bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization Ionomer Distribution on Porous Carbon Catalyst Support to Commercialize Low Pt Loaded PEMFCS
Authors: Ott Sebastian , Orfanidi Alin , Anke Björn , Lerch Martin 
Published: February 2020

One of the major drawbacks towards PEMFC (polymer exchange membrane fuel cell) commercialization is the high amount of platinum needed at the cathodic electrode, due to the inherent slow kinetics of the oxygen reduction reaction. It has been widely known that the reduction of the Pt loading at the cathodic electrode leads to significant voltage losses. The origin of which has been correlated to electrode structure, ionomer distribution, type of catalyst support, and location of the Pt particles on the carbon support. A recent study by Orfanidi et al showed that by introducing positively charged nitrogen groups into the carbon structure lead to a more homogeneous distribution of the ionomer, which results in higher performance even at low Pt loaded electrodes [1].
In the present study, a series of different N-functionalized Ketjenblack are synthesized and fully characterized to investigate their use as support material for Pt based electrodes. Pre-oxidized Ketjenblack was heat treated in ammonia at different temperatures [2] followed by Pt precipitation via an ethylenglycol method. This new type of catalyst significantly reduces the additional mass transport resistance and report an unprecedented high coverage of the ionomer over the high surface area carbon supports, especially under dry operating conditions, in addition to high stability under voltage cycling. Those enhanced transport behaviors are deduced to local transport phenomena in the porous carbon structure and we give a tailoring approach for such a carbon material within this work. Our catalyst presents significant advantages as it facilitates manufacturing processes of the electrodes, due to the columbic interaction between the ionomer and the –NHx groups on carbon support, ensuring homogeneous ionomer distribution.
This work sheds light into the effect of the different N based groups towards better understanding of the interaction of ionomer with the carbon support. Our concept can be transferred to other kinds of partially amorphous carbon and is not limited to Pt as an active material. Introduction of such a modification step in the production line of electrocatalysts paves the way for PEMFC commercialization in automotive applications, due to enhancement in mass transport and stability.

Literature

[1] A. Orfanidi, P. Madkikar, H.A. El-Sayed, G.S. Harzer , T. Kratky, H.A. Gasteiger, Journal of the Electrochemical Society
2017, 164, F418-F26.
[2] K.F. Ortega, R. Arrigo, B. Frank, R. Schlöten, A. Trunschke, Chemistry of Materials
2016, 28, 6826-6839.
Co-Axial Nafion Nanowire Electrode
Authors: Komini Babu Siddharth , Mukundan Rangachary , Cullen David A. , Spendelow Jacob S 
Published: February 2020

State-of-the-art polymer electrolyte fuel cells rely on platinum (Pt) or Pt-alloy on carbon supports mixed with ionomer for high power density. The high Pt loading in the cathode is still a barrier for commercialization of PEFCs. Conventional electrodes are fabricated in an uncontrolled ink deposition process that produces random aggregates of catalyst, ionomer, and pore volume (1). The high tortuosity and poor percolation of ionomer in these random aggregates cause low effective conductivity, requiring the use of high ionomer content to minimize Ohmic losses due to proton conduction. This causes severe mass transport limitations during high current density operation and requires a higher loading of Pt to meet the performance targets. The diffusion of reactants through the thick ionomer film adds an additional transport resistance and becomes significant at lower Pt loadings (2). The ionomer also poisons the surface of the catalyst, reducing the activity of the catalyst. Decreasing the negative effects of ionomer films would enable a significant increase in performance.
In our previous work, we have shown that aligned Nafion pillars in the cathode catalyst layer can improve ionic conductivity enabling reduction of ionomer in the catalyst layer (3). In this work, we present a novel electrode architecture where the three functional domains (catalyst, ionomer, and pore) are separated and aligned vertically as shown in Figure 1a. Pt nanofilm is coated surrounding the Nafion nanowire to fabricate a coaxial nanowire electrode. Figure 1b. shows the High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of the coaxial nanowire electrode. The pore domain provides an additional modifiable parameter to control the wettability of the electrode.

