Improving the DMFC performance with Ketjen Black EC 300J as the additive in the cathode catalyst layer

Ketjen Black EC 300J with an extremely high mesoporous area and electrical conductivity, was used as an additive in the cathode catalyst layer to improve the DMFC (direct methanol fuel cell) performance. Ketjen Black EC 300J and the catalyst ink were characterized by TEM. The cathode catalyst layers were characterized by SEM, in situ cyclic voltammetry and I–V curve measurements. Ketjen Black EC 300J additive increased the dispersion extent of Pt black particles and improved the Pt utilization. In addition, the pore size and porosity was increased when Ketjen Black EC 300J was added into the cathode catalyst layer. The cathode catalyst layer with Ketjen Black EC 300J additive showed a greater single cell performance than the cathode catalyst layer without any additive, especially in the air-breathing mode. These results suggested that the performance improvement was attributed to the increased Pt utilization, oxygen diffusion and water removal capability when Ketjen Black EC 300J was added into the cathode catalyst layer.     

Effect of carbon black support corrosion on the durability of Pt/C catalyst

The work intends to clarify the effect of carbon black support corrosion on the stability of Pt/C catalyst. The corrosion investigations of carbon blacks with similar structures and characteristics were analyzed by cyclic voltammograms (CV) and X-ray photoelectron spectroscopy (XPS). The results indicate that a higher oxidation degree appears on the Black Pearl 2000 (BP-2000) support, i.e. BP-2000 has a lower corrosion resistance than Vulcan XC-72 (XC-72). The durability investigation of Pt supported on the two carbon blacks was evaluated by a potential cycling test between 0.6 and 1.2 V versus reversible hydrogen electrode (RHE). A higher performance loss was observed on the Pt/BP-2000 gas diffusion electrode (GDE), compared with that of Pt/XC-72. XPS analysis suggests that higher Pt amount loss appeared in the Pt/BP-2000 GDE after durability test. X-ray diffraction (XRD) analysis also shows that Pt/BP-2000 catalyst presents a higher Pt size growth. The higher performance degradation of Pt/BP-2000 is attributed significantly to the less support corrosion resistance of BP-2000.     

The preparation of Pt/C catalysts using various carbon materials for the cathode of PEMFC

Various 60 wt% Pt/C catalysts were prepared using LG precipitation method with Vulcan XC-72, Ketjen black EC 300J, and Ketjen black EC 600JD. The average Pt particle size decreases with increasing the surface area of carbon black supports. The 60 wt% Pt/C catalyst with 1.6 nm of Pt particle size and good dispersion could be prepared using Ultra high Surface Area Carbon (USAC, Ketjen black EC 600JD). In single cell test, the activity of electrode catalysts was enhanced with Pt surface area increase above 0.6 V but the correlation between activity of catalysts and Pt surface area was not clear below 0.6 V. Pt catalyst supported on USAC showed good oxygen reduction activity in all voltage regions and also showed stable voltage of 0.6 V at 900 mA cm⁻² without degradation over 180 h of durability test.     

Double microporous layer cathode for membrane electrode assembly of passive direct methanol fuel cells

A novel membrane electrode assembly (MEA) is described that utilizes a double microporous layer (MPL) structure in the cathode of a passive direct methanol fuel cell (DMFC). The double MPL cathode uses Ketjen Black carbon as an inner-MPL and Vulcan XC-72R carbon as an outer-MPL. Experimental results indicate that this double MPL structure at the cathode provides not only a higher oxygen transfer rate, but enables more effective back diffusion of water; thus, leading to an improved power density and stability of the passive DMFC. The maximum power density of an MEA with a double MPL cathode was observed to be ca. 33.0 mW cm⁻², which is found to be a substantial improvement over that for a passive DMFC with a conventional MEA. A. C. impedance analysis suggests that the increased performance of a DMFC with the double MPL cathode might be attributable to a decreased charge transfer resistance for the cathode oxygen reduction reaction.     

