bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Characterization of Electrocatalysts for the Hydrogen Evolution and Hydrogen Oxidation Reactions in Alkaline Environment
Authors: Williams Stefan T. D. , Goenaga Gabriel A. , Elgammal Ramez A. , Zawodzinski Thomas A. 
Published: February 2020

The development of catalysts for the electrochemical processes of hydrogen systems (e.g. fuel cells and electrolyzer systems) continues to be a significant area of research for renewable energy technologies. One significant challenge has been the development of hydrogen catalysts that can be utilized in alkaline environments as the kinetics of hydrogen reactions decrease by two orders of magnitude in alkaline environments compared to acidic[1,2]. Chemical vapor deposition (CVD) is a conventional tool used in the synthesis of such catalysts[3,4]. This presentation discusses the extending work being done using a variant CVD process known as “Poor Man’s” CVD (PMCVD), to further its impact in electrochemical catalyst application[5]. PMCVD is utilizes an inexpensive vacuum oven to sublime commercially available metal-organic precursors; lowering synthesis cost while providing increased control of particle size and distribution. This work describes the work done to assess the PMCVD mechanisms as well as its use to develop catalysts for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in alkaline environments.
Preliminary studies have shown that PMCVD can develop catalysts with highly dispersed nanoparticles on various supports. As depicted in Figure 1, PMCVD synthesized Pt/C and PtRu/C catalysts have shown to have improved kinetics over commercial developed catalysts exhibiting approximately a 40% and 45% increase in average exchange current densities respectively when compared to Tanaka Kikinzoku catalysts of the same loading. An extended function of the PMVCD process is the ability to synthesize alloyed catalysts in a single deposition process. By understanding the parametric effects of temperature and pressure on the deposition process with respect to particle size and distribution, we can optimize the PMCVD process to develop highly active catalysts that can be used in alkaline hydrogen systems.
[1] Durst, J. et al. New insights into the electrochemical hydrogen oxidation and evolution reaction mechanism. Energ. Environ. Sci. 7, 2255–2260 (2014).
[2]Sheng, W. et al. Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes. . Electrochem. Soc. 2010 volume 157, issue 11, B1529-B1536
[3] Garcia, Vargas, et al. “Chemical Vapor Deposition of Iridium, platinum, Rhodium, and Palladium.” Materials Transactions, Vol. 44, No. 9 (2003) pp. 1717-1728
[4] Serp, Philppe, et. al. “Chemical Vapor Deposition Methods for the Controlled Preparation of Supported Catalytic Materials.” Chem. Rev. 2002, 102, 3085−3128
[5] Papandrew, A. et al. Advanced Electrodes for Solid Acid Fuel Cells by Platinum Deposition on CsH2PO4. Chem. Mater. 2011, 23, 7, 1659-1667

Figure 1
Towards High-Performancepgm-Free ORR Electrocatalysts: Interplay between Theory and Experiment
Authors: Chen Zhongfang 
Published: February 2020

Fuel cells are clean and sustainable energy conversion devices for power generation, and platinum and other platinum-group-metal (PGM) have been long known as the most effective catalystsfor the oxygen reduction reaction (ORR) in fuel cells. However, the scarcity and high costof the PGM-based ORR catalysts are main obstacles forcommercialization of the fuel cell technology. Therefore, searching high-performance PGM-free ORR catalysts has been a key scientific issue in the development of fuel cells.
In this talk, we will present our recent progress on computational design of ORR catalysts based on two-dimensional nanomaterials, especially single-atom catalysts and metal-free catalysts. Notably our designed nanocatalysts can be experimentally realized by standard procedures, as evidenced by our recent collaborations with experimental peers. We are calling for more interplays between theory and experiment, which will greatly facilitate the catalyst discovery and innovation.
(Invited) Chemical and Structural Factors Affecting the Hydrated Morphology of Anion Exchange Membranes
Authors: Paddison Stephen J. 
Published: February 2020

