Chemistry Commons^™

Low-Crystallinity And Heterostructured Aupt-Ru@Cnts As Highly Efficient Multifunctional Electrocatalyst, Tuan-Jie Gan, Jian-Ping Wu, Shi Liu, Wen-Jun Ou, Bin-Ling Bin-Ling, Xiong-Wu Kang

Journal of Electrochemistry

The catalytic activity of the catalysts is strongly dependent on the structure of the catalysts, and the exploration of their correlation and structure-controlled synthesis of the high-performance catalysts are always at the central. Currently, platinum (Pt) is the optimum catalyst for hydrogen evolution reaction (HER), oxygen reduction reaction (ORR) and alcohol oxidation reaction, while ruthenium (Ru) behaves as the champion catalyst for oxygen evolution reaction (OER) during water splitting. Preparing alloy catalysts with these precious metals can modulate the catalytic activity of these catalysts from the perspective of strain effect, ensemble effect and ligand effect. Here, we developed a strategy …

Synthesis And Characterization Of Ternary Pt Nanoally Catalysts For Fuel Cells, Ylith Peck

Undergraduate Honors Theses

A hydrogen fuel cell is an electrochemical device that converts oxygen and hydrogen into electrical energy while producing water as the only by-product, which has attracted growing interest, especially in the automotive industry. This technology is efficient and has zero pollution to the environment, in contrast to the direct use of fossil fuels in combustion engines which produce pollution and greenhouse gas emissions. One of the key components for hydrogen fuel cells is the catalyst that operates at the cathode, which currently use platinum. Due to the scarce amount of platinum in the world, the manufacturing cost for fuel cells …

Synthesis And Conductivity Analysis Of A Methyl (Polyethylene Glycol) Comb Polymer, Olivia Fox

Honors Theses

The overall goal of work in this field is to improve materials for use in a variety of applications in fuel cell and battery production. This thesis specifically investigates the synthesis of two variations of a methyl (polyethylene glycol) comb polymer electrolyte (MePEG_nwhere n=7) to understand how the molecular structure of an ion-conducting polymer affects its electrochemical properties. The MePEG used in this synthesis contains seven ethylene glycol groups and was added to a poly (methylhydrosiloxane) comb polymer backbone. In the first sample, the polymer contained only the MePEG sidechain, and in the second sample, the polymer contained …

Evaluation Of The Fuel Cell Performances Of Tio2/Pan Electrospun Carbon-Based Electrodes, Sema Aslan

Turkish Journal of Chemistry

Electrocatalytic effect of the untreated and TiO2+polyacrylonitrile (PAN) modified discarded battery coal (DBC) and pencil graphite electrodes (PGE) were evaluated in fuel cell (FC) applications. TiO2+PAN solution is coated on PGE and DBC electrodes by electrospinning. According to the FESEM and EDS characterizations, TiO2 and PAN nanofibers are found to be approximately 40 and 240 nm in size. TiO2+PAN/PGE showed the best FC performances with 2.00 A cm-2 current density and 5.05 W cm-2 power density values, whereas TiO2+PAN/DBC showed 0.68 A cm-2 current density and 0.62 W cm-2 power density values. Electrochemical characterizations of PGE and TiO2+PAN/PGE electrodes were …

A Model For The Anodic Carbonization Of Alkaline Polymer Electrolyte Fuel Cells, Qi-Hao Li, Ying-Ming Wang, Hua-Long Ma, Li Xiao, Gong-Wei Wang, Jun-Tao Lu, Lin Zhuang

Journal of Electrochemistry

The alkaline polymer electrolyte fuel cell (APEFC) has made appreciable progress in recent years but is still suffering performance loss during discharge with air as the oxidant. Several theories have been suggested to interpret the loss. However, efforts are still needed to reach a clear quantitative understanding. Based on the major experimental findings in combination with thermodynamics and kinetics of the reactions involved in the anode, this paper presents a model featuring layered carbonization in the anode and relevant grouped equations. The simulation results generated from the latter are compared with experiments, and possible principles to suppress the performance loss …

