Porous carbon-based supercapacitor has been regarded as a promising candidate for powering wearable electronics. To improve its energy density and mechanical flexibility, great efforts have been made to design ideal porous carbon. However, it is still difficult to synthesize ideal porous carbon with reasonable pore size distribution. Herein, glucose-derived two-dimensional nitrogen-doped hierarchical porous carbon nanosheets (2D-NPC) are synthesized through a one-step pyrolysis-activation process. Melamine and potassium oxalate are used to provide synergistic blowing/activation effect and tailor the physicochemical properties of 2D-NPC for energy-storage applications, including 2D morphology, high specific surface area, well-defined hierarchical pores, and rich N-content (6.1 at. %). Benefiting from these unique features, the 2D-NPC-based electrode exhibits a high specific capacitance of 523 F g–1 in 6 M KOH electrolyte in a three-electrode system. The symmetric supercapacitor exhibits a high energy density of 108 W h kg–1 at 900 W kg–1 in an organic electrolyte. The fabricated flexible supercapacitor manifests an areal energy density of 83 μW h cm–2 at an areal power density of 625 μW cm–2. Our work provides a simple method to tune the physicochemical properties of porous carbon toward high-performance flexible supercapacitors.

No abstract

The renewable energy technologies require electrocatalysts for reactions, such as the oxygen and/or hydrogen evolution reaction (OER/HER). They are complex electrochemical reactions that take place through the direct transfer of electrons. However, mostly they have high over-potentials and slow kinetics, that is why they require electrocatalysts to lower the over-potential of the reactions and enhance the reaction rate. The commercially used catalysts (e.g., ruthenium nanoparticles—Ru, iridium nanoparticles—Ir, and their oxides: RuO2, IrO2, platinum—Pt) contain metals that have poor stability, and are not economically worthwhile for widespread application. Here, we propose the spinel structure of nickel-cobalt oxide (NiCo2O4) fabricated to serve as electrocatalyst for OER. These structures were obtained by a facile two-step method: (1) One-pot solvothermal reaction and subsequently (2) pyrolysis or carbonization, respectively. This material exhibits novel rod-like morphology formed by tiny spheres. The presence of transition metal particles such as Co and Ni due to their conductivity and electron configurations provides a great number of active sites, which brings superior electrochemical performance in oxygen evolution and good stability in long-term tests. Therefore, it is believed that we propose interesting low-cost material that can act as a super stable catalyst in OER.

This study reveals a simple approach to recycle wasted coffee grounds into highly valuable carbon material with superior electrochemical performance. Activated carbon prepared from wasted coffee grounds has been formed via hydrothermal acidic hydrolysis followed by a KOH chemical activation at 800 ∘C. To understand the electrochemical properties of the sample, a set of characterization tools has been utilized: N2 and CO2 adsorption–desorption isotherms, thermal gravimetric analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and scanning electron microscopy. The specific surface area obtained from a Brunner–Emmett–Teller (BET) analysis reached 2906±19m2g−1. Prepared sample (designated as ACG-800KOH) was tested as electrode material in an electric double layer capacitor (EDLC) device with ionic liquid PYR13-TFSI as an electrolyte. The EDLC test was conducted at temperatures ranging from 20 to 120 ∘C. The specific material capacitance reached 178 Fg−1 measured at 20 ∘C and 50 A g−1 and was in the range 182 to 285 Fg−1 at the 20 to 120 ∘C temperature range.

Herein, we report fabrication of MoSe 2 functionalized with bimetal Co/Ni particles, which shows promising electrochemical performance in oxygen and hydrogen evolution reactions (OER and HER) due to its physicochemical properties such as electronic configuration and great electrochemical stability. We propose functionalization with two transition metals, cobalt and nickel, expecting a synergic effect in electrocatalytic activity in a water splitting reaction. These electrocatalytic reactions are essential for efficient electrochemical energy storage. The thin flakes were obtained by exfoliation of bulk molybdenum diselenide. Next, after deposition of metals, precursors were carbonized. Electrochemical data reveal that the presence of Ni and Co particles boosts electrocatalyst performance, providing a great number of active sites due to their conductivity. Interestingly, the material exhibited great evolution potential and good stability in long-term tests.