bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Water Oxidation Catalyst Made By the Facile Deposition of Ruthenium on Graphene Oxide
Authors: Fruehwald Holly M , Moghaddam Reza B. , Zenkina Olena V , Easton E. Bradley 
Published: February 2020

As populations grow worldwide, there is an ever-increasing need for sustainable and renewable energy sources to keep up with the high demand of energy. One promising technology is electrochemical water-splitting, which creates hydrogen and oxygen at the cathode and anode, respectively. Developing viable, stable catalysts for water splitting is critical since this reaction is truly a green, sustainable method to generate hydrogen fuel.
However, more active electrocatalysts for the water oxidation reaction (WOR) are needed to improve the viability of this technology. Currently, these catalysts are most often composed of rare and expensive earth metals such as iridium. More sustainable materials such as those based on ruthenium have been recently investigated as alternatives to the rare metal systems. Ruthenium-based materials are an ideal choice as Ru offers multiple available oxidation states to help facilitate the water-splitting reaction and possibly lower overpotentials[1]. However, many ruthenium-based materials are prone to stability issues in acidic media at high over potentials. In addition, sluggish kinetics are often observed [2].
In this work we synthesized graphene oxide, via a simple and low-cost method, and utilized it as a support for the Ru oxide nanocatalyst[3]. We used graphene oxide due it high mechanical strength, favorable electronic properties, and the ease at which it can be doped with metals[4]. Ruthenium oxide nanoparticles were deposited on the surface of the graphene oxide at a 5wt% metal loading by a facile method. The materials were examined electrochemically in acidic media for the water oxidation reaction, where we observed low overpotentials and high stability during prolonged testing. This simple preparation method could be used to efficiently synthesize active and highly stable water-oxidation catalysts that are more cost-effective. This novel ruthenium stabilized on graphene catalyst could aid in the future development of more sustainable materials for the future of renewable energy technology.

References

[1] Kamdar, J.M.; Grotjahn, D.B. Molecules
2019, 24, 494.
[2] Haschke, S.; Pankin, D.; Mikhailovskii, V.; Barr, M. K. S.; Both-Engel, A.; Manshina, A.; Bachmann, J. Beilstein J. Nanotechnol.
2019,
10, 157–167
[3] Liu, J.; Poh C. K.; Zhan, D.; Lai, L; Lim, S. H.; Wang, L.; Liu, X.; Sahoo, N. G.; Li, C.; Shen, Z.; Lin, J. Nano Energy. 2013, 3, 377-386
[4] Tu, W.; Lei, J.; Zhang, S.; Ju, H. Chemistry – A European Journal. 2010,
16, 10771-10777.

Figure 1
Understanding Interfaces of PEM Electrolyzers with Operando Synchrotron X-Ray Computed Tomography and Radiography
Authors: Leonard Emily , Shum Andrew , Sabarirajan Dinesh C , Capuano Christopher B , Ayers Katherine E. , Danilovic Nemanja , Pant Lalit M. , Weber Adam Z. , Xiao Xianghui , Parkinson Dilworth Y. , Zenyuk Iryna V. 
Published: February 2020

