bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Internal Stress of Ni Electroplated Samples in Sulphamate Solutions
Authors: Aykac Busra , Erdogan Metehan , Karakaya Ishak
Published: February 2020

Electroplating is a surface modification process that does not alter the bulk properties of the substrate and is conducted for improving the surface appearance, generally increasing the corrosion and wear resistance of the material to be electroplated [1]. There are several metals that can be electroplated such as Ni, Cu, Au, Co, Cd, Zn, etc. or the alloys thereof. Among these metals, Ni is the most commonly preferred one. Through the last five decades, the technology of electroplating of nickel extensively developed into a broad range of industrial coatings for both decorative and functional applications. The annual commercially electroplated nickel is over 150,000 tones worldwide [2] due to the useful properties of Ni as a coating and its versatility.

There are several types of baths based on nickel chloride, nickel sulfate and nickel sulphamate [3] for Ni electroplating. Among these, the advantages of Ni electrodeposition from Ni sulphamate based solutions are low internal stress and high current efficiency (>90%). The functionalities of coatings are affected by internal stress which is a common problem of the electroplating process. The parameters of electrodeposition and additive particles which are insoluble in the bath, in the case of composite coatings [4], change the characteristics of the plating and affect the internal stress of the coatings. The influence of the electrodeposition parameters and their interaction effects on the internal stress of Ni deposits were studied by fractional factorial design. Self-interactions and cross correlations of temperature, pH, current density and bath composition on internal stress were determined by statistical analysis of results obtained from sulphamate baths. It was found that increasing temperature and deposit thickness and decreasing boric acid and chloride ion concentrations resulted in decreasing the internal stress within the parameter ranges covered in this study.

[1] Popov,K.I., Djokic,S.S., Grgur,B.N.(2002), Fundamental Aspects of Electrometallurgy, Kluwer Academic Publishers, pp.1-3

[2] Nickel Plating Handbook. (2014). June 28, 2016, retrieved from; https://www.nickelinstitute.org/~/media/Files/TechnicalLiterature/NPH_141015.ashx

[3] DuRose, A.H. (1997), Nickel Solution Buffers and Limiting Current Density, Surface Finishing, 48-52

[4] Saraloğlu Güler, E., Karakaya, İ. and Konca, E. (2014) Effects of current density, coating thickness, temperature, pH and particle concentration on internal stress during Ni-MoS2 electrocodeposition, Surface Engineering, 30, 109-114.
Electrocapping Gold Nanopores with Porous Manganese Dioxide
Authors: Experton Juliette , Wu Xiaojian (James) , Martin Charles R
Published: February 2020

Nano- and micropores functionalized with responsive or reactive materials offer defined high rates of mass transport which are beneficial for applications in sensing, nanofluidics and catalysis.1,2 They can also act as model systems for material characterization and fabrication.2,3 However, precisely controlling the functionalization reactions inside such tiny volumes is a challenge. Moreover, it is frequently desired to deposit the material at a specific location within the pore, for example, on the inside wall or just at the opening. When the functionalization requires electrodeposition, achievement of such site specificity is difficult as it necessitates a continuous electrical contact that is exposed only at the desired sites. Bipolar electrochemistry is a powerful tool capable of localized electrodeposition in the absence of an electrical contact.4 It offers a precise way to grow materials on 3D substrates.

In our work, two electrodes are placed on either side of a conductive nanoporous membrane and a potential bias is applied (1-4 V). Redox reactions, one cathodic and one anodic, occur at either end of the nanopore. One reaction is chosen such that it forms a porous material which is selectively electrodeposited at one pore orifice. These capped pores allow the study of the properties of this porous material, such as conductivity, reactivity, stability and surface charge.

Figure 1 shows porous manganese dioxide (MnO2) that was selectively electrodeposited at one end of a pore by bipolar electrochemistry. Manganese oxides are interesting materials for sensing, catalysis, supercapacitor and battery applications.5 Their well-defined porous structures exhibit high specific surface areas and lattices that allow the intercalation of ions, such as lithium. We report on the mechanism of formation and growth rate of these MnO2 structures on gold nanopores as studied by electrochemistry and complementary techniques. We also report electrochemical measurements of the synthesized material, including its permselectivity towards lithium, potassium and sodium ions. Finally, we address the performance of this material for applications in batteries and catalysis.

Xu, Y.; Jin, S.; Xu, H.; Nagai, A.; Jiang, D. Chem. Soc. Rev.
2013, 42, 8012-8031.

Wang, C. M.; Kong, D. L.; Chen, Q.; Xue, J. M. Front. Mater. Sci.
2013, 7(4), 335-349.

