Electrode Support Materials Research Articles

Multiwalled Carbon Nanotube/PEDOT: PSS Coated on Pineapple Fiber Paper Based Flexible Electrode for Electrochemical Application

In this study, a green electrode made from natural fiber paper was investigated. A pineapple fiber paper was used as electrode support material. A mixture of multiwalled carbon nanotubes and PEDOT: PSS (MWCNTs/ PEDOT: PSS) was used as active electrode material. PEDOT: PSS, a conducting polymer, was applied as binder to connect between MWCNTs and the surface of pineapple fiber paper, and this setup showed decrease in electrode resistivity. Varying the MWCNT concentration mixed with PEDOT: PSS on pineapple fiber paper was explored. The 3 wt.% MWCNT device gave the maximum conductivity value of 10.87 S cm-1. Cyclic voltammetry and impedance analysis indicated that 3 wt.% MWCNT device showed considerable promise as a flexible electrode for electrochemical devices for energy storage applications.

Activity and Stability of Oxides During Oxygen Evolution Reaction‐‐‐From Mechanistic Controversies Toward Relevant Electrocatalytic Descriptors

Plotting the roadmap of future “renewable energy highway” requires drastic technological advancement of devices like electrolyzers and fuel cells. Technological breakthrough is practically impossible without advanced fundamental understanding of interfacial energy conversion processes, including electrocatalytic water splitting. Particularly challenging is the oxygen evolution reaction which imposes high demands on the long-term activity of electrocatalysts and electrode support materials. To cross the “Rubicon” and in a deterministic manner claim that we developed principles of rational catalyst design, we need first to comprehend the determinants of electrocatalytic activity as well as character of their time evolution. How reliable are reported activity and stability trends, could we interrelate activity and stability, and how meaningful that relation really is are some of the important questions that have to be tackled in building of a more comprehensive view on critically important anodic oxygen evolution.

Depletion Effect-mediated Association of Carbon Nanotube-Polymer Composites and Their Application as Inexpensive Electrode Support Materials.

The association between carbon nanotubes (CNTs) and polymers to afford functional composites has been attributed to enthalpic interactions, neglecting the entropic depletion effect, in which bound solvents are released during the association process. Here, we show that association between multiwalled CNTs and common polymers is governed by the depletion effect, generating a corresponding entropic free energy up to ca. 13 kJ mol-1 at room temperature, while the enthalpic contribution is insignificant or even negative. Notably, association between the polymers and the CNTs takes place preferentially at the highly stacked CNT junctions, leading to mechanical reinforcement without impacting conductivity. Consequently, high-performance composite membranes were fabricated from inexpensive multiwalled CNTs and polyacrylonitrile (PAN) and were used as electrode supports for platinum (Pt) nanoparticles, affording specific currents 6-7-fold higher than that of Pt foil in the hydrogen evolution reaction and displaying outstanding stability.

Balancing the electron conduction and mass transfer: Effect of nickel foam thickness on the performance of an alkaline direct ethanol fuel cell (ADEFC) with 3D porous anode

Nickel foam has been applying as the electrode support material for alkaline direct ethanol fuel cells, since its unique three-dimensional network structure helps efficiently use the catalyst to improve the cell performance. In this work, the effect of the thickness of nickel foam electrodes on cell performance is investigated. The experimental results show that the nickel foam thickness influences both the electron conduction and mass transfer, and the optimal thickness is a trade-off between them. Through XRD, SEM image, polarization curve test, EIS test and CV test, it is found that the nickel foam electrode with the thickness of 0.6 mm has better performance than that of 0.3 mm and 1.0 mm. The thinner the nickel foam, the better the conductivity. However, the corresponding three-dimensional space becomes narrower, which leads to partial agglomeration of the catalyst and hindrance of mass transfer. In addition, the influence of catalyst loading on the performance of 0.6 mm nickel foam electrode is explored. The maximum power density of 1.0 mg cm−2 Pd loading reaches 56.3 mW cm−2 at 60 °C, which is higher than that of 2.0 mg cm−2 loading, indicating that the three-dimensional network structure of nickel foam can efficiently utilize the catalyst, and fully exert the catalytic function of the catalyst even at a lower catalyst loading. Moreover, the effects of operating temperature and ethanol concentration on cell performance are also studied. The cell performance increases with the increase of temperature, and it reaches the highest with 3 M ethanol.

