bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of a Correlation Between Carbon Corrosion and Proton Conductivity of Ionomers in PEFC Under the Low Humidity Operation
Authors: Hayashi Akari , Miyamoto Hidemasa , Kitamura Masahiko , Sasaki Kazunari 
Published: February 2020

One of the strategies to further increase PEFC performance is elevation of the operation temperature. However, durability of materials used in PEFC is assumed to be lowered at the higher temperature condition, which is also accompanied by the lower humidity condition. We have been studying degradation phenomena of cathode catalyst layers at the higher temperature. During our study, we have found carbon corrosion is related to the proton conductivity of ionomers in cathode catalyst layers when PEFC is operated at the higher temperature with lower humidity. Therefore, in this study, a correlation between carbon corrosion and proton conductivity of ionomers has been investigated.
MEAs were prepared using a standard catalyst and two types of electrolytes, Pt/Ketjen black catalyst (TEC10E50E, TKK Corp.), and Nafion® and Aquivion®, respectively. Here, The Aquivion® has higher proton conductivity than Nafion®. The operating condition of the higher temperature with lower humidity, 105 °C-RH57%, was applied. Durability of MEAs was studied through the potential cycles between 1.0 and 1.5 V assuming “stop/start cycles” of FCVs.[1], [2]

Durability of two different MEAs (Nafion® MEA and Aquivion® MEA) was evaluated in terms of electrochemical and structural changes before and after the cycle test. Here, structural changes were analyzed using a FIB-SEM technique followed by 3D reconstruction of cathode catalyst layers. Although current–voltage curves were not very much different between two types of MEAs even after 2000 cycles, the macroporous structures of catalyst layers were different. Porosity was almost homogeneous through the catalyst layer in Aquivion® MEA, but larger pores intensely formed near the Nafion® membrane side in the case of Nafion® MEA. The possible degradation mechanism is illustrated in Fig.1 and explained in the following. The carbon oxidation reaction probably occurs mainly by reacting with H2O being formed by a fuel cell reaction if it is under the low humidity condition. If proton conductivity is high enough like Aquivion® ionomer, H2O is probably generated more uniformly and carbon oxidation also occurs uniformly throughout the cathode catalyst layers. On the other hand, when proton conductivity is low like Nafion® ionomer, H2O is mainly generated at the interface between the cathode layer and Nafion® membrane. Then, carbon oxidation intensely occurs at the interface between the cathode and the electrolyte membrane.
Reference
[1] A. Ohma et al., ECS Trans, 41 (2011) 755.
[2] H. Miyamoto et al., ECS Trans, 75 (2016) 329.

Figure 1
High Performance Pt-Ni Nanocage Catalyst for the Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells (PEMFCs)
Authors: Peng Xiong , Omasta Travis J , Rigdon William A. , Mustain William E 
Published: February 2020

PEMFCs have long been considered to be among the most promising next-generation energy conversion systems for portable devices and transportation vehicles due to their zero or low pollution, high power density and low temperature operation1,2. However, the widespread commercialization of PEMFCs remains challenged by the high cost of cell components and limited cell durability. Therefore, there is a significant need to develop new catalyst materials with high intrinsic oxygen reduction reaction (ORR) activity and stability, as well as a fabrication process that leads to high cell performance and durability with low catalyst loadings.
In this work, we investigate the activity and stability of Pt-Ni nanocage oxygen reduction electrocatalysts (Figure 1a) both ex-situ and in-situ in an operating PEMFC. Ex-situ, the catalysts were both physically and electrochemically characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and both cyclic and linear sweep voltammetry using a rotating disk electrode (RDE). The nanocages showed 2 and 4 times greater specific and mass activity than Pt/C, respectively, for the ORR with high durability.
The catalysts were transitioned from the RDE platform to operating PEMFCs by application onto a Nafion® 212 membrane to form a catalyst-coated membrane (CCM) with a low cost, custom-built air-assisted cylindrical liquid jet spraying system (ACLJS). Several ACLJS parameters were investigated and the optimized parameters were used to produce CCMs that were tested by scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), electrochemical impedance spectroscopy (EIS), PEMFC polarization and cyclic voltammetry. The CCM prepared with the Pt-Ni nanocage catalyst showed no obvious Pt and Ni dissolution and redeposition in the membrane even after 30K cycles. The performance and mass activity retention of the Pt-Ni nanocage catalyst was far superior to commercial Pt/C and just short of the US Department of Energy (DOE) 2020 targets3 (Figure 1 b,c), suggesting that Pt-alloy nanocages are very promising candidates for high-performing commercial PEMFCs.

