bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulse Reverse Alloy Plating for Increased Lifetimes for Biocombustors
Authors: Xu Jing , Hall Timothy D. , Vijapur Santosh H. , Wang Dan , Taylor E. J. , Inman Maria , Snyder Stephen , Brady Michael
Published: February 2020

Biomass embodies tremendous potential as a renewable energy resource. According to the biomass Thermal Energy Council (BTEC), biomass energy is renewable, carbon neutral, domestic and technologically mature. In addition, the low cost per BTU of wood chips and pellets relative to fossil fuels makes biomass an attractive thermal energy source. Furthermore, ~7% of global energy consumption comprises small-scale biomass combustion,[1] representing a tremendous market for technologies that facilitate enhanced biomass utilization. However, a major challenge associated with utilization of biomass is its combustion behavior. The moisture content, chemical composition, and combustion efficiency varies depending on the source of biomass. Small scale biomass combustors (Figure 1) which for cost reasons are often constructed of mild or low-alloy steels, during operation are subjected to corrosive environments which include alkali halides (borne, e.g., by fly ash particulates), mineral/halogen acids and water; as well as various others such as sulfur and nitrogen oxides. There is a need to create more efficient, longer lasting, cleaner, and cost effective cookstoves for use in burning biomaterials. The materials used for cookstoves must improve burning efficiency, must be able to operate at higher temperatures, and should be low cost material systems to durably perform in the corrosive environments.

Within this context, Faraday Technology is working on developing low cost and high value corrosion-resistant alloy coatings for existing bio-combustors or lower cost steels with the goal of increasing their functional lifetime, while reducing the component cost. The manufacturing process involves electrodeposition of binary/ternary/quaternary alloys consisting of [Ni/Co]-Cr-[Mo/Fe] onto a low cost substrate and subsequent accelerated high temperature corrosion evaluation. A wide array of electrolytes and processing parameters were evaluated in order to understand these effects on the deposit composition, structure, and high-temperature corrosion resistance properties towards the goal of developing an ideal alloy coating. Specifically, 100 wt% Cr, 7 wt% Co- 93 wt% Cr binary and 15 wt% Ni – 20 wt% Cr – 55 wt% Co (NiCoCr) ternary alloy coatings demonstrated enhanced corrosion resistance when exposed to an aggressive environment (~700°C, 1000 hr, coating surface salted with ~1 mg/cm2 every 100 hours). When compared to the SS base material the Cr/CoCr alloy coatings exhibited effective protection to the substrate and over 10 times lifetime improvement to its base material.

Acknowledgements: The financial support of DOE Contract No. DE-SC0013870 is acknowledged.

[1] Biomass Production Now 10 Percent of World Energy, http://www.realclearenergy.org/charticles/2013/09/26/biomass_production_now_10_percent_of_world_energy_107257.html. Accessed 12 Jan 2015.

Figure 1
Influence of Pulse Parameters on a b Cuzn Alloys Electrodeposited Coatings
Authors: Dridi Amina , Dhouibi Leila , Hihn Jean-Yves , Bercot Patrice , Rezrazi El-Mustafa , Sassi Wafa
Published: February 2020

Cu-Zn alloys is the most manufactured copper alloy in the word since it offers a wide range of properties depending on its zinc content. Although brass plating has been studied since 1841 by Ruoltz, and despite several studies devoted process improvement, CuZn coatings from non-cyanide baths shows low reproducibility, poor adhesion, inhomogeneous color and frequently cannot be deposited directly on steel. These problems are mainly attributed to an unusual crystalline phase distribution[1] [2]. Therefore, to obtain a higher quality of metallic electrodeposited alloy, it is mandatory to control the activity of the nobler ion in the solution, which is much more likely to be reduce. To that end, copper and zinc reduction potentials have to be bring closer by the use of a complexing agent of the copper ions. An electrolyte with a low citrate concentration has been developed and its electrochemical behavior extensively studied [3]. Varying Citrate concentrations will influence zinc electrodeposition and bath stability, giving the hand of the control of alloy element content. For the optimum conditions, CuZn coatings were obtained in a large range of Zn content (from 11% to 100%) as a function of Zn concentration and current density. Crystalline structures of the α β brass deposits were then identified in the range of 35% to 45% in Zn content, in order to be compared to commercial cast brass. The present study discusses the effect of pulse current for a selection of electrolytes, at the optimum of copper and citrate concentration. Wave modulation is investigated in order to compare Zn content and phase distribution for the same average current density. A particular focus was made on the quantification by XRD phase determination and its comparison with anodic dissolution. The best conditions have been tested on larger samples, to check adherence, homogeneity and to try to reach a maximum coating thickness and the right physical aspect than for the cast brass alloys.

[1] J.C. Ballesteros, L.M. Torres-Martínez, I. Juárez-Ramírez, G. Trejo, Y. Meas, Study of the electrochemical co-reduction of Cu2+ and Zn2+ ions from an alkaline non-cyanide solution containing glycine, J. Electroanal. Chem. 727 (2014) 104–112. doi:10.1016/J.JELECHEM.2014.04.020.

[2] T. Vagramyan, J.S.L. Leach, J.R. Moon, On the problems of electrodepositing brass from non-cyanide electrolytes, Electrochim. Acta. 24 (1979) 231–236. doi:10.1016/0013-4686(79)80030-4.

[3] A. Dridi, L. Dhouibi, J.Y. Hihn, P. Berçot, W. Sassi, E.M. Rezrazi, Study of the influence of complexes stability on the kinetic of CuZn electroplating in a citrate bath, Submitted Electrochim. Acta.