New RuO2 and carbon–RuO2 composite diffusion layer for use in direct methanol fuel cells

A RuO₂ diffusion layer is examined for use in direct methanol fuel cells (DMFC) by comparison with acetylene black and Vulcan XC-72R. In the test with a DMFC unit cell, the RuO₂ diffusion layer is superior to the other two materials. The difference in performance is interpreted in terms of structural and electrical properties which are evaluated by porosity, scanning electron microscopy and resistance measurements. The RuO₂ diffusion layer displays different behaviors at the anode and cathode sides. These characteristics can be attributed to a reduced loss of catalyst in the active catalyst layer, which leads to increased methanol diffusion at the anode and prevention of water flooding in the cathode. The effect of the RuO₂ diffusion layer on cell performance becomes more pronounced at lower temperatures and during operation in the presence of air. Finally, a carbon–RuO₂ composite is evaluated as a diffusion layer material for a DMFC.     

Physical and electrochemical evaluation of commercial carbon black as electrocatalysts supports for DMFC applications

This work presents results with noble metal catalysts, Pt and PtRu supported on Black Pearl with a higher surface area in comparison with carbon black Vulcan XC-72R and Vulcan XC72. The nanoparticles were synthesized following the alcohol reduction method. Brunauer–Emmet–Teller (BET) surface area analysis, X-ray diffraction (XRD), energy dispersive analysis by X-rays (EDAX), and high resolution transmission electronic microscopy (TEM) experiments were carried out to characterize the materials obtained. Cyclic voltammograms (CV) of catalysts using the porous thin layer electrode technique were obtained for the catalysts surface evaluation and for methanol oxidation to check the electrocatalytic behavior of these nanocatalyst systems.     

Enhanced membrane electrode assembly performance by adding PTFE/Carbon black for high temperature polymer electrolyte membrane fuel cell

Phosphoric acid used as a proton-conductive medium in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) poisons the Pt surface and prevents oxygen transport in the cathode catalyst layer. The hydrophobic binders in the catalyst not only maintain the catalyst layer structure but also control the phosphoric acid distribution. In this study, polytetrafluoroethylene (PTFE)/carbon black (Vulcan XC-72R) added to the catalyst layer generates an oxygen transport channel. The catalyst layers coated on the gas diffusion layer by the bar-coating method serve as the cathode. High PTFE content causes hydrophobicity in the catalyst layer. The membrane electrode assembly (MEA) with 6 wt% PTFE/Vulcan results in the highest peak power density (0.347 W cm⁻²) and voltage (0.653 V) at 0.2 A cm⁻². A critical reason for its high performance is having the lowest R_ct + R_mt values measured at 0.6 V and 0.4 V. These results could contribute to improving the MEA performance for HT-PEMFCs.     

Activities of Pt/Sibunit-1562 catalysts in the ORR in PEMFC: Effect of Pt content and Pt load at cathode

In this paper, a systematic investigation was carried out of activities at 80 °C of Pt supported on Sibunit-1562 graphitized carbon in the electroreduction of oxygen in the polymer electrolyte fuel cell. Pt content in the Pt/Sibunit-1562 catalysts was 20, 40, and 60 wt.% and Pt load at the cathode was varied in the 200–6.25 μg_Pt cm⁻² interval. The results were compared with the activity of commercial 20 wt.% Pt/Vulcan XC-72 catalyst. To optimize the transport properties of the cathode layer and maintain its thickness upon using Pt/Sibunit −1562 catalysts with varied Pt content and Pt loads a definite amount of Vulcan-XC-72 carbon support was added to the cathode catalytic inks. Higher activity of Pt/Sibunit-1562 catalysts was found as compared to that of commercial 20 wt.% Pt/Vulcan XC-72 with similar particle size of the active component.     

Pt-Ru electrocatalysts supported on ordered mesoporous carbon for direct methanol fuel cell

Pt-Ru electrocatalysts supported on ordered mesoporous carbon (CMK-3) were prepared by the formic acid method. Catalysts were characterized applying energy dispersive X-ray analyses (EDX) and X-ray diffraction (XRD). Methanol and carbon monoxide oxidation was studied electrochemically by cyclic voltammetry, and current-time curves were recorded in a methanol solution in order to establish the activity towards this reaction under potentiostatic conditions. The physicochemical and electrochemical properties of the Pt-Ru catalysts supported on CMK-3 carbon were compared with those of electrocatalysts supported on Vulcan XC-72 and commercial catalyst from E-TEK. Additionally, in order to complete this study, Pt electrocatalysts supported on CMK-3 and Vulcan XC-72 were prepared by the same method and were used as reference. Results showed that the Pt-Ru/CMK-3 catalyst presented the best electrocatalytic activity towards the CO oxidation and, therefore, good perspectives to its application in DMFC anodes. On the other hand, the activity of the Pt-Ru/CMK-3 catalyst towards methanol oxidation was higher than that of the commercial Pt-Ru/C (E-TEK) catalyst on all examined potentials, confirming the potential of the bimetallic catalysts supported on mesoporous carbons.     