Electrochemical Detection of Superoxide Anion Released by Living Cells by Manganese(III) Tetraphenyl Porphine as Superoxide Dismutase Mimic

Superoxide anion, one of the most active reactive oxygen species, is associated with the development of many diseases. So monitoring superoxide anion in living cells is of great significance for the pathological research of many diseases. In this work, a new non-enzymatic sensor for the detection of superoxide anion(O2•− ) was developed, which was fabricated by the nanocomposites composed of manganese(III) tetraphenyl porphine(MnTPP) as superoxide dismutase mimic and electrochemical reduced graphene oxide(ERGO) as electrode support material to modify the glassy carbon electrode(GCE). The electrochemical behavior of the fabricated electrode(MnTPP/ERGO/GCE) was performed by electrochemical impedance spectroscopy(EIS) and cyclic voltammetry(CV), which revealed that MnTPP/ERGO/GCE possessed good catalytic ability to the electrochemical reduction of O2•− . The MnTPP/ERGO/GCE showed excellent electroanalysis performance towards O2•− using the technique of differential pulse voltammetry(DPV) with a linear relationship in the range of 0.2–110.0 µmol/L, a sensitivity of 445 µA·L·mmol−1·cm−2 and a detection limit of 0.039 µmol/L(S/N=3). The real-time monitoring of O2•− from MCF-7 breast cancer cells stimulated by zymosan was realized in this work, which indicates that the MnTPP/ERGO/GCE hold potential application for electrochemical quantification of superoxide anions in biological applications.

Enhanced Adsorptions to Polysulfides on Graphene-Supported BN Nanosheets with Excellent Li-S Battery Performance in a Wide Temperature Range.

For Li-S batteries, the catalysis for S redox reaction is indispensable. A lot of multifunctional sulfur electrode support materials with have been investigated widely. However, most of these studies were carried out at room temperature, and the interaction between different components in the matrix is not often paid enough attention. Here, we report a graphene supported BN nanosheet composite in which the synergistic effect between BN and graphene greatly enhanced the adsorption for polysulfides, thus leading to excellent performance in a wide temperature range. When used as a host material of sulfur, it can make the Li-S battery apply to a wide range of temperatures, from -40 to 70 °C, delivering a high utilization of sulfur, an excellent rate capability, and outstanding cycling life. The capacity can stabilized at 888 mAh g-1 at 2 C after 300 cycles with a capacity attenuation of <0.04% per cycle at 70 °C, and the battery can deliver a capacity above 650 mAh g-1 at -40 °C.

Synthesis and characterisation of MnGaxCr2−xO4 (0.1≤x≤1) spinels as potential electrode support materials for intermediate-temperature solid oxide fuel cells

MnGaxCr2−xO4 (MGCO, x=0.1, 0.2, 0.4, 0.8, 1) oxides are synthesised using a citric acid nitrate combustion method. The influence of Ga substitution on the structure, electrical conductivity and electrochemical performance are systematically investigated. The chemical and thermal compatibility of MGCO materials with yttrium-stabilised zirconia (YSZ) are also studied. All the samples exhibit a single phase spinel structure. Thermal expansion coefficients (TECs) of the MGCO oxides are in the range of 9–12×10−6K−1, indicating a good thermal match with the YSZ electrolyte. No chemical reactions are detected between MGCO materials and YSZ, indicating their good chemical compatibility with YSZ. The magnitude of electrical conductivity of all the obtained samples is in the order of about 10−3Scm−1at 800°C measured in air. The polarisation resistance reaches a value as low as 5.2Ωcm2 for x=0.4 at 800°C. The preliminary results demonstrate that MGCO materials could be used as electrode support materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs).

