Defect
engineering is a reasonable solution to improve the surface
properties and electronic structure of nanomaterials. However, how
to introduce dual defects into nanomaterials by a simple way is still
facing challenge. Herein, we propose a facile two-step solvothermal
method to introduce Fe dopants and S vacancies into metal–organic
framework-derived bimetallic nickel cobalt sulfide composites (NiCo-S).
The as-prepared Fe-doped NiCo-S (Fe-NiCo-S) possesses improved charge
storage kinetics and activities as electrode material for supercapacitors
and the oxygen evolution reaction (OER). The obtained Fe-NiCo-S nanosheet
has a high specific capacitance (2779.6 F g–1 at
1 A g–1) and excellent rate performance (1627.2
F g–1 at 10 A g–1). A hybrid supercapacitor
device made of Fe-NiCo-S as the positive electrode and reduced graphene
oxide (rGO) as the negative electrode presents a high energy density
of 56.0 Wh kg–1 at a power density of 847.1 W kg–1 and excellent cycling stability (capacity retention
of 96.5% after 10,000 cycles at 10 A g–1). Additionally,
the Fe-NiCo-S composite modified by Fe doping and S vacancy has an
ultralow oxygen evolution overpotential of 247 mV at 10 mA cm–2. Based on the density functional theory (DFT) calculation,
defects cause more electrons to appear near the Fermi level, which
is conducive to electron transfer in electrochemical processes. Our
work provides a rational strategy for facilely introducing dual defects
into metal sulfides and may provide a novel idea to prepare electrode
materials for energy storage and energy conversion application.
During the past decades, nano-structured metal oxide electrode materials have received growing attention due to their low development cost and high theoretical specific capacity, accordingly, quite a lot of metal oxide electrode materials are being used in electrochemical energy storage devices. However, the further development was limited by the relatively low electrical conductivity and the volume expansion during electrochemical reactions. Thus, many approaches have been proposed to obtain high-efficiency metal oxide electrode materials, such as designing nanomaterials with ideal morphology and high specific surface area, optimizing with carbon-based materials (such as graphene and glucose) to prepare nanocomposites, combining with conductive substrates to enhance the conductivity of electrodes, etc. Owning to the advantages of low cost and high chemical stability of carbon materials, core–shell structure formed by carbon-coated metal oxides is considered to be a promising solution to solve these problems. Therefore, this review mainly focuses on recent research advances in the field of carbon-coated metal oxides for energy storage, summarizing the advantages and disadvantages of common metal oxides and different types of carbon sources, and proposing methods to optimize the material properties in terms of structure and morphology, carbon layer thickness, coating method, specific surface area and pore size distribution, as well as improving electrical conductivity. In addition, the double or multi-layer coating strategy is also a reflection of the continuous development of carbon coating method. Hopefully, this rereview may provide a new direction for the renewal and development of future energy storage electrode materials.
Preparing low-cost and highly efficient electrocatalysts for hydrogen evolution reaction in a simple strategy is still facing challenges. In this work, we proposed a facile phosphating process to successfully transform...
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