bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards Understanding of the Anode Catalyst Layer Structure for Extended Reversal Tolerance: An Advanced Characterization Approach
Authors: Susac Darija , Jankovic Jasna , Ash Arash , Putz Andreas Michael Vincent , Lei Chao , Zhang Hao , Lee Wendy , Stumper Jürgen 
Published: February 2020

Proton exchange membrane fuel cells for automotive applications (PEMFC) frequently experience transient conditions such as start-up/shut-down, freeze start-up and local fuel starvation at the anode catalyst layer (ACL) that are responsible for the loss of performance and durability as a result of irreversible carbon corrosion [1].

To mitigate such degradation, oxygen evolution catalysts have been incorporated into ACL and studied for effects on membrane electrode assembly (MEA) performance and reversal tolerance. Ru and Ir oxides are among the most studied catalysts for oxygen evolution reaction (OER) in both PEMFCs and water electrolyzers [2-5]. Although comparative measurements have been performed to investigate the OER activity trends, systematic studies focusing on effects of particle/agglomerate size and distribution within ACL on PEMFC MEA reversal tolerance have not yet been reported.

In order to be able to design anode catalyst layer structures that meet the performance and reversal tolerance requirements, it is necessary to obtain a better understanding of structure versus performance relationships. This requires the capability to fabricate different anode catalyst layer structures, as well as efforts in development of methodologies to characterize the spatial distribution of all components within the catalyst layers. The ultimate goal is to use the experimentally measured structural parameters as inputs for the development of models for understanding of the relationship between anode structures and reversal tolerance. The objective of this work is to present the methodology for structural characterization of anode catalyst layers containing OER materials. Structural parameters correlating with the extended reversal tolerance will be discussed.

References

S. Enz, T.A. Dao, M. Messerschmidt and J. Scholta, Investigation of degradation effects in polymer electrolyte fuel cells under automotive-related operating conditions, J. Power Sources, 274 (2015) 521-535

E. Antolini, Ir as catalyst and cocatalyst for oxygen evolution/reduction in acidic polymer electrolyte membrane electrolyzers and fuel cells, ACS Catal. 4 (2014) 1426-1440

T. Reier, M. Oezaslan and P. Strasser, Electrocatalytic oxygen evolution reaction (OER) on Ru, Ir and Pt catalysts: a comparative study of nanoparticles and bulk materials, ACS Catal. 2 (2012) 1765-1772

S. Cherevko, T. Reier, A.R. Zeradjanin, Z. Pavolek, P. Strasser and K.J.J. Mayrhofer, Stability of nanostructure iridium oxide electrocatalysts during oxygen evolution reaction in acidic environment, Electrochem. Commun. 48 (2014) 81-85

M. Bernicke, E. Ortel, T. Reier, A. Bergmann, J.F. de Araujo, P. Strasser and R. Kraerhnet, Iridium oxide coatings with template porosity as highly active oxygen evolution catalysts: structure-activity relationship, ChemSusChem, 8 (2015) 1908-1915
Hydrogen Oxidation Reaction Activity of RuO2 Nanosheets Modified Pt−Ru / C
Authors: Ohnishi Tomohiro , Takimoto Daisuke , Ayato Yusuke , Mochizuki Dai , Sugimoto Wataru 
Published: February 2020