Baker, L. A.; Choi, Y.; Martin, C. R. Curr. Nanosci.
2006, 2(3), 243-255.

Fosdick, S. E.; Knust, K. N.; Scida, K.; Crooks, R. M. Angew. Chem. Int. Ed.
2013, 52, 10438-10456.

Brock, S. L.; Duan, N.; Tian, Z. R.; Giraldo, O.; Zhou, H.; Suib, S. L. Chem. Mater.
1998, 10, 2619-2628.

Figure 1
Characterization of Ni Filled Luminescent Porous Silicon By Optical and Magnetic Methods
Authors: Granitzer Petra , Rumpf Klemens , Reissner Michael , Poelt Peter
Published: February 2020

Porous silicon (PSi) gained by electrochemical etching of a silicon wafer can be fabricated with various morphologies ranging from pore diameters of a few nanometers to tens of micrometers. In the nanoporous regime the material offers a branched structure with pore diameters of 2 – 5 nm. Such microporous silicon (IUPAC notation) is known to emit light in the visible regime since 1990 and is still under investigation [1].

The aim of this work is to combine luminescent porous silicon with a ferromagnetic metal (Ni) to influence on the one hand the photoluminescence by the presence of metal deposits and on the other hand the optical properties by an external magnetic field. The porous silicon samples are fabricated by anodization of moderately doped p-type silicon in an aqueous hydrofluoric acid solution under a constant current density of 10 mA/cm2 for 20 minutes. The metal deposition within these small pores is challenging but succeeded. First the optical properties of the luminescent PSi are investigated, second Ni is electrochemically deposited in the porous silicon sample under cathodic conditions and subsequently the nanocomposite specimens are characterized optically and magnetically. Furthermore the structural characterization of the samples is carried out by SEM and TEM.

Photoluminescence spectra of bare porous silicon show a maximum around 620 nm whereas in the case of Ni filled samples the peak is blue-shifted to around 580 nm and the luminescence intensity is increased. Concerning the magnetic properties of the nanocomposite the embedded Ni structures are superparamagnetic from the size of the pore diameters but due to the branched morphology the achieved deposits are interconnected and thus do not offer necessarily a superparamagnetic behavior. Field dependent magnetization measurements with the magnetic field applied perpendicular to the sample surface show a low coercivity of about 200 Oe and a squareness (magnetic remanence/saturation magnetization) of about 0.2 which is indicative for a film like behavior due to the interconnected Ni structures (figure 1). Temperature dependent magnetization measurements give no hint for a superparamagnetic behavior.

The optical characterization of luminescent PSi with respect to photoluminescence intensity and decay times compared with Ni filled samples is discussed in detail as well as the corresponding magnetic properties of the nanocomposites. Furthermore the influence of a magnetic field on the optical properties is elucidated. The presented systems give not only rise to optoelectronics but also to magneto optical integrated devices.

[1] J. Joo, T. Defforge, A. Loni, D. Kim, Z.Y. Li, M.J. Sailor, G. Gautier, L.T. Canham, Appl. Phys. Lett. 108, 153111 (2016).

Figure 1: Field dependent magnetization curve of microporous silicon filled with Ni.

Figure 1
Effects of Pulse-Reverse Currents on Nickel Deposited from Sulphamate Solutions
Authors: Çetinöz Bilgehan , Erdogan Metehan , Aras Mustafa Serdal , Karakaya Ishak
Published: February 2020

Electroplating is widely used in many fields for decorative and engineering purposes. Nickel is mostly used for engineering applications beacause of its enchanced mechanical properties such as low internal stress and high corrosion and erosion resistance. It was reported that the use of pulse or pulse reverse currents instead of direct current produced homogenous deposits of better surface finish [1,2]. Nickel sulphamate bath was used in this study to attain better mechanical properties, lower internal stresses and good surface quality. The effects of pulse reverse current (PRC) method on the hardness, microstructure and roughness of the deposits were investigated and compared with direct current (DC) plating. In PRC electroplating, current value is alternated between anodic and cathodic currents to provide higher ion concentrations near electrodes compared to DC plating. In this way, the increased nucleation rate and the number of grains per unit area leads to a decrease in grain size [1]. In addition, the homogenity of the deposits can be improved and the growth of the planes can be controlled by the use of PRC coating [3]. In the design of experiments, special emphasis was given to the ratio of the anodic and cathodic current densities. Scanning electron microscopy (SEM) analyses, roughness measurements and vickers hardness tests were used to characterize the deposits. The results of selected DC and PRC deposits can be seen in Figure 1.

