Effect of pulse electrodeposition parameters on electrocatalytic the activity of methanol oxidation and morphology of Pt/C catalyst for direct methanol fuel cells

Ye, Feng,Xu, Chao,Liu, Guicheng,Yuan, Mengdi,Wang, Zhiming,Du, Xiaoze,Lee, Joong Kee Pergamon 2018 Energy Conversion and Management Vol. No.

<P><B>Abstract</B></P> <P>The electrodeposition technique for preparing direct methanol fuel cell electrodes has been developed to increase the Pt utilization and lower the Pt loading. The performance of the Pt/C electrode for methanol oxidation reaction (MOR) was optimized by adjusting the electrodeposition parameters such as applied electrical signal types, ratios of t<SUB>on</SUB>/t<SUB>off</SUB>, deposition temperatures, and electrolyte concentrations, systematically. Furthermore, the effects of two kinds of additives, i.e. polyethylene glycol (PEG) and sodium dodecyl sulfonate (SDS), on the catalytic performance and morphology of Pt catalyst were investigated for MOR by SEM, XRD, cyclic voltammetry and linear sweep voltammetry. The results show that the optimal Pt catalyst has been prepared by the square wave current method with t<SUB>on</SUB>/t<SUB>off</SUB> of 1 s/5 s at 30 °C in a 1.0 mmol L<SUP>−1</SUP> H<SUB>2</SUB>PtCl<SUB>6</SUB> solution with a 10<SUP>−4</SUP> mmol L<SUP>−1</SUP> PEG additive. Moreover, the effect of the additive type and amount on the formation mechanism of the Pt crystallite morphology has also been discussed. From the results, introducing additives into the deposition solution in the pulse electrodeposition process is useful for designing and fabricating electrocatalytic electrodes for direct methanol fuel cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Signals include square wave current and potential, cyclic voltammetry and constant current pulse. </LI> <LI> Effects of four applied electrical signal types on Pt catalytic performance are compared. </LI> <LI> Parameters for Pt electrodeposition in constant current pulse mode are optimized systematically. </LI> <LI> Effect mechanism of additive on growth of Pt catalyst is studied in pulse electrodeposition. </LI> <LI> Optimal condition is t<SUB>on</SUB>/t<SUB>off</SUB> of 1 s/5 s, 30 °C, 1 mmol L<SUP>−1</SUP> H<SUB>2</SUB>PtCl<SUB>6</SUB> solution with 10<SUP>−4</SUP> mmol L<SUP>−1</SUP> PEG. </LI> </UL> </P>

Epigallocatechin gallate has pleiotropic effects on transmembrane signaling by altering the embedding of transmembrane domains

Ye, Feng,Yang, Chansik,Kim, Jiyoon,MacNevin, Christopher J.,Hahn, Klaus M.,Park, Dongeun,Ginsberg, Mark H.,Kim, Chungho American Society for Biochemistry and Molecular Bi 2017 The Journal of biological chemistry Vol.292 No.24

<P>Epigallocatechin gallate (EGCG) is the principal bioactive ingredient in green tea and has been reported to have many health benefits. EGCG influences multiple signal transduction pathways related to human diseases, including redox, inflammation, cell cycle, and cell adhesion pathways. However, the molecular mechanisms of these varying effects are unclear, limiting further development and utilization of EGCG as a pharmaceutical compound. Here, we examined the effect of EGCG on two representative transmembrane signaling receptors, integrin alpha IIb beta 3 and epidermal growth factor receptor (EGFR). We report that EGCG inhibits talin-induced integrin alpha IIb beta 3 activation, but it activates alpha IIb beta 3 in the absence of talin both in a purified system and in cells. This apparent paradox was explained by the fact that the activation state of alpha IIb beta 3 is tightly regulated by the topology of beta 3 transmembrane domain (TMD); increases or decreases in TMD embedding can activate integrins. Talin increases the embedding of integrin beta 3 TMD, resulting in integrin activation, whereas we observed here that EGCG decreases the embedding, thus opposing talin-induced integrin activation. In the absence of talin, EGCG decreases the TMD embedding, which can also disrupt the integrin alpha-beta TMD interaction, leading to integrin activation. EGCG exhibited similar paradoxical behavior in EGFR signaling. EGCG alters the topology of EGFR TMD and activates the receptor in the absence of EGF, but inhibits EGF-induced EGFR activation. Thus, this widely ingested polyphenol exhibits pleiotropic effects on transmembrane signaling by modifying the topology of TMDs.</P>

Significantly Elevated Dielectric and Energy Storage Traits in Boron Nitride Filled Polymer Nano-Composites with Topological Structure