Figure 1
Optimal Pulse Charging for the Dendritic Electrodeposition in Mesoscale Electrodes
Authors: Aryanfar Asghar , Colussi Agustin J , Goddard William A , Hoffmann Michael R.
Published: February 2020

We develop an analytical criterion, for the optimal pulse-charging of the sharp dendrites on coarse time period, beyond time-scales of inter-ionic collision, verified by our experimental investigation. We quantify the optimum rest period based on the competitive interplay between diffusion and electromigration as key factors for ionic flux. Additionally, we define a measure for the formation and relaxation of concentration gradients in the vicinity of curved dendrites, which is has critical role on the rate of growth. The accumulation such charge carriers during pulse period, in fact, can relax during a subsequent rest/reverse pulse period, preventing further local quickening ramified growth. Our dimension-free analysis permits the application of our results to a variety of electrochemical systems in all scales.

Figure 1
Pulse Reverse Current Surface Finishing for Plating on Passive Surfaces
Authors: Hall Timothy D. , Xu Jing , Inman Maria , Taylor E. J.
Published: February 2020

Faraday will describe our recent work on the development of a one-step electrochemical surface preparation process to prepare aluminum (6061) for direct electrodeposition. Coating on aluminum commonly requires extensive and specialized surface pretreatment processes prior to deposition, owing to aluminum’s reactive nature and affinity for oxygen. However, Faraday has recently developed a simple pretreatment process utilizing our pulse reverse electrofinishing approach that can dramatically reduce the procedures to prepare the surface for the deposition on Al in an environmentally benign solution. In our ongoing programs we have demonstrated the potential of a single step pretreatment process that can prepare the surface for deposition such that functional layers of Ni, NiP, or ZnNi can be electrodeposited directly to the 6061 Al surfaces.
Insights Onto the Active Sites and Reactivity of Metal-Doped Carbonaceous Electrocatalysts for the CO2 Reduction Reaction
Authors: Asset Tristan , Matanovic Ivana , Chen Yechuan , Artyushkova Kateryna , Atanassov Plamen
Published: February 2020

The CO2 valorization, i.e. its use in various electrochemical processes resulting in the production of carbon-based fuels and value-added chemicals, is of critical importance. Hence, the CO2 reduction reaction (CO2RR) has been widely investigated on electrocatalysts ranging from Cu-based nanostructures to carbonaceous materials. The latter often consist of carbon with atomically dispersed nitrogen and metals atoms (M-N-C, see Figure 1c). Such materials have been discussed in the literature, mostly using Fe as the metallic element 1 (but also Mn, Ni, Co and Cu 2–4), thus providing insights onto this family of electrocatalysts reactivity. But most of those electrocatalysts, as a result of their synthesis process, presents unwanted metallic contaminants 2. Here, we synthesized M-N-C electrocatalysts (with M = Cr, Mn, Fe, Co, Ni, Cu & Zn) using the sacrificial support method, that resulted into non-contaminated M-N-C materials. We then combined electrochemistry and density functional theory to separate the electrocatalysts in several categories, based on their COads binding strength. The strong COads binder electrocatalysts (e.g. Cr, Mn and Fe-N-C) achieved a Faradaic efficiency up to 50% at 0.35 V vs. RHE (at pH = 7.5, in 0.1 M phosphate buffer), as well as a metal-free electrocatalyst synthesized by the same method. This phenomenon was further investigated using near-ambient pressure XPS, which evidenced that the preferential adsorption site for CO2 was dependent of the metallic element nature: for Fe-N-C, the CO2 preferentially adsorb on pyridinic and hydrogenated (pyrrolic) nitrogen moieties (see Figure 1), hence evidencing the key role played by said moieties in the reactivity of the M-N-C electrocatalysts for the CO2RR.

(1) Varela, A. S.; Ju, W.; Strasser, P. Adv.
Energy Mater.
2018, 8 (30), 1–35; (2) Ju, W.; Bagger, A.; Hao, G. P.; Varela, A. S.; Sinev, I.; Bon, V.; Roldan Cuenya, B.; Kaskel, S.; Rossmeisl, J.; Strasser, P. Nat.
Commun.
2017, 8 (1), 1–9; (3) Varela, A. S.; Ranjbar Sahraie, N.; Steinberg, J.; Ju, W.; Oh, H. S.; Strasser, P. Angew.
Chemie - Int. Ed.
2015, 54 (37), 10758–10762; (4) Hu, X. M.; Hval, H. H.; Bjerglund, E. T.; Dalgaard, K. J.; Madsen, M. R.; Pohl, M. M.; Welter, E.; Lamagni, P.; Buhl, K. B.; Bremholm, M.; Beller, M.; Pedersen, S. U.; Skrydstrup, T.; Daasbjerg, K. ACS Catal.
2018, 8 (7), 6255–6264.

Figure 1
Leveraging Advanced Manufactured Catalysts and Reactors for Electrochemical CO2 Conversion
Authors: Feaster Jeremy T. , Lucci Felicia , Qi Zhen , Wood Marissa , Deotte Joshua , Dudukovic Nikola , Liang Siwei , Druzgalski Clara , Beck Victor A , Li Wenqin , Baker Sarah E , Duoss Eric B
Published: February 2020

With the realization of the global impact of waste carbon on the atmosphere, coupled with a clear and growing demand for abundant electricity, there are both environmental and economic driving forces for capturing and electrochemically converting carbon dioxide (CO2) into high value hydrocarbon products. While much of the recent focus in this area has been driven by catalyst discovery, there is a lack of understanding on how the partnership of the catalyst and the reactor can be optimized for product selectivity and overall performance. The development of novel and optimized electrochemical reactors for this reaction is critically important; to address this gap, we report the use of advanced materials and manufacturing capabilities to design and construct electrocatalysts and electrochemical reactors for CO2 reduction. We report that by 3D printing catalysts and reactors, we can affect catalyst morphology, environment and reaction conditions, and thereby improve performance of Ag and Cu catalysts for electrochemical CO2 reduction. Our work at LLNL demonstrates our ability to leverage 3D printing and advanced manufacturing as tools to help study and improve catalyst activity, product faradaic efficiency, and overall energy efficiency.
Low-Overpotential Electrochemical Reduction of CO2 to Formic Acid on Surface-Modified Doped Tin Oxide Pellets
Authors: Abdul Emmanuel Oluwaseun , Pitts Jason , Rajput Deepak , Rananavare Shankar
Published: February 2020