Acknowledgments

This research is supported by DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Technology manager: Greg Kleen.

References

S. Litster and G. McLean, Journal of Power Sources, 130, 61 (2004).

N. Nonoyama, S. Okazaki, A. Z. Weber, Y. Ikogi and T. Yoshida, Journal of The Electrochemical Society, 158, B416 (2011).

S. K. Babu, J. S. Spendelow and R. L. Borup, in Meeting Abstracts, p. 1385 (2017).

Figure 1
In-Situ Heating and TEM Characterization of Pt-Cu Nanoframes
Authors: Gong Mingxing , Zhao Tonghui , Wang Deli 
Published: February 2020

Increasing the atomic utilization and catalytic activity of Pt is an effective way to promote the commercial application of fuel cells. In this paper, platinum-copper nanoframes (Pt-Cu NFs) were prepared by a simple solvothermal method. For electrocatalytic activity, the Pt-Cu NFs exhibit enhanced oxygen reduction activity due to the unique open structure, electronic effect and geometric effect regulation. However, the dissolution of the transition metal Cu leads to a rapid decay of its stability, which is unable to adapt to long-term operation. Further improvement of its stability is highly desired. Thus, we have attempted to prepare Pt-Cu intermetallic compounds to achieve the phase transition from disordered alloys to ordered intermetallic to enhance their catalytic stability. The results show that the high temperature treatment can achieve its transformation into an ordered phase, and the stability is improved to a large extent, but the activity is reduced because of the aggregation during the high temperature treatment thus the structure was difficult to maintain. In order to explore the structural evolution in the process of ordering, in-situ electron microscopy is used to characterize the structural change trend in the heating process, and it is expected to provide guidance and help for the follow-up works.

Figure 1 is here.

Figure 1. In-situ TEM observation of Pt-Cu NFs during heating treatment.

Keywords: Oxygen Reduction Reaction, Pt-Cu Nanoframes, Intermetallics, In-situ heating

References:

[1] C. Chen, Y. Kang, H. Xin, P. Yang, Highly Crystalline Multimetallic Nanoframes with Three-Dimensional Electrocatalytic Surfaces, Science, 2014, 343, 1339-1343.
[2] D. Wang, H. L. Xin, R. Hovden, D. A. Muller, F. J. DiSalvo, H. D. Abruna, Structurally Ordered Intermetallic Platinum-cobalt Core–shell Nanoparticles with Enhanced Activity and Stability as Oxygen Reduction Electrocatalyst, Nat. Mater. 2013, 12, 81-87.

Figure 1
Effect of Nitrogen Doping on Oxygen Reduction Activity of TiO2 in Acidic Media
Authors: Ishihara Akimitsu , Nagai Takaaki , Murase Noriko , Arao Masazumi , Kuroda Yoshiyuki , Matsuzawa Koichi , Mitsushima Shigenori , Furukawa Kou , Imai Hideto , Lee Kunchan , Ota Ken-ichiro 
Published: February 2020

