Research On Structure Controls And Pseudocapacitive Performances Of Mesoporous Carbons And Mesoporous Metal Oxides

As a new kind of green energy storage device, supercapacitor has been of wide interest for applications in many fields, such as automobile, telecommunication, and military force, due to high energy density, high power density, and long cycle life, attracting more and more attention from researchers around the world. Ordered mesoporous carbons and mesoporous metal oxides have been recognized as ideal electrode materials due to their ordered mesoporous structures, uniform pore size distributions, high surface areas and high pore volumes. It is significative to research on the preparation of different mesoporous structures of ordered mesoporous carbons and mesoporous metal oxides and the influence of mesoporous structures on the pseudocapacitive performance.In this paper, ordered mesoporous silicas SBA-15, MSU-H, and KIT-6 were firstly synthesized by using the triblock copolymer P123 as the surfactant and TEOS or sodium silicate as the silicate precursor. Ordered mesoporous carbons OMC-M and OMC-K were further synthesized by using two-dimensional hexagonal MSU-H and three-dimensional cubic KIT-6, respectively, as the hard template and the sucrose as the carbon precursor. Ordered mesoporous carbons with tunable pore sizes in the range of 4 to 10 nm were obtained by adding some amount of boric acid in the carbon precursor. The as-synthesized samples were characterized by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy experiments. The results reveal that, as to OMC-M and OMC-K, OMC-M-6 and OMC-K-4 exhibited the highest specific capacitances of up to 203.8 and 190.4 F/g, respectively, at the scan rate of 5 mV/s. All ordered mesoporous carbons maintained 81⁸6 % of the specific capacitances when the scan rate changed from 5 mV/s to 100 mV/s. The specific surface capacitances of ordered mesoporous carbons increased with the increase of the pore sizes in the range of 4 to 8 nm and OMC-M-2 reached the highest value of 27.5μF/cm² at the scan rate of 5 mV/s.Ordered mesoporous NiO and NiO/Co₃O₄ composite were synthesized by using two-dimensional SBA-15 as the hard template and corresponding metal nitrates as the precursors, and the influence of the addition of citric acid into the precursors on the structure of metal oxides was also investigated. The characterization results reveal that, because of the adding of the citric acid into the precursors, the specific surface areas of NiO and NiO/Co₃O₄ composite increased from 123.8 and 115.8 m²/g to 238.4 and 170.8 m²/g, respectively. The results of electrochemical characterization show that the specific capacitances of NiO-CA and NiO/Co₃O₄-CA reached 220.1 and 625.8 F/g, respectively, which were 1.7 and 2.7 times of the NiO and NiO/Co₃O₄.