Cycles Of Durability Test Research Articles

Stable Reference Electrode in Polymer Electrolyte Membrane Electrolyser for Three-Electrode Measurements

In this study, various methods to study individual electrodes in polymer electrolyte membrane cells are reviewed and a novel reference electrode design is developed for a laboratory scale single cell polymer electrolyte membrane water electrolyser. The design uses an internal pseudo-reference electrode which is proven to enable galvanostatic electrochemical impedance spectroscopy studies. The setup is used to study the state-of-the-art electrode materials with high loadings in a start-stop cycling durability test. The cycled catalyst layers are characterized ex-situ with SEM, TEM and XRD. As a result, on the anode the mass transport resistance increases, the macro porosity increases and a structural change from amorphous IrOx toward crystalline IrO2 is detected. On the cathode the platinum particle size increases and an intensifying corrosion phenomenon is detected. In overall, this degradation has still low effect on the full cell performance during the studied 1750 hours. However, there is a clear indication that if the start-stop cycling is further continued, the cell will experience a dramatic performance loss much sooner than when operating it in a constant current mode.

Poly(4-vinylpyridine) based novel stationary phase investigated under supercritical fluid chromatography conditions

A novel poly(4-vinylpyridine) based stationary phase was investigated for its performance under supercritical fluid chromatography (SFC) mode. Due to its unique structure, this stationary phase has high molecular planarity recognition ability for aromatic samples possessing the same number of aromatic rings and π-electrons. Taking advantage of the planarity recognition ability observed, separations of structurally similar polycyclic aromatic hydrocarbons and steroids were achieved. This novel stationary phase afforded good peak symmetry for both acidic and basic active pharmaceutical ingredients even when excluding the use of additives such as acids, bases, and salts. These findings may be attributed to the polymeric pyridyl groups covalently-attached on silica gel, which will effectively shield the undesirable interaction between residual silanol groups on the surface and the analytes. Moreover, the properties of pyridyl group on the selector can be reversibly tuned to cationic pyridinium form by eluting trifluoroacetic acid containing modifier. Column robustness toward cycle durability testing was also confirmed.

Effects of Ionomer Content on Both Performance and Load Cycle Durability for PEFCs Using Pt/Nb-SnO2 Cathode Catalyst Layers