The hydrated morphology of ion containing polymers is a critically important property affecting ion and water transport. Anion exchange membranes (AEMs) are increasingly of interest as the electrolyte in energy and conversion devices due, in part, to their suitability with non-noble metal catalysts. However, the rather low chemical stability under alkali conditions and only meager ionic conductivity present difficulties in their application. A promising strategy to enhance the conductivity of these materials may be through tailoring of the phase segregation of the polymer. Recently, AEMs based on the triblock copolymer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS), and functionalized with various cationic groups have shown satisfactory chemical stability.
We are continuing an extensive investigation to understand how various molecular features (degree of functionalization, placement of alkyl spacer(s) on the side chain, choice of the cationic group, and the associated anion) determine the hydrated morphology of functionalized SEBS ionomers. With this goal we are utilizing dissipative dynamics (DPD) simulations, a meso-scale technique, to probe relatively large time and length scales and thereby elucidate the morphology of the polymer systems. The optimized structure and the interaction parameters used in these DPD simulations were calculated using a recently developed methodology employing DFT based electronic structure calculations. The morphology was determined over a broad range of hydration and our results underscore the complexity of the effects of these parameters.
(Invited) Kinetic Parameters in Anion-Exchange Membrane Fuel Cells
Authors: Carlson Annika Elisabet , Grimler Henrik , Ekström Henrik , Lagergren Carina , Lindbergh Göran , Wreland Lindström Rakel 
Published: February 2020

Anion-exchange membrane fuel cells (AEMFC) are promising mainly due to the possibility to use none-PGM catalysts in the alkaline media [1]. However, before elaborating with alternative catalysts a better understanding is needed on which electrode is limiting and what the limitations are for the reference Pt/C catalyst. In fact, the rate constants for the ORR and HOR are not determined in the in the fuel cell [2]. On top of this the influence of water on the kinetics and water transport in and between the electrodes is debated [3]. In this study we have measured the influence of partial pressure in both a symmetrical H2/H2cell a H2/O2cell. Experimental I-V and impedance data has been modelled by two separate physic-based models. The experimental results show that the hydrogen reaction has two separate time-constants in the impedance spectra for the symmetrical cell, indicating a two-step reaction at the anode (see Figure below). From the O2/H2cell the ORR is found to be the limiting reaction at low currents densities, while the HOR has a greater impact at high currents densities. From the model, a limiting current is observed at the anode. The level of humidity is likely not determining the direct catalytic reaction kinetics but may affect indirectly through its impact on ionomer conductivity and swelling.
Fig. Nyqvist plots of H2/H2symmetrical cell at OCP at different H2mixtures in Ar at 50°C, 95% RH, 125 ml/min. MEA: 0.4 mg/cm2Pt/C, AS4 ionomer and A201 Tokuyama membrane [4].
[1] D. R. Dekel. Journal of Power Sources, 375:158–169, 2018.
[2] E. S. Davydova, S. Mukerjee, F. Jaouen, D. R. Dekel, ACS Catal. 8 , 665-6690, 2018.
[3] B. Eriksson, H. Grimler, A. Carlson, H. Ekström, R. Wreland Lindström, G. Lindbergh, C. Lagergren, Int. J. Hydrognen Energy 44, 4930-4939, 2019.
[4] A. CarlsonShapturenka, B. Eriksson, G. Lindbergh, C. Lagergren, R. Wreland Lindström, Electrochimica Acta 277 (2018) 151-160
Durability-Limiting Factor of Anion Exchange Membrane Fuel Cells
Authors: Leonard Daniel Philip , Maurya Sandip , Lee Albert S , Li Dongguo , Kim Yu Seung 
Published: February 2020

Anion exchange membrane fuel cells (AEMFCs) hold the promise of low-cost energy conversion. However, one of the most significant challenges in the development of AEMFCs has been their limited durability, ca. < 1,000 h, when compared to proton exchange membrane fuel cells (PEMFC). The most common explanations for loss in fuel cell performance (AEM degradation, (bi)carbonation, water management, and catalyst aggregation) do not fully explain the irreversible performance degradation that limits the durability of AEMFCs.
In our study, we set out to identify the source or causes of that performance loss in AEMFCs. To mitigate known sources of degradation, we applied fully humidified conditions and periodically replenished the cell with a dilute NaOH solution. To resolve the current density dependence of cell degradation we conducted several extended duration experiments at different current densities and observed the lifetimes of those cells. Finally, we conducted a rotating disk electrode (RDE) and 1H NMR spectroscopic experiments to identify the durability-limiting factor.
We found that when controlling for the known mechanism of performance loss significant and accelerating performance degradation was present. This pointed to a previously unreported means of performance loss. Lower current densities (higher operating potential) resulted in decreased cell lifetime. These tests led to the electrode rather than membrane degradation as the source for performance loss. Our studies with RDE and 1H NMR experiments identified the generation of phenolic compounds that accumulate at the cathode throughout fuel cell operation. Once produced, the phenolic groups remain tethered to the ionomer, and cannot be removed by replenishment of the cell with a caustic solution. While quick recovery of cell performance occurs after caustic treatment continued to fuel cell operation inevitably leads to more phenol group formation that consumes quaternary ammonium counter ions. Eventually, these compounds reach a critical concentration that results in cell failure. The proposed mechanism is consistent with the degradation behaviors during our long-term test. Finally, we will discuss the mitigation strategy of the observed AEMFC degradation.
Electrocatalyst Performance in Acidic Aqueous and Solid Polymer Electrolytes
Authors: Knöppel Julius , Ehelebe Konrad , Escalera López Daniel , Paul Michael T.Y. , Mayrhofer Karl J. J. , Cherevko Serhiy 
Published: February 2020