Fundamentals Of Distribution Of Relaxation Times For Electrochemical Impedance Spectroscopy, Jia Wang, Qiu-An Huang, Wei-Heng Li, Juan Wang, Quan-Chao Zhuang, Jiu-Jun Zhang

Journal of Electrochemistry

Electrochemical impedance spectroscopy (EIS) is a powerful electrochemical characterization technology, which has been widely used in the field of electrochemical energy, such as lithium-ion batteries, supercapacitors, fuel cells, etc. Distribution of relaxation time (DRT) is an EIS deconvolution technique which does not depend on the prior knowledge of the targeted research object. Furthermore, DRT can serve to separate and analyze physical and chemical processes which are highly overlapped in their EIS data. In order to encourage the application and popularization of DRT deconvolution technology, several core questions are addressed in this paper: (1) DRT deconvolution principle, implementation steps and important …

Research Progress Of Metal-Nitrogen-Carbon Catalysts Toward Oxygen Reduction Reaction Inm Changchun Institute Of Applied Chemistry, Ming-Jun Xu, Jie Liu, Jun-Jie Ge, Chang-Peng Liu, Wei Xing

Journal of Electrochemistry

The development of highly active and stable catalysts toward oxygen reduction reaction (ORR) has been facing severe challenges. In recent years, pyrolytic M-N-C catalysts and metal-organic framework derived materials made the performance of non-noble metal catalysts greatly improved, however, the molecular and atomic level understanding in the reaction active sites and the mechanism are still lacking. Here, we summarize the recent research progress made in the Changchun Institute of Applied Chemistry. We present a microporous metal-organic-framework confined strategy toward the preferable formation of ORR catalysts. Firstly, we studied the active site and proposed a new active site structure for the …

Research Progresses In Polymeric Proton Exchange Membranes For Fuel Cells, Xu-Po Liu, Yun-Feng Zhang, Shao-Feng Deng, De-Li Wang, Han-Song Cheng

Journal of Electrochemistry

Proton exchange membrane (PEM) is one of the key components in PEM fuel cells, which possesses the function of separating the cathode and anode, affording proton transport channels and preventing fuel permeability. The property of PEM significantly influences the performance and service life of fuel cells. Nowadays, the commercially used Nafion membranes have the shortcomings of serious fuel permeability, low proton conductivity at elevated temperature and high price, which limits the rapid development of PEM fuel cells. Therefore, it seems to be urgent to develop novel PEMs with low cost and good comprehensive properties. Polymeric proton exchange membrane is an …

Highly Improved Electrocatalytic Oxidation Of Dimethylamine Borane On Silvernanoparticles Modified Polymer Composite Electrode, Çağri Ceylan Koçak, Süleyman Koçak, Şükri̇ye Karabi̇beroğlu, Zekerya Dursun

Turkish Journal of Chemistry

Dimethylamine borane (DMAB) is a promising fuel alternative for fuel cell applications. In this work cyclic voltammetric behavior of DMAB was investigated on the polymerized aminophenol film decorated with Ag nanoparticles in alkaline media. The polymer film was formed on the glassy carbon electrode by electrochemical technique and then, the surface was modified with Ag nanoparticles. The surface of the modified electrode was identified by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy techniques. The developed electrode has displayed high electrocatalytic activity for DMAB oxidation in alkaline media depending on the supporting electrolyte concentration. Experimental …

Recent Process In Transition-Metal-Oxide Based Catalysts For Oxygen Reduction Reaction, Yao Wang, Zi-Dong Wei

Journal of Electrochemistry

Transition metal oxides (TMOs) based catalysts have become the most promising catalysts to be employed in anion exchange membrane fuel cell for the sluggish oxygen reduction reaction (ORR). However, their ORR activity is still far from that of the Pt-based catalysts. Therefore, it is important to develop high performance TMO based catalysts. Electrical conductivity and intrinsic activity have been regarded as the two keys to affect the ORR activity of the TMOs based catalysts. In this review, we focused on the recent progresses in the fundamental viewpoints on the electrical conductivity and intrinsic activity of the TMOs based ORR catalysts. …

Synthesis And Characterization Of Molybdenum Sulfide And For Hydrogen Evolution Reaction And Supercapacitor Applications, Zhuo Wang