In order to develop low-cost nonprecious metal cathodes that have both high activity of oxygen reduction reaction (ORR) and high durability as alternatives to Pt-based electrocatalysts for practical fuel cell vehicle application, we have focused on group 4 and 5 oxide-based compounds because they are insoluble in acidic media and are much less expensive than platinum. We already demonstrated that titanium and zirconium oxide-based compounds prepared from these oxy-phthalocyanines showed definite ORR activities [1,2]. However, these types of the catalysts used multi-walled carbon nano-tubes as a support and deposited carbon derived from phthalocyanine as a local electron conduction path. Carbons are fundamentally oxidized at high potential and temperature. Therefore, carbon-free nonprecious ORR catalysts are required for fuel cell vehicle application. An arc-plasma deposition method is useful to control the oxidation state of the oxides without heat-treatment. We prepared zirconium oxide-based cathode using tin-oxide based electroconductive support by arc-plasma deposition as a carbon-free nonprecious metal cathode. Fig. 1 shows the potential-ORR current density curves of the ZrOx/SnO2-based support prepared by arc-plasma deposition method, the SnO2-based support, and the TixNbyOz+Ti4O7 [3] in 0.1 M H2SO4 at 30 oC. The ZrOx/SnO2-based support had superior ORR activity. Fig. 2 shows comparison of the onset potential of the ZrOx/SnO2-based support and the TixNbyOz+Ti4O7 in 0.1 M H2SO4 at 30 oC. Both onset potentials are above 1.1 V vs. RHE, indicating that these active sites are superior in quality. Figs. 1 and 2 suggested the great potential of carbon-free nonprecious metal oxide-based cathodes.

Acknowledgment

The authors thank the New Energy and Industrial Technology Development Organization (NEDO) for financial support. This work was conducted under the auspices of the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Program for Promoting the Reform of National Universities.

References

[1] M. Chisaka, A. Ishihara, H. Morioka, T. Nagai, S. Yin, Y. Ohgi, K. Matsuzawa, S. Mistushima, K. Ota, ACS Omega, 2, 678-684, (2017).
[2] S. Tominaka, A. Ishihara, T. Nagai, K. Ota, ACS Omega, 2, 5209-5214, (2017).
[3] A. Ishihara, M. Hamazaki, M. Arao, M. Matsumoto, H. Imai, Y. Kohno, K. Matsuzawa, S. Mitsushima, K. Ota, J. Electrochem. Soc., 163, F603-F609 (2016).

Figure 1
Comparison of in-Situ 57 Fe Mössbauer Spectroscopic Data for Differently Prepared Fe-N-C Catalysts
Authors: Ni Lingmei , Gallenkamp Charlotte , Wagner Stephan , Wallace David , Paul Stephen , Kübler Markus , Krewald Vera , Kramm Ulrike Ingrid 
Published: February 2020

Electrochemical energy conversion in proton exchange fuel cells (PEFCs) is very promising device for world-wide energy demand, especially in the transportation sector [1]. Fe-N-C catalysts are promising materials as alternative for platinum-based catalyst because of the low cost and high activities especially for the ORR. However, a fundamental understanding of the nature of active site structures and the ORR reaction mechanism is missing. Especially also considering the question, to what extent differently prepared catalysts obtain similar trends or not.

57Fe Mössbauer Spectroscopy (MS) is a very good technique in distinguishing FeN4 centers with changing local coordination environment [2,3]. So far, the electronic and geometric structure have been investigated under in-situ / operando conditions by spectroscopic techniques, like XAS [4], XES [5]. However, only once Mössbauer spectroscopy was applied quasi in-situ by Bouwkamp-Wijnoltz et al. on frozen electrodes [6] and there are only a rare number of publications on carbon supported macrocycles [7,8].
In this work, we have designed a feasible electrochemical cell for in-situ Mössbauer spectroscopy. Two different types of Fe-N-C catalysts were studied under in-situ conditions and we will present the structural changes induced by the effect of applied potential. By comparing different catalysts, we are able to show to what extent Mössbauer sites remain the same, independent of the preparation route or are changing. The data will be correlated with selectivity measurements of the catalysts. Based on this, further fundamental insights on the nature of the active site structure in Fe-N-C catalysts can be gained which could guide the preparation for highly active non precious metal catalyst for commercialization.
References:
[1] Debe, M. K., Nature., 486 (2012), 43−51.
[2] Kramm, U.I. et al., J. Am. Chem. Soc.
136 (2014), 978-985.
[3] Kramm, U. I. et al., Phys. Chem.Chem.Phys.
14 (2012), 11673-11688.
[4] Zitolo, A. et al., Nat Mater 14 (2015), 937-942.
[5] Niwa, H. et al.,
Electrochemistry Communications
35 (2013), 57-60.
[6] Bouwkamp-Wijnoltz et al., J. Phys.
Chem. B, 106, (2002), 12993-13001.
[7] Blomquist, J.et al., Electrochimica Acta, 1982, 27(10), 1445-1451.
[8] Scherson. D.A. et al., J. Electroanal. Chem.,
184 (1985), 419-426.
Non-PGM Electrocatalysts for Oxygen Reduction Reaction Inspired By Metalloenzyme Active Sites
Authors: Kato Masaru , Fujibayashi Natsuki , Matsubara Naohiro , Muto Marika , Murotani Takeshi , Yagi Ichizo 
Published: February 2020

