Commercial Carbon Paper Research Articles

Stochastic microstructural modeling of fuel cell gas diffusion layers and numerical determination of transport properties in different liquid water saturation levels

Gas diffusion layer (GDL) materials in polymer electrolyte membrane fuel cells (PEMFCs) are commonly made hydrophobic to enhance water management by avoiding liquid water blockage of the pores and facilitating reactant gas transport to the adjacent catalyst layer. In this work, a stochastic microstructural modeling approach is developed to simulate the transport properties of a commercial carbon paper based GDL under a range of PTFE loadings and liquid water saturation levels. The proposed novel stochastic method mimics the GDL manufacturing process steps and resolves all relevant phases including fiber, binder, PTFE, liquid water, and gas. After thorough validation of the general microstructure with literature and in-house data, a comprehensive set of anisotropic transport properties is simulated for the reconstructed GDL in different PTFE loadings and liquid water saturation levels and validated through a comparison with in-house ex situ experimental data and empirical formulations. In general, the results show good agreement between simulated and measured data. Decreasing trends in porosity, gas diffusivity, and permeability is obtained by increasing the PTFE loading and liquid water content, while the thermal conductivity is found to increase with liquid water saturation. Using the validated model, new correlations for saturation dependent GDL properties are proposed.

Improvement of the adhesion between polyaniline and commercial carbon paper by acid treatment and its application in supercapacitor electrodes

Commercial carbon paper was coated with polyaniline (PANI) using in situ polymerization of aniline. Prior to the PANI coating, acid treatment was performed to carboxylate the surface of the carbon paper for enhancing PANI adhesion by sonication of the carbon paper in a mixture of concentrated sulfuric and nitric acids. The loading mass density of PANI on the acid-treated carbon paper increased more than three times compared to that on the carbon paper without acid treatment. The specific capacitance also increased from 112 to 174 F/g in a two-electrode system (calculated using a total mass of carbon paper and PANI) due to better PANI coating on the acid-treated carbon paper. The simple acid treatment provides good adhesion of PANI to the commercial carbon paper and can be applied to prepare supercapacitor electrodes.

Preparation of activated carbon paper by a novel method and application as high-performance supercapacitors

In this paper, the commercial carbon papers were firstly treated by potassium dichromate lotion. Their surfaces became rougher and specific surface areas were enlarged. Accordingly, their surface hydrophilicity were enhanced due to the intake of hydrophilic groups such as hydroxyl (–OH), carbonyl (>C=O), and carboxyl (–COOH), and they act as strong polar sites to absorb water molecules. Supercapacitors were then constructed with the treated carbon paper as electrode and PVA-H3PO4 gel as electrolyte, and they provided high areal capacitances, high-rate capability, long-life cycle, and low resistance due to the synergistic effect of enlarged specific surface area and enhanced surface hydrophilicity.

Surface activation of carbon paper with potassium dichromate lotion and application as a supercapacitor

In this paper, an effective strategy using potassium dichromate lotion to activate surfaces of commercial carbon papers leading to enhanced electrochemical capacitances was reported. It is revealed that surfaces of activated carbon papers became rougher and their specific surface areas enlarged after treatment. Further, surface hydrophilicity of the treated carbon papers enhanced due to the generation of hydrophilic groups such as hydroxyl (–OH), carbonyl (〉CO) and carboxyl (–COOH) and they act as strong polar sites to absorb water molecules. With the synergistic effect of enlarged specific surface area and enhanced surface hydrophilicity, the activated carbon papers provide high areal capacitances. In general, this strategy offers a feasible pathway to make commercial carbon paper a promising candidate for practical supercapacitors and is expected to extend to other carbon based electrode materials.

Effect of Sputtering Power on the Electrochemical Properties of Low Loaded Pt Catalysts for PEM Fuel Cell

A series of thin Pt films were deposited by dc magnetron sputtering with different power directly on a commercial hydrophobic carbon paper substrate at room temperature. Their electrochemical properties toward the oxygen reduction reaction were investigated in 0.5 M H2SO4 solution by means of cyclic voltametry (CV) and linear sweep voltametry (LSV) on rotating disc electrode (RDE). It was found that the increase of power leads to rise in the electrochemical active surface area (EASA) slightly up to 25 W, but further increase in power decreases surface area significantly. Electrochemical surface area is reaching a maximum of 29.68 m2 gPt−1 for 25 W. Rotating disk electrode experiments, also, show that increase of power yield more active catalyst toward to oxygen reduction reaction. As a result, 25 W coating power is the optimum for the preparation of the smallest and the most active Pt particle in catalytic film.