Polymer electrolyte membrane (PEM) electrolyzers are electrochemical energy-conversion devices that convert electricity into hydrogen fuel at high efficiencies. The state-of-the-art systems use high IrOx loading (~2-3 mg/cm2), largely due to a lack of stable electrocatalyst supports that can effectively disperse the catalyst particles. Currently, the catalyst layers are made of IrOx and ionomer without an additional support. Without micro-porous layers (MPLs), the rough contact between the porous transport layer (PTL) and catalyst layer presents a challenge.
In this study we use operando x-ray computed tomography (CT) and x-ray radiography to visualize operation of PEM electrolyzer under two current densities: 500 and 800 mA/cm2. First, we compare performance of electrolyzer with catalyst-coated membrane (CCM) and that with porous transport electrode (PTE) and correlate polarization curves to morphology of the interfaces observed with x-ray CT. At 1 A/cm2, the micro-CT CCM electrolyzer showed 200 mV improvement in potential primarily due to better contact between the electrocatalyst, membrane, and PTL. From the nano-CT imaging we discovered non-homogeneous distribution of IrOx electrocatalsyt and from the images it is also not clear whether the larger IrOx agglomerates are electrically connected via a percolating conductive network of nanoparticles. The modeling study shows that the primary reason for performance loss in PTE configuration is low connectivity of catalyst particles with membrane. This causes bottlenecks in proton transport and results in high potential losses in anode.
We also compared the polarization behavior and morphology of cells with CCMs but two types of PTLs. One was made with sintered Ti and the other with Ti fiber. The Ti fiber PTL showed higher porosity and lower tortuosities, both in-plane and thru-plane. However these better morphological properties did not necessarily translate into lower potentials, as 1 A/cm2 was not a high enough current density to resolve differences attributable to improved two phase flow. This was also confirmed by radiography study, where oxygen residence fraction in the channels showed similar fractions for both types of the PTLs.
Modeling Electrolyte Composition Effects on Anion-Exchange-Membrane Water Electrolyzer Performance
Authors: Stanislaw Lauren N. , Gerhardt Michael R. , Weber Adam Z. 
Published: February 2020

Anion-exchange membrane (AEM) electrolyzers are an attractive alternative for hydrogen production due to the potential stability and activity of non-precious metal catalysts in alkaline environments. Recently, AEM electrolyzers have been demonstrated using various membranes, ionomers, porous-transport layers, and catalysts (1). The influence of these materials and their properties on AEM electrolyzer performance, however, is underdeveloped. Furthermore, recent studies have shown (2) and hydrogen-evolution reaction kinetics (3), offering additional routes to decreasing cost and reducing operating voltage.
In this work, we use a coupled, nonisothermal, multiphase model of an AEM electrolyzer to understand the role of material properties, transport phenomena, and reaction kinetics in improving device pformance. We use the model to identify performance bottlenecks through applied voltage breakdowns (AVBs) and provide guidance for next-generation electrolyzer materials and designs by evaluating sensitivity to membrane and catalyst-layer properties. Finally, we explore the effects of various electrolyte solution feeds and operating paradigms on cell performance, with a particular interest in the influence of ion transport on reaction kinetics.

Acknowledgements

This work was funded under the HydroGEN Consortium, by the Office of Energy Efficiency and Renewable Energy (EERE), of the U.S. Department of Energy under contract number DE-AC02-05CH11231. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program. This work was also supported in part by Workforce Development & Education at Berkeley Lab. We thank Sanjeev Mukerjee, Ian Kendrick, Yu Seung Kim, and Dongguo Li for helpful discussions.

References

I. Vincent and D. Bessarabov, Renewable and Sustainable Energy Reviews, 81, 1690 (2018).

H. Ito, N. Kawaguchi, S. Someya, T. Munakata, N. Miyazaki, M. Ishida and A. Nakano, International Journal of Hydrogen Energy, 43, 17030 (2018).

Q. Jia, E. Liu, L. Jiao, J. Li and S. Mukerjee, Current Opinion in Electrochemistry, 12, 209 (2018).
Highly Active and Durable Perovskite OER Catalyst for Pure Water Anion Exchange Membrane Electrolysis
Authors: Chung Hoon T , Li Dongguo , Lee Albert S , Fujimoto Cy , Kim Yu Seung 
Published: February 2020

