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Asymmetric supercapacitors (ASCs) have attracted growing interest and attention in the field of supercapacitors owing to their high energy density and power density. In this work, ordered mesoporous Co3O4 samples with different pore sizes (ca. 20 nm and ca. 70 nm) are prepared via a hard template method. Flexible solid-state ASC devices based on mesoporous Co3O4 with pore size of 20 nm and activated carbon possesses a specific capacitance of 215 mF cm−2 (at 1.5 mA cm−2) and show excellent cycling performance. Electrochemical tests reveal that the mesoporous material with a larger specific surface area, that is, a smaller primary particle size, is more suitable for solid-state ASC device. The results provide a potential electrode material for ACSs. [ABSTRACT FROM AUTHOR]

Ordered porous CoO materials with pore sizes of 5 nm (CoO-5), 20 nm (CoO-20), and 70 nm (CoO-70) have been synthesized via a hard-template method and were studied as catalysts to bring insight into non-enzymatic electrochemical sensing of glucose. A glassy carbon electrode modified with CoO-70 responds more quickly and sensitively to glucose than those modified with CoO-5 or CoO-20. The sensor based on the use of CoO-70 and operated at a working voltage of 0.6 V (vs. Ag/AgCl) in 0.1 M NaOH solution shows a lower detection limit of 0.025 μM, good repeatability and high selectivity over ascorbic acid, uric acid, dopamine, and KCl. These results suggest that ordered porous CoO is a promising material for quantitative electrochemical determination of glucose, and that the pore size has a strong effect on performance. [ABSTRACT FROM AUTHOR]

Graphical abstract Using graphene as a conductive matrix, the homogeneous distribution of Co 3 O 4 nanoparticles was accomplished and volume changes in the nanoplates during charge–discharge process were effectively accommodated, resulting in the excellent electrochemical performance of the composites. The mesoporous structure of the Co 3 O 4 nanoparticles was suitable for the transfer of Ionic electrolyte by the electrochemical reaction. Co 3 O 4 /graphene nanocomposites are a candidate material for high-capacity, low-cost, and nontoxic electrode for supercapacitors. Highlights • Co 3 O 4 /graphene composites were prepared via an in situ thermal deposition method. • Graphene serves as an efficient conductive network for electrochemical reactions. • The nanocomposites exhibited high performance as supercapacitor electrodes. Abstract In situ synthesis of mesoporous Co 3 O 4 nanoparticles embedded in reduced graphene oxide nanosheets (GNSs) was implemented through coprecipitation method and pyrolytic process. In the charge-discharge process, electrolyte ions can fill with three-dimensional GNS matrix with connected pore network structures and mesoporous Co 3 O 4 nanoparticles with uniform nanoscale structures as double ion buffer reservoirs. The capacitance value of Co 3 O 4 /GNS nanocomposites is 1085.6 F g−1 at the current density of 2 A g−1 in 2 M KOH solution. The composite has good cyclic stability, and the maximum capacitance loss is only 17.3% in 10,000 successive cycles. [ABSTRACT FROM AUTHOR]

Amorphous core–shell CoO@C and Mn 3 O 4 @C composites have been synthesized by documenting a simple glucose–ethanol-assisted approach and characterized by SEM, TEM, X-ray diffraction, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Electrochemical measurements are performed to examine the CoO@C composites, and the result shows that CoO@C structure has much higher capacitance, higher energy and power density and better cycling performance than that of C/CoO hybrids. This improvement can be attributed to the nature of core–shell structure, which promotes fast Faradaic charging and discharging reaction and also minimizes both the ionic and electronic transportation distances and therefore improves the resulting electrode kinetic performance. [ABSTRACT FROM AUTHOR]

Abstract: Co3O4/graphene nanosheet (GNS) composites were synthesized via the in situ growth of mesoporous Co3O4 nanoparticles on graphene. The as-prepared Co3O4/GNS composites exhibited superior Li-ion battery performance and showed a large reversible capacity, excellent cycling, and good rate capability when used as an anode material in lithium ion batteries (LIBs). The uniform coating of Co3O4 around the graphene surface ensured tight electrical contact, resulting in a material with higher specific capacity and enhanced cycling performance compared with pure Co3O4 electrodes. The composites delivered a reversible capacity of 900mAhg−1 at a discharge current density of 100mAg−1 with good cycling ability. Moreover, the composites showed exceptional high-current charge–discharge performance, achieving 650mAhg−1 at a current density of 1000mAg−1. [Copyright &y& Elsevier]