A novel multi-porous and hydrophilic anode diffusion layer for DMFC

The effect of hydrophilic treatment within the anode diffusion layer for direct methanol fuel cell (DMFC) has been investigated. By nitrated treatment, the surface structure and wettability of diffusion layer can be tuned. The anode micro-porous surface of carbon paper with hydrophilic adhesive after nitrated treatment presents more multi-hole structures with about 30 μm large pores and about 5 μm small pores, which were significantly larger than commercial carbon cloth and carbon paper without nitrated treatment. FTIR and EDS show that the surface of micro-porous layer has more oxygenic groups and the contact angles test also indicates that it becomes more hydrophilic after nitrated treatment. It is indicated that the anode charge transfer resistance and internal resistance dramatically decrease after nitrated treatment on the EIS test. The performance of assembled cell is also evaluated of which the power density of cell using novel diffusion layer (260 mW/cm2) is significantly higher than cell using commercial diffusion layer. The results indicate that this novel multi-porous and hydrophilic anode diffusion layer is suitable to DMFC.

Influence of GDL Coated with MPL Containing CNTs on PEFC Performance Under Low and High Humidity Conditions

A hydrophobic microporous layer (MPL) coated on a gas diffusion layer (GDL) has been commonly used to improve the water management characteristics and thereby enhance the performance of polymer electrolyte fuel cells (PEFCs). However, the appropriate design parameters for the MPL coated GDL are different under low and high humidity conditions [1]. It is highly desirable to have a PEFC that can be operated under a wide range of conditions varying from low (or no) to high humidity [2, 3]. In the present study, a new GDL coated with an MPL containing hydrophilic carbon nanotubes (CNTs) was developed to achieve further enhancement of the PEFC performance under both low and high humidity conditions.The GDL used at the anode was a commercial carbon paper without an MPL (SGL24BA). MPL coated GDLs were used at the cathode. The MPL coated GDL without the CNTs consisted of a substrate (SGL24BA) coated with an MPL composed of 80 mass% carbon black and polytetrafluoroethylene (PTFE). The MPL coated GDL with the CNTs consisted of a substrate coated with an MPL made from 4 mass% CNTs (NITTA CORPORATION), 76 mass% carbon black and PTFE. The contact angle of the MPL without the CNTs was 132° [1]. The contact angle of the CNT surface was 30°, which exhibited relatively high hydrophilicity. However, because the MPL pore surfaces consist of a combination of the CNTs, carbon black and PTFE, the contact angle of the MPL with the CNTs was 111°.PEFC performance tests were conducted under both low and high humidity conditions. The cell temperature was set at 75 °C. The hydrogen and air utilizations were set to 70 and 60%, respectively. During tests under low humidity conditions, the relative humidity (RH) of the gas supplied to the cathode was set to 0%, while that supplied to the anode was maintained at 60% RH. During tests under high humidity conditions, the RH of the gases supplied to both the anode and cathode was set to 100%.In the case of the MPL without the CNTs, decreasing the maximum pore diameter of the MPL from 40 to 5 μm enhanced the ability to prevent dehydration of the MEA, which improved the PEFC performance under low humidity conditions. Under high humidity conditions, decreasing the maximum pore diameter to 20 μm was effective to reduce flooding and also enhance the PEFC performance. However, when the pore diameter became too small, such as at 5 μm, the discharge of excess water through the MPL was inhibited, which promoted flooding, so that no significant enhancement in the PEFC performance was possible. The appropriate pore diameter for a conventional MPL is different under low and high humidity conditions. An MPL coated GDL designed to prevent dehydration of the MEA under low humidity conditions is inferior at reducing flooding under high humidity conditions.In the case of the MPL with the CNTs, decreasing the maximum pore diameter from 40 to 5 μm was effective to enhance the ability to prevent dehydration of the MEA. The performance obtained with the MPL containing the CNTs was higher than that observed when using an MPL without the CNTs. Since the hydrophobicity of the MPL with the CNTs was reduced, its ability to retain humidity in the catalyst layer was improved. This resulted in higher PEFC performance compared with that for an MPL without the CNTs. Under high humidity conditions, decreasing the pore diameter to 5 μm enhanced the PEFC performance. For an MPL with the CNTs, the less hydrophobic pores promoted the transport of excess water from the catalyst layer through the MPL to the substrate. As a result, it was possible to decrease the maximum pore diameter to 5 μm without lowering the PEFC performance under high humidity conditions. These results demonstrate that the MPL with the CNTs is effective to achieve further enhancement of the PEFC performance under both low and high humidity conditions compared to that for a conventional MPL coated GDL.