Toward the widespread application of polymer electrolyte fuel cells (PEFCs) in electric vehicles, the enhancement of the cathode catalyst activity for the oxygen reduction reaction (ORR) and the improvement of the durability are needed. Pt catalysts loaded on graphitized carbon black (Pt/GCB) have been confirmed to moderate degradation during startup and shutdown, compared with that of Pt/CB, but these carbons have not been able to completely overcome corrosion at high potential. Electronically conducting oxides, without the use of carbon, such as the Magneli phase titanium oxides and tin dioxide, are promising candidate supports [1,2]. Our group also has reported that Pt catalysts loaded on Nb-doped SnO2 (Pt/Nb-SnO2) and Ta-doped SnO2 (Pt/Ta-SnO2), without any carbon additive, showed high durability during startup/shutdown, while maintaining high ORR activity, by means of rotating disk electrode and membrane electrode assembly (MEA) measurements [3-9]. The high ORR activity of Pt/Nb-SnO2 and Pt/Ta-SnO2 is dependent on a strong interaction between the Pt catalyst and the tin oxide. The low cell resistivity of an MEA using our Pt/Nb-SnO2 cathode, as low as that using a Pt/CB cathode, is ascribed to a unique microstructure involving a fused aggregate network structure, which constructs effective gas diffusion pathways, electronically conducting pathways and high surface area in the catalyst layer (CL). For the further improvement of the cell performance, the optimization of the volume and dispersion of the ionomer in the CL is important. In this research, we have evaluated the cell performance and the load cycle durability of single cells using a Pt/Nb-SnO2 CL with a range of volume ratios of Nafion® ionomer and the support material (I/S). The current-voltage performance and resistivity of the cell using Pt/Nb-SnO2 CL (I/S = 0.24) were equal to those using Pt/GCB CL (I/S = 0.67, optimized I/S ratio, Fig. 1).The apparent mass activity at 0.80 V (MAapp@0.80 V) of the cell using Pt/Nb-SnO2 CL improved with decreasing I/S, and, at I/S = 0.12, approached a value a factor of 2 higher than that using a commercial Pt/GCB CL with an optimized I/S ratio (Fig. 2). The current density at 0.60 V of the cell using Pt/Nb-SnO2 (I/S = 0.12) CL approached the same value of the cell using Pt/GCB CL. The electrochemically active surface area (ECA) of the Pt/Nb-SnO2 CL was twice as large at the initial stage than that of Pt/GCB CL and continued to maintain higher values during a load cycle durability test (0.6 - 1.0 V, 3 s, Fig. 3). We consider that the utilization of Pt and the load-cycle durability of Pt/Nb-SnO2 are higher than those of Pt/GCB. The Nafion® ionomer covered uniformly on the hydrophilic surface of the Pt/Nb-SnO2 (Fig. 4), in contrast to the poor coverage of the ionomer on the hydrophobic surface of the Pt/GCB, based on an evaluation with low acceleration voltage transmission electron microscopy. We suggest that the thin, uniform coverage of the Nafion® ionomer on the Pt/Nb-SnO2 surface, due to the appropriate low level of ionomer, moderates both the oxygen diffusion overpotential in the Nafion® ionomer and the Pt catalyst degradation. This work was partially supported by funds for the “Superlative, Stable, and Scalable Performance Fuel Cell” (SPer-FC) project from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, and JSPS KAKENHI Grant Number 17H03410 from the Ministry of Education, Culture, Sports, Science and Technology. T. Ioroi, Z. Siroma, N. Fujiwara, S. Yamazaki, K. Yasuda, Electrochem. Commun., 7, 183 (2005).A. Masao, S. Noda, F. Takasaki, K. Ito, K. Sasaki, Electrochem. Solid-State Lett., 12, B119 (2009).K. Kakinuma, M. Uchida, T. Kamino, H. Uchida, M. Watanabe, Electrochim. Acta, 56, 2881 (2011).K. Kakinuma, Y. Chino, Y. Senoo, M. Uchida, T. Kamino, H. Uchida, S. Deki, M. Watanabe, Electrochim. Acta, 110, 316 (2013).Y. Senoo, K. Kakinuma, M. Uchida, H. Uchida, S.Deki, M. Watanabe, RSC Adv., 6, 321800 (2014).Y. Senoo, K. Taniguchi, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, M. Watanabe, Electrochem. Commun., 51, 37 (2015).Y. Chino, K. Taniguchi, Y. Senoo, K. Kakinuma, M. Watanabe, M. Uchida, J. Electrochem. Soc., 162, F736 (2015).Y. Chino, K. Kakinuma, D.A. Tryk, M. Watanabe, M. Uchida, J. Electrochem. Soc., 163, F97 (2016).K. Takahashi, R. Koda, K. Kakinuma, M. Uchida, J. Electrochem. Soc., 164, F235 (2017). Figure 1

Evaluation of performance and durability of platinum–iron–copper with L10 ordered face-centered tetragonal structure as cathode catalysts in polymer electrolyte fuel cells

We evaluated the performance and durability of platinum–iron–copper with an L10 ordered face-centered tetragonal structure (fct–PtFeCu) as cathode catalysts of membrane-electrode assemblies (MEAs) in polymer electrolyte fuel cells. The exchange current density per unit active surface area of Pt in fct–PtFeCu/C, measured in the MEA, was sufficiently higher than that of commercial Pt/C. The durability of the MEAs was evaluated by three accelerated degradation tests: (1) a load cycle durability test, which mainly accelerates the degradation of catalysts; (2) an open-circuit voltage (OCV) hold test, which mainly degrades membranes; and (3) a hybrid of the load cycle test and OCV hold test. Despite the possible negative effects of dissolved transition metals on the durability of MEAs, fct–PtFeCu/C showed higher durability than commercial Pt/C and at least comparable durability with in-house Pt/C in the OCV hold test, and showed high durability in the hybrid test up to 200 h. These results suggest that the presence of Fe and Cu did not negatively affect the durability of the MEA with fct–PtFeCu/C, and rather the other factor, carbon support, affected more in retaining the durability.

Kirigami-Inspired Nanoconfined Polymer Conducting Nanosheets with 2000% Stretchability.

