bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Elucidation of the Oxygen Reduction Volcano in Base on a Pt Alloy Single Crystal
Authors: Jensen Kim Degn , Tymoczko Jakub , Bandarenka Aliaksandr S , Chorkendorff Ib , Escudero-Escribano María , Stephens Ifan E. L. 
Published: February 2020

It is of fundamental importance to understand the factors controlling trends in activity for electrocatalytic reactions as a function of pH. In the case of the oxygen reduction reaction, numerous reports suggest significant divergences between noble metals surface catalytic performances in acid and base.[1,2]

In our earlier studies, we mapped out the experimental Sabatier volcano for the oxygen reduction reaction in 0.1 M HClO4 using the Cu/Pt(111) near-surface alloy system, see Figure 1 for near-surface alloy schematic.[3,4]

In this study, as those of [3,4], we found that by changing the subsurface coverage of Cu we could tune the surface binding of the key reaction intermediate, OH; we thus monitored the OH binding energy shift through the observable shifts in the base voltammograms in both acidic and alkaline media.
Further, we elucidate the experimental oxygen reduction volcano in 0.1 M KOH for the Cu/Pt(111) near-surface alloy system. Remarkably, we observe that the same trend persists between OH binding shifts and Cu/Pt(111) oxygen reduction activities between acid and alkaline electrolyte, with the optimum catalyst in alkaline exhibiting an 8-fold improvement in activity, relative to Pt(111). However, all surfaces show a ~4 fold improvement in activity in 0.1 M KOH, relative to the same surface in 0.1 M HClO4. At the peak of the volcano the surface exhibits an exceptionally high specific activity of 90 mA/cm2 at 0.9 V with respect to the reversible hydrogen electrode. Thus, our results confirm that OH binding energy is the key descriptor in both alkaline and acid electrolytes.
[1] R. Rizo, E. Herrero, J. M. Feliu, Phys. Chem. Chem. Phys. 2013, 15, 15416–25.
[2] J. Staszak-Jirkovský, R. Subbaraman, D. Strmcnik, K. L. Harrison, C. E. Diesendruck, R. Assary, O. Frank, L. Kobr, G. K. H. Wiberg, B. Genorio, et al., ACS Catal. 2015, 5, 6600–6607.
[3] I. E. L. Stephens, A. S. Bondarenko, F. J. Perez-alonso, F. Calle-vallejo, L. Bech, T. P. Johansson, A. K. Jepsen, R. Frydendal, B. P. Knudsen, J. Rossmeisl, et al., 2011, 5485–5491.
[4] A. S. Bondarenko, I. E. L. Stephens, I. Chorkendorff, Electrochem. commun. 2012, 23, 33–36.

Figure 1
Highly Efficient Nitrogen and Sulfur Co-Doped Three-Dimensional Graphene-Based Nanocatalysts for the ORR
Authors: Wang Jie , Wu Min , Wu Zexing , Xin Huolin L. , Wang Deli 
Published: February 2020

a, Key Laboratory of Material Chemistry for Energy Conversion and Storage (Huazhong University of Science and Technology), Ministry of Education, Hubei Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, P.R. China. *Email: wangdl81125@hust.edu.cn
b, Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA
Graphene, a single-atom-thick hexagonally arrayed sp2 carbon atoms bonded sheet, has attracted tremendous interest in renewable energy conversion and storage devices due to its extraordinary properties, especially ultrahigh specific surface area and predominant electron conductivity1. However, graphene based two-dimensional catalysts suffer from an irreversible re-stacking of the nanosheets due to the strong π-interaction during thermal annealing process and electrochemical measurements which would result in a lower surface area, limiting the mass transfer rate and even decreasing the catalytic activity as well as electrochemical stability.
Figure 1 (a) TEM image of NSGCB; (b) ORR activity of NSGCB and the corresponding comparative catalysts; (c) TEM image of NSCNT-3; (d) ORR activity of NSCNT-3 and the corresponding comparative catalysts.
Herein, we report two strategies for the synthesis of nitrogen and sulfur co-doped three-dimensional graphene intercalated structure nanomaterials as electro-catalysts for ORR in alkaline medium. One is the insertion of Vulcan XC-72 carbon spheres into the graphene layer, forming a graphene-Vulcan XC-72- grapheme “sandwich-like” structure2. The other way is partially unzipping of multi-walled carbon nanotubes to form a graphene nanoribbon-carbon nanotube-graphene nanoribbon structure. Both of the prepared three-dimensional structured nanocomposites were experienced to nitrogen and sulfur co-doping process, and moreover, the resulting doped electro-catalysts exhibited outstanding ORR performance.
Acknowledgements
This work was supported by the National Natural Science Foundation (21306060, 21573083), the Program for New Century Excellent Talents in Universities of China (NCET-13-0237), the Doctoral Fund of Ministry of Education of China (20130142120039).
References
(1) Li, Y., Zhao, Y., Cheng, H., Hu, Y., Shi, G., Dai, L., & Qu, L. Nitrogen-doped graphene quantum dots with oxygen-rich functional groups. Journal of the American Chemical Society, 2011, 134, 15-18.
(2) Wu, M., Wang, J., Wu, Z., Xin, H. L., & Wang, D. Synergistic enhancement of nitrogen and sulfur co-doped graphene with carbon nanosphere insertion for the electrocatalytic oxygen reduction reaction. Journal of Materials Chemistry A, 2015, 3, 7727-7731.