Oxygen reduction reaction (ORR) is a key reaction in future energy generation devices such as polymer electrolyte fuel cells (PEFCs) and metal–air batteries. To drive the ORR in state-of-the-art PEFCs, platinum group metal (PGM) alloys have been used. Since platinum is rare and expensive, there is a need to develop highly active PGM-free ORR electrocatalysts for wide spread applications of PEFCs. In nature, catalytic active sites based on 3d transition metals are widely utilized as catalytic reaction centers in metalloenzymes: for example, laccases and cytochrome c oxidases are known to catalyze the ORR with almost no energy loss at the active sites of multinuclear metal complexes.[1,2]

We present ORR electrocatalysts with multinuclear copper active sites incorporated in nitrogen-doped carbon nanosheets, which were inspired by the active site of laccases. Our copper-based electrocatalyst exhibited high ORR activity in alkaline aqueous solution. Physicochemical measurements including in situ X-ray absorption spectroscopy[3] revealed that multinuclear copper sites were embedded in nitrogen-doped carbon nanosheets and worked as the catalytic active center.[4] We also prepared a Fe–Cu-codoped carbon electrocatalyst inspired by the active site of cytochrome c oxidase.[5] Optimization of synthetic conditions and doping ratios of Fe to Cu into carbon resulted in the improvement of the ORR activity in acidic media. The electrocatalyst codoped with Fe and Cu showed higher ORR activity than those with Fe or Cu. Our bioinspired approaches will offer guidance for developing non-PGM ORR electrocatalysts with high activity.
References
[1] N. Mano, V. Soukharev, A. Heller, J. Phys. Chem. B, 110, 11180 (2016).
[2] C. H. Kjaergaard, J. Rossmeisl, J. K. Nørskov, Inorg. Chem. 49, 3567 (2010).
[3] M. Kato, K. Kimijima, M. Shibata, H. Notsu, K. Ogino, K. Inokuma, N. Ohta, H. Uehara, Y. Uemura, N. Oyaizu, T. Ohba, S. Takakusagi, K. Asakura, I. Yagi, Phys. Chem. Chem. Phys., 17, 8638 (2015).
[4] M. Kato, M. Muto, N. Matsubara, Y. Uemura, Y. Wakisaka, T. Yoneuchi, D. Matsumura, T. Ishihara, T. Tokushima, S. Noro, S. Takakusagi, K. Asakura, I. Yagi, ACS Appl. Energy Mater., 1, 2358 (2018).
[5] M. Kato, T. Murotani, I. Yagi, Chem. Lett., 45, 1213 (2016).
A Universal Picture of the HER/HOR Kinetics of Pt in Alkaline Solution
Authors: Liu Ershuai , Jiao Li , Mukerjee Sanjeev , Jia Qingying 
Published: February 2020