Currently, aqueous electrolytes represent a model system for testing electrocatalyst performance. It is relatively easy to examine activity and stability of electrocatalysts performing simple half-cell electrochemical measurements in such electrolytes. On the other hand, modern electrochemical energy conversion devices such as fuel cells and water electrolysers use solid polymer electrolytes and ionomers in the catalyst layers, while water circulated in the system is deionized. An obvious question arises: "How good are aqueous electrolytes in representing operational conditions of real devices?” This presentation aims to address this question. While electrochemical activity of most catalysts is relatively similar in both environments, stability is not. Both, the extent of catalyst degradation and mechanisms responsible for stability depend on the electrolyte.1,2 Our recent work revealed that dissolution of iridium, as one of the degradation mechanisms, is significantly higher in aqueous acidic electrolytes.3 In order to understand this and other differences, several hybrid systems, i.e. repressing both aqueous and solid electrolytes, have been developed and tested. The main results of these experiments will be shown and discussed in this presentation.
Acknowledgements:
The project CREATE leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 721065.
Literature:
1 Cherevko, S. Current Opinion in Electrochemistry
8, 118-125 (2018).
2 Lafforgue, C. et al.
ACS Catalysis
8, 1278-1286 (2018).
3 Geiger, S. et al. Nature Catalysis
1, 508-515 (2018).
Elucidating the Catalyst-Ionomer-Membrane Interface in Alkaline Exchange Membrane Electrolysis Cells
Authors: Ghoshal Shraboni , Pivovar Bryan S. , Alia Shaun M 
Published: February 2020

In modern day zero gap electrolyzer cells, the fabrication of membrane electrode assembly (MEA) has a pivotal role in determining the performance of a cell. Intricate detail such as choice of membrane and ionomer, ionomer to catalyst ratio and catalyst loadings have been found to affect MEA performances. These factors become more critical in the case of non-precious catalysts where minute modifications can influence the MEA activity to a larger extent than compared to precious group metal catalysts which have high inherent activity. In this work, a combinatorial study using different types of ionomers and alkaline exchange membranes (AEMs) with a variety of supporting electrolytes have been carried out to delineate the effect of membranes and ionomers in an MEA.

References:

1. Leng, L. Wang, M.A. Hickner, C-Y Wang, Electrochim. Acta, 152 93(2015)
2. G-F Li, D. Yang, P-Y. A. Chuang, ACS Catal, 8, 11688 (2018)
Fabrication of CZTSSe Thin Film Solar Cell By Single Step Sulfo-Selenization of Stacked Metal Precursors
Authors: Son Dae-Ho , Kim Seung-Hyun , Kim Se-Yun , Kim Young-Ill , Knag Jin-Kyu , Yang Kee-Jeong , Kim Dae-Hwan 
Published: February 2020