Gas sensors fabricated with antimony doped tin oxide (ATO) nanomaterials exhibit remarkable sensitivity for detecting oxidizing and reducing gases. This study highlights the enhanced selectivity and stability of the porous ATO nanomaterial electrode made for electrochemical reduction of CO2 in aqueous media. During electrochemical reduction, these electrodes prepared from compressed powders tend to crumble within a few hours in aqueous media. To overcome this electrode disintegration effect, we modified the surface of the doped tin-Oxide nanoparticles and nanowires with Nafion and a dipodal silane (1,2-Bis(triethoxysilyl)ethane). The electrode characterization studies include Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). Scanning electron microscopic investigation of electrode surface morphology and roughness before and after electrochemical CO2 reduction for derivatized and underivatized electrode revealed lower surface roughness for former than the latter.

The derivatized electrodes allowed CO2 electrochemical reduction at low overpotentials and high current density without any electrode crumbling over more than 24 hours of continuous operation. Formate/formic acid and methanol were the major products of reduction at electrode potentials ranging from -0.4 to -1.0V vs. RHE in the CO2 saturated 0.1M KHCO3 electrolyte. Higher current density and Faradaic Efficiency of formic acid was observed when compared to planar tin electrode materials and tin oxide nanoparticles deposited on FTO glass.
Not Your Ordinary Etching: Metal-Assisted Chemical Etch (MacEtch) for III-V and Wide Bandgap Semiconductors
Authors: Li Xiuling
Published: February 2020

Metal-assisted chemical etching (MacEtch) is an unorthodox anisotropic etching method, that defies the isotropic nature of wet etch through local electrochemical effect. In this talk, I will discuss the history, mechanism, and its applicability at the device level to Si, Ge, GaAs, InP, InGaAs, and wide bandgap semiconductors including beta-Ga2O3
. In particular, forward MacEtch, where etching takes place directly underneath the metal catalyst patterns, produces site-controlled semiconductor nanostructures with unpresented aspect ratio (> 100:1). Inverse-MacEtch (I-MacEtch), bypassing the metal edge roughness, allows the formation of atomically smooth and damage-free sidewalls. Magnetic-field guided MacEtch (h-MacEtch) enables 3D control of the etching trajectory. Self-anchored catalyst (SAC)-MacEtch, using porous catalyst patterns, leads to the fabrication of vertical vias by preventing the catalyst from detouring. This etching method could have profound impact on a wide range of semiconductor fabrication processes, because of its simplicity, versatility, and the absence of high energy ion-induced damage.
The Influence of Anode/Cathode Capacity Ratio on Cycle Life and Potential Variations of Lithium-Ion Capacitors
Authors: Naderi Roya , Shellikeri Annadanesh , Hagen Mark Andrew , Zheng Jim P.
Published: February 2020

Lithium-ion capacitors (LICs) incorporate the fundamental features of intercalation battery materials and double-layer capacitor materials, to bring together the desirable combination of high energy and power densities, long cycle life and materials stability. But, the presence of battery materials in anode also contribute towards LIC’s long-term capacity fade, based on its extent of utilization. This work studies the importance of anode to cathode capacity ratio, and its influence on the electrodes potential variation and capacity decay behaviors. In a LIC system based on activated carbon (AC) and hard carbon (HC), we show that increasing the HC:AC capacity ratio from 1.1 to 3, boosts the capacity retention of the LIC by 10% after 2,000 cycles at 1C rate, and by 28% after 20,000 cycles at 60C rate. During the intermittent EIS and 3-electrode galvanostatic tests at 0.25C rate, lower anode over-potential is observed for LIC with larger anode to cathode capacity ratio. Pointing towards a reduced charge transfer and Warburg diffusion resistances, based on the potential at which the anode was operating.Attached Figure illustrates the relationship between the anode potential and cell impedance. Points marked as a,b,c, and d represent the deintercalated anode potential of LIC-1.1, LIC-2, LIC-3 and intercalated potential of all three LICs, respectively. The 1C and 60C rates long term tests , and intermittent EIS and 3-electrode tests at 0.25C rate were all in agreement that LIC with larger HC:AC capacity ratio had a better electrochemical performance.

Figure 1
(Invited) Two-Dimensional Layered Materials Toward Phase-Engineered Hybrid Films
Authors: Chueh Yu-Lun
Published: February 2020