Stretchable conductors are essential components of wearable electronics. However, such materials typically sacrifice their electronic conductivity to achieve mechanical stretchability and elasticity. Here, the nanoconfinement and air/water interfacial assembly is explored to grow freestanding mechanical endurance conducting polymer nanosheets that can be stretched up to 2000% with simultaneously high electrical conductivity, inspired by kirigami. Such stretchable conductors show remarkable electronic and mechanical reversibility and reproducibility under more than 1000 cycle durability tests with 2000% deformability, which can be accurately predicted using finite element modeling. The conductivity of nanoconfined freestanding conductor nanosheets increases by three orders of magnitude from 2.2 × 10-3 to 4.002 S cm-1 is shown, due to the charge-transfer complex formation between polymer chain and halogen, while the electrical conductance of the stretchable kirigami nanosheets can be maintained over the entire strain regime. The nanoconfined polymer nanosheets can also act as a sensor capable of sensing the pressure with high durability and real-time monitoring.

Poly(butylene terephthalate) based novel achiral stationary phase investigated under supercritical fluid chromatography conditions

Poly(butylene terephthalate) based novel stationary phase (SP), composed of planar aromatic phenyl group together with ester group monomer units, was designed for supercritical fluid chromatography (SFC) use. As expected from its structure, this phase shows planarity recognition of isomeric aromatics and closely similar compounds. Interestingly, for most analytes, the retention behavior of this SP is significantly distinct from that of the 2-ethylpyridine based SPs which is among the most well-known SFC dedicated phases. Although the poly(butylene terephthalate) is coated on silica gel, the performance of the column did not change by using extended range modifiers such as THF, dichloromethane or ethyl acetate and column robustness was confirmed by cycle durability testing.

Influence of Ionomer Content on Both Cell Performance and Load Cycle Durability for Polymer Electrolyte Fuel Cells Using Pt/Nb-SnO2 Cathode Catalyst Layers

The steady-state current-voltage performance and load cycle durability of polymer electrolyte fuel cells using Pt catalysts supported on Sn0.96Nb0.04O2-δ (Pt/Nb-SnO2) cathode catalyst layers (CLs), without any carbon additive, were evaluated with various ionomer contents. The apparent mass activity at 0.80 V (MAapp @0.80 V) of the cell using Pt/Nb-SnO2 CL improved with decreasing volume ratio of the Nafion ionomer to the support (I/S). At I/S = 0.12, surprisingly, the MAapp @0.80 V of the cell using Pt/Nb-SnO2 CL approached 2 times higher than that using a commercial Pt catalyst supported on GCB (Pt/GCB) CL with the optimized I/S ratio. The current density at 0.60 V of the cell using Pt/Nb-SnO2 (I/S = 0.12) CL also reached the same value of the cell using Pt/GCB CL. The electrochemically active surface area and MAapp @0.80 V of Pt/Nb-SnO2 CLs during the load cycle durability test maintained higher values than those of Pt/GCB throughout the test, indicating that the Pt/Nb-SnO2 CL had higher durability than the Pt/GCB CL. Evaluation by means of low acceleration voltage transmission electron microscopy proved that the Nafion ionomer covered the hydrophilic surface of the Pt/Nb-SnO2 uniformly, whereas the ionomer did not do so on the hydrophobic surface of the Pt/GCB. The thin, uniform coverage of the Nafion ionomer, which was thus easily obtained on the Pt/Nb-SnO2 surface, was able to lower the overpotential originating from the oxygen diffusion resistance in the Nafion ionomer, thus improving the cell performance while maintaining the high load cycle durability.