Anion exchange membrane (AEM) water electrolysis can afford cheaper hydrogen (H2) production compared to the current state-of-the-art of proton exchange membrane (PEM) electrolysis. In AEM electrolysis, i.e., in alkaline environment, platinum group metal (PGM)-free catalysts can be adopted as oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts, contrary to the PEM electrolysis in which PGM-catalysts should be used. Furthermore, expensive titanium flow-field that is indispensable in acidic PEM electrolyzer can be replaced by inexpensive stainless flow-field. These advantages of AEM electrolysis make AEM electrolysis attractive technology to produce H2 in low cost. However currently performance of AEM electrolysis is much lower than that of PEM electrolysis. Therefore to make the AEM electrolysis technology viable, significant advancement in AEM electrolysis technology is needed.
Many PGM-free OER catalysts measured in aqueous alkaline electrolytes, such as 0.1 M KOH or NaOH, have demonstrated as high activities as that of PGM IrO2 OER catalysts measured in an aqueous acid electrolytes in an electrochemical cell test. This implies that the low AEM electrolysis performance is possibly caused by some detrimental effect of AEM/anion exchange ionomer (AEI) onto catalysts. In this work we exploited different types of catalysts and AEIs to investigate the effect of catalyst-AEI interaction on AEM electrolysis performance. We observed that catalyst-AEI interaction substantially affects the AEM water electrolysis performance. The higher activity and durability of perovskite oxide OER catalyst than IrO2 OER catalyst in AEM water electrolysis can be explained by this catalyst-AEI interaction.
In this talk, we will discuss the causes for low AEM electrolysis and possible pathways to improve AEM water electrolysis performance.

Acknowledgements

The authors gratefully acknowledge research support from the HydroGEN Advanced Water Splitting Materials Consortium, established as part of the Energy Materials Network under the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office.
Balancing Reactant Transport and PTL-CL Contact in PEM Electrolyzers by Optimizing PTL Design Parameters via Stochastic Pore Network Modeling
Authors: Lee Jason Keonhag , Bazylak Aimy 
Published: February 2020

Optimizing the porous transport layer (PTL) structure is crucial for high current density operation of polymer electrolyte membrane (PEM) electrolyzers. Previous studies from the literature demonstrated that PTL structures, mainly porosity and titanium powder diameter, can be strategically chosen to improve the performance (1-3). However, transport mechanisms in the PTL can be further explained from the perspective of mass transport. In this work, we employed modelling approaches to investigate the effect of porosity and titanium particle size of the sintered titanium powder based PTL on mass transport. PTLs were numerically generated using a stochastic model (Figure 1) with three titanium powder diameters, 25 µm, 50 µm, and 75 µm, and three porosities, 26.5%, 40.5%, and 63.5%. Pore network modelling was used to calculate the gas saturation and the permeability of liquid water in the presence of oxygen gas. We observed that all simulated PTLs exhibited similar gas saturation profiles and relative permeabilities, yet the PTLs with higher porosities had significantly higher liquid water permeabilities. For a constant powder diameter of 25 μm, increasing the porosity from 26.5% to 63.5% led to an increase in the average surface roughness from 8.9 μm to 38.6 μm. For a constant porosity of 26.5%, increasing the powder size from 25 μm to 75 μm resulted in an increase in the average surface roughness from 8.9 μm to 18.3 μm. Larger open pore spaces were acquired for PTLs with higher surface roughness, resulting in higher liquid water permeabilities (two-phase permeability). Therefore, PTLs with higher porosities and larger particle sizes provide superior liquid water permeation and gas removal.
Figure 1. The 3D reconstruction of the PTL generated with titanium powder diameter of (a) 25 µm, (b) 50 µm, and (c) 75 µm at overall porosity of 40.5%.
References

S. A. Grigoriev, P. Millet, S. A. Volobuev and V. N. Fateev, Int J Hydrogen Energy,
34, 11, p. 4968-4973 (2009).

J. O. Majasan, F. Iacoviello, P. R. Shearing and D. J. Brett, Energy Procedia,
151 (2018).

L. Zielke, A. Fallisch, N. Paust, R. Zengerle and S. Thiele, Royal Society of Chemistry Advances,
4, p. 58888-58894 (2014).

Figure 1
The Synthesis of Zirfon-Type Porous Separator with Reduced Gas Crossover for Pressurized Alkaline Water Electrolyzer
Authors: Cho Won-Chul , Cho Hyun-Seok , Kim Sangkyung , Kim Chang Hee 
Published: February 2020

