A significant challenge in developing high-performance hybrid supercapacitors (HSCs) is the need to reasonably construct advanced architectures that consist of various components and exhibit superior electrochemical capacitance performance. The FeCoNi-layered double hydroxide (FeCoNi-LDH) porous material has a specific capacitance of 1960 F·g⁻¹ when used as the anode material at 1 A·g⁻¹. The FeCoNi-LDH material exhibits nanoplates with a distinct spindle morphology on their surface. Due to the combined action of the three metals and abundant oxygen vacancies, they exhibit unique rate performance and cycle stability. The electronic structure of LDH and the regulation of oxygen vacancy were confirmed by density functional theory (DFT) calculations. This suggests that the strength of hydroxide can reduce the energy required for oxygen vacancy formation in FeCoNi-LDH nanosheets and enhance ion and charge transfer, as well as electrolyte adsorption on the electrode surface. The FeCoNi-LDH//activated carbon (AC) HSC has an energy density of 53.2 Wh·kg⁻¹ at a power density of 800 W·kg⁻¹, surpassing other devices composed of comparable materials during the same timeframe. This study made significant advances in the design and synthesis of a ternary LDH porous structure with distinct oxygen vacancies, as well as its potential application in electrochemical energy storage.

The effective, stable, and secure catalysts are essential for sulfate radical (SO₄^·−)-based advanced oxidation processes (SR-AOPs) to the degradation of organic contaminants in water. Heterogeneous supported cobalt-based catalysts are commonly used to activate peroxymonosulfate (PMS) to achieve the degradation. In this work, we synthesized Co₃O₄@Al₂O₃ three-dimensional (3D) mesoporous nanocomposite (denoted as Co₃O₄@Al₂O₃ 3DPNC) in just one step by calcining cheap and green deep eutectic solvent (DES) solution containing Co salt. Co₃O₄@Al₂O₃ 3DPNC with the high specific surface area (93.246 m²/g), uniform pore distribution (3.829 nm) and rich porosity (0.255 cm³/g) were attained in a beautiful hierarchical structure which exhibited the open 3D propeller-like microstructure, two-dimensional lamellar substructure with rich folds, as well as the decoration of highly dispersed Co₃O₄ nanoparticles on mesoporous amorphous Al₂O₃. The excellent chemical and thermal stability of Al₂O₃ ensures the high stability of the catalyst, and the formation of the complex hierarchical structure makes the active Co₃O₄ be homogenously dispersed for effective catalysis. The catalyst demonstrated outstanding performance for catalytic degradations of organic pollutants (acetaminophen, oxytetracycline, 5-sulfosalicylic acid, orange G and Rhodamine B) by generated SO₄^·−, ·OH and ¹O₂. With a very low cobalt content (equal to 28.2 mg/L of Co), the catalyst exhibited very high stability and excellent reusability in the recycling usages, while the leaching of the cobalt element (< 0.145 mg/L) was also at a low level. Our catalyst achieved effective degradations of acetaminophen in cycles without losing its stable hierarchical nanostructure.