Development of PEFC Alloy Electrocatalysts Supported on SnO2

Pt/C is widely used as polymer electrolyte fuel cell (PEFC) electrocatalysts. However, under a high potential at the cathode, Pt detachment and aggregation due to carbon corrosion can occur. Therefore, Pt/C has a difficulty in durability. Electrocatalysts with tin oxide (SnO2) support are thus developed where vapor grown carbon fiber (VGCF-H) acts as a conducting backbone, achieving both high activity and high durability [1-3]. However, their electrocatalytic activity should be further improved. For this reason, here, we are focusing on the improvement in catalytic activity by preparing PtxMy (M = Co, Ni) alloy catalyst (PtxMy/Sn(Nb)O2/VGCF-H). Co and Ni are relatively stable in the PEFC electrocatalyst environment and PtxMy alloy catalysts are known to be capable of exhibiting higher activity over Pt catalysts [4]. The aim of this study is thus to develop PtxMy alloy electrocatalysts on doped SnO2support. Sn0.98Nb0.02O2 was prepared on the VGCF-H (Sn0.98Nb0.02O2/VGCF-H) by the ammonia coprecipitation method. Co-impregnation of Pt-M alloy (M = Co, Ni) nano-particles was made using acetylacetonate (acac) complexes [5]. In this procedure, a 2-step procedure was applied, i.e., after impregnating Pt, M was impregnated. The amount of SnO2 on the VGCF-H was determined to set the SnO2 loading to 50 wt.% to maintain a high specific surface area of SnO2 without SnO2 particle aggregation and to secure conductive passway among the VGCF-H fibers. In case of PtxMy alloy, various heat-treatment conditions were applied to realize PtxMy alloying without the reduction of SnO2to Sn metal. In order to evaluate Pt and M loadings, ICP analysis was performed. The nanostructure of the electrocatalysts prepared was observed by using FESEM and STEM. We then made half-cell tests to evaluate electrochemical activity and durability of these electrocatalysts. From the ICP results, the atomic Pt/Co ratio measured was 73.5/26.5, confirming that Pt3Co alloy electrocatalyst has been successfully prepared. Figure 1 shows Pt-based catalyst particles with a diameter of 2 to 3 nm are selectively impregnated on the SnO2particles rather than on the VGCF-H. Figure 2 shows that ORR activity was improved, exceeding that of Pt/SnO2/VGCF-H electrocatalyst. The mass activity improvement by the alloying has been confirmed. The highest mass activity of 273 Ag-1 at 0.9 VRHE has been obtained, for the Pt3Co/Sn(Nb)O2/VGCF-H electrocatalyst. The mass activity of this electrocatalyst has reached beyond 1800 Ag-1 measured at 0.85 VRHE. Especially, for Pt : Co = 3 : 1 and heat treatment from 210 oC (3 h) to 240 oC (3 h) and 270 oC (1 h), the mass activity reached the highest value both before and after the voltage cycling durability test, clearly indicating the positive effect of the alloying. In terms of durability, 38% of the initial MA remained even after the 60,000 voltage cycling test, which is larger than that of the Pt/C and is almost the same as that of the Pt/SnO2/VGCF-H electrocatalyst (39%). From these results, we can conclude that SnO2support is applicable also for Pt alloy catalysts, exhibiting high start-stop cycle durability.

Battery-type column for caesium ions separation using electroactive film of copper hexacyanoferrate nanoparticles

We reported a novel and compact battery-type column using nanoparticles film of copper hexacyanoferrate (CuHCF NPs film) for sequential removal of Cs from wastewater. Different from the electrochemical deposition, chemical spray or chemical bath deposition, our film was prepared by coating water dispersed CuHCF NPs ink on the electrode surface through a simple wet process similar to ink printing. The battery-type column indicated Cs adsorption and desorption can be achieved by electrochemical redox of CuHCF NPs film, through switching the potentials between two sandwiched electrodes. Kinetic studies revealed both the static attraction and electrochemical oxidation-reduction of Fe (II/III) contributed to Cs separation. Insignificant change in the current after 100 cycles of durability test indicated the CuHCF NPs film is relatively stable, suggesting the battery-type column has a long service life for Cs removal from wastewater.

Alternative SOFC Anode Materials with Ion- and Electron-Conducting Backbones for Higher Fuel Utilization