Figure 1
Mimicking Active Pt3ni (111) Surface on Pt3ni Icosahedron for Oxygen Reduction
Authors: Xing Wei , Zhu Jianbing , Xiao Meiling , Li Songtao , Ge Junjie , Liu Changpeng 
Published: February 2020

The oxygen reduction reaction (ORR) is a corner stone for energy conversion techniques such as fuel cells and metal-air batteries[1]. The use of Pt unfortunately generate a number of obstacles including the high cost, scarcity and readily poisoning by impurity and the cross-over of fuel9. Shaped bimetallic nanocrystals (NCs) with precisely controlled structure and composition at the atomic level, e.g. PtxNi1−x alloy NCs[2], intermetallic PtCo core–shell nanoparticles[3] and Pt3Ni nanoframes[4], represent a class of exciting and promising ORR catalysts.
Herein, we demonstrate a one-pot protocol for the controlled synthesis of icosahedral Pt3M nanocrystal with twenty active Pt3M (111) facets using glucosamine as both reducing and structure-directing agent. Among the investigated catalysts, the Pt3Ni icosahedral with nano-segregated Pt-skin displays the unexpected 32-fold enhancement in specific activity and 12-fold improvement in mass activity relative to state-of-the-art Pt/C catalyst. Besides, the catalyst was found ultra-robust during 20,000 potential cycling tests. The Pt3Ni icosahedral thus represents one class of the most efficient ORR electrocatalysts ever reported and demonstrates an effect technique in mimicing the active extended surface in nano-scale.
Fig.1 (a) TEM image of the typical icosahedral Pt3Ni nanocrystal, (b) HRTEM micrograph showing the twin boundaries of five-fold symmetry, (c) the (111) and (200) planes, (d)cyclic voltammetry curves of Pt/C, Pt NI/C and Pt3Ni/C catalysts, (e) ORR polarization curves for Pt/C, Pt NI/C and Pt3Ni/C catalysts in O2-saturated 0.1M HClO4, (f) comparative ORR activities of Pt/C and Pt3Ni/C catalysts before and after 20,000 potential cycles.

Acknowledgments

The study was financed by the National Basic Research Program of China (973 Program, 2012CB215500), the National Natural Science Foundation of China (21373199, 21433003) and the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA09030104).

References

[1] Stamenkovic, V.R., B. Fowler, B.S. Mun, G. Wang, P.N. Ross, C.A. Lucas, and N.M. Marković, Science, 315(5811), 493-497,(2007).
[2] Zhang, C., S.Y. Hwang, A. Trout, and Z. Peng, Journal of the American Chemical Society, 136(22), 7805-7808,(2014).
[3] Wang, D., H.L. Xin, R. Hovden, H. Wang, Y. Yu, D.A. Muller, F.J. DiSalvo, and H.D. Abruña, Nat Mater, 12(1), 81-87,(2013).
[4] Chen, C., Y. Kang, Z. Huo, Z. Zhu, W. Huang, H.L. Xin, J.D. Snyder, D. Li, J.A. Herron, M. Mavrikakis, M. Chi, K.L. More, Y. Li, N.M. Markovic, G.A. Somorjai, P. Yang, and V.R. Stamenkovic, Science, 343(6177), 1339-1343,(2014).

