Papers by Author: Ren Qing Wang

Abstract: In order to improve capacitance in supercapacitors application, activated carbon (AC) was modified by nitric acid oxidizing treatment. Oxygen-containing functional groups (OCFG) were detected by using FTIR techniques. Cyclic voltammetry and constant current charge-discharge were used to characterize the electrochemical performance of the samples in 6 mol/L KOH solution. FTIR studies showed that chemical modification promoted the formation of OCFG on the surface of AC. It was found that the contribution rate of pseudo-capacitance to the total capacitance increased significantly with the extent of oxidization treatment. When oxidized by 50% HNO3, AC achieved a specific capacitance of 197.26F/g at a current density of 20mA/cm2 corresponding to an increasing rate up to 20%.

Abstract: In this work, activated carbon was modified by ammonia water. Cyclic voltammetry and constant current charge-discharge were used to characterize the electrochemical performance of the samples in 1.0 mol/L Et₄NBF₄-PC solution. As a result, optimal conditions for surface modification of activated carbon have been examined as an ammonia solution concentration of 5wt.%. Specific capacitance can be improved significantly by surface modification of carbon materials. The specific capacitance of the carbon modified with 5.0wt.% ammonia water reached 114 F/g at a current density of 3.0 mA/cm2, which is 14% higher than that of untreated sample. In addition, the modified carbon materials possess excellent power performance.

Abstract: Commercial activated carbon was modified by surface treatment using nitric acid, The modified carbons were characterized by X-ray photoelectron spectroscopy (XPS). The resultant carbon electrode-based electric double-layer capacitors (EDLCs) were assembled with 1 mol/L (NH₄)₂SO₄ as the electrolyte. The influence of introduced functional groups, such as hydroxyl and carbonyl, on the performance of EDLCs was studied by Constant current charge-discharge. These functional groups significantly improved the wettability of AC. As a result, the specific capacitance of the carbon modified with 40wt.%HNO₃ achieved a specific capacitance of 223.45 F/g at a current density of 5mA/cm², which is 100.9% higher than that of original AC.

Abstract: SiO₂, CaO and MgO was chosen as main raw material and Solid State method was used to prepare the samples. The precursor was directly sintered at 1000°Cfor 3h to obtain new green CaMgSi₂O₆:Eu³⁺,Li⁺Phosphors.The effects of the content of the doping ions Eu³⁺ on the luminescent properties have been studied. The structure, morphology and luminescent properties of the phosphors were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM),UV and PL-PLE spectra respectively.The results showed that the CaMgSi₂O₆:Eu³⁺,Li⁺ was base-centered monoclinic crystals, the phosphor particle distributed uniformly.The phosphor has a strong absorptive capacity excited by 248 nm ultraviolet ray, and could emit the strong red light with the wavelength of 590nm(⁵D₀→⁷F₁)and 615nm(⁵D₀→⁷F₂). The CaMgSi₂O₆:Eu³⁺,Li⁺ is a new type of red fluorescent material.

Abstract: SiO2，CaO and MgO was chosen as main raw material and Solid State method was used to prepare the sample. The precursor was directly sintered at 1000°C with reducing atmosphere for 3 h to obtain new green CaMgSi2O6:Tb3+,Li+Phosphors.The effects of the content of the doping ions Tb3+ on the luminescent properties have been studied. The structure, morphology and luminescent properties of the phosphors were characterized by XRD,SEM,UV and PL-PLE spectra respectively.The results showed that the CaMgSi2O6:Tb3+,Li+ was base-centered monoclinic crystals, the phosphor particle distributed uniformly.The phosphor has a strong absorptive capacity excited by 230 nm ultraviolet ray, and could emit the strong green light with the wavelength of 543 nm(5D4→7F5). The CaMgSi2O6:Tb3+,Li+ is a new type of green fluorescent material.

Abstract: Activated carbon was fabricated by using phenolic resin as carbon source, tween-80 as organic template, KOH as activator. The samples were analyzed by N2 adsorption, scanning electron microscopy (SEM). Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical performance of the samples. The results showed that specific surface area of the prepared sample was 1935.99 m2/g, pore size was mainly in the range of 1.0～4.0 nm and showed typical capacitance characteristics in cyclic voltammetry. At a current density of 15mA/cm2, a specific capacitance of 246.18F/g was achieved and the resistance was 1.11Ω. Supercapacitors based on the sample had low ESR and excellent power property.

Abstract: Activated carbon was fabricated by using phenolic resin as carbon source, PEG as organic template, KOH as activator. The samples were analyzed by N2 adsorption, scanning electron microscopy (SEM). Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical performance of the samples. The results showed that the specific surface area of the prepared sample (AC1) was 2469 m2/g, the pore size was mainly in the range of 1.0～4.0 nm. At a current density of 7.5 mA/cm2, a specific capacitance of 327F/g was achieved, the equivalent series resistance (ESR) was 0.8Ω. Supercapacitors based on the sample have low ESR and excellent power property. For comparison, commercial AC (AC2) was also studied.

Abstract: CaCO3 was chosen as main raw material and wet chemical method was used to prepare the precursor. The precursor was directly sintered at 1060oC with reducing atmosphere for 3 h to obtain new green CaO:Tb3+ ,Li+ Phosphors. The effects of the content of the doping ions Tb3+ and Li+ on the luminescent properties have been studied. The structure, morphology and luminescent properties of the phosphors were characterized by XRD, laser particle size analyzer, SEM, UV and PL-PLE spectra respectively. The results showed that the CaO:Tb3+,Li+ was a single face-centered cubic crystals, the phosphor particle distributed uniformly, the average size of particle was 2μm. The phosphor has a strong absorptive capacity excited by 282 nm ultraviolet ray, and could emit the strong green light with the wavelength of 543 nm(5D4→7F5). The CaO:Tb3+,Li+ is a new type of green fluorescent material.