Introduction &Solid oxide fuel cells (SOFC) have a great potential to generate electricity with a high efficiency. Currently, Ni-YSZ cermet is widely used as the SOFC anode material. As anode Ni can be oxidized under a high fuel utilization, however, SOFC fuel can not be fully used. In this study, we analyzed alternative anode materials composed of GDC (Ce0.9Gd0.1O2; ionic conductor), LST (Sr0.9La0.1TiO3; electronic conductor), both of which act as stable ion- and electron-conducting frameworks, respectively, and Ni acts only as an electrocatalyst, as described in Fig. 1. Experimental &Electrolyte-supported cells with ScSZ (10 mol % Sc2O3-1 mol % CeO2-89 mol % ZrO2) plate (20 mmφ×&0.2 mmt) were used in this study. Mixture of LST and GDC (1 : 1 ; vol. %) was used for the anode and was sintered at 1300 oC for 3 h. Mixture of (La0.8Sr0.2)0.98MnO3 (LSM) and ScSZ with a weight ratio of 1:1 was used for the cathode. In order to further improve the anodic performance, Ni nanoparticles were impregnated into the porous LST-GDC composite anode. Electrode area was 8×&8 mm2 and Pt mesh was used as the current collector. Cell performance such as I-V characteristics, anodic overvoltage, and anode-side ohmic loss were measured at 800 oCby feeding humidified fuel. The amount of the catalytic Ni loading was optimized through the I-V measurements, FESEM analysis, and Red-Ox cycling tests. Results and discussion &The optimized amount of Ni loading was difficult to be judged only from the I-V measurements and the SEM figures because there were no obvious difference in the anode performance of the cells impregnated more than 0.0833mg-Ni/cm2. Then, Red-Ox cycling tests were conducted according to the procedure shown in Fig. 2, in order to investigate the stable distribution in which Ni catalytic particles are difficult to aggregate. As a result, the best Ni loading in this study was 0.0833mg-Ni/cm2for which anode voltage degradation was only 2% after 50 Red-Ox cycles, whereas that of Ni-ScSZ, conventional Ni-cermet anode was more than 20%. The STEM-EDX micrographs of the optimized anode are shown in Fig. 3, showing that catalytic Ni nanoparticles were supported on the LST-GDC composite frameworks in highly dispersed manner. Anode degradation mechanisms during cycle durability test suggested from these results are shown in Fig. 4. In the conventional Ni-cermet anodes, Ni grains increase in size with Red-Ox cycling and then its electron conducting framework is broken which deteriorates cell performance. On the other hand, in the best impregnated Ni-cermet anodes, Ni nanoparticles loaded on the LST –GDC composite anodes are difficult to aggregate during Red-Ox cycling. Consequently, the stable electrode frameworks exhibit negligible degradation.

Platinum Alloy Nanocatalyst with Manipulated Particle Composition and Morphology for Improved ORR Property

Electrocatalyst for oxygen reduction reaction (ORR) has been an area of intensive research for decades because of both its fundamental complexity and practical importance for many applications, including polymer electrolyte membrane fuel cells (PEMFCs) and metal-air batteries. The ORR activity and electrocatalyst durability are two confronted difficulties in the research. Pt remains the most effective element for ORR in acidic electrolyte for both reaction kinetics and durability considerations. Because of a high Pt price and its insufficient activity, extensive studies have been devoted to decreasing the Pt usage by searching new Pt nanostructures with improved ORR property. The discovery that single crystalline Pt3Ni (111) can exhibit exceptionally high ORR activity (18 mA/cm2 Pt at 0.9 V), which is about 90 times the activity of commercial Pt/C, points to an ideal strategy for solving the problem by using octahedral Pt alloy nanoparticles, which are enclosed by the (111) planes and have large specific active area. Several research groups have made good progresses by synthesizing these shaped particles and reporting high ORR activity. However there are two challenges remained with the octahedral Pt alloy nanocatalyst strategy: (1) The developed wet synthetic methods have low scaling-up capacity and surface contamination issue and are thus not suitable for mass production of the shaped Pt alloy nanoparticles, and (2) Currently researched octahedral Pt alloy nanoparticles have insufficient durability. We realize scalable and surfactant-free production of octahedral Pt alloy nanoparticle catalysts by developing a facile solid-state chemistry method. The prepared octahedral Pt1.5Ni/C exhibited high ORR activities of 3.99 mA/cm2 Pt and 1.96 A/mg Pt at 0.90 V vs. RHE, which are about 20 and 10 times the values for commercial Pt/C specifically.[1] The prepared octahedral Pt2CuNi/C uniform alloy nanoparticle catalyst exhibited both excellent ORR mass activity of 2.35 A/mg Pt at 0.90 V vs. RHE and promising stability, with 81.3% and 68.1% retained activity after 4,000 and 10,000 cycles of durability test.[2] The values make the octahedral Pt2CuNi/C a significantly more stable catalyst than the octahedral Pt-Ni/C, which retained only 52.9% and 35.0% of the initial mass activity after the two tests. The much improved durability was attributed to a uniform alloy composition of the ternary nanoparticles, which slowed down the leaching process of Ni and Cu and helped to preserve the octahedral morphology. The finding provides insights on factors determining the particle stability and offers guidance on development of highly active and durable ORR catalyst for real applications.

