Qingyu Li

Porous nano-MnO2: large scale synthesis via a facile quick-redox procedure and application in a supercapacitor

A new type of porous nano-MnO2 for supercapacitors has been synthesized for the first time by a facile sonochemistry route from a quick-redox reaction between KMnO4 and D-glucose. The crystal structure, morphology and chemical composition of the MnO2 product were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). The results show that the porous MnO2 nanoparticles in the range 20–50 nm are interestingly composed of nanorods with diameters of about 2 nm and lengths of 4–8 nm. A possible growth mechanism of this nanostructure has been identified based on the experimental results. The electrochemical properties of the porous MnO2 were investigated in a symmetric capacitor cell using both 1 M Na2SO4 and 9 M KOH aqueous solutions. The results indicate that the MnO2 electrodes have a good capacitive performance in both cases.

Electrolytic Boronizing of Titanium in Na2B4O7-20%K2CO3

Using Na2B4O7-20%K2CO3 as molten salt, the electrolytic boronizing process was used to prepare TiB whiskers on the surface of the titanium. X-ray diffraction (XRD) and electron probe micro analysis (EPMA) techniques were applied to determine the phases and their contents in boride layer. The cross-section morphology of the boride layer was measured by scanning electron microscope (SEM). The results showed that the boride layer was composed of TiB2 and TiB, with continuous phase TiB2 as the outer layer and TiB whisker as the intermediate layer. The maximum length of TiB whisker could reach 230 µm, with an aspect ratio of over 1,000. The TiB whiskers were embedded into titanium substrate. The hardness of boride increase from 2,049.7 MPa to 3,270.6 MPa.

Tween20 surfactant effect on the electrocatalytic performance of porous carbon micro-spheres supported MnO2

This study is concerned with the electrocatalytic evolution of oxygen at polyoxyethylene sorbitan monolaurate (Tween20) modified porous carbon micro-spheres (PCS) supported MnO2 catalyst in 0.1 M KOH solution. The Super P (SP) was used to improve the electrical conductivity of the catalyst. The electrochemical measurements revealed a significant enhancement of the electrocatalytic activity of the MnO2/PCS towards the oxygen evolution reaction (OER) upon the Tween20 modification. The onset potentials of the OER at the Tween20 modified MnO2/PCS particles electrode are more negative by about 0.162 V compared with the bare (i.e. unmodified) MnO2/PCS electrode. Tween20 is absorbed on the surface of MnO2/PCS and covers the entire surface of the MnO2/PCS particles homogeneously. The Tween20 plays a vital role as a catalytic mediator, which facilitates the ion transfer during the water oxidation into molecular oxygen and thus the OER is accomplished at less positive potentials.