Tianyi Kou

Abstract: Carbonaceous materials are attractive supercapacitor electrode materials due to their high electronic conductivity, large specific surface area, and low cost. Here, a unique hierarchical porous N,O,S‐enriched carbon foam (KNOSC) with high level of structural complexity for supercapacitors is reported. It is fabricated via a combination of a soft‐template method, freeze‐drying, and chemical etching. The carbon foam is a macroporous structure containing a network of mesoporous channels filled with micropores. It has an extremely large specific surface area of 2685 m2 g−1. The pore engineered carbon structure is also uniformly doped with N, O, and S. The KNOSC electrode achieves an outstanding capacitance of 402.5 F g−1 at 1 A g−1 and superior rate capability of 308.5 F g−1 at 100 A g−1. The KNOSC exhibits a Bode frequency at the phase angle of −45° of 18.5 Hz, which corresponds to a time constant of 0.054 s only. A symmetric supercapacitor device using KNOSC as electrodes can be charged/discharged within 1.52 s to deliver a specific energy density of 15.2 W h kg−1 at a power density of 36 kW kg−1. These results suggest that the pore and heteroatom engineered structures are promising electrode materials for ultrafast charging.

TL;DR: In this article, a functionalized oxygen-deficient Co 3 O 4 nanorods were used for supercapacitor and water splitting dual applications, achieving a significantly high specific capacitance of 739 F ǫ g − 1 and an ultralow overpotential of 275 mV at 10mV at OER with ultralong stability of over 300 mV.

TL;DR: The Ni foam-supported Fe-doped β-Ni(OH)2 nanosheets achieved an overpotential of 219 mV at the geometric current density of 10 mA cm-2.

Abstract: Nickel sulfide (Ni3S2) is a promising hydrogen evolution reaction (HER) catalyst by virtue of its metallic electrical conductivity and excellent stability in alkaline medium. However, the reported catalytic activities for Ni3S2 are still relatively low. Herein, an effective strategy to boost the H adsorption capability and HER performance of Ni3S2 through nitrogen (N) doping is demonstrated. N‐doped Ni3S2 nanosheets achieve a fairly low overpotential of 155 mV at 10 mA cm−2 and an excellent exchange current density of 0.42 mA cm−2 in 1.0 m KOH electrolyte. The mass activity of 16.9 mA mg−1 and turnover frequency of 2.4 s−1 obtained at 155 mV are significantly higher than the values reported for other Ni3S2‐based HER catalysts, and comparable to the performance of best HER catalysts in alkaline medium. These experimental data together with theoretical analysis suggest that the outstanding catalytic activity of N‐doped Ni3S2 is due to the enriched active sites with favorable H adsorption free energy. The activity in the Ni3S2 is highly correlated with the coordination number of the surface S atoms and the charge depletion of neighbor Ni atoms. These new findings provide important guidance for future experimental design and synthesis of optimal HER catalysts.