Figure 1
Performance of Platinum-Nickel Nanowires in a PEMFC
Authors: Mauger Scott A , Neyerlin K.C. , Alia Shaun M , Hurst Katherine , Shulda Sarah , Ngo Chilan , Weker Johanna Nelson , Pylypenko Svitlana , Pivovar Bryan S 
Published: February 2020

Platinum-coated nickel nanowire (PtNiNW) catalysts have shown high mass activity, specific activity, and exceptionally high surface areas in oxygen-reduction reaction (ORR) rotating disc-electrode experiments, all several times higher than platinum on carbon and well above DOE targets.1,2 However, their subsequent incorporation into proton exchange membrane fuel cell (PEMFC) membrane electrode assemblies (MEA) has been exceedingly difficult, resulting in substantially lower mass and specific activities and lower than anticipated electrochemical areas (ECAs).2 This presentation will focus on the challenges associated with the incorporation of extended surface Pt alloys in PEMFC MEAs, the ensuing conditioning protocols and the large discrepancy between RDE and MEA data. It is found that soaking the MEA in dilute sulfuric acid to remove nickel and increase the platinum weight fraction increases cell performance metrics such as open-circuit voltage, mass activity, and specific activity, as shown in Figure 1. Decreases in membrane resistance are also observed. The effects of ionomer, carbon and unsupported electrocatalyst ratios on MEA performance will also be discussed. Scanning transmission electron microscopy (STEM) and transmission x-ray microscopy (TXM) tomography will be examined as tools to elucidate the relationship between electrocatalyst/electrode structure and MEA performance.
1. Alia, S. M. et al. Platinum-Coated Nickel Nanowires as Oxygen-Reducing Electrocatalysts. ACS Catal.
4,1114–1119 (2014).
2. Pivovar, B. S. Extended, Continuous Pt Nanostructures in Thick, Dispersed Electrodes. 2015 DOE Hydrogen and Fuel Cells Program Review (2015).

Figure 1
The Impact of Fuel Impurities on Pemfcs Using a Hydrogen Fuel Re-Circulation System
Authors: Rockward Tommy , Valdez Jacob , Mukundan Rangachary 
Published: February 2020

Research has shown that contaminants in the hydrogen fuel stream have an impact on Polymer Electrolyte Membrane Fuel Cells (PEMFCs) performance that is influenced by the platinum loading, membrane thickness, the impurity, its concentration and PEMFC operating conditions such as cell temperature, relative humidity, and back pressure. A significant portion of previous reported results were conducted with the fuel cell being operated in single-pass mode where the exhaust hydrogen is vented from the fuel cell. While these findings have proven useful in improving the fundamental understanding of the poisoning mechanisms of non-hydrogen species (contaminants) in operating single fuel cells; the question remains whether or not these findings correlate to PEMFC systems that use a re-circulating fuel stream as being designed by the OEMs. Some advantages of re-circulating the anode exhaust gas back into the anode inlet are: 1) the anode outlet water is returned into the dry H2 fuel stream to obtain proper humidification and also 2) the excess H2 fuel is returned to enhance fuel utilization. While these advantages are attractive, there are some inherent challenges that are introduced in fuel re-circulation mode. Two of the more notable drawbacks involve inert gas build-up due to crossover and the accumulation of contaminants in the anode. In this study, we focus our efforts on correlating the impact of CO and H2S on fuel cell performance in H2 single-pass versus H2 re-circulation mode using the SAE J27191 and ISO 14687-2 Hydrogen Fuel Product Specification2
limits (4 ppb H2S and 200 ppb CO). This study was conducted on Membrane Electrode Assemblies (MEAs) at the 2015 DOE target loadings for platinum (anode: 0.05 mg/cm2 and cathode: 0.1 mg/cm2).

References:

SAE J2719: Hydrogen Fuel Quality for Fuel Cell Vehicles, www.sae.org

ISO 14687-2, Hydrogen Fuel – Product Specification, Part 2: PEM fuel cell applications for road vehicles, http://www.iso.org/iso/catalogue_detail.htm?csnumber=55083

Acknowledgements:

The authors gratefully acknowledge the financial support of the DOE Fuel Cell Technologies Office and the support of Technology Development Manager, Charles (Will) James, Jr.
Characterization of Water Cluster Connectivity and Fluid Transport in PEFC Gas Diffusion Layers
Authors: Eller Jens , Büchi Felix N 
Published: February 2020