Comparison of test results on load cycle durability of polymer electrolyte fuel cell cathode catalysts

The Fuel Cell Commercialization Conference of Japan (FCCJ) has proposed methodologies for testing MEAs focusing on the evaluation of the durability of electrode materials. In this study, we applied a load cycle durability test protocol proposed by FCCJ in 2011 to a standard and a highly durable catalyst, and verified whether the difference in the durability of the two catalysts could be estimated appropriately by the protocol. The highly durable catalyst consists of the same carbon support as the standard catalyst, and its durability was increased by heat treatment of the carbon-supported platinum. We examined the durability of each catalyst according to the conditions specified in the protocol using a JARI standard single cell. Cyclic voltammetry for electrochemical surface area measurement and I–V measurement were conducted as a diagnostics of degradation condition. During the durability test, CO2 concentration in the gas exhausted from the cathode was measured with a non-dispersive infrared analyzer. The highly durable catalyst needed larger number of cycles until the ECA maintenance ratio falls to 50% as initial than that of the standard catalyst. The release rate of CO2 from carbon support was equivalent for both catalysts. We have demonstrated that the protocol effectively differentiated degradation of the platinum from that of carbon support.

PEM-Type Water Electrolysis/Fuel Cell Reversible Cell with Low PGM Catalyst Loadings

To utilize fluctuating renewable energy stably and effectively, large-scale energy storage systems such as Li-ion, redox-flow and Na-S batteries have been extensively studied. Battery storage system have advantages of high efficiency in energy utilization and rapid response for energy demand, however initial system cost tend to be expensive. Electrochemical hydrogen production and storage is recently attracting attentions as another practical technology because of high energy efficiency of electrochemical water splitting, relatively low technological barrier for large-scale storage, and ease of long-term energy storage and long-range transport without self-discharge. Regenerative fuel cell is an energy storage system using hydrogen as an energy medium. In particular, reversible (unitized) regenerative fuel cells (RFCs) can be functioned both as water electrolyzer and fuel cell in the same electrochemical cell by switching the operation mode, so that much more compact and cheaper system could be realized. In the PEM-type RFC, unsupported platinum/iridium-based catalysts are usually selected in terms of activity and stability for both operation modes. Loading amount of platinum group metals (PGMs) of RFC is relatively high (typically >1 mg cm-2) compared to the fuel cell dedicated system due to stability issue at high potentials during OER. Therefore, reducing PGM loadings without expense of performance and durability is high priority to meet the capital cost of the systems. To reduce the PGM loadings of oxygen electrode of RFC, we examined electro-conductive Magneli phase titanium oxides (in particular Ti4O7) as a catalyst support material [1,2]. High surface area oxide support was prepared by UV laser technique; TiO2 nano particles dispersed in an appropriate solvent (typically acetonitrile) are reduced by pulsed UV laser irradiation [3]. Pt, Ir, and Pt-Ir alloy nano particles were deposited on the oxide support, and their electrocatalytic activities were examined by rotating disk electrode and MEA. Ti4O7-supported Pt catalyst showed 3 times larger electrochemical active area (ECA) than that of commercially available Pt black, and 2.9 and 2.4-fold mass activity was obtained for ORR@0.9V and OER@1.7V, respectively. Initial ORR/OER cycle durability test was conducted for Pt/Ti4O7 catalyst MEA at 80oC between >1.8V for OER and <0.8V for ORR, and almost no performance loss was observed. These results show titanium oxide based materials can be applied as RFC catalyst support, which leads to effective use and lowering PGM loading in the oxygen electrode.