Cu2o/Nanocarbon Architectures for Photoelectrochemical CO2 Conversion: Synthetic Aspects and Structure-Property Relationships

Carbon nanomaterials, especially carbon nanotubes and graphene (either alone, or as building blocks of organized 3-D superstructures), are attracting significant attention as large surface area electrode support materials. Their composites with both inorganic and organic semiconductors represent an interesting class of new functional materials. In the first part of my talk I will briefly focus on the use of electrosynthetic (and photoelectrosynthetic) methods for preparing semiconductors on nanocarbon-modified electrode surfaces.1,2I will show how electrodeposition can be used to tune composition, crystal structure, and morphology of the nanocomposites for targeted applications. In the second part of my talk, selected examples will be given for how these electrosynthesized hybrid assemblies can be deployed in photoelectrochemical CO2 conversion. Given that CO2 is a greenhouse gas, using sunlight to convert CO2 to transportation fuel (such as methanol) represents a value-added approach to the simultaneous generation of alternative fuels and environmental remediation of carbon emissions from the continued use of conventional fuels.3 I will present the controlled synthesis and photoelectrochemical behavior of Cu2O/CNT4 and Cu2O/3D graphene composites for the CO2 reduction application. A carefully designed, multiple-step electrodeposition protocol was developed that ensured homogeneous coating of the CNTs with the Cu2O nanocrystals. This enhanced charge transport property for the hybrids resulted in a drastic increase in the photocurrents measured for the CO2 reduction. In addition to this superior performance, long term photoelectrolysis measurements proved that the Cu2O/CNT hybrids were more stable than the oxide alone. Structure property relationships will be shown, which may act as guidelines for the rational design of nanocomposite photoelectrodes. Figure 1. Illustration of the structure of the Cu2O/CNT composite and the increasing photocurrent with the increasing CNT-content. [1] C. Janáky and K. Rajeshwar: The Role of (Photo)electrochemistry in the Rational Design of Hybrid Conducting Polymer / Semiconductor Assemblies: From Fundamental Concepts to Practical Applications, Prog Pol Sci, 43 (2015) 396-435 [2] C. Janáky, E. Kecsenovity, K. Rajeshwar: Electrodeposition of Inorganic Oxide/ Nanocarbon Composites: Opportunities and Challenges, ChemElectroChem, 3 (2016) 181-192 [3] G. Ghadimkhani, N. R. De Tacconi, W. Chanmanee, C. Janaky, K. Rajeshwar: Efficient solar photoelectrosynthesis of methanol from carbon dioxide using hybrid CuO/Cu2O semiconductor nanorod arrays, Chem. Commun. 49 (2013) 1297–1299 [4] E. Kecsenovity, B. Endrődi, Z. Pápa, K. Hernádi, K. Rajeshwar, C. Janáky: Decoration of ultralong carbon nanotubes with Cu2O nanocrystals: a hybrid platform for enhanced photoelectrochemical CO2 reduction, J Mater Chem A, 4 (2016) 3139-3147 Figure 1

Alkali Metal Ion Storage Properties of Single-Walled Carbon Nanotube Encapsulation Systems