2D materials have attracted much attention because of frontier electronic materials due to its superior electronic transport properties and mechanical flexibility in the future, making it a potential material for high performance and wearable electronics. Graphene is a typical 2D materials with high carrier mobility; however, it still cannot be applied in transistor due to the lack of bandgap. A new type of 2D semiconducting materials called transition metal dichalcogenides (TMDCs), which are layered structure with the strong in-plane bonding and weak out-of-plane interactions similar to graphite, have been intensively studied. Recent studies have predicted exceptional physical properties upon reduced dimensionality attracting lots of attention due to the versatile physical chemical behaviors. Nevertheless, the synthesis and the study of the fundamental physical properties of TMDs are still in early stages. The lack of a large-area and reliable synthesis method restrict exploring all the potential applications of the TMDs. Chemical vapor deposition (CVD) is a traditional approach for the growth of TMDs; nevertheless, the high growth temperature is a major drawback for its to be applied in flexible electronics. In this talk, an inductively coupled plasma (ICP) was used to synthesize Transition Metal Dichalcogenides (TMDs) through a plasma-assisted selenization process of metal oxide (MOx) at a low temperature, as low as 250 °C. Compared to other CVD processes the use of ICP facilitates the decomposition of the precursors at lower temperatures; therefore, the temperature required for the formation of TMDs can be drastically reduced. WSe2 was chosen as a model material system due to its technological importance as a p-type inorganic semiconductor with an excellent hole mobility. Large-area synthesis of WSe2 on polyimide (30 x 40 cm2) flexible substrates and 8-inch silicon wafers with good uniformity was demonstrated at the formation temperature of 250 °C as confirmed by Raman and X-ray Photoelectron (XPS) spectroscopy. Furthermore, by controlling different H2/N2 ratios, hybrid WOx/WSe2 films can be formed at the formation temperature of 250 ºC as shown by TEM and confirmed by XPS. The applications including (1) water splitting, (2) gas sensors and (3) photodetectors will be reported.
Between Physical Complexity and Simplicity: Nailing Down the Cathodic Activation Overpotential in a Small-Scale PEM Fuel Cell
Authors: Gerling Christophe , Hanauer Matthias , Berner Ulrich , Friedrich K. Andreas
Published: February 2020

Understanding the kinetics of polymer electrolyte fuel cells (PEFC) remains a key issue for the optimization of the catalyst layer structure with respect to fuel cell performance and ageing.

In this study, firstly the impact of hydrogen crossover from anode to cathode through the membrane on the measurable open circuit voltage (OCV) is analyzed extensively. For this purpose, all the other parasitic reactions like platinum oxide formation or carbon corrosion are neglected in a first approach and the influences of the operating conditions on the crossover flux by means of voltammetry measurements and also mass spectrometry in the cathode exhaust gas are examined. These experimental results yield an efficient parameterization of the crossover rate. Incorporated into a physical 1D through-plane cell simulation model, it allows for consistent predictions at and close to OCV conditions.

Subsequently, the activation overpotential is parameterized experimentally thanks to electrochemical impedance spectroscopy on a 25 cm2 cell with a straight parallel channel flowfield under differential conditions. Therefore, spectra are recorded for a large range of conditions (Fig. 1a) and the distribution of relaxation times (DRT) is evaluated (Fig. 1b). As a result, an equivalent circuit is set up. Hence, it is possible to fit the experimental data and to extract the kinetic parameters for our model, as functions of electrical load, oxygen partial pressure and temperature. We finally use this extensive dataset for comparing different approaches for modelling the oxygen reduction reaction (ORR) on platinum, ranging from single-step Butler-Volmer kinetics to advanced microkinetic models that take into account the intermediates of the ORR and thereby also the potential dependent surface coverage of the electrode [1-2].

References:

Huang, J. Zhang, M. Eikerling, Phys. Chem. Chem. Phys., 2018, 20, 11776

Holewinski, S. Linic, J. Electrochem. Soc., 159 (11) H864-H870 (2012)

Figure 1
(Invited) Exploring Sub-Second and Sub-Micron X-Ray Tomographic Imaging of Liquid Water in PEFC Gas Diffusion Layers
Authors: Xu Hong , Marone Federica , Nagashima Shinya , Nguyen Hai , Kishita Keisuke , Büchi Felix N. , Eller Jens
Published: February 2020

In the last decade X-ray tomographic microscopy (XTM) has become a powerful 3D characterization technique for polymer electrolyte fuel cells (PEFCs). Extensive work has been implemented to characterize the gas diffusion layer's (GDL) microstructure and its influence on gas phase transport, degradation phenomena within the membrane or catalyst layer, the wetting behavior of GDLs, as well as the water distribution during cell operation. Especially sub-second operando XTM [1] is essential to enable the fundamental understanding of the water transport modes in the GDL which is vitally important for improving PEFCs performance, cost and durability. Thanks to recent microscope upgrades and the use of a wider energy range of the synchrotron radiation it is meanwhile possible to realize operando XTM scans of PEFCs with scan times of 0.1 s to 0.25 s at voxel sizes of 2.75 µm [2] or 0.4 µm, respectively, at the TOMCAT beamline of the Swiss Light Source at Paul Scherrer Institut (PSI). This presentation will give insights into these recent achievements and discuss selected case studies benefiting from the improved temporal and spatial resolution.

References

[1] J. Eller, F. Marone, F. N. Büchi, ECS Trans. 69(17), 523–531 (2015).

[2] M. Bührer, M. Stampanoni, X. Rochet, F. Büchi, J. Eller, F. Marone, J. Synchrotron Rad., (accepted).
Beyond Nafion: Structure-Property Relationships in Novel Perfluorinated Ionomers with Tunable Transport Properties
Authors: Modestino Miguel Antonio , Katzenberg Adlai , Fang Minfeng , Okamoto Yoshiyuki , Kusoglu Ahmet
Published: February 2020