Polymer electrolyte fuel cells (PEFC) require an effective water management to operate efficiently, especially at high current densities which are needed to reach system cost targets [1]. The description of the complicated two-phase water transport remains a challenge in PEFC models and requires experimental validation on various length scales. In this work, operando X-ray tomographic microscopy (XTM) with scan times of 10 s was used to depict the liquid water at defined differential conditions at the technically relevant cell temperature of 80 °C at the TOMCAT beamline of the Swiss Light Source.
Cells with Toray TGP-H060 GDL with MPL were operated at high feed gas humidity (0.75 A/cm2, 108 % rH, H2/Air) or high current density (3.0 A/cm2, 78 % rH, H2/O2) conditions. The liquid water in the cathode GDL was analysed in terms of the local and average saturation, water cluster sizes, connectivity of the water clusters and the permeability of the water filled GDL pores. While fully through-plane connected water clusters contribute to the transport of water in the liquid phase, only partly connected water clusters do not (see Figure 1a). The majority of liquid water volume (> 80 %) is found in a limited number of fully through-plane connected water clusters (< 20 %) (see Figure 1b). Even though the water phase occupies in average the larger pores of the GDL, as reported earlier [2], still some large pores and percolation paths remain liquid free. Nevertheless, the available fully through-plane liquid paths provide liquid permeabilities that result in no noteworthy pressure losses to drain the product water of today's and upcoming current densities.
As research in industry and academia strive for the separation of the transport paths of the liquid and the vapour phase [3], the effect of the presence or absence of the partly connected water clusters on the gas phase transport parameters (permeability & effective diffusivity) of the GDL is discussed as well.
References
[1] O. Gröger et al., J. Electrochem. Soc. 162 (2015), A2605-A2622.
[2] T. Rosén et al., J. Electrochem. Soc. 159 (2012), F536-F544.
[3] A. Forner et al., Advanced Materials 27 (2015), 6317-6322.
Figure 1: a) Sketch of the different cluster types that can be found in the GDL domain; blue: full connected water clusters (FC); green: top connected (TC); red: bottom connected (BC); purple: non connected (NC). b) Volume and cluster number fractions of the different cluster types for the high humidity condition.

Figure 1
Iron-Based Spinel Oxide Nanoparticles for Electrocatalysis of Oxygen Evolution Reaction
Authors: Liu Weiyan , Fan Shaoxun , Li Jia , Gan Lin 
Published: February 2020

The design of cost-effective and highly active, durable electrocatalysts for the sluggish oxygen evolution reaction (OER) is critical for promoting various energy conversion process such as water splitting and rechargeable metal-air batteries. Due to a wider selection of earth-abundance and low cost catalyst candidates (e.g., mixed 3d-transition metal oxides), OER in alkaline environment has attracted considerable interests during past years. Besides the recently developed Ni-Fe layered double hydroxides (LDH) catalysts, spinel phase transition metal oxides have also drawn particular interests owing to their well-defined rigid structure and thus potentially high stability during electrocatalysis. While improved OER activities have been demonstrated, currently most spinel transition metal oxides (mainly Co-based spinel oxides) still underperformed the state-of-the-art benchmark OER catalyst IrO2and the Ni-Fe LDH catalysts. Moreover, atomic insights into the surface structure that governs their OER reactivities and stabilities still remain very limited.
We report here the exploration of iron-based spinel oxide nanoparticles (MxFe3-xO4, M= Mn, Fe, Co, Ni, Cu) as a new class of alkaline OER electrocatalysts with potentially both high electrocatalytic activity and high stability. Emphasis will be placed on atomistic understanding on the surface cation chemistry and surface atomic structures of the spinel oxide nanoparticles and their correlations with OER activities and stabilities. This will be achieved by comparative microscopic and spectroscopic studies of the nanoparticle surfaces before and after OER electrocatalysis using high-resolution (scanning) transmission electron microscopy, electron energy loss spectroscopy and X-ray photon spectroscopy, which will be further complemented by density functional theory calculations. The results will provide important insights into the structure-activity-stability relations of spinel phase transition metal oxides as well as other mixed metal oxides for OER electrocatalysts.
PEMFC Stack Diagnostics Using EIS
Authors: Smon Araya Samuel , Jeppesen Christian , Kær Søren Knudsen 
Published: February 2020