Electronic Theses & Dissertations

To meet the constantly rising requirement of energy other than traditional fossil fuel and environment protection, it is a perfect time to development low cost, and efficient materials for clean energy production. Hydrogen generation by water splitting is one of the cleanest ways to produce cheaper energy. Hydrogen evolution reaction (HER) is one of the key steps in water splitting process. Ideally, the thermodynamic potential for HER should be at 0 V (vs. SHE). However, without an efficient catalyst, this reaction occurred at higher potential, called overpotential. A good HER catalyst is needed to lower the overpotential and hence to …

The “Apparent” Diffusion Coefficient Of Electrons Through A Nafion Membrane, Marissa Kayle Reynolds

Graduate Theses and Dissertations

The hydrogen/oxygen fuel cell is a greener, more efficient energy solution. However, there are many problems with the fuel cell including storage, infrastructure, cost, the oxygen reduction reaction, and the durability of the proton exchange membrane (PEM). The PEM is not only used as the electrolyte for the cell but also as a physical barrier between the anode and the cathode. The integrity of this membrane is crucial to the functioning of the fuel cell. This thesis will examine using ferricyanide as a probe molecule for diagnostic experiment of Nafion membrane integrity. Using hydrodynamic voltammetry with a rotating disk electrode …

A Characterization Study On Catalyst Layers In Proton Exchange Membrane Fuel Cells, Luyue Li

Doctoral Dissertations

This thesis describes the work for the catalyst layer (CL) characterization study of proton exchange membranes (PEM) for fuel cells. In particular, both the structure and performance of catalyst layers with alternative ionomers were studied. Structure wise, the morphology, surface area and pore size distribution studies were accomplished with scanning electron microscopy (SEM), transmission electron microscope (TEM) and nitrogen adsorption processed through Brunauer–Emmett–Teller (BET) and Barrett-Joyner-Halenda (BJH) theory. Water uptake isotherms of the CLs have been developed under well controlled relative humidity (RH) levels. The performance characterization focuses on polarization study, catalyst layer proton conductivity measurement and estimation of the …

Dynamic Simulation Of Oxygen Reduction Reaction In Pt/C Electrode For Proton Exchange Membrane Fuel Cells, Li Shang, Zhou Fen, Chen Lei, Pan Mu

Journal of Electrochemistry

It is an urgent need to reduce the Pt loading in electrode for practical fuel cell applications worldwide. Herein, we theoretically investigate the oxygen distribution, generated current, and minimum Pt loading of Pt/C electrode for practical applications based on kinetic model of oxygen reduction reaction. The results indicate that with increasing electrode effective thickness to 40 mm, serious concentration polarization is expected for Pt/C electrode. To generate a power density of 1.4 W•cm^-2 (2.1A•cm^-2 @0.67 V) for fuel cell, the cathode catalyst layer thickness in PEMFC should be as thin as 3 mm. The minimum Pt loading will …

Multi-Scaled Carbon Supported Platinum As A Stable Electrocatalyst For Oxygen Reduction Reaction, Yu-Ping Li, Lu-Hua Jiang, Su-Li Wang, Gong-Quan Sun

Journal of Electrochemistry

The stability of carbon supports is essential for electrocatalysts of fuel cells. Herein, the mesoporous carbon with the high graphitic degree (highly graphitic mesoporous carbon, HGMC) was synthesized by using resorcinol as the carbon precursor, SiO2 as the templates and urea as the reducing agent. The as-prepared HGMC was characterized by XRD, Raman spectroscopy, TEM, N2 adsorption. The stability of HGMC was evaluated by mimicking the start-up/shut-down conditions of fuel cells in a three-electrode system referring to the NREL standard. The obtained HGMC is of moderate surface area (187.4 m²•g^-1) and is chemically stable under potentiodynamic …

Hydroxy Polybenzimidazoles For High Temperature Fuel Cells And The Solution Polymerization Of Polybenzimidazole, Kayley Fishel