Rapid improvements in fuel cell performance have been driven by the development of commercially available ionomers used as membranes and catalyst binders in membrane electrode assemblies (MEAs). Commercially available ionomers share a semi-crystalline polytetrafluoroethylene (PTFE) matrix, which imparts low gas permeability and high mechanical and makes them attractive membrane materials. At the same time, the slow permeation of gases (i.e., oxygen and hydrogen) through the ionomers introduces significant mass-transport losses in the catalyst layers, ultimately limiting fuel cell performance. In this study, we present a new family of perfluorinated ionomers that incorporate an amorphous matrix based on a perfluoro(2-methylene 4-methyl-1,3-dioxolane) (PFMMD) backbone. The introduction of a PFMMD backbone disrupts the crystallinity of the matrix, increases the ionomers’ free volume, and significantly improves their gas permeability (permeability >3x that of Nafion). On the other hand, the dioxolane backbone increases the glass transition temperature of the matrix, restricting its mobility, which in turn limits the ionomer domain swelling and reduces its proton conductivity. In this presentation, I will present a facile and flexible synthesis method for PFMMD-based ionomers with tunable sulfonic acid content. Furthermore, I will describe structure-property relationships in these materials derived from a combination of transport measurements (i.e., water uptake, proton conductivity, and permeability) and morphological characterization through Small- and Wide-angle X-ray scattering. Lastly, I will discuss the implication and potential utilization of these new materials for improved fuel cell performance. The results presented here underscore the significance of tailoring materials chemistry to specific requirements of fuel cell or electrolysis MEAs.
Multiwalled Carbon Nanotubes As Non-Precious Metal Catalyst for the Oxygen Reduction Reaction
Authors: Kübler Markus , Theis Pascal , Ni Lingmei , Wagner Stephan , Jurzinsky Tilman , Kramm Ulrike Ingrid
Published: February 2020

Fuel cells are regarded as environmentally friendly energy converters. This, in combination with national and global intentions of energy transition from fossil based resources to renewable ones, makes fuel cells a possible key technology regarding the future energy economy. Because of their advanced state of development, proton exchange membrane fuel cells (PEMFCs) are considered to be the most promising type of fuel cells in terms of commercial use in automotive propulsion. Nevertheless, the high requirements of precious platinum metal for the cathodic oxygen reduction reaction (ORR) is one major reason that still prevents a wide-spread use of this technology to this day. A promising alternative to platinum based catalysts are the so-called non-precious metal based materials. To this day, these catalysts already achieve high current density during PEMFC operation but still need major improvements regarding their durability.

In this work, the preparation and characteristics of nanotube based non-precious metal catalysts for the ORR are presented. For the commonly applied platinum based ORR catalysts the positive impact on durability and activity of using carbon nanotubes (CNTs) as carbon support has already widely been proven [1-3]. Here, three different catalyst preparations are presented. First, utilization of commercially available CNTs together with Fe-phenathroline leads to catalyst where FeNxCy moieties are present in-between the CNTs. Secondly, a preceding surface modification step of the commercially available CNTs leads to a material with the active sides directly attached onto the CNTs surface. The third preparation route gives a material where the FeNxCy moieties are directly incorporated into the nanotubes wall. TEM pictures are presented in order to show the structural morphology of the resulting catalysts and the nature of the iron nitrogen active sides is studied via Mößbauer spectroscopy. ORR activity and durability of the resulting nanotube based materials in acidic electrolyte is investigated. PEMFC performance tests clearly show that the connection between active side and nanotube play a crucial role for the activity of the catalyst. Hence, a significantly enhanced performance is found for the catalyst with the active sides incorporated into the nanotube walls.

References:

[1] X. Wang, W. Li et al., Journal of Power Sources
158 (2006) 154-159.

[2] F. Hasché, M. Oezaslan et al., Phys Chem Chem Phys
12 (2010) 15251-15258.

[3] T. Maiyalagan, B. Viswanathan et al., Electrochem. Comm.
7 (2005) 905-912.
Molten Hydroxide Dual-Phase Membranes for Intermediate-Temperature Fuel Cells
Authors: Vedharathinam Vedasri , Ivanovskaya Anna N , Cerón Maira R. , Campbell Patrick G. , Elangovan S , Hartvigsen Joseph J , Frost Lyman J
Published: February 2020

Anion exchange membrane (AEM) fuel cells are sought after due to its enabled adoption of non-precious metals as electrocatalysts and enhanced reaction kinetics at high pH conditions[1]. Typical polymer membranes contain quaternary ammonium or phosphonium group polymers that conduct ions at temperature below 90°C[2], limiting their applications at elevated temperatures. Nevertheless, elevated temperature operations allow for improved electrode kinetics, system efficiency and simplified heat management. Hence, there is a need to develop hydroxide ion conducting membranes that are chemically and mechanically stable and can operate at intermediate temperature ranges (150 - 400°C) without compromising its ionic conductivity. Here we report a novel hydroxide-ceramic dual-phase (HCDP) membrane technology that utilizes molten alkaline hydroxides (e.g. sodium, potassium, and lithium) impregnated into the porous zirconia matrix[3]. When using air as oxidant, hydroxide ions react with from air to form carbonates leading to performance degradation of the fuel cell due to loss of ionic conductivity. The poisoning effects are rapid and severe, necessitating the use of pure oxygen instead of air as cathode feed. Our proposed technology overcomes the poisoning issue while air feed operation by shifting the chemical equilibrium of the undesired carbonate ions toward hydroxide and in the presence of water at elevated temperatures, thus releasing from the electrolyte in situ during fuel cell operation. This contribution will highlight our recent developments in this area.