Single-walled carbon nanotube (SWCNT) encapsulation systems have been paid much attention since the discovery of C60 peapod in 1998. So far, several kinds of molecules (e.g. coronene, β-carotene, 9,10-dichloroanthracene, water, iodine) have been encapsulated. The eager studies on structural and electronic properties of the encapsulation systems revealed that some of the encapsulated molecules show properties different from their bulk forms. Due to such findings, it has been concluded that the tube interior provides a unique field to the encapsulated molecules to alter their properties. However, there are not many reports describing the applications of encapsulation systems. Lithium ion batteries (LIBs) have been widely used in portable electronic devices such as cell phones and lap-top computers, owing to their high energy density. However, new energy source with higher capacity and better rate performance is required because LIBs are not good enough for larger and higher power machines such as electric vehicles. Recently, metal-air, lithium-sulfur (LIS), sodium-ion batteries and others have been attracting much attention as post-LIB energy devices. LIS battery is one alternative that has higher energy density than LIB has, and is expected to be used for large-scale devices. However, in order for the practical use of LIS battery to be realized, we have to solve the problem that polysulfide ions (Sn−) are easily dissolved in electrolyte. This dissolution problem leads to capacity fading with charge-discharge cycles. Several investigations have been carried out to improve the cycle performance of LIS battery. For example, Kaneko et al. reported the encapsulation of sulfur into the hollow core of single-walled carbon nanotube (SWCNT) [1]. Another post-LIB is sodium-ion battery (SIB) that has received increasing attention in the recent years, because SIB is very advantageous in regards to cost and resources. However, good anode materials having high capacity for SIBs have not been found yet. Graphite, which is used as a negative electrode of LIBs, does not adsorb Na ions. So far, SIB negative electrode properties of several kinds of carbon materials have been studied. Although some kinds of hard-carbons and Na alloys can adsorb and desorb sodium ions, we should explore better anode materials to realize SIBs. Phosphorus is also expected as alternative electrode materials because of its high theoretical capacity (2596 mAh/g) and relatively low volume expansion when adsorbing sodium ions. However, phosphorus electrode still suffers from instability problems, despite the numerous attempts that have been made with different phosphorus polymorphs and/or different kinds of electrode support materials. In the present study, we use the unique environment provided by the hollow core inside SWCNTs to encapsulate both sulfur and phosphorous molecules, in order to address some of the unanswered questions and performance issues of both LIS and SIB. First, we compare the physical stability of sulfur molecules inserted in SWCNTs having different tube diameters, then we report the LIS battery electrode properties of sulfur encapsulated SWCNTs (S@SWCNTs). We also report on the negative electrode properties of phosphorus encapsulated single-walled carbon nanotubes (P@SWCNTs), in which phosphorus atoms are inserted into the pores of SWCNT [2]. Since SWCNTs have good electric conductivity, they should work as a conductive component for the highly resistive phosphorus electrode. In the conference, I will also talk about another types of SWCNT encapsulation systems.

Electrodeposition of Inorganic Oxide/Nanocarbon Composites: Opportunities and Challenges

AbstractCarbon nanomaterials, especially carbon nanotubes and graphene (either alone, or as building blocks of organized 3D superstructures), are attracting significant attention as large‐surface‐area electrode support materials. Their composites with inorganic oxides represent an interesting class of new functional materials. This Minireview critically focuses on the use of electrosynthetic (and photoelectrosynthetic) methods for preparing oxide nanoparticles on nanocarbon‐modified electrode surfaces. We focus on how electrodeposition can be used to tune composition, crystal structure, and morphology of the nanocomposites for targeted applications. Finally, selected examples will be given for how these electrosynthesized hybrid assemblies can be deployed in various application avenues.

2D nanosheet molybdenum disulphide (MoS2) modified electrodes explored towards the hydrogen evolution reaction.

We explore the use of two-dimensional (2D) MoS2 nanosheets as an electrocatalyst for the Hydrogen Evolution Reaction (HER). Using four commonly employed commercially available carbon based electrode support materials, namely edge plane pyrolytic graphite (EPPG), glassy carbon (GC), boron-doped diamond (BDD) and screen-printed graphite electrodes (SPE), we critically evaluate the reported electrocatalytic performance of unmodified and MoS2 modified electrodes towards the HER. Surprisingly, current literature focuses almost exclusively on the use of GC as an underlying support electrode upon which HER materials are immobilised. 2D MoS2 nanosheet modified electrodes are found to exhibit a coverage dependant electrocatalytic effect towards the HER. Modification of the supporting electrode surface with an optimal mass of 2D MoS2 nanosheets results in a lowering of the HER onset potential by ca. 0.33, 0.57, 0.29 and 0.31 V at EPPG, GC, SPE and BDD electrodes compared to their unmodified counterparts respectively. The lowering of the HER onset potential is associated with each supporting electrode's individual electron transfer kinetics/properties and is thus distinct. The effect of MoS2 coverage is also explored. We reveal that its ability to catalyse the HER is dependent on the mass deposited until a critical mass of 2D MoS2 nanosheets is achieved, after which its electrocatalytic benefits and/or surface stability curtail. The active surface site density and turn over frequency for the 2D MoS2 nanosheets is determined, characterised and found to be dependent on both the coverage of 2D MoS2 nanosheets and the underlying/supporting substrate. This work is essential for those designing, fabricating and consequently electrochemically testing 2D nanosheet materials for the HER.

