Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

https://hal.archives-ouvertes.fr/hal-02417326/document

Materials for electrochemical capacitors

There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.

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Graphene and Graphene Oxide: Synthesis, Properties, and Applications

In this critical review, metal oxides-based materials for electrochemical supercapacitor (ES) electrodes are reviewed in detail together with a brief review of carbon materials and conducting polymers. Their advantages, disadvantages, and performance in ES electrodes are discussed through extensive analysis of the literature, and new trends in material development are also reviewed. Two important future research directions are indicated and summarized, based on results published in the literature: the development of composite and nanostructured ES materials to overcome the major challenge posed by the low energy density of ES (476 references).

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A review of electrode materials for electrochemical supercapacitors

Electrochemical energy storage technology is based on devices capable of exhibiting high energy density (batteries) or high power density (electrochemical capacitors). There is a growing need, for current and near-future applications, where both high energy and high power densities are required in the same material. Pseudocapacitance, a faradaic process involving surface or near surface redox reactions, offers a means of achieving high energy density at high charge–discharge rates. Here, we focus on the pseudocapacitive properties of transition metal oxides. First, we introduce pseudocapacitance and describe its electrochemical features. Then, we review the most relevant pseudocapacitive materials in aqueous and non-aqueous electrolytes. The major challenges for pseudocapacitive materials along with a future outlook are detailed at the end.

https://hal.archives-ouvertes.fr/hal-01171774/document

Pseudocapacitive oxide materials for high-rate electrochemical energy storage

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Photo-triggered conversion of hydrophilic fluorescent biomimetic nanostructures for cell imaging.

Porous Cobalt-nickel Phosphides Prepared from Al-doped NiCo-LDH Precursors for Supercapacitor and Electrocatalysis applications

Herein, low Ag doping MnFe2O4 (AgxMn1−xFe2O4) was synthesized by an easy sol–gel process and applied for anti-bacteria in the water. Without any special light irradiation, it was found that Ag0.01Mn0.99Fe2O4 (AMFO-0.01) significantly enhanced the antimicrobial activity by a simple contact with the bacteria. The antimicrobial performances under different AMFO-0.01 dosages, initial bacteria concentrations, temperature and pH were conducted. A good stability was still possessed for AMFO-0.01 after an ultrasonic washing. It was uncovered that the interaction between AMFO-0.01 and cell membrane could restrict the activities of bacteria to cause severe membrane injury. The antimicrobial efficiency was not due to the toxicity of elemental Ag or dissolved metal ions. The doping Ag existed as monovalence ions inside the crystal lattice. Continuous electron transfer of Ag(0)/Ag(I) accelerated the electron delivery of Mn(II)/Mn(III), Fe(II)/Fe(III). Such synergistic effect of Ag, Mn, Fe on the surface induced the generation of reactive species (·OH, O2·−, H2O2, 1O2) for the death of bacteria. Considering such easy magnetic separation, room light condition, and high antimicrobial activity of AMFO-0.01, it is a promising candidate in the disinfection application for drinking or waste water treatment.

Low-energy disinfection under natural light by magnetic AgxMn1−xFe2O4 in the water: Efficiency and mechanism

Movement-induced voltage properties of stable graphite nanoplatelet suspensions

Developing efficient and robust metal-nitrogen-carbon electrocatalysts for oxygen reduction reaction (ORR) is of great significance for the application of hydrogen-oxygen fuel cells and metal-air batteries. Herein, a coordination engineering strategy is developed to improve the ORR kinetics and stability of cobalt-nitrogen-carbon (Co-N-C) electrocatalysts by grafting the oxygen-rich graphene quantum dots (GQDs) onto the zeolite imidazole frameworks (ZIFs) precursors. The optimized oxygen-rich GQDs-functionalized Co-N-C (G-CoNOC) electrocatalyst demonstrates an increased mass activity, nearly two times higher than that of pristine defective Co-N-C electrocatalyst, and retains a stability of 90.0% after 200 h, even superior to the commercial Pt/C. Comprehensive investigations demonstrate that the GQDs coordination can not only decrease carbon defects of Co-N-C electrocatalysts, improving the electron transfer efficiency and resistance to the destructive free radicals from H2 O2 , but also optimize the electronic structure of atomic Co active site to achieve a desired adsorption energy of OOH- , leading to enhanced ORR kinetics and stability by promoting further H2 O2 reduction, as confirmed by theoretical calculations and experimental results. Such a coordination engineering strategy provides a new perspective for the development of highly active noble-metal-free electrocatalysts for ORR.

Zhuangjun Fan

Papers

Photo-triggered conversion of hydrophilic fluorescent biomimetic nanostructures for cell imaging.

Porous Cobalt-nickel Phosphides Prepared from Al-doped NiCo-LDH Precursors for Supercapacitor and Electrocatalysis applications

Low-energy disinfection under natural light by magnetic AgxMn1−xFe2O4 in the water: Efficiency and mechanism

Movement-induced voltage properties of stable graphite nanoplatelet suspensions

Coordination Engineering of Defective Cobalt-Nitrogen-Carbon Electrocatalysts with Graphene Quantum Dots for Boosting Oxygen Reduction Reaction.