Carbon supported Pt-Ru systems such as PtRu/C and Pt2Ru3/C have been investigated as anode catalysts of polymer electrolyte membrane fuel cells. However, hydrogen oxidation reaction (HOR) activity for Pt-Ru/C is significantly degraded due to adsorption of carbon monoxide (CO) on the active Pt sites and dissolution of Ru. The addition of metal oxide nanosheets enables to enhance the performance of catalysts. We have reported that RuO2 nanosheets [1] as an additive to Pt/C (RuO2ns-Pt/C) and PtRu/C (RuO2ns-PtRu/C) enhances CO tolerance at room temperature [2]. The HOR current of RuO2ns-Pt/C was improved by 25% compared to Pt/C. RuO2ns-PtRu/C had higher HOR activity and enhanced CO tolerance. Thus, CO poisoning is suppressed by the addition of RuO2 nanosheets. However, it is necessary to measure the performances at higher temperature near actual operating of PEFC. In this study, we report the addition effect of RuO2 nanosheets to PtRu/C and Pt2Ru3/C at 25◦C as well as 70◦C.
Chronoamperograms (CA) of commercial and RuO2 nanosheests modified catalysts at 25 and 70◦C are shown in Figures A and B. At 25◦C (Fig. A), the addition of RuO2 nanosheets increased the initial HOR activity and the activity after accelerated durability tests (ADT) in 300 ppm CO containing H2 (CO/H2) as well as pure H2. The current was enhanced in the entire range of CA. The addition of RuO2 nanosheets slightly enhanced CO tolerance and durability which were represented by ratio of density current j (in H2) divided by j (initial in CO/H2) and j (initial in CO/H2) divided by j (after ADT in CO/H2), respectively. This behavior is similar to the previous result of comparing RuO2ns-PtRu/C and PtRu/C [2].
The HOR current at 70◦C showed the different behavior compared to 25◦C (Fig. B). At 70◦C, there was a difference of HOR current between composite and commercial catalysts in CO/H2 while HOR activity of the catalysts was almost the same in pure H2. Thus, the decline in HOR current of composite catalysts was slower than non-modified catalysts. Therefore, the composite catalysts suppresses CO adsorption. In particular, the durability of RuO2ns-Pt2Ru3/C at 70◦C shows higher (93%) than the other catalysts (78~86%).
This work was supported in part by the “Polymer Electrolyte Fuel Cell Program” from the New Energy and Industrial Technology Development Organization (NEDO), Japan
[1] W. Sugimoto, H. Iwata, Y. Yasunaga, Y. Murakami, and Y. Takasu, Angew.
Chem. Int. Ed., 42, 4092 (2003).
[2] D. Takimoto, T. Ohnishi, and W. Sugimoto, ECS Electrochem. Lett., 4(5), F35-F37 (2015).

Figure 1
Preparation of Ultrathin Palladium Nanosheet and Its Application in Pd@Pt Core-Shell Catalyst for Oxygen Reduction Reaction
Authors: Shen Zhongrong , Takimoto Daisuke , Nutariya Jeerapat , Ayato Yusuke , Mochizuki Dai , Sugimoto Wataru 
Published: February 2020

High cost, sluggish kinetics, and poor durability of Pt catalysts predominantly hinder the wide-spread commercialization of fuel cells. Pt-based core-shell nanosheet catalyst may resolve　these problems listed above because of the following 3 advantages. 1) The Pt content can be greatly reduced via core−shell nanostructures consisting of a Pt shell on appropriate monometallic or alloy cores; 2) Nanosheets have high surface-to-volume ratio and terrace sites. The active sites for the oxygen reduction reaction (ORR) have been suggested to be located on the terrace sites of the nanocrystals.[1] 3) Nanosheets should dramatically reduce Pt dissolution due to few edges and corners with their low coordinate sites. Terraced facets have been reported to be more stable than edges and corners.[2]

Here, we present a novel method to synthesize palladium (Pd) nanosheets by a wet-chemical preparation at room temperature (Fig.A). The Pd precursor (Pd(acac)2) is reduced by CO in the presence of decylamine (DA). The protection agent (DA) was easily removed by washing with acetic acid. Using this nanostructure as a core, Pd@Pt core-shell nanosheets were prepared by surface limited redox replacement (SLRR). AFM indicates Pd nanosheets are synthesized with a thickness around 0.9 nm to 1.6 nm and lateral size from tens to several hundred nanometers (Fig.B). After dispersing the Pd nanosheet on a carbon support, Pd@Pt core-shell nanosheets with different Pt shell thickness were prepared, i.e. Pd6.0ML@Pt2.7ML, Pd6.0ML@Pt4.4ML, and Pd6.0ML@Pt5.9ML. The electrochemically active surface area (ECSA) of Pd@Pt nanosheets are 56, 48, 60 m2/g-PGM (90, 66, 77 m2/g-Pt), respectively (Fig. C). The linear sweep voltammetry is applied by using a rotating disc electrode (RDE) in 0.1 M HClO4 at room temperature. The ORR activity is evaluated from jk values at 0.9 V (vs RHE) estimated from Koutecky-Levich Plots. The Pd@Pt nanosheets demonstrated mass activity of 364, 685, 598 A/g-Pt (227, 501, and 492 A/g-PGM), which is much higher than the benchmark Pt/C catalyst (177 A/g-Pt) for the oxygen reduction (Fig. D).
This research was supported in part by the “Polymer Electrolyte Fuel Cell Program” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
Fig. A) TEM of Pd@DA nanosheets; B) AFM image of Pd nanosheets; C) CV profiles of the Pd@Pt nanosheets recorded in N2-saturated 0.1 M HClO4 solution at a sweep rate of 50 mV/s; and D) The mass activity of Pd@Pt nanosheets and commercial Pt/C.