Alkaline water electrolysis is one of the most efficient ways to produce hydrogen in a large scale with mature technique. It employs porous separators to provide the ionic conductivity of alkaline electrolyte between the electrodes, while separating the evolved gases. Zirconia nanoparticles and polysulfone composite separator exhibits satisfactory performance of high bubble point (2.5 bar) and low area resistance (~0.3 Ωcm2). However, the alkaline water electrolysis shows the efficiency loss in the lower partial load mainly due to the gas crossover through the separator. Therefore, detailed characterization and its effects on bubble point, resistance, and gas crossover are investigated.
In this study, we synthesized a porous ZrO2/polysulfone composite separator varying the amount of ZrO2 (70-85 wt.%) via film casting method. Scanning electron microscopy and thermogravimetric analysis show that the increased amount of ZrO2 reduces the bubble point and area resistance and increases the gas crossover, mainly due to the instability of the composite separator. 80wt.% ZrO2/20wt.% polysulfone composite separator shows a bubble point of 2.1 bar, low area resistance (~0.2 Ωcm2) and reduced hydrogen permeability (<2 E-11 mol cm-1 bar-1 sec-1) compared to the Zirfon PERL® separator. The enhanced performance is attributed to large portion of small size pore (< 100 nm from Hg porosimetry) and increased concentration of ZrO2 nanoparticles on the skin surface (XPS analysis), resulting in the high wettability. This experimental study suggests the various characterization methods that determine the performance of the composite separator for alkaline water electrolysis coupled with the renewable energy sources.
(Invited) Critical Parameters for GW Scale Perovskite PV Manufacturing
Authors: DeLuca Stephan J , Tombs Thomas 
Published: February 2020

A recent NREL white paper proposing a new US Perovskite Energy Consortium states “Fulfilling the world’s demand for PV requires continued exponential growth of production capacity without exponential growth in capital expenditure and remains a major challenge due to the inadequate capital efficiency of PV using existing technologies. There is an opportunity and a need for disruptive and fundamentally profitable technologies to supplement the ongoing growth of the PV manufacturing industry”.
Perovskite technology promises high conversion efficiency, low manufacturing cost, and low capital expense (CapEx) to build manufacturing capacity. Fulfilling that promise requires a manufacturing process with a very high throughput. The ability to fabricate perovskite films using low-temperature, solution based methods has been touted as a path to low cost and low CapEx manufacturing, however fast deposition of the perovskite layer alone is not sufficient to create the throughput that transforms the PV manufacturing landscape; an in-line process that integrates the deposition of all the functional layers of the device, as well as cell interconnects and module lamination, is required. Any slow vacuum deposition step (e.g., sputtering ITO for the transparent conductor) or long thermal annealing step (e.g., forming a charge transport barrier by forming a compact TiO2 layer) commonly used in lab-scale perovskite device fabrication must be avoided.
Our cost modeling shows that the throughput of a single line needed to get to disruptive CapEx and manufacturing cost will be on the order of 45 m2/min. That results in over 3GW/year production capacity at conservative uptime and yield values. An integrated in-line roll-to-roll (RtR) process with a 1.5m wide web would require all deposition steps to run at 30 m/min; much faster than processes cited in the academic literature for lab scale devices. That line speed is not taxing to most commercially available RtR systems, but practical limitations on oven size means a tight window for drying and annealing steps of all solution coated layers. The challenges of creating high performance transparent conductors, inorganic charge transport and barrier layers, perovskite layers and cell interconnects at those speeds will be discussed. The implied TAKT time is less than 3 seconds for 2m2 modules coming off of a single production line. The final assembly and test operations take much longer for each module, so methods of dealing with the mismatch must be implemented. We will also describe the practical considerations, including material sourcing and process requirements for production at GW scale.
(Invited) A Novel Optical Characterization of a-Si:H/c-Si Interface Microstructures Based on Data of Positron Annihilation Spectroscopy
Authors: Matsuki Nobuyuki , Matsui Takuya , Michishio Koji , O' Rourke Brian , Oshima Nagayasu , Uedono Akira 
Published: February 2020