Synthesis of SAPO-34/graphite composites for low temperature heat adsorption pumps

Low temperature heat adsorption pumps represent the innovative cooling systems, where cold is generated through adsorption/desorption cycle of water by a suitable adsorbent with good adsorption and high thermal conductive properties. In this work, the hydrothermal synthesis of zeolite SAPO-34 on thermal conductive graphitic supports, aiming at the development of highly performing adsorbent materials, is reported. The synthesis was carried out using as-received and oxidized commercial carbon papers, and graphite plate. Composites were characterized by XRD, SEM and also by a thermogravimetric method, using a Cahn microbalance. The water adsorbing capacity showed typical S-shape trend and the maximum water loading was around 25 wt%, a value close to water adsorption capability of pure SAPO-34. These results are very promising for their application in heat adsorption pumps.

Investigation of Different Carbon Materials with Different Coating Methods as Micro Porous Layer for Proton Exchange Membrane Fuel Cells

In this work, two types of carbon - Vulcan XC-72R, and vapor-grown carbon fiber (VGCF, 7μm in length and 100 nm in diameter) were investigated as materials composing a micro porous layer (MPL). These carbon materials were either sprayed or doctor bladed on commercial carbon paper (GDS 340, CeTech Co., Ltd., Taiwan) to form an MPL with various carbon loadings and various polytetrafluoroethene (PTFE) contain ratio. All of the home-made GDLs were assembly with commercial catalyst coated membranes (CCMs, General Optics Corp., Taiwan) for fuel cell performance test. All of the membrane electrode assembly (MEA) samples were investigated by the polarization curve and Electrochemical Impedance Spectroscopy (EIS).

The capacitive properties of amorphous manganese dioxide electrodeposited on different thermally-treated carbon papers

The surface structure of the commercial carbon paper (CP) has been modified through thermal treatment, and then MnO2 was electrodeposited on the thermally-treated carbon paper (TTCP) by cyclic voltammetry (CV) method in the phosphate buffer solution (PBS, pH 9.18) containing KMnO4. The obtained samples were characterized by X-ray diffraction (XRD), X-ray photoelectron energy spectroscopy (XPS) and scanning electron microscopy (SEM). The results showed that the phase of the obtained MnO2 was amorphous, and that the morphology of the MnO2 deposited on the substrates was influenced strongly by the substrates. The capacitive properties of MnO2 deposited on the carbon substrates were investigated by CV, galvanostatic charge/discharge, electrochemical impedance spectroscopy technique. It was found that the specific capacitance of MnO2 deposited on the optimum TTCP can reach to 749Fg−1 based on the charge/discharge measurement, which was far larger than that on the CP (345Fg−1).

Characterization of a monolithic mesoporous carbon as diffusion layer for micro fuel cells application

The preparation and characterization of a monolithic mesoporous carbon structure, which could be used as diffusion layer in PEM and DMPEM micro fuel cells, is described. Several characteristics of the monolithic carbon were studied, such as specific surface area, pore size distribution, bulk electrical resistivity, contact resistance with graphite plates, along with the wettability, imbibition and permeability of methanol aqueous solution. These properties were compared to those reported for commercial carbon paper and carbon cloth materials commonly used as diffusion layers in PEM fuel cells. The electrical properties of the mesoporous carbon meet the requirements to be employed as diffusion layers in PEM stacks assembled at pressures above 15bar. The rapid spreading and imbibition of concentrated methanol solutions in the mesoporous carbon, as well as the permeability of the aqueous methanol through it, also make this mesostructured carbon a possible candidate for diffusion layer and catalyst support in passive direct methanol micro fuel cells.

High Performance plasma sputtered PdPt fuel cell electrodes with ultra low loading

A PdPt (10 wt% Pt) catalyst is used to replace platinum at the cathode of a proton exchange membrane fuel cell membrane electrode assembly (PEMFC MEA) whereas pure palladium is used as the anode catalyst. The catalysts are deposited on commercial carbon woven web and carbon paper GDLs by plasma sputtering. The relations between the depth density profiles, the electrode support and the fuel cell performances are discussed. It is shown that the catalyst gradient is an important parameter which can be controlled by the catalyst depth density profile and/or the choice of electrode support. An optimised electrode structure has been obtained, which allows limiting the platinum requirement. Under suitable conditions of a working PEMFC (80 °C and 3 bar absolute pressure), very high catalysts utilization is obtained at both electrodes, leading to 250 kW g Pt −1 and 12.5 kW g Pd −1 with a monocell fitted with a PdPt (10:1 weight ratio) cathode and a pure Pd anode.