References:

1. Service, R. F. FUEL CELLS: Shrinking Fuel Cells Promise Power in Your Pocket. Science (80-. ).
296, 1222–1224 (2002).
2. CLEGHORN, S. Pem fuel cells for transportation and stationary power generation applications. Int. J. Hydrogen Energy
22, 1137–1144 (1997).
3. (U.S. Department of Energy). Fuel Cell Technical Team Roadmap. Usdrive 9 (2013).

Figure 1
Porous Iron-Nitrogen-Carbon Nanofiber As Efficient Oxygen Reduction Reaction Catalyst and Durable Support for Platinum
Authors: Kim MinJoong , Lim Jeonghoon , Cho EunAe 
Published: February 2020

Polymer electrolyte membrane fuel cells (PEMFCs) have been considered as one of the most promising energy conversion devices for future due to their high efficiency, and environmental friendly system. However, large-scale applications of PEMFCs have still faced some challenges in terms of cost and durability. Catalyst plays a great role in determining cost and durability of PEMFCs. Conventional catalyst for PEMFCs is a state-of-the-art carbon supported platinum nanoparticles (Pt/C). Pt/C has an outstanding catalytic activity for both hydrogen oxidation reaction (HOR) at anode and oxygen reduction reaction (ORR) at cathode. But, high price of Pt is a major contributory factor in increasing PEMFCs cost. And, conventional carbon support is vulnerable to corrosion under oxidative potential, which leads to serious degradation of cell performance. Therefore, it has been one of the major issue in PEMFCs to develop low-priced and durable catalysts without sacrificing catalytic performance. Recent studies proposed that co-doping of transition metal (Fe, Co, Mn..) and nitrogen into graphene-like carbon structure can draw remarkable ORR activity under PEMFCs operating conditions. In addition, this graphene-like carbonaceous materials also can have higher corrosion resistance than conventional carbon support with amorphous structure.
Herein, we synthesized iron (Fe) and nitrogen co-doped carbon nanofiber (Fe-N-CNF) with highly porous structure as efficient oxygen reduction reaction catalyst and durable support for platinum catalyst. We could successfully synthesize porous CNF by using silica nanoparticles (SiO2 NPs) as sacrificing materials. After leaching of SiO2 NPs, BET surface area and electrochemical surface area (ECSA) were 3-times and 6-times enhanced, respectively. So, porous Fe-N-CNF has excellent ORR activity and durability in acidic media.
Fig. 1. TEM images of Fe-N-CNF and porous Fe-N-CNF

Figure 1
Evaluation of Order Mesoporous Carbon As Anode Catalyst for Microbial Fuel Cells
Authors: Garcia-Mayagoitia S. , Fernández-Luqueño F. , Morales-Acosta D. , Sanchez-Padilla N. M. , Rodriguez-Varela F.J. 
Published: February 2020

Ordered Mesoporous Carbon (OMC) synthesized via self-assembly in aqueous phase, was evaluated as anode catalyst for Microbial Fuel Cells (MFCs) applications. Prior to electrochemical characterization, OMC was functionalized with methanol. The catalytic activity of non-funtionalized and functionalized OMC was compared to that of commercial Vulcan XC-72 and Graphite flakes (non-functionalized and functionalzied with methanol as well). Gas diffusion electrodes containig a catalytic layer of the catalysts were prepared by the painting technique. The Bacilus Subtilis microorganism was used to grow a biofilm over the carbonaceous catalysts and promote the bioelectrochemical reactions, while residual water directly from a pharmaceutical company (pH=9.6) was the electrolyte. Half-cell characterization was carried out in a three-electrode cell, at which Functionalized OMC showed the highest current density generated from the bioelectrochemical reactions occurring from the residual water. A dual chamber MFC was implemented, where the anode chamber contained residual water in N2 atmosphere, while the electrolyte at the cathode was O2-saturated KOH (pH=9.6). The anode catalysts were: Functionalized OMC, non-Funtionalized OMC, Functionalized Vulcan and commercial 20 % Pt/C, all containing a biofilm by Bacilus Subtilis. The cathode catalyst was commercial 20 % Pt/C. The characterization of the the MFC showed a significantly higher catalytic activity of Functionalized OMC + Bacilus Subtilis for the reactions. It delivered an Open Circuit Voltage (OCV) of 0.58 V and a maximum current density (jcell) of 854 mA m-2. These values were higher than those of Pt/C (2.6 and 4.7 higher OCV and jcell, respectively). The results showed that methanol-Functionalized OMC is a metal-free catalyst with high performance for MFCs.
Evaluation of the Dimensional Stability and Conductivity of PEM in Aqueous Solutions of Formic Acid for Use in Dfafcs
Authors: Holmes Stuart , Gonzalez Rodriguez Romeo , Perez Page Maria , Sellin Remy 
Published: February 2020