Theses and Dissertations

In this dissertation, two different hompolymers of polybenzimidazole (PBI) containing hydroxyl functional units were synthesized via the PPA Process to produce gel membranes. These polymers and their phosphoric acid doped membranes were characterized to further explore structure-property relationships in functionalized PBI's. Fuel cell performance of the doped membranes was evaluated and compared to previously reported PBI membrane chemistries. Copolymers of p-OH PBI and para-PBI were prepared at five different copolymer compositions to examine the effects of hydroxy content on membrane properties and compared to the respective homopolymers. The reactivity of the hydroxy groups and the formation of phosphate bridges were …

Vapor Synthesis And Thermal Evolution Of Supportless, Metal Nanotubes And Application As Electrocatalysts, Robert William Atkinson

Doctoral Dissertations

One of the major limitations of proton exchange membrane fuel cells (PEMFCs) is the high cost and poor durability of the currently preferred catalyst design, small Pt nanoparticles supported on high surface area carbon (Pt/C). Unsupported, high-aspect ratio nanostructured catalysts, or extended surface catalysts, are a promising paradigm as electrocatalysts for a number of electrochemical reactions. These extended surface catalysts generally exhibit higher specific activities compared to their carbon-supported nanoparticle counterparts that have been ascribed to their unique electronic, surface and structural properties. Extended surface catalysts frequently maintain enhanced durability over supported catalysts during fuel cell operation because they are …

Nanostructured Cerium Oxide Based Catalysts: Synthesis, Physical Properties, And Catalytic Performance, Yunyun Zhou

Department of Chemistry: Dissertations, Theses, and Student Research

Cerium oxide is an extensively used industrial catalyst with applications as diverse as catalysts for automobile exhaust, petroleum cracking and organic chemicals synthesis. The catalytic activity of cerium oxide is dependent upon its structural properties, especially the oxygen vacancy defects. While recent advances in characterization techniques have dramatically improved our understanding of cerium oxide functionality, many atomic features in cerium oxide contributing to the overall catalytic reactivity are not yet well-understood. This dissertation focuses on the structural studies of catalytically active cerium oxides with different compositions, phases and morphologies, and their utilizations to establish fundamental understandings of cerium oxide based …

Recent Progress In Heteroatoms Doped Carbon Materials As A Catalyst For Oxygen Reduction Reaction, Wei Ding, Xue Zhang, Li Li, Zi-Dong Wei

Journal of Electrochemistry

Developing catalytic materials for oxygen reduction reactions (ORR) with high performance and low cost has been one of the major challenges for large-scale applications of fuel cells. In this review, we summarize the recent progress in the heteroatoms doped carbon materials as a catalyst for the catalysis of ORR, with an emphasis on the universal origin of their catalytic mechanisms. The future prospects of the metal-free catalyst were to find precisely controlled doping methods, to explore the role of heteroatoms in the catalysis, and to generate more active catalysts with suitable nanostructure.

Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark

Doctoral Dissertations

A molecular-level understanding of the factors that contribute to transport properties of proton exchange membranes (PEMs) for fuel cell applications is needed to aid in the development of superior membrane materials. Ab initio electronic structure calculations were undertaken on various PEM ionomer fragments to explore the effects of local hydration, side chain connectivity, protogenic group separation, and specific side chain chemistry on proton dissociation and transfer at low hydration. Cooperative interactions between both intra- and inter-molecular acidic groups and hydrogen bond connectivity were found to enhance proton dissociation at very low degrees of hydration. The energetics associated with proton transfer …

Study On Carbon Supported Pd Catalysts Modified By Phosphomolybdic Acid For H2O2 Electrocatalytic Reduction, Li-Mei Sun, Cheng Zhang, Ying-Rong Bao, Hong-Xia Li

Journal of Electrochemistry

The Pd/C catalyst was prepared with the chemical reduction method, and phosphomolybdic acid (PMA) was modified on the Pd/C catalyst using the dipping method. The compositions and structures of the Pd/C and Pd/C modified by phosphomolybdic acid (PMA-Pd/C) catalysts were characterized with X-ray diffraction and Fourier Transform infrared spectroscopy analyses. The electrocatalytic activity and stability of the catalysts for the reduction of hydrogen peroxide (H₂O₂) were studied using cyclic voltammetry and chronoamperometry. The results showed that the phosphomolybdic acid was tightly fixed on the surface of Pd/C catalyst through the chemical interaction. The eletrocatalytic activity of …

