Papers by Author: Qun Jie Xu

Abstract: With the development of the portable electronics industry, the need for more efficient power sources has been enlarged. Lithium-ion batteries are able to deliver high energy densities, high capacity and long cycle life at reasonable costs among competing energy storage technologies. The major goal of this paper is to introduce the promising Li-rich cathode material xLi₂MnO₃·(1-x) LiMO₂(M=Ni, Co, Mn...), which owns enhanced energy and power density, high energy efficiency, superior rate capability and excellent cycling stability due to different modification methods.

Abstract: As a fascinating two-dimensional nanomaterial, graphene is attractive for electrocatalytical application in direct methanol fuel cells due to its unique structure and outstanding physical properties. Graphene and its derivatives have been widely used as a support material to improve electrocatalytical activity of catalyst particles for methanol and ethanol oxidations. In this review, discussion is focused on the graphene supported monometallic and bimetallic nanocrystals hybrid materials for electrocatalysts. Additionally, the nitrogen-doped graphene utilized for promising support material in electrocatalysts was also mentioned. We believe that the article will be useful to researchers interested in graphene-based catalyst and related materials for direct methanol fuel cells and provide the present status of the subject.

Abstract: Ascorbic acid (VC) was used as carbon source for Li₂MnSiO₄/C composite synthesized by a sol-gel method. By comparing the electrochemical performance of the Li₂MnSiO₄/C composite and pure Li₂MnSiO₄, it was found that VC adding can improve the capacity of Li₂MnSiO₄. The Li₂MnSiO₄/C with 10% VC shows a discharge capacity of 212 mAh/g at 0.05C and Li₂MnSiO₄/C with 15% VC shows discharge capacity of 192 mAh/g at 0.1C, that were higher than the capacity of pure Li₂MnSiO₄.

Abstract: With copper and copper alloys widely used, copper corrosion has already caused huge economic losses. Super-hydrophobic surface treatment, a new kind of corrosion resistant technology, can effectively inhibit metal corrosion. This paper introduces the basic issues and the construction methods of copper and copper alloys super-hydrophobic surface. The effect of super-hydrophobic surface on the corrosion performance of copper and copper alloys is analyzed emphatically. Recent developments of super-hydrophobic surface and the existed technical barriers are also summarized in the paper.

Abstract: SnO₂ coatings were supplied on the surface of 304 stainless steel (304SS) by a sol-gel process followed by hydrothermal treatments at different reaction temperature and time, respectively. The effects of hydrothermal temperature and time in pure water on the anticorrosion performances of the SnO₂ films in simulated proton exchange membrane fuel cells (PEMFC) environments were investigated by potentiodynamic polarization curves, open circuit potential-time curves and electrochemical impedance spectroscopy (EIS). It was found that the SnO₂ coated 304SS via the hydrothermal treatment showed a better corrosion resistance than the sample without hydrothermal treatment and bare 304SS. The SnO₂ coated 304SS hydrothermally treated at 160°C for 3h showed the highest corrosion resistance among the samples. The results have been discussed in terms of surface structure of SnO₂ film and its anticorrosion performance in simulated PEMFC environments.

Abstract: Due to the intensifying energy crisis, the fuel cell research gradually becomes a hot spot, because it is non-toxic, cleaning, inexpensive and easy to obtain. However, there are still many problems in DEFC research, such as cathode, anode catalyst, battery electrode preparation and others. This paper reviews the preparation methods of DEFC anode catalyst, including impregnation reduction method, microemulsion method, and the other methods.

Abstract: Li-rich layered xLi₂MnO₃-(1-x) LiMO₂(M=Ni,Co,Mn...) solid solution materials possess high energy density, high capacity, and long cycle life. Meanwhile, the electrochemical charge/discharge mechanism is quite different. In this paper, Li-rich cathode material xLi₂MnO₃-(1-x) LiMO₂(M=Ni,Co,Mn...) is introduced though its structure, charge/discharge mechanism, synthetic methods and electrochemical performance. What is more, the characteristics and development trend of this series of cathode material are summarized.

Abstract: Fuel cell is one of the most promising power sources towards high-efficiency, low-emission and environmental benign application. In pursuit of a higher performance, electrocatalyst is a crucial research focus. Compared with commercial carbon support, TiO₂ exhibits the advantages of higher stability, higher porosity and stronger metal-support interaction. In this article, we give a brief overlook on the influence of diverse crystal and morphology structures on their eletrocatalytic property in fuel cells. Besides, to better meet the demand of practical electrocatalysts, three different methods are summarized to overcome its relatively poor electrical conductivity. Overall, TiO₂ is a promising support material of electrocatalysts in fuel cells.

Abstract: Direct ethanol fuel cells are considered a promising power source for future portable electronic and automotive applications. This article reviewed the synthetic methods commonly used to prepare Pd-based catalysts for the ethanol electrooxidation in alkaline media. The progress in the mechanism studies of ethanol oxidation reaction (EOR) on Pd electrode in alkaline medium by cyclic voltammetry and electrochemical in situ FTIR spectroscopy was also reviewed. The recent studies revealed that the EOR is fairly complicated, and it is difficult in CC bond cleavage for the complete oxidation of ethanol to CO₂, and ethanol is selectively oxidized to acetate on Pd-based catalysts in alkaline media. Overall, what is most important is to explore new Pd-based alloy catalysts with high ability to break the CC bond to promote complete oxidation of ethanol as well as increase the efficiency of DEFCs.

Abstract: SnO₂ films were supplied on the surface of 304 stainless steel (304SS) by a sol–gel process followed by a hydrothermal post treatment. The measurements of XRD, SEM and water contact angles were carried out to characterize the as-prepared samples. The effect of hydrothermal post treatments in different media such as deionized (DI) water, HF solution and NaOH solution on the corrosion performances of the SnO₂ films in simulated proton exchange membrane fuel cells (PEMFC) environments was investigated by electrochemical impedance spectroscopy (EIS) and polarization measurements. The results suggested that the SnO₂ films via the hydrothermal post treatment in 0.3 M NaOH solution showed a highest corrosion resistance and could act as an optimal barrier layer to metallic bipolar plates in simulated PEMFC environments. It could be attributed that the hydrothermal post treatment in NaOH solution was beneficial to improve the compact structure and enhance the hydrophobic property of the SnO₂ films.