Global energy consumption is one of the greatest problems humanity is facing and the need for viable and environmentally friendly alternative energy sources is rising. One of these alternative technologies is Direct Formic Acid Fuel Cells (DFAFCs) a promising alternative energy source for the constantly increasing energy demand; they have major potential for use in portable devices as they can perform extremely well at ambient temperatures and have a low environmental footprint.
Due to the low permeability of formic acid through the polymer exchange membrane (PEM) it allows work at higher concentrations leading to higher energy production compared to other fuel cells. Working under similar operating conditions DFAFCs can generate power densities of 233 mW/cm2 outperforming Direct Methanol Fuel Cells (DMFCs) with power densities of 53 mW/cm2 (1).
However, no fundamental studies about the intrinsic conductivity and dimensional stability of PEM have been carried out whilst under use of formic acid with the purpose of understanding how PEM behave under such highly acidic conditions. This is vital for understanding the long term performance and durability of such fuel cells, should they be used on a wider scale.
The studies carried out have examined how the PEM, including Nafion 115,117,211 and 212, behave and perform under varying acidic conditions. For the dimensional stability study optical analysis was carried out to determine the changes occurring in-situ to the material. In addition, determining changes in resistance using impedance spectroscopy allows for the selection of the most efficient membrane configuration for optimal cell operation.
Previous research has shown that Nafion with a lower equivalent weight has an increased hydrophilic region, compared with membranes with higher equivalent weight. Using this relationship to understand the performance of Nafion suggests that a higher hydrophilic region leads to deformity by the formic acid on the membrane. We have observed this as a change in the dimension of the membrane in only one direction; a change that is not observed when the membrane is immersed in water alone, where the changes in the dimensions are uniform in two directions. There are two possible causes of this; firstly by the production process of the membrane or that a change is taking place in the hydrophobic regions the continuous semi- crystalline TFE structure of the material. In this work we will explain the cause of the deformation.
1. 2-D Crystals Significantly Enhance the Performance of a Working Fuel Cell. Stuart M. Holmes*, Prabhuraj Balakrishnan, Vasu. S. Kalangi, Pulickel M. Ajayan, Xiang Zhang, Marcelo Lozada-Hidalgo and Rahul R. Nair. 27.09.2016., Advanced Energy Materials.
Durable Engineered Carbon Supports
Authors: Halevi Barr , Lubers Alia , McCool Geoff , McKinney Samuel , Romero Henry 
Published: February 2020

A key limitation to catalysts today arises from reliance on carbon black (CB) supports that serve to disperse the precious metal catalyst nanoparticles, but which corrode under certain operating conditions. Carbon support modifications that rely on "top-down" graphitization of CB supports have so far improved resistance to carbon corrosion, but at the cost of reduced stabilization of precious metal dissolution.
Pajarito Powder developed a "bottom-up" approach where Engineered Carbon Supports (ECSs) made using the VariPoreTM manufacturing platform, which is cased on technologies licensed from the University of New Mexico, Northeastern University, and Los Alamos National Laboratory. This method allows manufacture of highly graphitic carbonaceous powders with excellent pore size and particle roughness control, and produces highly tailorable carbon support with great corrosion resistance.
Pt/C electro-catalysts made using these Engineered Carbon Supports maintain performance under carbon corrosion test protocols and thus demonstrate their utility in achieving the performance/price balance needed for commercializing PEMFCs. The catalyst characteristics and performance, as well as economics of this approach will be presented and discussed.
Tomography Aided Development of Membrane Electrode Assemblies for PEM Water Electrolysis
Authors: Hegge Friedemann , Vierrath Severin , Ogawa Shohei , Zielke Lukas , Bühler Melanie , Klose Carolin , Zengerle Roland , Litster Shawn , Thiele Simon 
Published: February 2020