Reference

F. J. Perez-Alonso, D. N. McCarthy, A. Nierhoff, P. Hernandez-Fernandez, C. Strebel, I. E. L. Stephens, J. H. Nielsen, I. Chorkendorff, Angew. Chem. Int. Ed.
2012, 51, 4641–4643.

F. N. Büchi, M. Inaba, T. J. Schmidt, Polymer Electrolyte Fuel Cell Durability, Springer Science+ Business Media, New York, 2009.

Figure 1
Synthesis of Two-Dimensional Nanosheets Catalyst with Ru-Core@Pt-Shell Towards Oxygen Reduction Reaction
Authors: Takimoto Daisuke , Ohnishi Tomohiro , Nutariya Jeerapat , Shen Zhongrong , Ayato Yusuke , Mochizuki Dai , Demortiere Arnaud , Boulineau Adrien , Sugimoto Wataru 
Published: February 2020

Improvement in the activity and durability of electrocatalysts for the oxygen reduction reaction (ORR) is an essential issue for wide-spread commercialization of polymer electrolyte fuel cells. Nanoparticle catalysts with alloy, skin, and/or core-shell structures have been developed to improve the activity and durability. However, these nanoparticle catalysts often suffer from degradation under harsh conditions. On the other hand, extended surfaces including thin-films possess high durability; however, the surface area is lower than that of nanoparticles due to low surface area.
Nanosheets with atomic thickness have large specific surface area and two dimensionally extended surface. We previously reported the synthesis of metallic ruthenium nanosheets with monoatomic thickness via thermal reduction of RuO2 nanosheets.1,2In this study, we demonstrate the synthesis of Ru-core@Pt-shell nanosheets and the catalytic performance towards the oxygen reduction reaction.
Metallic Ru nanosheets supported on carbon composite was prepared via thermal reduction.3 Pt shell was successively formed on metallic Ru nanosheets supported on carbon via galvanic displacement reaction between Cu and Pt2+. The electrochemically active Pt surface area of Ru-core@Pt-shell nanosheets with 3.5 monolayer Pt-shell (Ru@Pt-3.5ML(ns)/C) was 148 m2 (g-Pt)‒1and showed 4.5 times higher activity than benchmark commercial Pt/C catalyst for the oxygen reduction reaction. In addition, the activity retention of Ru@Pt-3.5ML(ns)/C after durability test (0.6-1.0 V and 1.0-1.5 V for 5000 cycles) was higher than that of Pt/C. The high activity could be attributed to the core-shell structure, and the durability originates from the extended surface structure.
This research was supported in part by the “Polymer Electrolyte Fuel Cell Program” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
1) W. Sugimoto, H. Iwata, Y. Yasunaga, Y. Murakami, and Y. Takasu, Angew. Chem. Int. Ed., 42, 4092 (2003).
2) K. Fukuda and K. Kumagai, e-Journal Surf. Sci. Nanotechnol., 12, 97 (2014).
3) D. Takimoto, T. Ohnishi, Y. Ayato, D. Mochizuki, and W. Sugimoto, J. Electrochem. Soc., 163, F367 (2016).