One way of improving the durability and reliability of a fuel cell stack or system is to isolate faults within the fuel cell and perform targeted condition-based maintenance on the affected components, to remove or limit the conditions that caused the fault. This can be done by on-line monitoring of the fuel cell system's state of health to locate and isolate faults and prevent sudden failures before they occur and correcting faulty conditions to prolong the lifetime of the fuel cell. This paper presents electrochemical impedance spectroscopy (EIS) results obtained on PEMFC stacks, with the aim of investigating the fuel cell stacks’ response to different faults, for a possible use of EIS as an advanced monitoring and diagnostics tool. The stacks used in this study are from Dantherm Power A/S, intended for stationary microCHP application. Four different faults were considered; change in fuel composition, air starvation, fuel starvation and water management, both for flooding and drying. Each fault simulation was performed in a separate fuel cell stack to avoid the mixing of the impedance signatures of the different faults. The same continuous, steady state operations under nominal condition were recorded prior to fault simulations as healthy-state references. Then the different faults were induced at varying current densities and varying fault levels.
Morphology of Elastomeric Anion Exchange Membranes: A Dissipative Particle Dynamics Study
Authors: Sepehr Fatemeh , Paddison Stephen J. 
Published: February 2020

The design and optimization of stable and highly conductive anion exchange membranes (AEMs) is essential to the development of energy and conversion technologies.1
,
2 There has been an increased interest and research to address the low stability and ionic conductivity of polymeric AEMs. However, a fundamental understanding of stability and transport in AEMs is still in its infancy3 and the effects of the choice of the cationic functional group and polymer architecture are still not known. Recently developed elastomeric AEMs4 exhibiting satisfactory chemical stability are investigated in this study. These AEMs are based on the elastomeric triblock copolymer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS), that are functionalized with various cationic groups.
Dissipative particle dynamics (DPD) is a meso-scale simulation technique5
,
6 which enables the simulation of large time- and length-scales with reasonable computational expense has been selected to investigate the morphology and dynamical behavior of such systems. The system of hydrated AEM is coarse-grained to a degree that the consideration of both chemical distinction and fine structural variants are satisfied. The structures of the DPD beads were optimized using first principles electronic structure calculations and the interaction parameters were determined using a recently developed methodology.7

The effects of several microstructural parameters including the length of the tether chains, type of the cationic group (trimethylammonium [(CH3)3NH]+; dimethylimidazolium [DMIm+]; and triphenylphosphonium [(C6H5)3PH]+ ), and the polymer architecture on the morphology and transport of anions in the aforementioned elastomeric AEMs were investigated. The effect of water content in the membrane and the effect of ion exchange capacity (IEC) were also studied. The results are compared with the widely studied proton exchange membrane Nafion.
References:
1. G. Couture, A. Alaaeddine, F. Boschet and B. Ameduri, Prog Polym Sci, 2011, 36, 1521-1557.
2. J. R. Varcoe, P. Atanassov, D. R. Dekel, A. M. Herring, M. A. Hickner, P. A. Kohl, A. R. Kucernak, W. E. Mustain, K. Nijmeijer, K. Scott, T. W. Xu and L. Zhuang, Energ Environ Sci, 2014, 7, 3135-3191.
3. M. G. Marino, J. P. Melchior, A. Wohlfarth and K. D. Kreuer, J Membrane Sci, 2014, 464, 61-71.
4. A. D. Mohanty, C. Y. Ryu, Y. S. Kim and C. Bae, Macromolecules, 2015, 48, 7085-7095.
5. P. Espanol and P. B. Warren, Europhys Lett, 1995, 30, 191-196.
6. R. D. Groot and P. B. Warren, J Chem Phys, 1997, 107, 4423-4435.
7. F. Sepehr and S. J. Paddison, Chem Phys Lett, 2016, 645, 20-26.
(Invited) Recent Progress in Analysis Methods of PEFCs: From Catalysts to Meas
Authors: Imai Hideto 
Published: February 2020

Understanding the relationship between structures and properties in PEFC materials and/or components are essential in designing better PEFCs and their materials. Recent progress in analysis methods point toward this direction: combination of basic and advanced structure analyses and imaging methods using x-rays and electron probes, as well as computational simulations correlate structural information and electrode properties.
Quick overview of x-ray and electron beam analysis methods using various physical phenomena, such as, diffraction, scattering, x-ray absorption, x-ray photo-emission, and latest challenges of their application to the catalyst and catalyst-layer developments for both platinum-based and non-platinum catalysts will be presented.