3-옥틸티오펜의 전기화학적 중합법에 의한 탄소재료의 표면 전착

탄소재료의 표면을 재질하고 이를 광전자 기능소자의 전극 재료로서 응용하는 가능성을 모색하기 위하여 탄소재료의 표면을 폴리(3-옥틸티요펜)으로 전기화학적 방법에 의하여 전착하는 것을 연구하였다. 전착의 기질로 사용되는 탄소재료의 형태로는 시판되는 탄소종이 및 탄소섬유를 택하였으며, 전기중합에 사용되는 단량체의 농도 전해질의 농도 인가전압의 변화, 순환전압전류법 사이클 회수를 달리하여 그 영향을 관찰하였다. 단량체의 농도와 전해질 농도의 증가, 인가전압의 증가, 순환전압전류법 사이클 회수의 증가에 따라 탄소종이와 탄소섬유에 중합된 폴리(3-옥틸터오펜)의 양이 증가함을 관찰하였으며, 중합속도에 미치는 영향을 각각의 변수에 대한 지수를 측정해서 분석하였다, 폴리(3-옥틸티오펜)이 중합된 탄소재료의 표면은 주사전자현미경을 통해 관찰하였고 그 구조를 FTIR-ATR로 분석하였다.

Effect of Ti sublayer on the ORR catalytic efficiency of dc magnetron sputtered thin Pt films

A series of thin Pt films were deposited by dc magnetron sputtering directly on a commercial hydrophobic carbon paper substrate having a thin microporous Vulcan-XC72 layer or upon a thin Ti sublayer sputtered on the top of the microporous carbon film. The electrocatalytic properties of the sputtered Pt films toward the oxygen reduction reaction were investigated in 0.5 M H 2SO 4 solution and in a hydrogen PEM fuel cell. The catalyst with ultralow Pt loading of 22 μg cm −2 deposited on a 33 Å thick Ti sublayer is robust, mechanically stable, possesses highly developed surface area and improved catalytic efficiency. Its performance as a MEA cathode in a single hydrogen PEM fuel cell (577 mA cm −2 at 0.4 V cell voltages and a maximum power of 0.954 W) proved to be much superior compared to that of MEA with the same cathode Pt loading but without Ti sublayer (173 mA cm −2 at 0.4 V, 0.231 W, respectively).

A silk derived carbon fiber mat modified with Au@Pt urchilike nanoparticles: A new platform as electrochemical microbial biosensor

We present here a facile and efficient route to prepare silk derived carbon mat modified with Au@Pt urchilike nanoparticles (Au@Pt NPs) and develop an Escherichia coli ( E. coli)-based electrochemical sensor using this material. Silk is a natural protein fiber, and it is abundant with kinds of functionalities which are important in the development of the derived material. The S-derived carbon fiber mat have amino, pyridine and carbonyl functional groups, these natural existent functionalities allow the Au@Pt NPs to self-assemble on the carbon fiber surface and provide a biocompatible microenvironment for bacteria. The Au@Pt NPs modified S-derived carbon fiber is sensitive to detect the E. coli activities with a low detection limit, where glucose is used as a prelimiltary substrate to evaluate them. The performance of Au@Pt/carbon fiber mat based biosensor is much better than that of commercial carbon paper based biosensor. The high sensitivity of this biosensor stems from the unique electrocatalytic properties of Au@Pt urchilike NPs and quinone groups presented in S-derived carbon fiber. This biosensor is also tested for detection of organophosphate pesticides, fenamiphos. The relative inhibition of E. coli activity is linear with −log[fenamiphos] at the concentration range from 0.5 mg/L to 36.6 mg/L with lowest observable effect concentration (LOEC) of 0.09 mg/L. The Au@Pt NPs modified S-derived carbon fiber mat possesses high conductivity, biocompatibility and high electrocatalytic activity and be can used as advanced electrode materials for microbial biosensor improvement. The microbial biosensor based on this material shows potential applications in environmental monitoring.