Some progress has been recently made in understanding the sluggish kinetics of hydrogen evolution and oxidation reactions (HER/HOR) of Pt in alkaline solutions. The pH dependence of the HER/HOR activity of Pt was reasonably accounted for by the potential of zero free charge (pzfc) theory.1 We lately proposed the 2B theory to account for the alkali cation effects on the HER/HOR activity of Pt and the beneficial roles of the second metal such as the Ni on the HER/HOR activity of Pt.2,3 Meanwhile, the Ru-induced improvement of the HOR activity of Pt was ascribed to the bifunctional mechanism4,5 or the hydrogen binding energy.6,7 However, these different theories often conflict with each other, and have not been unified into a coherent picture depicting the kinetics of HER/HOR in alkaline solutions. Herein, we propose a new theory to account for the Ni and Ru induced improvement of the HOR activity of Pt in alkaline solutions, on the basis of combined electrochemical and in situ spectroscopic data. The combination of this new theory with the pzfc and 2B theories appears to give a coherent picture of the HER/HOR kinetics of Pt in alkaline solutions.

Acknowledgements

This work was supported by the Office of Naval Research (ONR) under award number N00014-18-1-2155. The authors declare no competing financial interests. Use of Beamline ISS 8-ID of the National Synchrotron Light Source (NSLS) II was supported by the NSLS-II, Brookhaven National Laboratory, under U.S. DOE Contract No. DE-SC0012704. Use of beamline 5-BM-D at the Advanced Photon Source was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31–109-Eng-38. Jia acknowledged the help from Eli Stavitski, Klaus Attenkofer from ISS, NSLS-II; Qing Ma from DND-CAT, APS at ANL; and Todd E Miller, Lynne LaRochelle Richard from Northeastern University on the XAS data collection.

References

(1) Ledezma-Yanez, I.; Wallace, W. D. Z.; Sebastián-Pascual, P.; Climent, V.; Feliu, J. M.; Koper, M. T. M., Nat. Energy
2017, 2, 17031.
(2) Liu, E.; Li, J.; Jiao, L.; Doan, H. T. T.; Liu, Z.; Zhao, Z.; Huang, Y.; Abraham, K. M.; Mukerjee, S.; Jia, Q., J. Am. Chem. Soc.
2019, 141, 3232.
(3) Jia, Q.; Liu, E.; Jiao, L.; Li, J.; Mukerjee, S., Current Opinion in Electrochemistry
2018, 12, 209.
(4) Li, J.; Ghoshal, S.; Bates, M. K.; Miller, T. E.; Davies, V.; Stavitski, E.; Attenkofer, K.; Mukerjee, S.; Ma, Z.-F.; Jia, Q., Angew. Chem. Int. Ed.
2017, 56, 15594.
(5) Strmcnik, D.; Uchimura, M.; Wang, C.; Subbaraman, R.; Danilovic, N.; Van Der Vliet, D.; Paulikas, A. P.; Stamenkovic, V. R.; Markovic, N. M., Nat. Chem.
2013, 5, 300.
(6) Schwämmlein, J. N.; Stühmeier, B. M.; Wagenbauer, K.; Dietz, H.; Tileli, V.; Gasteiger, H. A.; El-Sayed, H. A., J. Electrochem. Soc.
2018, 165, H229.
(7) Wang, Y.; Wang, G.; Li, G.; Huang, B.; Pan, J.; Liu, Q.; Han, J.; Xiao, L.; Lu, J.; Zhuang, L., Energy Environ. Sci.
2015, 8, 177.
Alkaline Stability and Fuel Cell Performance of Piperidinium-Based Anion Exchange Membranes
Authors: Wang Zhongyang , Zhao Yang , Ramani Vijay 
Published: February 2020