Preparation Of Pd/Tio2/C Catalyst And Its Electrocatalytic Performance In Basic Solution For Ethanol Oxidation, Qiao-Xia Li, Yi-Chao Yang, Ming-Shuang Liu, Hong-Min Mao, Qun-Jie Xu

Journal of Electrochemistry

Nanoparticles TiO₂ were prepared by hydrothermal method using precursor tetrabutyl titanate. The Pd/TiO₂/C catalyst was synthesized by liquid phase reducing method supported on nano TiO₂ and Vulcan carbon XC-72. The Pd/TiO₂/C catalyst was characterized by XRD, TEM, cyclic voltammetry, and chronopotentiometry. XRD confirmed the face-centered cubic structure of Pd particles, and TEM indicated that Pd particles (size 3 ~ 4 nm) dispersed uniformly on TiO₂ and carbon XC-72. The results from cyclic voltammogram and chronopotentiogram showed the higher ethanol oxidation activity and stability of Pd/TiO₂/C catalyst (20% Pd) as compared with …

Structure-Property Relationships In Polybenzimidazole Materials For Gas Separation And Fuel Cell Applications, Xin Li

Theses and Dissertations

The central theme of my research lies in the investigation of novel polybenzimidazole (PBI)-based materials for different energy related applications ranging from proton exchange membrane fuel cells (PEMFC) to high temperature gas separation. With the aid of a deeper understanding of the structure-property relationships in this class of materials, a better control on PBI chemistry - from monomer structure to polymer morphology to membrane/film processing method was able to be performed in order to achieve greater performance in targeted applications.

In Chapter 1, the overall background of two energy related applications - fuel cells and gas separation was first introduced …

Electrocatalytic Activity Of Palladium Nanocatalysts Supported On Carbon Nanoparticles In Formic Acid Oxidation, Jie Huang, Zhiyou Zhou, Yang Song, Xiongwu Kang, Ke Liu, Wancheng Zhou, Shaowei Chen

Journal of Electrochemistry

Palladium nanostructures were deposited onto carbon nanoparticle surface by a chemical reduction method. Transmission electron microscopic studies showed that whereas the resulting metal-carbon (Pd-CNP) nanocomposites exhibited a diameter of 20 to 30 nm, the metal components actually showed a cauliflower-like surface morphology that consisted of numerous smaller Pd nanoparticles (3 to 8 nm). Electrochemical studies showed that the effective surface area of the Pd-CNP nanoparticles was about 40% less than that of Pd black, possibly because the Pd nanoparticles were coated with a layer of carbon nanoparticles; yet, the Pd-CNP nanocomposites exhibited marked enhancement of the electrocatalytic activity in formic …

Microemulsion Preparation And Electrochemical Characterization Of Pt/C，Ptir/C Electrocatalysts, Ya-Ping Zeng, Sheng Sui

Journal of Electrochemistry

The Pt/C electrocatalysts were prepared by three different systems and the PtIr/C electrocatalysts were prepared with four different Ir contents. The samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), cyclic voltammetry (CV), potentiostatic and potentiodynamic polarizations measurements. The experimental results confirmed that the electrocatalyst particles prepared by the microemulsion method were well distributed on XC-72R supports with the active particle sizes of 5～10nm and good electrocatalysts activity. The Pt85Ir15/C electrocatalysts showed the highest overall electrochemical activity in unitized regenerative fuel cell.