Carbon nanotubes based gas diffusion layers in direct methanol fuel cells

A carbon nanotube based gas diffusion layer (CNT-GDL) for direct methanol fuel cells (DMFCs) was prepared by sintering the wet carbon paper made of CNT, polyacrylonitrile-based carbon fibre (PCF) and PTFE, completely replacing the commercial carbon paper based GDL (Toray-GDL). The results of X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimeter (MIP) showed that CNT-GDL is of higher graphitization degree, more abundant pores in the pore diameter range of 1000–3000 nm and better mass transfer ability, compared with those of Toray-GDL. Electrochemical impedance spectroscopy (EIS) results display that the cell with CNT-GDL had better electrical conductivity and mass transfer ability than those of Toray-GDL. As a result, the limiting current density and peak power density of DMFC single cell with CNT-GDL are improved by 40% and 27%, respectively.

Electrospinning-derived carbon fibrous mats improving the performance of commercial Pt/C for methanol oxidation

The carbon fibrous mats (CFMs) formed by carbon nanofibers whose average diameter is about 150 nm have been fabricated by thermally treating the electrospun polyacrylonitrile fibrous mats. The electrocatalytic activity of commercial Pt/C supported on the CFMs for methanol oxidation in a sulfuric acid solution has been investigated by cyclic voltammetry, chronoamperometry, quasi-steady state polarization, and electrochemical impedance spectroscopy (EIS) methods. The results show that the commercial Pt/C supported on the CFMs exhibits higher electrocatalytic activity, more stability, larger exchange current and smaller charge transfer resistance than that on commercial carbon papers (CPs), which reveals that the CFMs could be developed as suitably-supporting materials for Pt/C catalyst due to their special porous and continuous fibrous structures.

Influence of the Teflon loading in the gas diffusion layer of PBI-based PEM fuel cells

The influence of the PTFE content in commercial Toray graphite paper gas diffusion layer (GDL) on the performance of a PBI-based polymer electrolyte membrane fuel cell (PEMFC) has been studied. These materials have been characterised by evaluating the porosity, pore size distribution, SEM micrographs, hydrophobicity, air permeability and electrical resistance. Fuel cell results show that the lower the Teflon content, the better the cell performance and the lower the losses when oxygen was replaced by air. These results led to non-Teflonized carbon paper to be postulated as the most suitable candidate, provided that its mechanical integrity can be maintained throughout the whole process of preparation and testing of the MEA. However, some practical problems with this type of commercial non-Teflonized carbon paper were experienced in this work and led to damage of the support. The detrimental effects are described and discussed. As conclusion, the use of a minimally PTFE-loaded (10%) carbon paper is suggested because the inclusion of this level of Teflon improved properly the mechanical properties of the carbon support and only caused a very small drop in the performance.

Characterization of Pt Nanoparticles Deposited onto Carbon Nanotubes Grown on Carbon Paper and Evaluation of This Electrode for the Reduction of Oxygen

Multiwalled carbon nanotubes (MWCNTs) were grown on the fibers of a commercial porous carbon paper used as carbon-collecting electrodes in fuel cells. The tubes were then covered with Pt nanoparticles in order to test these gas diffusion electrodes (GDEs) for oxygen reduction in H2SO4 solution and in H2/O2 fuel cells. The Pt nanoparticles were characterized by cyclic voltammetry, transmission electron microscopy, and X-ray photoelectron spectroscopy. The majority of the Pt particles are 3 nm in size with a mean size of 4.1 nm. They have an electrochemically active surface area of 60 m2/g Pt for Pt loadings of 0.1-0.45 mg Pt/cm2. Although the electroactive Pt surface area is larger for commercial electrodes of similar loadings, Pt/MWCNT electrodes largely outperform the commercial electrode for the oxygen reduction reaction in GDE experiments using H2SO4 at pH 1. On the other hand, when the same electrodes are used as the cathode in a H2/O2 fuel cell, they perform only slightly better than the commercial electrodes in the potential range going from approximately 0.9 to approximately 0.7 V and have a lower performance at lower voltages.

3D carbon nanotube network based on a hierarchical structure grown on carbon paper backing

Two successive generations of multiwalled carbon nanotubes (MWCNT/1 and MWCNT/2) have been produced by a unique CVD procedure using fibers of a commercial carbon paper as support. MWCNTs/1 have diameters comprised between 30 and 50 nm and are about 10 μm long. They are firmly attached to the carbon paper support. MWCNTs/2 have diameters of 10–20 nm and lengths of several 100 nm. They are grown on MWCNTs/1 and have a density of about 40 nanotubes per micrometer length of MWCNTs/1. This hierarchical nanostructure may find application as support for electrochemical catalysts, especially those used in fuel cells.