Structure‐Controlled, Vertical Graphene‐Based, Binder‐Free Electrodes from Plasma‐Reformed Butter Enhance Supercapacitor Performance

AbstractVertical graphene nanosheets (VGNS) hold great promise for high‐performance supercapacitors owing to their excellent electrical transport property, large surface area and in particular, an inherent three‐dimensional, open network structure. However, it remains challenging to materialise the VGNS‐based supercapacitors due to their poor specific capacitance, high temperature processing, poor binding to electrode support materials, uncontrollable microstructure, and non‐cost effective way of fabrication. Here we use a single‐step, fast, scalable, and environmentally‐benign plasma‐enabled method to fabricate VGNS using cheap and spreadable natural fatty precursor butter, and demonstrate the controllability over the degree of graphitization and the density of VGNS edge planes. Our VGNS employed as binder‐free supercapacitor electrodes exhibit high specific capacitance up to 230 F g−1 at a scan rate of 10 mV s−1 and &gt;99% capacitance retention after 1,500 charge‐discharge cycles at a high current density, when the optimum combination of graphitic structure and edge plane effects is utilised. The energy storage performance can be further enhanced by forming stable hybrid MnO2/VGNS nano‐architectures which synergistically combine the advantages from both VGNS and MnO2. This deterministic and plasma‐unique way of fabricating VGNS may open a new avenue for producing functional nanomaterials for advanced energy storage devices.

Development and Performance of MnFeCrO4‐Based Electrodes for Solid Oxide Fuel Cells

AbstractImportant advances have been made in SOFC development utilizing a ceramic framework based upon yttria zirconia (YSZ) electrolytes supported upon porous YSZ electrode skeletons. This ceramic framework is sintered at high temperatures with subsequent impregnation and low temperature processing of the active electrode materials. Here we seek to develop this impregnated electrode concept by investigating a novel scaffold material similar to the main corrosion product of ferritic stainless steel. The chromium rich spinel (MnFeCrO4) was used as an electrode support material, either alone or impregnated with (La0.75Sr0.25)0.97Cr0.5Mn0.5O3‐δ, La0.8Sr0.2FeO3‐δ, Ce0.9Gd0.1O2‐δ, CeO2 and/or Pd. In these initial studies it was found that all of the impregnated phases adhere very well to the spinel and considerably enhance performance and stability to a level sufficient for SOFC applications.

Development and performance of MgFeCrO4 – based electrodes for solid oxide fuel cells

Composite anodes for solid oxide fuel cells (SOFC) developed on yttria stabilised zirconia (YSZ) porous supports by infiltration of electrode materials has been successfully applied for various anode and cathode compositions, resulting in high performance SOFC devices. The focus of this study is the performance of the chromium-rich spinel (MgFeCrO4) as an electrode support material when used alone or impregnated. The composite anodes were prepared by aqueous infiltration of nitrate salts to produce (La0.75Sr0.25)0.97Cr0.5Mn0.5O3−δ, Ce0.9Gd0.1O2−δ, CeO2 or Pd into a MgFeCrO4 scaffold with 45% porosity and studied by electrochemical impedance spectroscopy in symmetrical cell configuration. The performance was evaluated in humidified 5% H2/Ar in order to quantify their stability and performance up to 850 °C with respect to the MgFeCrO4 porous substrate. It was found that all the impregnated phases adhere very well to the spinel and considerably enhance performance and stability to a level required for SOFC applications. MgFeCrO4/LSCM/CGO and MgFeCrO4/LSCM/CGO/Pd showed the most substantial improvement in comparison to the scaffold’s performance, with ASR values of 1.74 Ω cm2 and 0.91 Ω cm2, respectively.

On-line monitoring of the live cell concentration in bioreactors based on a rocking platform

Background Aber Instruments first introduced the concept of using disposable live-biomass probes in 2009 [1]. The probe has been carefully designed to be welded into most single use bioreactors and is suitable for bags with agitators eg the Hyclone SUB and the Sartorius Stedim Biostat Cultibag STR, or those using the rocker type platform eg Sartorius Stedim Biostat Cultibag RM and GE Wave bioreactors . The disposable biomass probe has four electrodes with the same dimensions as the existing reusable production biomass probes with flush platinum electrodes that are used in cGMP manufacture worldwide. The electrode support material is HDPE that meets FDA and USP Class VI requirements and the probe can withstand gamma sterilisation and be stored for prolonged periods before use. The disposable probe is easily connected to a mini-lightweight Futura preamplifier so that the weight load or torque on the bag is minimal and the bulk of the electronics is then located well away from the bag. The disposable probe has already been welded into different bags including Sartorius Stedim Biotech CultiBag RM bioreactors.