Figure 1
Understanding Pt Nanoparticle Anchoring on Graphene Supports through Surface Functionalization
Authors: Xin Le , Rasouli Somaye , Yang Fan , Uzunoglu Aytekin , Sun Cheng-Jun , Ferreira Paulo Jorge , Liu Yuzi , Stanciu Lia , Xie Jian 
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) that use hydrogen as fuel to produce electricity have attracted extensive interests over the past decades.[1] The high efficiency and zero carbon- emission make PEMFCs promising candidates for viable propulsion systems in electric vehicels.[2] One of major challenges that hinder the commercialization of PEMFCs vehicles is the poor stability of Pt nanoparticles on carbon supports, which is mainly due to (1) the dissolution and re-deposition of Pt and (2) migration of Pt nanoparticles over carbon supports.[3],[4] Both of them will cause the agglomeration of Pt nanoparticles, resulting in loss of Pt electrochemical surface area (ECSA) and the increasing of activation over-potential. In this regard, the enhancement of Pt nanoparticle anchoring strength and dispersion on carbon supports is highly desirable in PEMFCs as well as in other catalysis processes.
Presented here is a comprehensive study of the interaction between catalyst nanoparticles and carbon supports in terms of the electronic structure change and its effects on the electrocatalytic performance of supported catalysts. Graphene was chosen as an ideal model system for catalyst support because the unique 2-D structure allows the direct investigation of the interaction with supported metal nanoparticles at their interface. We developed a facile strategy to covalently graft p-phenyl SO3H or p-phenyl NH2 groups onto the graphene surface. The functional groups were found to not only facilitate the homogeneous distribution of Pt nanoparticles over the surface of graphene supports and reduce the Pt average particle size but also strengthen the interaction of the Pt atoms with the functional groups and, consequently, minimize the migration/coalescence of the Pt nanoparticles in the course of accelerated durability tests. The experimental results from both X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) demonstrate the electron density shift from Pt to graphene supports with the strength of the Pt−graphene interaction following the trend of Pt/p-phenyl NH2-graphene > Pt/p-phenyl SO3H-graphene > Pt/graphene. This study will shed light on strategies to improve not only the durability but also the activity of the metal nanoparticles via the functionalization of the catalyst supports in the catalysis field
(1) Gasteiger, H. A.; Markovic, N. M. Science 2009, 324, 48.
(2) Debe, M. K. Nature 2012, 486, 43.
(3) Xie, J.; Wood, D. L.; More, K. L.; Atanassov, P.; Borup, R. L. Journal of The Electrochemical Society 2005, 152, A1011.
Porous Graphene Layers on Pt Catalyst for Long-Term Stability of Fuel Cell Electrode
Authors: Kim Heeyeon , Robertson Alex W , Warner Jamie H , Kim Sang Ouk 
Published: February 2020

With the development of various energy technologies, much interest is focused on the feasibility and efficiency study of energy devices such as fuel cells, batteries, supercapacitors and water electrolysis systems. Among them, polymer electrolyte fuel cell (PEFC), which convert hydrogen into electric energy with zero emission of pollutants, is one of the most promising environmentally friendly technologies. Despite innumerable studies for more than half a century, degradation of the key component, membrane electrode assembly (MEA), is still a big obstacle for the commercialization of PEFC system.
For the high performance and long-term stability of Pt/C electrode catalyst, the agglomeration of Pt particles and dissolution or detachment of Pt particles from carbon support have to be improved. For this purpose, we adopted a new shape of nano-carbon material for the surface modification of Pt catalyst.
Graphene has been an attractive two-dimensional carbon allotrope having large surface area and electronic conductivity. Graphene also shows high flexibility and mechanical strength so that it can be used for large number of applications such as flexible display or printable electronics, etc [1-2]. In most cases, people need large-area graphene films with little or no defect for high thermal and electronic conductivity. Also, people need to transfer the as-prepared graphene film for each application. All of these processes are not easy or simple, and they are also labor-intensive processes. However, in the case of catalysis, porous graphene films can be synthesized via very simple one-step process and can be used as effective protective layers for Pt catalysts.
In this study, we developed porous graphene films in order to improve the long-term stability of Pt catalysts maintaining the high performance of them. The graphene films were synthesized by single-step vaporization process, where the number of graphene layers and the defects in their structure are manipulated by temperature and composition of the precursors. In this process, the amounts of structural defects, pyridine was simultaneously introduced to the vaporization process, which is much easier and cost-effective compared to the conventional NH3-treatment at high temp [3].
Consequently, our Pt/C catalysts coated with porous graphene films showed similar initial activity compared with the commercial catalysts (Pt 40wt%, Johnson Matthey) showing more than 150% higher long-term stability [4].
[1] A.K. Geim and K. S. Novoselov, Nature Mater. 6 (2007) 183.
[2] X. L. Li, G. Y. Zhang, X. D. Bai, X. M. Sun, X. R. Wang, E. Wang and H. J. Dai, Nature Nanotech. 3 (2008) 538.
[3] Y. Wang, Y. Shao, D. W. Matson, J. Li and Y. Lin, ACS nano 4(4) (2010) 1790.
[4] H. Kim, A. Robertson, S. O. Kim, J. M. Kim and J. H. Warner, ACS nano 9(6) (2015) 5947.
Development of Nitrogen-Doped Titanium Oxide Electrocatalysts for PEFCs
Authors: Yamato Yoshinori , Lee Kunchan , Wang Hailin , Imai Takuya , Ishihara Akimitsu , Ota Kenichiro 
Published: February 2020