[1] Urquidi-Macdonald, M.; Sen, A.; Grimes, P.; Tewari, A.; Sambhy, V. NSF Report from Penn State. https://arxiv.org/pdf/physics/0504130

[2] Hibino, T.; Kobayashi, K., Journal of Materials Chemistry A
2013,
1 (24), 7019-7022

[3] Cerón, MR.; Lai, SZ.; Amiri, A.; Monte, M.; Katta, S.; Kelly, JC.; Worsley, MA.; Merrill, MD.; Kim, S.; Campbell, PG.; Journal of Membrane Science 2018, 567, 191-198
Improvements of CoPx Stability By Cathodic Protection in Discontinuous and Interrupted Operations of Alkaline Water Electrolysis
Authors: Kim Ik-Sun , Cho Hyun-Seok , Cho Won-Chul , Kim Sang-Kyung , Joo Jong Hoon , Kim Chang Hee
Published: February 2020

This paper presents a study of the degradation phenomena of Cobalt phosphides (CoPx), which is attracted as the hydrogen evolution reaction (HER) electrode for alkaline water electrolysis cells(AWEs).1-9 Although the HER activity of CoPx showed 100-fold HER activity enhancements over a nickel catalyst, the kinetic current for the HER after discontinuous and interrupted operations was observed to decrease as shown in Figure 1. During the shut-down of the AWEs, the cathode potential changed from -1.03V to -0.8V (vs. Hg/HgO), which is close to the equilibrium potential of Co oxidation reaction to Co(OH)2. Once Co(OH)2 was formed on CoPx electrode, the kinetic degradation was not recovered even though voltage sweep was applied. We employed cathodic protection to mitigate degradation of the CoPx electrode by shifting the potential of the electrode below the open circuit voltage of Co(OH)2. For the cathodic protection case, Mn was co-deposited with the CoPx electrode as a sacrificial species, which reduces the electrode degradation rate by negative polarization of the electrode. The results showed that by the co-depositing even small amount of Mn into the CoPx electrode could restrain HER performance loss during the repeat of discontinuous operation of the AWEs. That is, controlling the performance loss with the cathodic protection is applicable to ensure the stability of the CoPx electrodes of the AWE system for the integration with renewable powers.

Figure 1. Stability improvements for CoPx HER electrodes in 5 h discontinuous operation by the cathodic protection

Acknowledgements

The authors gratefully acknowledge financial support for this work by the Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) funded by the Ministry of Science and ICT (NRF-2015M1A2A2074657).

R
eferences

[1] A. Goryachev L. Gao, Y. Zhang, R. Y. Rohling, René. H. J. Vervuurt, A. A. Bol, J. P. Hofmann, E. J. M. Hense, ChemElectroChem 2018, 5, 1230-1239

[2] Q. Liu, J. Tian, W. Cui, P. Jiang, N. Cheng, A. M. Asiri, X. Sun, Angew., Chem. Int. Ed. 2014, 53, 6710–6714.

[3] E. J. Popczun, C. G. Read, C. W. Roske, N. S. Lewis, R. E. Schaak, Angew. Chem. Int. Ed. 2014, 53, 5427–5430.

[4] N. Jiang, B. You, M. Sheng, Y. Sun, Angew. Chem. Int. Ed. 2015, 54, 6251–6254.

[5] Z. Huang, Z. Chen, Z. Chen, C. Lv, M. G. Humphrey, C. Zhang, Nano Energy 2014, 9, 373–382.

[6] F. H. Saadi, A. I. Carim, E. Verlage, J. C. Hemminger, N. S. Lewis, M. P. Soriaga, J. Phys. Chem. C 2014, 118, 29294–29300.

[7] F. H. Saadi, A. I. Carim, W. S. Drisdell, S. Gul, J. H. Baricuatro, J. Yano, M. P. Soriaga, N. S. Lewis, J. Am. Chem. Soc. 2017, 139, 12927–12930

[8] S. Oh, H. Kim, Y. Kwon, M. Kim, E. Cho and H. Kwon, J. Mater. Chem. A, 2016, 4, 18272-18277

[9] J. F. Callejas, C. G. Read, E. J. Popczun, J. M. McEnaney and R. E. Schaak, Chem. Mater., 2015, 27, 3769–3774.

Figure 1
Microwave-Initiated Synthesis of Metal Chalcogenides/Graphene-Catalyst for Enhanced Hydrogen Evolution Reaction
Authors: Zhang Xinyu , Sarwar Shatila , Nautiyal Amit , Cook Jonathan
Published: February 2020

In present days, new types of renewable energy resources are being developed to resolve the world energy crisis. Nanomaterials, such as carbon nanotubes, metal oxides, metal chalcogenides (MCs) and conducting polymers with superior mechanical, thermal and electrical properties, lead to broad applications in composite materials, smart structures, chemical sensors, energy storage and nano-electronic devices. However, the high cost and difficulty in producing large scale, high quality nanomaterials remain challenges. The present work successfully demonstrates the production of MCs on graphene substrate through ultra-fast (60 seconds), facile and energy-efficient microwave-initiated approach. Graphene plays a vital role during the synthesis process by absorbing microwave energy and converting it to heat energy, which facilitates the precursors to react vigorously. Moreover, high specific surface area and conductivity of graphene delivers a favorable conductive network for the uniform growth of MCs, along with rapid charge transfer kinetics. The electrochemical characterizations reveal that the as-produced nanocomposites can be used for hydrogen evolution reaction (HER) to generate useful hydrogen fuel. As an example, the molybdenum disulfide on graphene (MoS2/graphene) composite exhibits superior electrocatalytic activity for the HER in acidic medium, with a low onset potential of only 100 mV and a Tafel slope of 43.3 mV per decade, suggesting the Volmer-Heyrovsky mechanism of hydrogen evolution. Beyond excellent catalytic activity, MoS2/graphene reveals an unusual ability to enhance the accessible active sites during the HER proceeds. This leads to a long cycling stability with a very high cathodic current density, providing the opportunity of practical application for scalable processing. Therefore, this single-step microwave approach can be universally employed to produce other useful MCs (e.g., MoSe2, WS2, WSe2 etc.), that will catalyze substantial development in more widespread uses of MC-based nanocomposites for successful energy applications.
New Avenues to MOF-Derived Cobalt Chalgogenides for Efficient Electrocatalysis
Authors: Das Debanjan , Nanda Karuna Kar
Published: February 2020

Metal–organic frameworks (MOFs) are a class of porous hybrid solids consisting of metal-containing nodes coordinated with multitopic organic linkers. Recently there has been tremendous interest in the exploration of MOFs and their derivatives for electrocatalysis, however slow charge-transport kinetics often limit the performance. Therefore, making suitable carbon composites would greatly improve their electronic conductivity and subsequently the electrocatalytic activity.