The Cu2ZnSn(S,Se)4 (CZTSSe) thin films are the most promising photovoltaic absorber to replace CIGS, because it is comprised of abundant and inexpensive elements, and have a very high absorption coefficient of over 104 cm−1 with a direct bandgap energy. The theoretical solar conversion efficiency of CZTS-based thin film solar cells is as high as 32.2%. However, the maximum conversion efficiencies reported for electrical characteristics of devices based on these materials are still far from those accomplished more grown CIGS technologies. In order to achieve the efficiency of 20 % or more required for commercial technology, it is necessary to understand the limiting factors of the CZTSSe thin film. A parameter impacting the performance of increasing photovoltaic efficiencies in CZTSSe solar cells is band gap control of absorber through the control of S/(S+Se) ratio of CZTSSe thin films. Most of reported synthesized CZTSSe with high efficiency, the chalcogen composition of the absorption layer was controlled to optimize the characteristics. Most of them explain only the role of S in controlling the band gap in the CZTSSe thin film. It also only describes the characteristics of CZTSSe thin films and devices with different S ratios. However, S element plays another important role in CZTSSe crystal growth process. In this work, we have discussed the different effects of S in the CZTSSe thin film synthesis process. We fabricated CZTSSe thin films using optimized SLG-Mo/Zn/Cu/Sn (MZCT) as a stack structure and described the volatilization phenomenon of Zn element using MZCT stack structure. In addition, we have introduced H2S gas to effectively control the S/(S+Se) of the film in the sulfo-selenization process and to suppress the volatilization of Zn. The S injection process using H2S gas is more uniform and reproducible than any other processes. Unlike the pure selenization process, it was confirmed that a stable ZnSSe thin film was formed on the surface of the precursor during the sulfo-selenization process. The formation of ZnSSe thin film inhibited the volatilization of Zn, which facilitated the control of thin-film stoichiometry and also played an important role in crystal growth. Finally, the characteristics of thin films and devices fabricated through the optimization process are discussed.
Acknowledge: This work was supported by the DGIST R&D Program of the Ministry of Science and ICT (19-BD-05) and the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20173010012980).
(Invited) Keeping It Simple: Anode Free Lithium Metal Cells with Liquid Electrolytes As a Path to Higher Energy Density
Authors: Genovese Matthew , Louli Alex , Weber Rochelle , Martin Cameron , Dahn Jeff R. 
Published: February 2020

In the pursuit of higher energy density, both academia and industry are intensely researching many alternative rechargeable battery concepts beyond conventional lithium-ion cells. The most promising alternatives will be those that can achieve cell level energy density larger than that of state-of-the-art lithium ion batteries at a comparable or lower cost. Based on these criteria, anode free lithium metal cells emerge as potentially useful lithium-ion alternatives as their simple cell construction can enable both high energy density and low cost assembly.
In anode free cells, the negative electrode begins as a bare copper current collector and the lithium metal anode is plated in-situ from the lithium inventory in the cathode. These cells can achieve energy density 40-50% greater than lithium-ion at the cell level and have a simpler cell construction that eliminates the need to handle lithium metal foils or coat active materials on the negative current collector. However, the cycling stability of these cells in conventional carbonate liquid electrolytes is often terrible due to the low CE of lithium metal and the lack of an excess lithium reservoir. In this way, anode free cells exaggerate the technical challenges of lithium metal which makes them excellent test vehicles for optimizing lithium metal cycling.
In this presentation we will highlight our progress in improving lithium metal cycling efficiency in liquid electrolytes toward the development of safe, practical, high energy density anode free cells. Much of this work focuses on the development and characterization of anode free LiNi0.5Mn0.3Co0.2O2 (NMC 532)//Cu wound pouch cells. We demonstrate that the cycling stability and safety of these cells is directly correlated to the morphology of the lithium plated during charge. High surface area mossy lithium deposits in conventional liquid electrolytes lead to fast capacity fade and high anode reactivity. We will also show how many different factors including, cycling rate, charge protocol, applied pressure, temperature, and electrolyte composition affect lithium morphology. Our latest results will be highlighted which show that with the appropriate electrolyte chemistry and cycling conditions, smooth lithium morphology with densely packed columns 50 um in diameter can be achieved after cycling in liquid electrolytes. This excellent lithium morphology significantly improves the capacity retention (Figure 1) of anode free cells and limits the reactivity of the deposited lithium. Cell failure mechanisms will also be addressed with insight as to how these failures can be overcome to further improve cycle life. These results demonstrates that stable cycling of dendrite free lithium metal is possible in simple anode free cells with liquid electrolytes which represents a promising and practical avenue for the design of high energy density batteries.