Graphitic mesoporous carbon as a durable fuel cell catalyst support

Highly stable graphitic mesoporous carbons (GMPCs) are synthesized by heat-treating polymer-templated mesoporous carbon (MPC) at 2600 °C. The electrochemical durability of GMPC as Pt catalyst support (Pt/GMPC) is compared with that of carbon black (Pt/XC-72). Comparisons are made using potentiostatic and cyclic voltammetric techniques on the respective specimens under conditions simulating the cathode environment of PEMFC (proton exchange membrane fuel cell). The results indicate that the Pt/GMPC is much more stable than Pt/XC-72, with 96% lower corrosion current. The Pt/GMPC also exhibits a greatly reduced loss of catalytic surface area: 14% for Pt/GMPC vs. 39% for Pt/XC-72.     

Key parameters of active layers affecting proton exchange membrane (PEM) fuel cell performance

The 2ⁿ full factorial design was applied to identify the key parameters of the active layer affecting the performance of a proton exchange membrane (PEM) fuel cell. Three main selected parameters were considered: carbon-type (Vulcan XC 72R and Black Pearls 2000 conducting furnace blacks, Cabot Corporation Boston, MA), Pt loading (0.1 and 0.5 mg/cm²), and Nafion™ sulfonic acid fluoropolymer (Du Pont de Nemours, Wilmington, DE) ionomer content (10% and 60%) for variables A, B, and C, respectively. The results from full factorial analysis indicated that the key factors affecting the exchange current density or activation loss were Pt loading whereas the key factors controlling the resistance due to ohmic loss were Nafion content and carbon type. In addition, there are the interactions between these parameters controlling the thin-film active layer performance, especially the interaction of carbon type and Nafion content. From cyclic voltammograms and cell performance testing, a Nafion content of 30% in a catalyst layer consisting of 0.5 mg/cm² Pt on Vulcan XC 72R is optimal.     

Study of different nanostructured carbon supports for fuel cell catalysts

Pt clusters were deposited by an impregnation process on three carbon supports: multi-wall carbon nanotubes (MWNT), single-wall carbon nanohorns (SWNH), and Vulcan XC-72 carbon black to investigate the effect of the carbon support structure on the possibility of reducing Pt loading on electrodes for direct methanol (DMFC) fuel cells without impairing performance. MWNT and SWNH were in-house synthesised by a DC and an AC arc discharge process between pure graphite electrodes, respectively. UV-vis spectrophotometry, scanning and transmission electron microscopy, X-ray diffraction, and cyclic voltammetry measurements were used to characterize the Pt particles deposited on the three carbon supports. A differential yield for Pt deposition, not strictly related to the surface area of the carbon support, was observed. SWNH showed the highest surface chemical activity toward Pt deposition. Pt deposited in different forms depending on the carbon support. Electrochemical characterizations showed that the Pt nanostructures deposited on MWNT are particularly efficient in the methanol oxidation reaction.     

Pt incorporated hollow core mesoporous shell carbon nanocomposite catalyst for proton exchange membrane fuel cells

In the present study, various commercial carbon black materials like Vulcan XC72, Black Pearl 2000, and Regal 330 were used as supporting material for polymer electrolyte membrane fuel cell (PEMFC) electrocatalysts. A promising carbon material exhibiting hollow core mesoporous shell (HCMS) structure was synthesized by the template replication of the silica spheres with solid core and mesoporous shell structure. Two carbon supports with similar pore texture were prepared by the injection of two different carbon precursors. 20 wt% Pt/C electrocatalysts were synthesized by microwave irradiation method as the cathode electrode for PEMFC. Ex situ characterization of the electrocatalysts was performed by N₂ adsorption analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). Electrochemical characterization of the electrocatalysts was conducted by cyclic voltammetry (CV) analysis. Effect of different carbon supports on the cathode performance was investigated in a single cell H₂/O₂ PEMFC. Fuel cell performance tests and additional ex situ characterizations showed that HCMS carbons exhibit good support characteristics with improved single cell performance. For the cathode electrode kinetics, promising fuel cell performance results were obtained as compared to the commercial carbon blacks.     