Herein, we have developed two different routes using cobalt imidazolate frameworks (ZIF-67) to design cobalt selenide (CoSe) hybridized with nitrogen doped carbon. The solid-state strategy involves direct conversion of ZIF-67 into CoSe nanoparticles with an average size of ~20 nm encapsulated within N-doped graphitic carbon shells with an average size of 300 nm. Interestingly, this method can easily be extended to similarly synthesize CoTe encapsulated N-doped graphitic carbon cages by simply changing the precursor.

The other method involved the self-templated conversion of ZIF-67 into Co nanoparticles encapsulated N-doped carbon polyhedral and their subsequent transformation into vertically aligned CoSe grafted N-doped carbon sheets via a hydrothermal selenization method. Both, these class of materials so synthesized were found to exhibit excellent electrocatalytic activity towards HER and OER in alkaline medium. It is believed that the methods being developed here may be extended to other transition metal chalcogenides for various applications.
Transient Gas Saturation in Porous Transport Layers of Polymer Electrolyte Membrane Electrolyzers
Authors: Lee ChungHyuk , Lee Jason Keonhag , Zhao Benzhong , Fahy Kieran F. , Bazylak Aimy
Published: February 2020

Intermittency of renewable energy sources, such as wind and solar, remains as a major barrier to the establishment of a sustainable energy infrastructure (1). Balancing the supply of intermittent energy with demand requires an energy storage technology capable of operating under dynamic conditions. Over the last decade, polymer electrolyte membrane (PEM) electrolyzers attracted much attention as the ideal energy storage technology for renewable energy generators (2). PEM electrolyzers are favorable due to their wide operating current density range (0.6 – 2.0 A/cm2) and rapid response to dynamic changes (3). However, PEM electrolyzers need to become significantly more efficient to become commercially-viable energy storage technology (4).

A major source of inefficiency stems from the undesired accumulation of oxygen gas in the anode porous transport layers (PTLs), which leads to blockage of reaction sites and water transport pathways in the PTL (5). The overpotential associated with this effect is termed mass transport overpotential, and it can contribute up to 25% of the total overpotential (6). Furthermore, mass transport overpotential could increase exponentially at higher current densities (7). Despite the extensive studies on gas transport in the PTL over the last decade, the effect of dynamic operating condition on the transient gas distribution in the PTL remains unknown. Understanding the transient gas transport through the PTL is an important first step for coupling PEM electrolyzer systems with intermittent renewable energy sources.

In this work, we studied gas transport through the PTL under dynamic operating conditions via in operando synchrotron X-ray imaging. Specifically, we used synchrotron X-ray imaging with high spatial (6.5 µm/pixel) and temporal (2.5 frames per second) resolution to quantify the change in gas volume in the PTL under changing current densities. We observed that the gas volume oscillated at a constant amplitude with a similar frequency over a series of repeating step currents (Fig. 1). We also operated the electrolyzer using a real output power profile acquired from a wind turbine. The results provide insights on the transient behaviour of gas distribution in the PTL of PEM electrolyzers coupled with renewable energy sources.

References

J. A. Turner, Science.,
285, 5428 (1999).

O. Schmidt, A. Gambhir, I. Staffell, A. Hawkes, J. Nelson and S. Few, Int J Hydrogen Energy.,
42, 52 (2017).

M. Carmo, D. L. Fritz, J. Mergel and D. Stolten, Int J Hydrogen Energy.,
38, 12 (2013).

C. K. Mittelsteadt, ECS Transactions.,
69, 17 (2015).

Ö F. Selamet, M. C. Acar, M. D. Mat and Y. Kaplan, Int.J.Energy Res.,
37, 5 (2013).

M. Suermann, T. J. Schmidt and F. N. Büchi, Electrochim.Acta.,
211(2016).

S. Sun, Y. Xiao, D. Liang, Z. Shao, H. Yu, M. Hou and B. Yi, RSC Adv.,
5(2015).

Figure 1
Transparent All-Oxide Photovoltaics and Invisible Photodetectors
Authors: Patel Malkeshkumar , Ban Dong-Kyun , Kim Joondong
Published: February 2020

Heterostructure of wide-bandgap materials have great potential for use in transparent optoelectronics for examples ultraviolet photodetectors, transparent solar cells, and transparent electronics. This study demonstrates the exciton, band-to-band and intermediate-band optical transitions in a ZnO/NiO heterostructure at room temperature. This heterostructure exhibits Ohmic current-voltage characteristics close to that of various metal contacts such as Ag, C, Ni, and Au. Temperature-dependence studies revealed that the open-circuit voltage (VOC) of ZnO/NiO heterostructure is limited by the charge-transfer potential, analogous to excitonic solar cells. A negligibly small dark current of 1.6 × 10-8 A, a large VOC of 675 mV and a photoresponse speeds of 9.4 ms make it promising for high-speed energy-efficient optoelectronics. The optoelectronic performances of the ZnO/NiO/Ag microink suggest that broadband photons can be utilized with incident photons to current conversion efficiencies (IPCEs) of 2% and 39% in the visible and ultraviolet regions, respectively which demonstrate that the ZnO/NiO heterostructure can acts as a broadband quantum photoelectric device.
Conical Nanopores for Efficient Ion Pumping and Desalination
Authors: Zhang Yu , Schatz George
Published: February 2020