The power conversion efficiency of amorphous/crystalline silicon (a-Si:H/c-Si) heterojunction solar cells has exceeded 26% recently.1) Such high efficiency is essentially achievable thanks to the notable passivation capability of the several-nm-thick amorphous silicon layer deposited on the c-Si surfaces. For further improvement of the performance, it is necessary to understand and to control the structural properties of the a-Si:H/c-Si heterointerface.
Recently, we have found that there is a systematic correlation between the microvoid size determined by the positron annihilation spectroscopy (PAS) and the optical constant of a-Si:H by spectroscopic ellipsometry (SE).2) However, it has been still not clear that this correlation is universally consistent for any a-Si:H thin-films that are fabricated under various preparation conditions using any different apparatus.
In this study, we prepared undoped a-Si:H films on H-terminated FZ Si(111) substrates under various chemical vapor deposition conditions including different source gases (SiH4 or Si2H6) and deposition systems. The average diameter of microvoids (D
void) and the dielectric function (ε = ε
1 - iε
2) in these a-Si:H films were estimated via PAS and SE measurements, respectively. The peak values of ε
2,
ε
2
peak, were extracted from the dielectric function determined based on the Tauc-Lorentz dispersion model.3) It is notable that the D
void vs. plots are aligned on a straight line; this result indicates that D
void in undoped nm-thin a-Si:H can be estimated readily from SE measurement results using the found D
voidーε
2
peak　linear correlation. Details in this method and results will be discussed in the presentation.
References
1. Yoshikawa, H. Kawasaki, W. Yoshida, T. Irie, K. Konishi, K. Nakano, T. Uto, D. Adachi, M. Kanematsu, H. Uzu and K. Yamamoto, Nature Energy
2, 17032 (2017).
2. N. Matsuki, A. Uedono, B. E.O’Rourke and N. Oshima., 8th Intl. Conf. on Plasma-Nano Technol. and Sci., 3-O-03 (2015).
3. S. Kageyama, M. Akagawa, and H. Fujiwara, Phys Rev. B 83, 195205 (2011).

Figure 1
Mechanofusion-Derived Si Alloy-Graphite Composite Electrode Material for Li-Ion Battery
Authors: Cao Yidan , Wang Jun , Hatchard Timothy , Wei Congxiao , Dunlap R. A. , Obrovac M. N. 
Published: February 2020

Silicon-graphite composites are extremely promising negative electrode materials for Li-ion batteries. However, simple and effective methods to synthesize silicon-graphite composites with engineered structures are needed to realize this technology in practical applications. Here, we show that the environmentally friendly and low-cost dry mechanofusion (MF) process can effectively synthesize silicon alloy-graphite composites, in which silicon alloy particles can be well dispersed and embedded between flake graphite layers, as shown in Figure 1(a)-(b). This results in increased tap density and reduced surface area. The special structure provides a way to buffer volume expansion and contraction of the silicon alloy during lithiation and delithiation. As a result of this hierarchical arrangement, superior cyclability and rate capability are achieved compared to simple mixtures, with capacities of 950 mAh/g (i.e. 1473 Ah/L) and 900 mAh/g (i.e. 1432 Ah/L) at 2C and 4C, respectively (Figure 1(c)).
Moreover, using this process, micron-sized silicon alloy particles can be well embedded within spherical natural graphite particles, as shown in Figure 1(d)-(e). The specially engineered structure created by the MF dry process leaves room for expansion and contraction of the silicon alloy during lithiation and delithiation process. In addition, the silicon alloy particles are protected within the graphite particle, which could be helpful to avoid excessive electrolyte exposure and improve cycle life.

Figure 1
(Invited) Thin Film Processing for Innovative Solid State Lithium Batteries
Authors: Oukassi Sami , Porthault Helene , Salot Raphaël 
Published: February 2020

With the emergence of novel multifunctional internet of things and wearable electronic devices, the development of high performance energy storage devices is becoming increasingly important. Thin film solid state lithium batteries (TFBs) are known to be one of the most promising candidates to meet these applications’ demands.
In this context, it is expected that the development of thick (20µm+) electrodes with active material only would provide opportunities to enhance the device performance and widen the scope of possible integration schemes. Several options have been explored at LETI, including key enabling technologies such as electrochemical, hydrothermal, physical vapor deposition as well as a combination thereof. Here we will discuss our efforts to develop advanced TFB electrodes based on the thick active material electrodes.