Lina Sui

Bio: Lina Sui is an academic researcher from Qingdao University of Science and Technology. The author has contributed to research in topics: Materials science & Supercapacitor. The author has an hindex of 11, co-authored 31 publications receiving 382 citations.

High-Performance Supercapacitor of Graphene Quantum Dots with Uniform Sizes.

Abstract: Graphene quantum dots (GQDs) with uniform sizes of less than 5 nm are synthesized by a novel top-down strategy. Nitric acid as a strong oxidant can be used to cut graphene oxide via sonication and ...

High Performance of N-Doped Graphene with Bubble-like Textures for Supercapacitors

Abstract: Nitrogen-doped graphene (NG) with wrinkled and bubble-like texture is fabricated by a thermal treatment. Especially, a novel sonication-assisted pretreatment with nitric acid is used to further oxidize graphene oxide and its binding with melamine molecules. There are many bubble-like nanoflakes with a dimension of about 10 nm appeared on the undulated graphene nanosheets. The bubble-like texture provides more active sites for effective ion transport and reversible capacitive behavior. The specific surface area of NG (5.03 at% N) can reach up to 438.7 m2 g-1 , and the NG electrode demonstrates high specific capacitance (481 F g-1 at 1 A g-1 , four times higher than reduced graphene oxide electrode (127.5 F g-1 )), superior cycle stability (the capacitance retention of 98.9% in 2 m KOH and 99.2% in 1 m H2 SO4 after 8000 cycles), and excellent energy density (42.8 Wh kg-1 at power density of 500 W kg-1 in 2 m KOH aqueous electrolyte). The results indicate the potential use of NG as graphene-based electrode material for energy storage devices.

Remarkable improvement of TiO2 for dye photocatalytic degradation by a facile post-treatment

Abstract: A simple hydrothermal post-treatment has been developed to construct a TiO2 photocatalyst with a desirable anatase phase, porous structure, large surface area, small particle size and hydrophilic surface. When aggregated nanoparticles are treated under a high temperature and pressure, the crystal structure of TiO2 is first deeply destroyed and then reconstructed. The dispersity can then be greatly improved and a typical mesoporous structure is simultaneously produced, accompanied with an increase in the specific surface area, average pore size, total pore volume and the production of oxygen vacancies. The structural changes have positive effects on the photocatalytic degradation of dye molecules. For example, the kinetic constant (0.085 min−1) can be increased by 10 times as compared with that for the untreated ones (0.0085 min−1). Other parameters including temperature, time, solvent, calcination treatment and type of TiO2 are also explored to optimize the treatment. In addition, electrochemical tests prove that the hydrothermal post-treatment for TiO2 results in an accelerated O2 reduction reaction and improved photo-induced charge transfer process. From radical quenching experiments, superoxide radicals (O2−˙) are proven to be the major oxidative species for both post-treated and untreated TiO2, but the production of hydroxyl radicals (˙OH) is dramatically promoted by the post-treatment, which is a key factor for the acceleration of the photocatalytic reaction.

Ultracapacitors: Why, How, and Where is the Technology

Abstract: The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

High Rates of Oxygen Reduction over a Vapor

Abstract: The air electrode, which reduces oxygen (O2), is a critical component in energy generation and storage applications such as fuel cells and metal/air batteries. The highest current densities are achieved with platinum (Pt), but in addition to its cost and scarcity, Pt particles in composite electrodes tend to be inactivated by contact with carbon monoxide (CO) or by agglomeration. We describe an air electrode based on a porous material coated with poly(3,4-ethylenedioxythiophene) (PEDOT), which acts as an O2 reduction catalyst. Continuous operation for 1500 hours was demonstrated without material degradation or deterioration in performance. O2 conversion rates were comparable with those of Pt-catalyzed electrodes of the same geometry, and the electrode was not sensitive to CO. Operation was demonstrated as an air electrode and as a dissolved O2 electrode in aqueous solution.

Fabrication of symmetric supercapacitors based on MOF-derived nanoporous carbons

Abstract: Nanoporous carbon (NPC) materials with high specific surface area have attracted considerable attention for electrochemical energy storage applications. In the present work, we have designed novel symmetric supercapacitors based on NPC by direct carbonization of Zn-based metal-organic frameworks (MOFs) without using an additional precursor. By controlling the reaction conditions in the present study, we synthesized NPC with two different particle sizes. The effects of particle size and mass loadings on supercapacitor performance have been carefully evaluated. Our NPC materials exhibit excellent electrochemical performance with a maximum specific capacitance of 251 F g-1 in 1 M H2SO4 electrolyte. The symmetric supercapacitor studies show that these efficient electrodes have good capacitance, high stability, and good rate capability.