Previous experimental and theoretical studies have demonstrated that nanofabricated synthetic channels are able to pump ions using oscillating electric fields. We proposed that conical pores with oscillating surface charges are particularly effective for pumping ions due to rectification that arises from their asymmetric structure. In this work, the energy and thermodynamic efficiency associated with salt pumping using the conical pore pump is studied, with emphasis on pumps needed to desalinate seawater. The energy efficiency is found to be as high as 0.60 to 0.83 mol/kJ when the radius of the tip side of the conical pore is two Debye lengths and the pump works with a concentration gradient smaller than 1.5. As a result, the energy consumption needed for seawater desalination with 20% salt rejection is 0.32 kJ/L. In addition, the energy consumption can be further reduced to 0.21 kJ/L (20% salt rejection) if the bias voltage is adaptively altered four times during the pump cycle while salt concentration is reduced. If the bias voltage is adaptively increased to higher values, then salt rejection can be improved to values that are needed to produce fresh water that satisfies standard requirements. Numerical analysis indicates that the energy consumption is 4.9 kJ/L for 98.6% salt rejection, which is smaller than the practical minimum energy requirement for RO-based methods. In addition, the pumping efficiency can be further improved by tuning the pump structure, increasing the surface charge, and employing more adaptive bias voltages. The conical pores are also found to more efficiently counteract the concentration gradient compared to cylindrical counterparts.
Cation Insertion Engineering of Multi-Gradient Oxygen Electrocatalysts for Rechargeable Quasi-Solid-State Zinc–Air Batteries
Authors: Xu Nengneng , Qiao Jinli , Zhou Xiao-Dong
Published: February 2020

There is an urgent need to develop high power density, economical, and safe energy-storage systems. In the last few decades, zinc-air batteries have attracted widespread interest because of the superior safety, high energy density (1086 Wh kg-1), low cost, and natural abundance of Zn. However, Zinc-air batteries are limited by the poor durability and sluggish kinetics of and oxygen evolution/ reduction reactions. In this work, different transition metal (M= Fe, Co and Ni) ions are doped on the surface of MnO2 to activate the neighbor Mn active sites via cation insertion engineering. As a result, M-MnO2-CNTs exhibits superior oxygen evolution/ reduction reactions activities with the low potential difference (ΔE) of 0.85 V, high power density of 534 mW cm-2, and high charge-discharge stability of 200 hours.
Preparation of Bacterial Cellulose Based Polymer Anion Exchange Membrane and Application for Fuel Cell
Authors: Guo Xiaojing , Qiao Jinli
Published: February 2020

Nowadays, due to the excellent situation of fuel cell with high energy conversion rate and environmental protection, domestic research on fuel cell is endless. Electrolytes, as an important part of it, are extremely important. However, the ordinary electrolyte is liquid, which causes a lot of trouble and is especially inconvenient to carry. Therefore, liquid electrolyte is replaced by solid electrolyte in this paper. In addition, because bacterial cellulose (BC) membrane has many characteristics such as ultra-fine mesh structure, high mechanical strength, low cost and nice degradability, etc., which was used as the matrix scaffold in this paper and was doped with quaternary ammonium salt (QA) of PDDA to prepare a new anion exchange membrane called BC-PDDA. Furthermore, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal analysis (TG), ion exchange capacity (IEC) and mechanical properties of BC-PDDA membrane were depicted in detail to explore their applicability in fuel cells. It was found that BC-PDDA membrane has strong mechanical properties and high anionic conductivity (OH-) , which reaches 0.051 S cm-1, and has broad application potential in fuel cells.
(Invited) Understanding the Solid-Electrolyte and Electrode Interface via First-Principles Prediction of Potentials and Space-Charge Layers in All-Solid-State Batteries
Authors: Qi Yue , Swift Michael
Published: February 2020

Solid-state electronic heterojunctions at the solid-electrolyte and electrode interfaces play a critical role in determining ionic transport, and therefore the performance of solid-state batteries and fuel cells. The formation of a “space-charge layer” at the solid electrolyte and electrode interface is often cited as a barrier for ion transport, but a comprehensive first-principles modeling approach is still missing. For solid-state-batteries (SSB), predicting the space-charge-layer formation at the solid-electrolyte-and-electrode interface is even more challenging, as ion insertion and/or reaction with the electrode alters the material and thus band alignments at the interfaces.

In this talk, we established a theoretical framework to predict the interface potential profiles from thermodynamic driving forces [1]. We first assumed the electrochemical potential for Li+ ions reached a constant at the open circuit equilibrium condition, then derived the relationship among the electrostatic potential, the lithium chemical potential, Fermi level, ionization potential, and the work function. This relationship yielded quantitative profiles of the electrostatic potential and electronic energy level alignments across the entire battery. This model complemented direct microscopic and macroscopic simulations by rigorously and simultaneously determining the potential drop, electrostatic dipole, and space-charge layer at the interface.

The application of this model to the Li/LiPON/LixCoO2 system led to the important discovery that the space-charge layer varies with the state of charge (SOC, i.e. Li concentration in LixCoO2). More specifically we predicted that Li+ transferred from LIPON to Li0.5CoO2, but transferred from Li1.0CoO2 to LiPON, this result unified the seemingly contradictory experimental observations. We also predicted that electron transfer caused the interface dipole that can accelerate or impede Li+ flow during the discharge process at the in LixCoO2/LiPON interface, depending on the SOC. This will have a profound impact on the overpotentials and the overall cycling efficiency. An important design rule was suggested that increasing solid electrolytes’ valence band or engineering the interlayer at the interface can overcome the additional barrier caused by the interface dipole.

This modeling framework is general for other solid-state energy storage devices with ionic and mixed conductor interfaces.

[1] Michael W. Swift and Yue Qi, Phys. Rev. Lett. 122, 167701 (2019)