosheet, or nanosphere . The specific structures are supposed to reduce the mechanical stress caused by volume expansion during cycling.…”

Facile Synthesis of Hollow Polyhedral (Cubic, Octahedral and Dodecahedral) NiO with Enhanced Lithium Storage Capabilities

“…From the adsorption branch of the isotherm, the specific surface areas become larger with increasing hollow polyhedral NiO facets. The BET specific areas of HC-NiO, HO-NiO and HD-NiO are calculated to be 44.9, 79.5 and 97.2 cm 2 g À1 , respectively, which are higher than those previously reported for NiO powders [10,[34][35][36][37]. The BJH pore size distribution curves show average pore sizes of 8.6, 6.7 and 3.8 nm for HC-NiO, HO-NiO and HD-NiO, respectively.…”