Yefeng Feng,Jianxiong Zhang,Jianbing Hu,Shichun Li,Cheng Peng 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.2

Interface induced polarization has a prominent influence on dielectric properties of 0–3 type polymer based composites containingSi-based semi-conductors. The disadvantages of composites were higher dielectric loss, lower breakdown strength andenergy storage density, although higher permittivity was achieved. In this work, dielectric, conductive, breakdown and energystorage properties of four nano-composites have been researched. Based on the cooperation of fluoropolymer/alpha-SiC layerand fluoropolymer/hexagonal-BN layer, it was confirmed constructing the heterogeneous layer-by-layer composite structurerather than homogeneous mono-layer structure could significantly reduce dielectric loss, promote breakdown strength andincrease energy storage density. The former worked for a larger dielectric response and the latter layer acted as a robust barrierof charge carrier transfer. The best nano-composite could possess a permittivity of 43@100 Hz (~ 3.3 times of polymer),loss of 0.07@100 Hz (~ 37% of polymer), discharged energy density of 2.23 J/cm3@249 kV/cm (~ 10 times of polymer)and discharged energy efficiency of 54%@249 kV/cm (~ 5 times of polymer). This work might enlighten a facile route toachieve the promising high energy storage composite dielectrics by constructing the layer-by-layer topological structure.

Size-Controlled Silver Nanoparticles Confined in Ordered Mesoporous Silica and Their Enhanced Catalytic Activities

Xiaofei Zhou,Jiawei Wan,Yefeng Liu,Di Liu,Hong Wang,Xiaoyong Lai,Yanzhao Zou,Guo Lin,Jian Chen 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.9

A cooperative assembly route has been developed, by which silver nanoparticles with controlled sizes are incorporated into the channels of ordered cubic mesoporous silica (KIT-6) with different pore sizes (4.3–6.4 nm). The samples were characterized by XRD, TEM, FT-IR, UV-Vis and N2 physisorption. The pore wall of mesoporous silica can efficiently confine the growth of silver nanoparticles within the channels and their average sizes decreased with the pore size reduction of KIT-6. Catalytic activities of the resultant Ag/KIT-6-x (x stands for hydrothermal temperature) composite for reducing harmful organic dye Rhodamine B (Rh B) by sodium borohydride (NaBH4) were investigated. All the Ag/KIT-6 composite samples show great catalytic activities, among which Ag/KIT-6-80 with higher loading and smaller size of Ag nanoparticles exhibits higher catalytic activity than those of Ag/KIT-6-60 and Ag/KIT-6-100.

Mirror symmetry for exceptional unimodular singularities

Li, Changzheng,Li, Si,Saito, Kyoji,Shen, Yefeng European Mathematical Society Publishing House 2017 Journal of the European Mathematical Society Vol.19 No.4

Finely-reconciled high dielectric constant and low dielectric loss in ternary polymer/Cr2C3/montmorillonite composite films by filler-synergy strategy

Deng Qihuang,Zhou Junquan,Li Xianping,Feng Yefeng,Liang Yurun,Liu Qihang 한국물리학회 2021 Current Applied Physics Vol.22 No.-

Polymer/conductive ceramic composites with high dielectric constant have become research hotspot of dielectric capacitor materials. However, the conductivity and dielectric loss increase when high dielectric constant is achieved. In order to reconcile high dielectric constant and low dielectric loss, in this study, poly (vinylidene fluoride) (PVDF)/chromium carbide (Cr2C3)/montmorillonite (MMT) ternary composite films were prepared by solution cast. Dielectric response based on interfacial polarization was improved and dielectric constant of composites was increased. MMT ceramic was used to suppress interface leakage current. Compared with PVDF/ Cr2C3 composites, the conductivity and dielectric loss of ternary composites were reduced.

Lowering Dielectric Loss and AC Conductivity of Polymer/HfC Composite Dielectric Films via Insulating Montmorillonite Barrier

Peiyao Chen,Binghe Chen,Ben Qin,Jiangqiong Wang,Qihuang Deng,Yefeng Feng 한국고분자학회 2021 Macromolecular Research Vol.29 No.9

Present work aimed at studying the effect of montmorillonite (MMT) on dielectric and conductive properties of composites based on polymer/hafnium carbide (HfC) mother composite system. Polymer/HfC/MMT composite films based on double-filler modification strategy were prepared by solution cast. To obtain control group, binary polymer/HfC composite films were prepared. MMT ceramic had excellent insulation property, which could suppress interface leakage current and thus reduce dielectric loss of composites. Compared with binary system, ternary system could show better overall electric features including mildly reduced permittivity, obviously reduced dielectric loss and conductivity. Optimized ternary composite bearing 3 wt% HfC and 3 wt% MMT exhibited a high permittivity of 34, low dielectric loss of 0.33 and low conductivity of 5.5 × 10-7 S m-1 at 100 Hz. This research might enable the fabrication of advanced composite dielectrics.