Enhanced Durability with Cu-Containing Chemically Ordered Pt-Alloy Catalyst for Oxygen Reduction Reaction in Polymer Electrolyte Fuel Cell

Large-scale commercialization of polymer electrolyte fuel cells (PEFCs) requires great improvement in activity and durability of the cathode catalyst [1]. We have reported enhanced activity and durability of the Pt-based intermetallics, Pt2FeCo/C, with L10 ordered face-centered tetragonal (fct) structure both in acidic solution [2] and as the cathode catalyst of a membrane-electrode assembly [3]. In this work, Cu with higher standard reduction potential was employed to form ordered fct-Pt2FeCu/C, and its activity of oxygen reduction reaction (ORR) and durability were compared with its counterpart bimetallic catalyst, fct-PtFe/C, and the commercial catalyst from Tanaka Kikinzoku Kogyo (TKK-Pt/C). Pt2FeCu/C and PtFe/C were fabricated by the heat treatment of the mixture of metallic precursors and carbon black at 800 °C under 20% H2 in N2 for 2 h. The metal content of the catalyst was around 40 wt%. ORR activity of the catalysts was evaluated in 0.1 M HClO4solution using the rotating disk electrode technique. The durability of the catalysts was examined in the same solution at 60 °C by applying square wave potential cycling, 0.6 V for 3 s and 1.0 V for 3 s, according to load cycle durability testing protocol recommended by the Fuel Cell Commercialization Conference of Japan (FCCJ). XRD patterns of Pt2FeCu/C and PtFe/C showed the formation of chemically ordered fct structures. Both the fct catalysts initially showed high mass activity above 0.5 A/mg-Pt. Figure 1 shows the change in electrochemical surface area (ECSA) and mass activity during load-cycle durability test at 60 °C. Cu-containing fct-Pt2FeCu/C retained more than 70% of mass activity and ECSA at 10K durability cycles, while fct-PtFe/C and TKK-Pt/C catalysts showed a significant loss of activity and ECSA: retention was about 50% for TKK-Pt/C and 40% for fct-PtFe/C. The mass activity of fct-Pt2FeCu/C catalyst was enhanced by more than twice with respect to TKK-Pt/C catalyst, both at the initial state and after 10K durability cycles. STEM-EDX line-scans of the catalysts before and after durability cycles showed that dissolution of Fe and Cu was much less in fct-Pt2FeCu/C than in fct-PtFe/C. The enhancement in the durability of the fct-Pt2FeCu/C catalyst may be ascribed to the synergistic effects of the presence of Cu with higher redox potential and the ordered structure of catalyst.

Highly active and durable chemically ordered Pt–Fe–Co intermetallics as cathode catalysts of membrane–electrode assemblies in polymer electrolyte fuel cells

A cathode catalyst with enhanced activity for the oxygen reduction reaction and high durability is greatly required in polymer electrolyte fuel cells (PEFCs). We report that chemically ordered intermetallics, Pt2FeCo/C with L10 ordered structure and Pt6FeCo/C with L12 ordered structure, achieve both higher activity in solution and higher durability as the cathode catalyst of a membrane–electrode assembly (MEA) under actual PEFC operating conditions, compared with a commercial Pt/C. The mass activity of Pt2FeCo/C is about twice as high as that of a commercial Pt/C, and Pt6FeCo/C has a slightly higher mass activity than a commercial Pt/C in solution. These intermetallics were evaluated for durability as the cathodes of MEAs. During the load cycle durability test, the electrochemical surface area (ECSA) of Pt2FeCo/C is retained, while that of Pt6FeCo/C decreases, although less than a commercial Pt/C. The retention of ECSA is consistent with smaller changes in the particle size, observed with transmission electron microscopy, of the intermetallics than of a commercial Pt/C. X-ray diffraction patterns after the durability test show that while some part of ordered intermetallics is transformed into pure Pt, the chemically ordered structure of Pt2FeCo/C is largely retained. Highly active and durable ordered intermetallics are promising as cathode catalysts of PEFCs.