In polymer electrolyte membrane water electrolysis (PEMWE) the anode is crucial for the overall performance. State-of-the-art anodes comprise Ir, IrOx or IrRuOx, typically bound by an ionomer and can be TiOx supported [1]. Besides the material also the microstructure of the anode has an impact on the electrolyzer’s performance as it determines catalyst accessibility and species transport [2]. Optimizing the microstructure therefore offers a potential to increase cell efficiency. In our approach we use tomographic methods in order to establish a microstructure-performance relation for PEMWE anodes (see microstructure of a FuelCellsEtc PEMWE anode in Fig.1). We then apply our findings from the reconstructed anodes in order to develop improved membrane electrode assemblies (MEAs) for PEMWEs with novel manufacturing and design approaches. The experimental data will then be used as input for our theoretical models.
References
1. Carmo, M., Fritz, D.L., Mergel, J., Stolten, D.: A comprehensive review on PEM water electrolysis. International Journal of Hydrogen Energy 38(12), 4901–4934 (2013). doi: 10.1016/j.ijhydene.2013.01.151
2. García-Valverde, R., Espinosa, N., Urbina, A.: Simple PEM water electrolyser model and experimental validation. International Journal of Hydrogen Energy 37(2), 1927–1938 (2012). doi: 10.1016/j.ijhydene.2011.09.027

Fig. 1 SEM image (a) and three-dimensional representation (b) of an anode catalyst layer from a FuelCellsEtc electrolysis MEA reconstructed via nano computed tomography.

Figure 1
3D Printed Bipolar Plate for Water Electrolysis
Authors: Zhang Feng-Yuan 
Published: February 2020

3D printed bipolar plate for water electrolysis

Gaoqiang Yang1, Jingke Mo1, Zhenye Kang[1], Frederick A. List III2, Johney B. Green Jr3, Sudarsanam S. Babu2,4, Feng-Yuan Zhang*1

Abstract
A proton exchange membrane electrolyzer is considered as a potential route to the hydrogen production in recent years. It offers a series of advantages, including high product purity, high working current and pressure. As a novel solution for manufacturing process, 3D printing technology is capable of fast and cost-saving prototyping with complex structure from digital models. By employing 3D printing technology, a stainless-steel (SS) component, which is functioned as both of bipolar plate and current distributor, was rapidly produced with selective laser melting (SLM) technique, and was then comprehensively investigated in a proton exchange membrane electrolyzer cell (PEMEC). The experimental results indicated the PEMEC with an 3D printed stainless steel bipolar plate provided an excellent performance, which reached 1.78 V at 2.0 A/cm2 and 80 °C. Furthermore, the 3D printed SS cathode bipolar plate was also ex-situ characterized before and after test by SEM and EDS. This research of 3D printed stainless steel bipolar plate not only provides a route to the quick development of light weight and cheap electrolyzer, but also lead to improvements for other energy related devices.

[1] Nano HELP, Department of Mechanical, Aerospace & Biomedical Engineering, UT Space Institute, University of Tennessee, Knoxville, USA.
2 Oak Ridge National Lab, USA

3 National Renewable Energy Laboratory
* Contacting Author: E-mail: fzhang@utk.edu; Tel: +1-(931)-393-7428
(Invited) Advancing Design and Discovery of New Materials for Solar Energy Conversion
Authors: Cooper Jason K. , Jiang Chang-Ming , Sharp Ian D. 
Published: February 2020

The development and advancement of new materials for solar-driven chemistry is an area of focused attention because there remains no material that meets the demanding criteria for semiconductor solar photoelectrochemistry, which include stability, efficiency, and scalability. Modern techniques of materials discovery, such as high throughput synthesis and computational screening methods, have proved effective at identifying new classes of materials. However, these materials will require efficient and comprehensive characterization to expose their underlying physics, governed by their electronic structure and native defects. Through utilization of BiVO4 as a testbed, we have developed a scalable synthetic method and a series of characterization tools to elucidate its underlying optical and electronic properties, as well as to mitigate photocarrier recombination at native defects and improve doping. These methods have since been applied to copper vanadate, an n-type semiconductor that has been newly identified as a candidate for use in photoelectrochemical energy conversion, to examine its apparent low performance efficiency.
(Invited) Novel Chalcopyrite Materials for Economical Photoelectrochemical Hydrogen Production
Authors: Gaillard Nicolas , DeAngelis Alexander D , Horsley Kimberly 
Published: February 2020