Synthesis and characterization of chromium spinels as potential electrode support materials for intermediate temperature solid oxide fuel cells

Several spinel compositions, i.e. Mn1+xCr2−xO4 (x = 0.7, 0.5, 0), MnFexCr2−xO4 (x = 0.1, 1), MgMnCrO4 and Mg1+xCr2−xO4 (x = 0, 0.1) were synthesised and studied in terms of phase analysis, density, stability in reducing atmosphere, electrical conductivity and thermal expansion behaviour. The spinel samples were single phase, with cell parameter values in a good correlation with cation sizes. Most of the studied spinels were found to be unstable under reducing conditions of thermal treatment, except MnCr2O4, MgCr2O4 and Mg1.1Cr1.9O4. Electrical properties have been investigated by impedance spectroscopy and DC conductivity measurements at temperatures between 200 and 900 °C.

Supercapacitor-battery hybrid energy storage devices from an aqueous nitroxide radical active material

A hybrid electrochemical energy storage device was fabricated in aqueous NaOH with the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) nitroxide radical as the active material, hydroquinone as the counter electrode active material, and an OH−-selective separating membrane. The working principle of this device was investigated and it can be considered as a supercapacitor-battery hybrid energy storage system. Device performance was characterized by cyclic voltammetry and galvanostatic charge-discharge testing. When using multi-walled carbon nanotubes (MWCNTs) as electrode support materials, a high pseudo-capacitance of 1280 F g−1 was obtained with the TEMPO nitroxide radical as the active material at a 1 mV s−1 scan rate. This was ∼33 times larger than the inherent double layer capacitance of MWCNTs. The electrode material and active material dissolved in solution could potentially be substituted with similar materials. This simple design provides a new approach for fabricating high performance supercapacitor-battery hybrid energy storage devices.

Mechanism of potentiostatic deposition of MnO 2 and electrochemical characteristics of the deposit in relation to carbohydrate oxidation

Cyclic voltammetric (CV) and chronoamperometric (CA) studies on potentiostatic deposition of MnO 2 on Pt from Mn(II) solution in very weakly alkaline media show the process to be controlled by a one-electron transfer step, which means that the deposition proceeds through the generation of Mn(III). The electrocatalytic activity of the deposited electrode towards carbohydrate oxidation is found to be maximum at an optimum amount of deposition. Chronopotentiometric (CP) and CV measurements show that the oxidation of carbohydrates on the deposited electrodes follows a catalytic EC (electrochemical–chemical) mechanism via electrolytic formation of Mn(V) and its subsequent consumption either by disproportionation or by chemical reaction in the presence of carbohydrates. The rate constants of the reaction of Mn(V) with dextrose and fructose have been obtained from CA results. The relative order of the oxidation currents for dextrose and fructose as well as their dependence on carbohydrate concentration has been discussed. Replacement of Pt by carbon as the electrode support material does not affect the electrocatalytic activity of the MnO 2 deposit. The observed linear variation of the steady state oxidation currents with carbohydrate concentration can be exploited for analytical application.

Direct methanol fuel cell Pt–carbon catalysts by using SBA-15 nanoporous templates

A mesoporous carbon structure based on SBA-15 silica template was used as a cathode catalyst support of platinum in the direct methanol fuel cell (DMFC). The inverse carbon replica of the SBA-15 template was synthesized by carbonization of sucrose exhibiting a large surface area, 1300 m 2/g. Introducing platinum clusters on the carbon support, a large surface area, 800 m 2/g, was maintained and the catalytic activation was confirmed by a DMFC single-cell test. The mesoporous carbon structure could be an ideal catalyst support for electrode support materials in DMFC providing favorable hosting morphology for the metallic catalyst clusters and interconnected pore network for a facile transport of feeds and products. The electrical percolation of the interconnected carbon rods also exhibited a great potentiality for the development of novel DMFC catalyst supports.