Figure 1
Fabrication of Carbon-Coated 3D Ni Nanomesh and Its Application As a High Surface Area Electrode Material for Li-O2 Battery
Authors: Kee Yongho , Bardé Fanny , Vereecken Philippe M. 
Published: February 2020

Over the last two decades, post lithium ion battery chemistries with even higher power and energy density, compared to those of conventional lithium ion batteries with intercalation hosts, have been widely researched for application in large scale energy storage. Among various candidates, Li-O2 battery is one of the most promising alternative chemistries, having a theoretical energy of 3505 Wh kg-1 via plating and stripping of Li2O2 with an average working potential of 3 V vs. Li+/Li. However, Li-O2 battery often shows insufficient areal capacity due to the insulating properties of thick Li2O2 layer.
Previously, our group reported the fabrication of a novel 3.3 μm thick 3D Ni nanomesh current collector, which shows excellent surface area to geometric footprint area ratio (100 cm2/1 cm2) and high theoretical porosity (76 %) with systematically controlled nanowire thickness via anodization of aluminum alloys (Fig. 1) [1, 2]. Thanks to its unique properties, the 3D Ni nanomesh qualifies as an excellent current collector candidate for reversible Li2O2 plating and stripping performance over large surface area with the enhanced areal capacity. In this study, we aimed to introduce amorphous carbon, one of the most studied electrode materials for Li-O2 battery, as a coating material for 3D Ni nanomesh via low temperature PECVD technique. To investigate its potential application as an electrode for Li-O2 battery, the galvanostatic charge and discharge profiles of glassy carbon and carbon-coated 3D Ni nanomesh are recorded with the discharging current rate of 0.1 mA cm-2 and the balanced charging current rate of 0.05 mA cm-2 under pure O2 atmosphere. During the preliminary electrochemical measurement, we observed that the carbon-coated 3D Ni nanomesh showed greatly increased discharge and charge areal capacity than those of glassy carbon (102 and 563 times higher than those of glass carbon). In addition to the above-mentioned findings, the ex-situ STEM images of carbon-coated 3D Ni nanomesh after charging and discharging processes will further be discussed.

References

[1] J. Vanpaemel, A. Abd-Elnaiem, S. De Gendt, and P.M. Vereecken, J. Phys. Chem. C, 2015, 119, 2105-2112.
[2] S.P. Zankowski and P.M. Vereecken, ACS Appl. Mater. Interfaces, 2018, 10, 44634-44644.

Fig. 1. Brief description of 3D Ni nanomesh fabrication process and SEM images of as-prepared 3.3 μm thick 3D Ni nanomesh current collector template.

Figure 1
Hydrogen Evolution Reaction on Atomic Layer Deposited Molybdenum Nitride (MoNx) Thin Film on Highly Porous Carbon Cloth-Based Substrate
Authors: Ramesh Rahul , Sawant Sandesh Y. , Nandi Dip K. , Cho Moo Hwan , Kim Soo-Hyun 
Published: February 2020

Using the atomic layer deposition (ALD) technique, a uniform, and conformal thin film of molybdenum nitride (MoNx) is successfully coated on to a highly porous carbon cloth-based substrate. The precursor used in ALD-MoNx is molybdenum hexacarbonyl (Mo(Co)6), and ammonia is used as the nitrogen source, while the temperature and number of ALD cycles are set at 225︒C and 700 cycles, respectively. The phase, surface characteristic, thickness, and conformal deposition of the film is established using XRD, XPS and SEM imaging, respectively. A conformal and uniform film with a thickness of 25–30 nm, and with overall composition c.a. Mo0.59N0.41 is observed. The as-deposited film exhibits predominantly amorphous characteristic, with a minor nanocrystalline nature. The film has noticeable oxygen contamination, mainly at the surface. Hydrogen evolution reaction (HER) performance of the as-prepared electrode is evaluated in 0.5 M H2SO4 electrolyte in a conventional three-electrode setup using the Ag/AgCl (3 M KCl) and graphite rod, as reference and counter electrode, respectively. The electrode exhibits good HER performance attributed to the high surface area of the substrate. Further, the porous structure of the electrode is systematically investigated using SEM imaging, and electrochemical impedance spectroscopy (EIS). A direct correlation of pore geometry is established by studying the HER at different overpotential, electrode composition, and nature of the electrolyte.
Acknowledgement
This work was financially supported by the MOTIE (Ministry of Trade, Industry & Energy (#10080651) and KSRC (Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device and the Advanced Technology Center Program (#10077265) funded by the MOTIE (Ministry of Trade, Industry & Energy) of the Republic of Korea