Electrocatalytic Oxidation Of Ethanol On Various Metal Ad-Layer Modified Au(111) Electrodes In Alkaline Solution, Zekerya Dursun, Şükri̇ye Ulubay Karabi̇beroğlu, Buket Gelmez, Aydan Başaran

Turkish Journal of Chemistry

Ethanol oxidation was studied on single-crystal Au(111) electrodes that were modified by platinum, palladium, and cadmium metal ad-layers. The metal ad-layer modification was carried out by the underpotential deposition process, in which controlled amounts of Pt, Pd, and Cd were electrodeposited onto the substrate as submonolayer or monolayer coverage. The activity of the metal ad-layer modified Au(111) electrodes toward ethanol oxidation was studied in alkaline media, and recorded voltammograms were compared to those of bare single crystal Au(111) and polycrystalline gold and platinum disk electrodes. In terms of the desired shift in reduction potential and increased current density, the best …

Electrocatalytic Reactivity Of Pt Ad-Layer Modified Au(111) Single Crystal Electrodes On Reduction Of Oxygen, Zekerya Dursun, Şükri̇ye Ulubay Karabi̇beroğlu, Buket Gelmez, Fatma Ni̇l Ertaş

Turkish Journal of Chemistry

Electrocatalytic reduction of oxygen at electrochemically deposited Pt ad-layer modified Au(111) electrodes was studied in an O_2-saturated NaOH (0.1 M) solution. The results were compared with those obtained by using a polycrystalline Pt electrode and another Pt-deposited electrode prepared by replacement with Cu on bare Au(111). Linear sweep voltammetry displayed a positive shift of the oxygen reduction potential by about 0.14 V compared to the bare Au(111) electrode. This shift was about 0.06 V compared to a Pt disk electrode. Tafel slopes gradually changed between 0.06 and 0.1 V/dec, from 0.075 to -0.10 V/dec, from lower to higher current density …

Electrocatalytic Oxidation Of Methanol At Pd And Pt Ad-Layer Modified Au(111) Electrodes In Alkaline Solution, Süleyman Koçak, Zekerya Dursun, Fatma Ni̇l Ertaş

Turkish Journal of Chemistry

The electrochemical oxidation of methanol was investigated by using various ad-layer modified Au(111) electrodes in alkaline media in comparison to Au(111), polycrystalline Pd, and polycrystalline Pt electrodes. Catalytic activity of gold toward methanol oxidation has tended to increase in more alkaline media, as reflected in the oxidation peak in the concentration range of NaOH (0.1-3.0 M) studied here. The oxidation peak potential of methanol shifted to more negative potentials, indicating a pH-dependent surface reaction. Among the electrodes studied, single-crystal gold electrode surfaces modified with Pd and Pt ad-layers displayed the highest catalytic activity for methanol oxidation. Additional shifts of about …

Electrocatalysis In Polymer Electrolyte Membrane Fuel Cells, Li Li, Si-Guo Chen, Xue-Qiang Qi, Yao-Qiong Wang, Meng-Bo Ji, Lan-Lan Li, Zi-Dong Wei

Journal of Electrochemistry

This review presents the study of Chongqing University in electrocatalysis for polymer electrolyte membrane fuel cells(PEMFCs).Based on the understanding to the performance degradation of PEMFCs' catalysts,the university has being concentrated on how to increase the activity,stability and utility of noble metal catalysts.It covers the molecular design of near-surface alloy catalysts for improvement of activity to oxygen reduction reaction(ORR) and resistance to foreign poison species,selective deposition of Pt on the so-called "three-phase interface" for a high Pt utility,and invention of anti-flooding electrode against water flooding in the catalyst layer of the membrane assemble electrode(MEA),and so on.The catalytic mechanism of electrode reactions …

Platinum Modified With Hydrogen Molybdenum/Tungsten Bronze As Electrocatalysts For Direct Small Organic Molecule Fuel Cell, Wei-Shan Li, Li-Peng Tian, Jun-Hua Du, Hong-Liang Huang, Wei Li, Li-Xia Zhang, Hong-Yan Yang, Pan-Pan Guo, Zhi-Hui Zhou, Xing-De Xiang, Zhao Fu

Journal of Electrochemistry

There are several problems that limit the application of direct small organic fuel cell,including the use of precious platinum and the activity loss of platinum due to the intermediates poisons from the oxidation of small organic molecules.These problems have attracted wide interest and many solutions have been proposed.We have developed a new method to reduce the platinum usage and improve its activity,based on the modification of platinum with hydrogen molybdenum/tungsten bronze(HxMo(W)O3,0