Inkjet printing of carbon supported platinum 3-D catalyst layers for use in fuel cells

We present a method of using inkjet printing (IJP) to deposit catalyst materials onto gas diffusion layers (GDLs) that are made into membrane electrode assemblies (MEAs) for polymer electrolyte fuel cell (PEMFC). Existing ink deposition methods such as spray painting or screen printing are not well suited for ultra low (<0.5 mg Pt cm⁻²) loadings. The IJP method can be used to deposit smaller volumes of water based catalyst ink solutions with picoliter precision provided the solution properties are compatible with the cartridge design. By optimizing the dispersion of the ink solution we have shown that this technique can be successfully used with catalysts supported on different carbon black (i.e. XC-72R, Monarch 700, Black Pearls 2000, etc.). Our ink jet printed MEAs with catalyst loadings of 0.020 mg Pt cm⁻² have shown Pt utilizations in excess of 16,000 mW mg⁻¹ Pt which is higher than our traditional screen printed MEAs (800 mW mg⁻¹ Pt). As a further demonstration of IJP versatility, we present results of a graded distribution of Pt/C catalyst structure using standard Johnson Matthey (JM) catalyst. Compared to a continuous catalyst layer of JM Pt/C (20% Pt), the graded catalyst structure showed enhanced performance.     

Nano-structured Pt–Cr anode catalyst over carbon support,for direct methanol fuel cell

In this study, several kinds of carbon were used as the support for the Pt-based catalyst of the direct methanol fuel cell (DMFC). Mesoporous carbons with large BET surface area and a commercial carbon were used as the support for the anode catalyst. The maximum current densities of the catalysts were compared by cyclic voltammogram. The catalyst supported on Vulcan XC-72, the commercial carbon support, showed the highest catalytic activity because of its high electric conductivity in spite of small BET surface area. Transition metals such as Cr, Mn, Y, or Zn were impregnated simultaneously with a Pt precursor on Vulcan XC-72, respectively, and then the catalytic activity was tested. The Pt–Cr/C catalyst showed the highest catalytic activity among this catalyst series, and was more active than the Pt/C catalyst. Furthermore, in order to improve the activity of the Pt–Cr/C catalyst, sintering of active metals by thermal reduction during the preparation should be avoided. Therefore, alkaline aluminum leaching method was applied for the purpose of decreasing the particle size of the active metals by reducing the sintering of Pt and Cr. Aluminum precursor was introduced together with Pt and Cr precursors into the commercial carbon support in the preparation process. After reduction of the sample, aluminum species were selectively leached out. The catalyst showed a much improved activity as expected and characterized by H₂ chemisorption and TEM analyses.     

Low-cost and durable catalyst support for fuel cells: Graphite submicronparticles

Low-cost graphite submicronparticles (GSP) are employed as a possible catalyst support for polymer electrolyte membrane (PEM) fuel cells. Platinum nanoparticles are deposited on Vulcan XC-72 carbon black (XC-72), carbon nanotubes (CNT), and GSP via ethylene glycol (EG) reduction method. The morphologies and the crystallinity of Pt/XC-72, Pt/CNT, and Pt/GSP are characterized with X-ray diffraction and transmission electron microscope, which shows that Pt nanoparticles (∼3.5 nm) are uniformly dispersed on supports. Pt/GSP exhibits the highest activity towards oxygen-reduction reactions. The durability study indicates that Pt/GSP is 2-3 times durable than Pt/CNT and Pt/XC-72. The enhanced durability of Pt/GSP catalyst is attributed to the higher corrosion resistance of graphite submicronparticles, which results from higher graphitization degree of GSP support. Considering its low production cost, graphite submicronparticles are promising electrocatalyst support for fuel cells.     

Effect of diffusion-layer morphology on the performance of solid-polymer-electrolyte direct methanol fuel cells

The performance of solid-polymer-electrolyte direct methanol fuel cells (SPE-DMFCs) is substantially influenced by the morphology of the gas diffusion-layer in the catalytic electrodes. Cells utilising gas diffusion-layers made with high surface-area Ketjen Black carbon, at an optimised thickness, show better performance compared with cells utilising Vulcan XC-72 carbon or ‘acetylene black’ carbon in the diffusion-layer. The cells with a hydrophilic diffusion-layer on the anodes and a hydrophobic diffusion-layer on the cathodes yield better performance. The cells with oxygen or air as the oxidant gave power density of 250 or 105 mW cm⁻², respectively, at an operational temperature of 90 °C and 2 bar pressure.     