Investigation of Performance and Durability of MEAs at Higher Temperature

Polymer electrolyte fuel cells (PEFCs) recently attract more attention because fuel cell vehicles (FCVs) are commercially available from 2015. Even though the technology for the first generation FCVs has been mainly established, for the next generation FCVs, the operation at high temperature is desired in order to improve the power generation efficiency and durability. The target operating temperature is about 120 °C for FCVs. Since there are still technological problems for electrolyte membranes over 100 °C, almost no report is found about either performance or durability under such a condition at present. Here, the objective of our study is to extract the problems on the catalytic degradation at higher temperature. In this study, we have evaluated performance and durability of MEAs under higher temperature like 105 °C and low humidity such as RH57%. MEAs were manufactured using a standard Pt/Ketjen black catalyst (TEC10E50E, TKK Corp.) and Nafion. Then, their IV characteristics were examined. Regarding to the durability evaluation, two protocols[1] recommended by Fuel Cell Commercialization of Japan (FCCJ), “load cycles” and “start-stop cycles”, were in use. Three different conditions of operation temperature and humidity (80 °C/RH100%, 105 °C/RH57%, and 80 °C/RH57%) were applied. Then, the effects of such conditions on both performance and durability of MEAs were evaluated.On evaluation of IV performance in three different conditions before and after the load cycle durability tests, the operation at 105 °C greatly deteriorated the performance than at 80 °C. Also, by comparing two different humidity conditions at 80 °C, the lower humidity led to the smaller degradation. Moreover, the change in electrochemical surface area (ECSA) was examined at the same time, and then the retention of ECSA was lower under both higher temperature and higher humidity, likewise. In addition, SEM observations were performed to see the change in Pt particle size. As a result, Pt grain growth was confirmed after the load cycle durability tests. The average particle size became larger at both higher temperature and higher humidity. In other words, a similar trend to the deterioration of IV performance was obtained. Here, we believe that one possible reason why the deterioration was suppressed at lower humidity comes from the existence of less water relating to the diffusion of Pt ions. Similarly, the examination on the start-stop cycle durability tests will also be reported. Reference[1] A. Ohma et al., ECS Trans, 41 (2011) 755.

The durability of carbon supported Pt nanowire as novel cathode catalyst for a 1.5 kW PEMFC stack

Carbon supported platinum nanowires (PtNW/C) synthesized by a simple and inexpensive template-free methodology has been used for the first time as a cathode catalyst in a 15 cell with an active area of 250cm2, 1.5kW proton exchange membrane fuel cell (PEMFC) stack. Drive cycle testing along with in-situ and ex-situ accelerated degradation testing (ADT) showed that the PtNW/C catalyst exhibited better durability than commercial Pt/C. After a 420h dynamic drive cycle durability testing, the PEMFC stacks exhibited a performance degradation rate of 14.4% and 17.9% for PtNW/C and commercial Pt/C based cathodes, respectively. It was found that the majority of performance loss was due to degradation of the commercial Pt/C anode materials, resulting from the rapidly changing load frequencies used in the testing protocol, ultimately leading to harsh fuel/air starvation conditions and subsequent Pt nanoparticle growth and agglomeration. Notably, based on post-testing characterization, the structure, electrochemically active surface area (ECSA) and oxygen reduction activity of the PtNW/C cathode catalyst remained unchanged during the drive cycling, indicating its excellent stability under these practical conditions. Conversely, when using commercial Pt/C as a cathode catalyst, significant Pt nanoparticle growth and agglomeration were observed, resulting in the reduced PEMFC stack durability. Therefore, PtNW/C materials are presented as promising replacements to conventional Pt/C as cathode electrocatalysts for PEMFCs, and particularly demonstrate improved stability under the practical conditions encountered for automotive applications.

Anomalously increased oxygen reduction reaction activity with accelerated durability test cycles for platinum on thiolated carbon nanotubes

We report an anomalous phenomenon in Pt supported on thiolated multi-walled carbon nanotubes (Pt-S-MWNT): oxygen reduction reaction (ORR) activity increases with accelerated durability test (ADT) cycles. Sub-nanometer-sized Pt clusters on S-MWNT were gradually agglomerated to an optimal size with ADT cycles, and finally showed increased ORR activity after the ADT.

Design and fabrication stable LNF contact for future IC application

Enable the design of a small contact spring for applications requiring high density, high speed and high durability. A low normal force (LNF) contact spring with high performance is fabricated using a unique combined MEMS photo resist lithography and electro fine forming (EFF) technology. Reducing a total contact material cost of a connector, a high-Hertz stress with LNF contact will be a key technology in the future. Only radius R 5μm tip with 0.1N force contact provides an excellent electrical performance which is much sharper than conventional contact. 0.30million cycle's durability test was passed at 300μm displacement and the contact resistance was ≤50mΩ.

Change in ORR Activity of Pd Core/Pt Shell Structured Catalyst With Potential Cycling Durability Test

not Available.