It is of great interest to develop new carbon-based materials as electrodes for supercapacitors because the conventional electrodes of activated carbons in supercapacitors cannot meet the ever-increasing demands for high energy and power densities for electronic devices. Due to their high electronic conductivity and improved hydrophilic properties, together with their easy syntheses and functionalization, N-doped carbons have shown a great potential in energy storage and conversion applications. In this review, after a brief introduction of electrochemical capacitors, we summarize the advances, in the recent six years, in the preparation methods of N-doped carbons for applications in supercapacitors. We also discuss and predict futuristic research trends towards the design and syntheses of N-doped carbons with unique properties for electrochemical energy storage.

Review on recent advances in nitrogen-doped carbons: preparations and applications in supercapacitors

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Heterostructures for Electrochemical Hydrogen Evolution Reaction: A Review

Heteroatom modification represents one of the largest studied areas of research related to nanostructured carbon materials, with integrated applications stretching from energy production and storage to sustainability and medical uses. While a wide variety of dopants (boron, phosphorus, iodine, fluorine, etc.) have been studied, doping carbon structures with nitrogen ad-atoms has arguably experienced the greatest progress and brought the most attention over the last several years. Research in this field has conclusively demonstrated that nitrogen doping is an effective way to tailor the properties of carbon and tune the material for various applications of interest. This review provides a comprehensive overview of advances in the last half decade on state-of-the-art carbon modification with nitrogen heteroatoms. Improvements in well-established fabrication/modification processes are discussed as well as novel strategies. Additionally, recent theoretical and experimental findings related to the benefits and effects of nitrogen modification for specific applications in the energy and environmental fields are reviewed.

Recent progress on nitrogen/carbon structures designed for use in energy and sustainability applications

The development of high-capacity, Earth-abundant, and stable cathode materials for robust aqueous Zn-ion batteries is an ongoing challenge. Herein, ultrathin nickel cobaltite (NiCo2 O4 ) nanosheets with enriched oxygen vacancies and surface phosphate ions (P-NiCo2 O4-x ) are reported as a new high-energy-density cathode material for rechargeable Zn-ion batteries. The oxygen-vacancy and surface phosphate-ion modulation are achieved by annealing the pristine NiCo2 O4 nanosheets using a simple phosphating process. Benefiting from the merits of substantially improved electrical conductivity and increased concentration of active sites, the optimized P-NiCo2 O4-x nanosheet electrode delivers remarkable capacity (309.2 mAh g-1 at 6.0 A g-1 ) and extraordinary rate performance (64% capacity retention at 60.4 A g-1 ). Moreover, based on the P-NiCo2 O4-x cathode, our fabricated P-NiCo2 O4-x //Zn battery presents an impressive specific capacity of 361.3 mAh g-1 at the high current density of 3.0 A g-1 in an alkaline electrolyte. Furthermore, extremely high energy density (616.5 Wh kg-1 ) and power density (30.2 kW kg-1 ) are also achieved, which outperforms most of the previously reported aqueous Zn-ion batteries. This ultrafast and high-energy aqueous Zn-ion battery is promising for widespread application to electric vehicles and intelligent devices.

Oxygen-Vacancy and Surface Modulation of Ultrathin Nickel Cobaltite Nanosheets as a High-Energy Cathode for Advanced Zn-Ion Batteries.

Supercapacitors are highly attractive for a large number of emerging mobile devices for addressing energy storage and harvesting issues. This mini review presents a summary of recent developments in supercapacitor research and technology, including all kinds of supercapacitor design techniques using various electrode materials and production methods. It also covers the current progress achieved in novel materials for supercapacitor electrodes. The latest produced EDLC/hybrid/pseudo-supercapacitors have also been described. In particular, metal oxides, specifically ZnO, used as electrode materials are in focus here. Eventually, future developments, prospects, and challenges in supercapacitor research have been elaborated on.

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Current progress achieved in novel materials for supercapacitor electrodes: mini review

Phosphorus-doped 3D hierarchical porous carbon for high-performance supercapacitors: A balanced strategy for pore structure and chemical composition

Ni nanoparticles supported on graphene layers: An excellent 3D electrode for hydrogen evolution reaction in alkaline solution

Owing to the scarcity of platinum resources and their visible flaw with poor durability and severe anode methanol crossover, Pt-based catalysts for catalyzing ORR have been experiencing some problems lately. Hence, nonprecious metal catalysts which are expected to replace platinum-based catalysts have become popular green sustainable development topics. We chose a facile pyrolysis method for the synthesis of this material, making the resulting coating material present a state of effectively encapsulating all cobalt nanoparticles into slim nitrogen-doped carbon nanotubes after process optimization, and the cobalt content even reached 20.9 wt %. In the catalytic aspect, the optimized Co@NSCNTs show a half wave potential equivalent to Pt/C in alkaline medium. Then, better durability (after 60,000 s chronoamperometry, the current retention still remains 95%) and commendable resistance to methanol crossover performed than the literature confirmed. All these characteristics superior to Pt/C should be ascribed t...

Facile Synthesis of Cobalt Nanoparticles Entirely Encapsulated in Slim Nitrogen-Doped Carbon Nanotubes as Oxygen Reduction Catalyst

Exploiting high-efficiency catalysts toward hydrogen evolution reaction (HER) is a significant assignment nowadays. We find a quick and straightforward means to produce large-scale g-C3N4, which does not use template and easily obtains uniform nanostructures. And, we fabricate one-step preparation of a non-noble-metal catalyst, consisting of carbon material and transition metal only, by coupling graphitic carbon nitride (g-C3N4) with Ni. The results show that Ni/C3N4 composite catalyst possesses coral-like structure and its unique morphology is in favor of electrochemical activity for HER. Simultaneously, the Ni/C3N4 composite catalyst presented prominent activity on HER with a high exchange current density of 1.91 × 10–4 A cm–2, a low Tafel slope of 128 mV dec–1 and small overpotentials of 356 and 222 mV to reach current densities of 100 and 10 mA cm–2, which are superior to those of the state-of-the-art HER-active Ni-based compositions, as well as majority other metal-free catalysts, and even rivaled th...

Xiujuan Qin

Papers

Phosphorus-doped 3D hierarchical porous carbon for high-performance supercapacitors: A balanced strategy for pore structure and chemical composition

Ni nanoparticles supported on graphene layers: An excellent 3D electrode for hydrogen evolution reaction in alkaline solution

Facile Synthesis of Cobalt Nanoparticles Entirely Encapsulated in Slim Nitrogen-Doped Carbon Nanotubes as Oxygen Reduction Catalyst

Coral-like-Structured Ni/C3N4 Composite Coating: An Active Electrocatalyst for Hydrogen Evolution Reaction in Alkaline Solution

Preparation and electrochemical characteristic of porous NiO supported by sulfonated graphene for supercapacitors