Durability investigation of carbon nanotube as catalyst support for proton exchange membrane fuel cell

Electrochemical surface oxidation of carbon black Vulcan XC-72 and multiwalled carbon nanotube (MWNT) has been compared following potentiostatic treatments up to 168 h under condition simulating PEMFC cathode environment (60 °C, N₂ purged 0.5 M H₂SO₄, and a constant potential of 0.9 V). The subsequent electrochemical characterization at different treatment time intervals suggests that MWNT is electrochemically more stable than Vulcan XC-72 with less surface oxide formation and 30% lower corrosion current under the investigated condition. As a result of high corrosion resistance, MWNT shows lower loss of Pt surface area and oxygen reduction reaction activity when used as fuel cell catalyst support.     

Performance of Pt/C catalysts prepared by microwave-assisted polyol process for methanol electrooxidation

Pt nanoparticles catalysts supported on the Vulcan XC-72 carbon black with different mean sizes have been synthesized by microwave-assisted polyol process and characterized by energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results of physical examinations show that Pt nanoparticles have a narrow size distribution and are highly dispersed on the surface of carbon support, and Pt loading in Pt/C catalyst is the similar with the theoretical value. The results of cyclic voltammetry and chronoamperometry demonstrate that the Pt/C catalyst prepared by microwave-assisted polyol process at the pH value of about 12 exhibits the highest catalytic activity for methanol electrooxidation. The activity of Pt/C catalyst is also related to the microwave heating time, and the optimal heating time is 40 s in this work.     

Carbon xerogels as Pt catalyst supports for polymer electrolyte membrane fuel-cell applications

Carbon xerogels prepared by the resorcinol-formaldehyde (RF) sol-gel method with ambient-pressure drying were explored as Pt catalyst supports for polymer electrolyte membrane (PEM) fuel cells. Carbon xerogel samples without Pt catalyst (CX) were characterized by the N₂ sorption method (BET, BJH, others), and carbon xerogel samples with supported Pt catalyst (Pt/CX) were characterized by thermogravimetry (TGA), powder X-ray diffraction (XRD), electron microscopy (SEM, TEM) and ex situ cyclic voltammetry for thin-film electrode samples supported on glassy carbon and studied in a sulfuric acid electrolyte. Experiments on Pt/CX were made in comparison with commercially obtained samples of Pt catalyst supported on a Vulcan XC-72R carbon black support (Pt/XC-72R). CX samples had high BET surface area with a relatively narrow pore size distribution with a peak pore size near 14 nm. Pt contents for both Pt/CX and Pt/XC-72R were near 20 wt % as determined by TGA. Pt catalyst particles on Pt/CX had a mean diameter near 3.3 nm, slightly larger than for Pt/XC-72R which was near 2.8 nm. Electrochemically active surface areas (ESA) for Pt as determined by ex situ CV measurements of H adsorption/desorption were similar for Pt/XC-72R and Pt/CX but those from CO stripping were slightly higher for Pt/XC-72R than for Pt/CX. Membrane-electrode assemblies (MEAs) were fabricated from both Pt/CX and Pt/XC-72R on Nafion 117 membranes using the decal transfer method, and MEA characteristics and single-cell performance were evaluated via in situ cyclic voltammetry, polarization curve, and current-interrupt and high-frequency impedance methods. In situ CV yielded ESA values for Pt/XC-72R MEAs that were similar to those obtained by ex situ CV in sulfuric acid, but those for Pt/CX MEAs were smaller (by 13-17%), suggesting that access of Nafion electrolyte to Pt particles in Pt/CX electrodes is diminished relative to that for Pt/XC-72R electrodes. Polarization curve analysis at low current density (0.9 V cell voltage) reveals slightly higher intrinsic catalyst activity for the Pt/CX catalyst which may reflect the fact that Pt particle size in these catalysts is slightly higher. Cell performance at higher current densities is slightly lower for Pt/CX than the Pt/XC-72R sample, however after normalization for Pt loading, performance is slightly higher for Pt/CX, particularly in H₂/O₂ and at lower cell temperatures (50 °C). This latter finding may reflect a possible lower mass-transfer resistance in the Pt/CX sample.