With their efficiency, high power density, and low/zero emissions, polymer electrolyte fuel cells (PEFCs) are recognized as promising energy converting system. However, high cost and insufficient durability currently hinder their commercialization. Especially, one of the major barriers is the high cost and low stability of platinum (Pt)-based catalysts 1). Thus, developing alternative catalysts with low cost and high stability has been strongly required for the commercialization of PEFCs.
In the effort to reduce the cost of PEFCs, we have been developing nitrogen doped titanium oxide (N- TiO2) as a non-noble metal electrocatalyst in NEDO (New Energy and Industrial Technology Development Organization, Japan) project. In this paper, we introduce a new and convenient synthesis method of N-doped TiO2electrocatalysts and their catalytic activities for oxygen reduction reaction (ORR).
In this study, we used phthalocyanine (Pc) as nitrogen source in order to dope nitrogen into TiO2. For the high surface area of electrocatalyst, TiO2 nanoparticles were deposited on high surface area carbon supports (C). The carbon supported TiO2 (TiO2/C) and phthalocyanine (Pc) were mixed and heat-treated at 900oC in inert gas atmosphere containing a small amount of hydrogen (H2) and oxygen (O2) in order to finally obtain N-TiO2/C electrocatalysts.
TiO2 nanoparticles of ca. 20 nm size deposited on the carbon supports were observed by transmission electron microscope (TEM), indicating that the synthesized N-TiO2/C may have considerably high surface areas. In X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) studies, it was found that the XPS core-level peaks of Ti was very similar to that of Ti-N binding energy and the XRD peak of TiO2 shifted to higher angles, respectively. These results well explain that the nitrogen was successfully doped into TiO2 nanoparticles by our synthesis process. Fig. 1 compares the ORR catalytic activities of the synthesized N-TiO2/C and TiO2/C. The synthesized N-TiO2/C electrocatalyst shows significantly higher ORR catalytic activity than that of TiO2/C. It is believed that the enhanced catalytic activity of N-TiO2/C is due to the doping effect of nitrogen into TiO2.

Acknowledgements

The authors wish to thank NEDO (New Energy and Industrial Technology Development Organization) for financial support.

References

Ken-ichiro Ota, Yoshiro Ohgi, Kyung-Don Nam, Koichi Matsuzawa, Shigenori Mitsushima, Akimitsu Ishihara, J. Power. Sources.,

196, 5256, ( 2011).

Figure 1
Electrochemical Decontamination of Platinum Nanocrystals and Its Electrocatalytic Performances for Methanol
Authors: Lu Leilei , Du Baozhong 
Published: February 2020

Platinum is the most widely used catalyst for fuel cells. The morphology of platinum has great influences on its catalytic activity and selectivity. Thus, the morphology controlled synthesis of platinum nanocrystals is attracting more and more attention in recent years [1-3]. Polyvinylpyrrolidone (PVP) is one of the most commonly used surface active agent for the morphology control of platinum nanocrystal. However, since PVP could strongly adsorb on the platinum surface and was difficult to remove thoroughly, the platinum surface couldn’t be utilized effectively and thus its catalytic activity will be reduced to a certain extent.
This work focused on the decontamination of PVP on platinum by electrochemical treatment. Platinum nanocrystals was synthesized by colloidal method using chloroplatinic acid as the metal precursor and PVP K30 as a stabilizer. Spherical, cubic, octahedral and truncated octahedral platinum nanocrystals were obtained by adding different concentrations of silver nitrate to the above colloidal solution. The morphology of platinum nanocrystals was characterized by transmission electron microscope (TEM). It was found that the as-preparation platinum nanocrystals were well dispersed with a narrow size distribution. Electrochemical decontamination was applied to the platinum nanocrystals by short pulse potential step before electrocatalytic performance measurements. Repeating potential steps were set up between high voltage and low voltage. As the potential step proceeding, more and more surface sites were exposed, which could be confirmed from the more and more clear hydrogen and oxygen adsorption/desorption peak of the cyclic voltammograms (CV) (as shown in Fig. 1A). The CV curves stabilized eventually. The electrocatalytic activity of the electrochemical cleaned platinum nanocrystals was characterized by CV (as shown in Fig. 1B) and chronoamperometry measurements. It was found that truncated octahedral platinum nanocrystals showed the best catalytic activity for metha nol electrooxidation in 0.5 mol·L-1 H2SO4 + 0.5 mol·L-1 CH3OH solution. The methanol electrooxidation peak current was much higher than the current on platinum nanocrystals with other morphology. This study put forward a simple and effective electrochemical decontamination method of the platinum surfaces capped by PVP.

Figure 1