Photoelectrochemistry (PEC) is theoretically one of the most efficient methods to produce alternative fuels, although the efficiency, cost, and durability of lab-scale systems are currently not at the level required to make this technology economically feasible. The chalcopyrite material class provides exceptional candidates to meet the requirements for cheap, sustainable solar fuels production. As we have previously reported, co-evaporated 1.7 eV CuGaSe2 offers very high-saturated photocurrent densities (>15 mA.cm-­2) and high Faradaic efficiency (>85%). However, CuGaSe2 photocathodes suffer from non-ideal surface energetics, requiring additional PV cells to drive the water splitting process. The hybrid photo-electrode (HPE) device, in which a PEC electrode is placed on top of a solar cell, is by far the most efficient approach for unbiased solar water splitting. Unfortunately, CuGaSe2’s narrow bandgap prohibits this integration scheme.
In the present communication, we report on our efforts to synthesize 1.8-2.2 eV band-gap chalcopyrite materials for PEC water splitting. Specifically, we investigated the effect of sulfur on the optical and photoelectrochemical characteristics of the copper chalcopyrite material class. Using co-evaporated 1 μm-thick CuGaSe2 as a baseline system, we demonstrate that the substitution of selenium with sulfur can be accomplished through a simple annealing step. As a result, a dramatic change in optical properties was observed, with a bandgap increase from 1.6 eV (CuGaSe2) to 2.4 eV (CuGaS2). Then, by simply adjusting the indium content during the initial growth process, the bandgap of sulfurized copper chalcopyrite was decreased from 2.4 eV to 2.0 eV. X-ray diffraction data indicated successful bulk sulfurization by the shift of the prominent (112), (220), and (312) reflections to higher angles. Saturated photocurrent densities of 5 mA/cm2 were achieved with 2.0 eV red CuIn0.3Ga0.7S2 photocathodes in 0.5M H2SO4 under AM1.5G simulated illumination. From this proof of concept experiment, we have further developed new synthesis approaches and innovative characterization protocols to achieve PV-grade wide bandgap sulfide-based chalcopyrites capable of generating photocurrent densities over 10 mA.cm-2.
(Invited) Photo-Induced Force Mapping of Plasmonic Nanostructures
Authors: Thomann Isabell 
Published: February 2020

Plasmonic nanoparticles serve as efficient optical nanoantennae that interact with light with an effective cross section exceeding their geometric size. We have recently exploited this antenna effect to engineer photoelectrodes for solar water splitting, optimizing for different plasmonic decay mechanisms such as near-field energy transfer to the surrounding semiconductor [1], plasmon-induced hot carrier generation and utilization [2], and broadband extreme light absorption within monolayer MoS2 [3]. However, often more than one plasmonic decay mechanism is at work, which makes it challenging to separate out the relative contributions and optimize them efficiently for solar water splitting. Novel characterization tools to study the heterogeneity of plasmonic photocatalysts both in terms of their morphology and optical near-field enhancements in-situ are therefore of widespread interest. Here we introduce a novel technique called photo-induced force microscopy that allows for simultaneous imaging of topographical features and spectroscopic characterization of near-field distributions with high spectral selectivity and temporal resolution. In this technique, a nanoscale tip is brought in the vicinity of the sample, which is optically excited. The photo-induced gradient forces between the tip and the sample can be detected with nanometer-scale spatial resolution, along with topographical information in atomic force microscopy tapping mode. I will show examples of our combined experimental-theoretical study [4] where we map force intensity enhancements in nanostructures and compare them to simulated force intensity enhancements in which a realistic tip-sample geometry is modeled using Maxwell-Stress tensor methods. Near-field inhomogenities with a spatial resolution less than 10 nm are easily resolved. As such, photo-induced force microscopy will be a welcome addition to the toolbox of nanoscale characterization methods, and will find additional useful applications for the characterization of precisely manufactured nanostructures and surface-enhanced Raman scattering (SERS) substrates. Time permitting, I will discuss charge carrier dynamics in hybrid nanoparticles composed of plasmonic / two-dimensional materials, and applications of photo-induced force microscopy to these study photocatalytic processes.
[1] Nano Letters 2011, 11, p 3440
[2] Nano Letters 2015, 15 (9), p 6155; Chemistry of Materials 2016, 28 (13), p 4546
[3] ACS Photonics 2016, 3 (5), p 853
[4] Nano Letters 2016, Articles ASAP (As Soon As Publishable)