A Noisy-Robust Approach for Facial Expression Recognition

( Ying Tong ),( Yuehong Shen ),( Bin Gao ),( Fenggang Sun ),( Rui Chen ),( Yefeng Xu ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.4

Accurate facial expression recognition (FER) requires reliable signal filtering and the effective feature extraction. Considering these requirements, this paper presents a novel approach for FER which is robust to noise. The main contributions of this work are: First, to preserve texture details in facial expression images and remove image noise, we improved the anisotropic diffusion filter by adjusting the diffusion coefficient according to two factors, namely, the gray value difference between the object and the background and the gradient magnitude of object. The improved filter can effectively distinguish facial muscle deformation and facial noise in face images. Second, to further improve robustness, we propose a new feature descriptor based on a combination of the Histogram of Oriented Gradients with the Canny operator (Canny-HOG) which can represent the precise deformation of eyes, eyebrows and lips for FER. Third, Canny-HOG`s block and cell sizes are adjusted to reduce feature dimensionality and make the classifier less prone to overfitting. Our method was tested on images from the JAFFE and CK databases. Experimental results in L-O-Sam-O and L-O-Sub-O modes demonstrated the effectiveness of the proposed method. Meanwhile, the recognition rate of this method is not significantly affected in the presence of Gaussian noise and salt-and-pepper noise conditions.

Realizing Rationally-Balanced Dielectric Properties in Fluoropolymer/Cr2AlC MAX Composites Modified by 2D-BN

Qin Li,Junquan Zhou,Yanhui Chen,Xiaofeng Xia,Maolin Bo,Qihuang Deng,Yefeng Feng 한국고분자학회 2020 Macromolecular Research Vol.28 No.13

Polymer/conductor composite dielectric materials have a high dielectric constant. In recent years, composite dielectrics have become a study hotspot in highdensity energy storage capacitors. However, high dielectric loss and high electrical conductivity make the application of the composite materials very limited. In order to obtain composite materials with high dielectric constant, low dielectric loss and low conductivity, we added the insulating boron nitride (BN) filler into polymer/Cr2AlC composites. As a conductive filler, Cr2AlC ternary-layered-compound (MAX) ceramic has an interface polarization with the polymer matrix, thereby increasing the dielectric constant of the composites. The insulating BN has a very low electrical conductivity, which can effectively reduce the electrical conductivity and dielectric loss of the composites. Compared with the binary polymer/Cr2AlC composite materials, the ternary polymer/Cr2AlC/BN composite materials can achieve the low dielectric loss and low conductivity as well as properly-lowered dielectric constant. The ternary composite material filled with 10 wt% Cr2AlC and 2 wt% BN has a dielectric constant of about 30, a dielectric loss of about 0.7 and a conductivity of about 4.6×10- 7 S m-1 at 100 Hz. In this work, high-performance composite dielectrics were prepared through good cooperation between conductive and insulating ceramic fillers, which might provide an idea for design of promising energy storage capacitors.

Effect of Heterogeneous Lamella Structure on Mechanical Properties of Double-Pass Friction Stir Processed Cu–30%Zn Alloy

Nan Xu,Yuzhui Xu,Boshuo Zhang,Qining Song,Jianhua Zhao,Yefeng Bao 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.11

Double-pass friction-stir processing (FSP) with different probe lengths and coolants was conducted on a 3 mm thick Cu–30%Zn alloy plate, and a heterogeneous lamella structure (HLS) was produced along the plate thickness direction. TheHLS can be divided into three layers with their volume ratio was approximately 1:1:1, i.e., ultra-fine grain layer, fine grainlayer, and coarsened grain layer which produced by cold source assisted FSP, conventional FSP, and annealing treatment,respectively. The average hardness in ultra-fine grain layer was about 123 HV, which was significantly higher than those ofcoarsened grain layer (94 HV) and fine grain layer (105 HV). In each layer, the hardness slightly decreased with distanceincreased from the surface, but the hardness value decreased sharply in the transition zones of different layers. The HLSCu–30%Zn alloy showed yield strength of 220 MPa, ultimate tensile strength of 462 MPa, and fracture elongation of 30%. The strength-ductility synergy was attributed to the back-stress strengthening between the different layers, which induceda remarkable strain hardening at the initial stage of plastic deformation. This study provided a possible way for preparingHLS copper alloys with relatively good mechanical properties, and the HLS copper alloys have an application potential inthe manufacture of bearing, propeller, and condenser.