There is a growing interest in using anion exchange membranes (AEMs) as separators in alkaline membrane fuel cells (AMFCs) and in other energy conversion and storage systems such as redox flow batteries (RFBs), alkaline water electrolyzers (AWEs) and reverse electrodialysis (RED) cells. The most commonly used cation group in AEMs is the benzyl trimethylammonium cation. However, it had been shown that quaternary ammonium-based AEMs are sensitive towards Hofmann elimination [1] and direct nucleophilic elimination reactions [2] that result in loss of ion exchange capacity (IEC) and ionic conductivity. To solve the alkaline stability issue inherent to quaternary-ammonium-group-containing AEMs, alternative cations such as piperidinium-based cations has been proposed and investigated.
The piperidinium-based AEM was able to maintain its ca. 90% of its initial IEC after immersion into 1M KOH at 80 ºC for 30 days. Such piperidinium-based AEMs showed higher alkaline stability than benzyl-trimethylammonium-based AEM (ca. 20% degradation in 1M KOH at 60 ºC for 30 days) [3]. The improved alkaline stability was mainly attributed to the avoidance of attaching quaternary ammonium onto benzylic position. The planar structure of piperidinium-based cation slows down the β-elimination phenomenon. Also, there is no ether linkage with the polymer backbone and hence, the stability of polymer backbone is superior. The chloride ion conductivity of the piperidinium-based AEM was 65 mS/cm at 80 ºC under an IEC of 2.26 mmol/g. An AEMFC was assembled using our piperidinium-based AEM with Pt/C catalysts used for both anode and cathode. A peak power density of 700 mW/cm2 with 2 A/cm2 current density was obtained at 70 ºC without any backpressure.

References

[1] C.G. Arges, L. Wang, J. Parrondo, V. Ramani, Journal of The Electrochemical Society, 160 (2013) F1258-F1274.
[2] S. Chempath, J.M. Boncella, L.R. Pratt, N. Henson, B.S. Pivovar, The Journal of Physical Chemistry C, 114 (2010) 11977-11983.
[3] Z. Wang, J. Parrondo, V. Ramani, Journal of The Electrochemical Society, 164 (2017) F1216-F1225.
Synthesis and Characterization of Composite Anion Exchange Membranes (AEM) Using Layered Double Hydroxides (LDH) with Ionic Liquids (IL) and Metal Organic Framework (MOF)
Authors: Narducci Riccardo , Di Vona Maria Luisa 
Published: February 2020

Anion Exchange Membranes (AEM) are used in alkaline fuel cells, electrolysers and redox-flow batteries. The main disadvantage of AEM is the degradation of the ionomer in basic conditions and high temperature. The formation of composite offers several advantages, such as enhanced hydrolytic stability and improved mechanical properties. The composite anion-conducting membranes were made by dispersion of Mg/Al layered double hydroxide (LDH) in the polymeric matrix made by polysulfone (PSU) grafted with trimethylamine (TMA) and 1,4-diazabicyclo[2.2.2]octane (DABCO) [1]. They presented a reduced swelling and the mechanical properties in fully humidified conditions were enhanced. Furthermore, the membranes can be treated in alkaline conditions at 60 °C without losing their properties. The Zn/Al and Mg/Al LDH were also modified by adding ionic liquids (IL) in the inter-lamellar space showing an improved ionic conductivity (Figure 1) [2]. The LDH-IL fillers were added to PSU-DABCO and poly(2,6-dimethyl-1,4-phenylene)oxide DABCO (PPO-DABCO) membranes, the resulting properties were studied. For the composite with metal organic frameworks (MOF) we used UiO-66 [3], consisting of a cluster of [Zr6O4(OH)4] and 1,4-benzodicarboxylic-NH2, preliminary studies were achieved.

Figure 1: Schematic of PSU-DABCO-LDH-IL (ZnAl-
1-butyl-3-methylimidazolium hydrogen sulphate).

References

[1] M.L. Di Vona, M. Casciola, A. Donnadio, L. Pasquini, R. Narducci, P. Knauth, International Journal of Hydrogen Energy, 42 (2017) 3197-3205
[2] R. Pizzoferrato, E. Ciotta, I.V. Ferrari, R. Narducci, L. Pasquini, A. Varrone, M. Richetta, S. Antonaroli, M. Braglia, P. Knauth, M.L. Di Vona, ChemElectroChem, 5 19 (2018) 2081-2088
[3] J. Escorihuela, R. Narducci, V. Compañ and F. Costantino, Advanced Materials Interfaces, 6 2 (2019) 1801146

Figure 1