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Oxygen evolution reaction is a significant half-reaction for water splitting, while its sluggish kinetics and high-cost catalyst hinder the commercial application. In this work, we report a novel nanocoral-like NiSe2/g-C3N4 composite as highly efficient catalyst for water oxidation in 1.0 M KOH solution. Based on the support of multi-layered g-C3N4, NiSe2/g-C3N4 composite exhibits favorable electrocatalytic performances with low overpotential of 290 mV at current density of 40 mA cm−2 and low onset potential of 1.38 V (vs. RHE). In addition, NiSe2/g-C3N4 composite delivers higher current density (199 mA cm−2) than those of pure NiSe2 (142 mA cm−2) and multi-layered g-C3N4 (112 mA cm−2) at potential of 2.0 V (vs. RHE). Furthermore, NiSe2/g-C3N4 composite exhibits an excellent long-term electrochemical stability for 10 h. The outstanding electrocatalytic properties above suggest that NiSe2/g-C3N4 composite is a candidate for the substitution of noble metal based catalyst for oxygen evolution reaction.

The development of highly efficient and stable noble-metal-free electrocatalysts towards HER is of great significance. Herein, an electrodeposition method for the preparation of samarium oxide modified Ni-Co vertical nanosheets assembled three-dimensional honeycomb film on porous Ni foam (Sm2O3-Ni-Co/NF) is proposed. As-prepared Sm2O3-Ni-Co vertical nanosheets interweave together into a honeycomb morphology and uniformly cover the entire surface of Ni foam. The influence of content of Sm2O3 in electroplating bath on the electrocatalytic performances of Sm2O3-Ni-Co/NF electrode towards HER is studied in 1.0 M KOH electrolyte. Polarization curve indicates that the self-supported Sm2O3-Ni-Co/NF electrode exhibits remarkably enhanced electrocatalytic activity towards HER. To attain a current density of 10 mA cm−2, Sm2O3-Ni-Co/NF electrode needs lower overpotential (276 mV) than Ni-Co/NF electrode (301 mV). In addition, Sm2O3-Ni-Co/NF electrode exhibits a lower Tafel slope, demonstrating more favorable HER kinetics. Sm2O3-Ni-Co/NF electrode has smaller charge transfer resistance than Ni-Co/NF electrode, indicating a faster Faradic process and better HER kinetics. Besides, Sm2O3-Ni-Co/NF electrode features satisfactory long-term durability in alkaline media. The results indicate that Sm2O3-Ni-Co/NF electrode has potential application to water splitting devices for hydrogen generation.

In this work, oxygen-rich activated carbon compounds were prepared from three kinds of biomass by simple carbonization and they were investigated as electrodes for supercapacitors. The selected biomasses were waste dragon fruit skin, Momordica grosvenori skin and Firmiana catkins. Three kinds of as-prepared activated carbons showed abundant oxygen-containing groups and typical amorphous characteristics with high specific surface areas of 911.2 m2 g−1, 597.5 m2 g−1 and 286.7 m2 g−1, respectively. This combination of high specific surface areas and abundant active surface functional groups resulted in capacitances of 286.9 F g−1, 238.7 F g−1 and 226.6 F g−1 at 0.5 A g−1, respectively. Furthermore, three kinds of as-prepared activated carbons also showed excellent cycling performance with nearly 100% retention over 5000 cycles at 4.0 A g−1 in 2.0 mol l−1 KOH solution. As a result, three kinds of as-prepared activated carbons exhibited favorable electrochemical performances in potential application as electrode materials for supercapacitors.