References

[1] Chandrasekar, M.S. and Pushpavanam, M. (2008) ‘Pulse and pulse reverse plating—Conceptual, advantages and applications’, Electrochimica Acta, 53(8), pp. 3313–3322.

[2] Arslan, B., Demirci, G., Karakaya, İ. and Erdoğan, M. (2015) ‘Formation of gold-plated electroformed copper structures’, Advances in Materials and Processing Technologies, 1(3-4), pp. 384–393.

[3] El-Sherik, A.M., Erb, U. and Page, J. (1997) ‘Microstructural evolution in pulse plated nickel electrodeposits’, Surface and Coatings Technology, 88(1-3), pp. 70–78.

Figure 1
(Invited) Electrodeposited Carbon Nanotube Ropes, Decorated with Electrodeposited Pd Nanoparticles for Fast, Sensitive, and Wide-Range, H2 Sensors
Authors: Penner Reginald , Li Xiaowei
Published: February 2020

Hydrogen (H2) gas sensors that are sensitive, rapid-responding, stable, selective, compact, and inexpensive are needed to support the operation of fuel cell-electric automobiles. Palladium absorbs hydrogen to form a hydride (PdHx
) with x saturating at 0.67 and since 1869 it has been known that the electrical resistivity of this hydride increases linearly with x by a factor of 1.8 – 1.9 over the range from x = 0 to 0.67. This property of PdHx was first exploited for hydrogen sensing by Hughes and Schubert in 1992. As hydrogen gas sensors, Pd thin film resistors are elegant in their simplicity and cheap, but they are much too slow. One solution is to use a Pd nanowire as a resistive H2 sensor instead of a film. In this talk, we describe a second approach involving palladium (Pd) nanoparticle (NP)-decorated carbon nanotube (CNT) ropes (or CNT@PdNP). In the devices we prepare here, the Pd NPs have a mean diameter below 6 nm and are highly dispersed on the CNT surfaces. Both the Pd NPs and the CNT ropes are prepared by pulsed electrodeposition methods. Such CNT@PdNP ropes produce a relative resistance change 20 - 30 times larger than is observed at single, pure Pd nanowires. Thus, CNT@PdNP rope sensors improve upon all H2 sensing metrics (speed, dynamic range, and limit- of-detection), relative to single Pd nanowires which heretofore have defined the state- of-the-art in H2 sensing performance. Specifically, response and recovery times in air at [H2] ≈ 50 ppm are one sixth of those produced by single Pd nanowires with cross- sectional dimensions of 40 × 100 nm Pd. The LODH2 is <10 ppm versus 300 ppm, and the dynamic range (10 ppm – 4%) is nearly twice that afforded by the Pd nanowire. CNT@PdNP rope sensors are prepared by the dielectrophoretic deposition of a single semiconducting CNT rope followed by the electrodeposition of Pd nanoparticles with mean diameters ranging from 4.5 (± 1) nm to 5.8 (± 3) nm. The diminutive mean diameter and the high degree of diameter monodispersity for the deposited Pd nanoparticles are distinguishing features of the CNT@PdNP rope sensors described here, relative to prior work on similar systems.

Figure 1
(Invited) Engineering Surface Structures and Energetics of α-Fe2O3 and p-Si for Efficient Solar Water Splitting
Authors: Shen Shaohua
Published: February 2020

Solar hydrogen conversion via photoelectrochemical water splitting is an important technology for energy and environment sustainability. Since the pioneering work of Fujishima and Honda in 1972, tremendous research on semiconductor-based photoelectrochemical water splitting has yielded better understanding of the processes as well as encouraging development of high efficiency photoelectrodes for solar hydrogen generation. In this talk, some recent progresses in heterostructures of α-Fe2O3and p-Si for photoelectrochemical solar water splitting in our group will be introduced.

Given the narrow band gap enabling excellent optical absorption, increased charge carrier density and accelerated surface oxidation reaction kinetics become the key points for improved photoelectrochemical performances for water splitting over α-Fe2O3 photoanodes. By engineering the surface structures of α-Fe2O3 nanorods with AgxFe2-xO3, TiO2 and HfO2overlayers, the surface charge recombination was greatly inhibited and the surface water oxidation kinetics were efficiently accelerated, resulting in remarkable enhancement in PEC water splitting performances.

p-Si has captured intensive attentions for solar hydrogen conversion due to its high natural abundance and narrow band gap (~1.1 eV). However, the slow charge-transfer kinetics at the p-Si/electrolyte interface lead to large overpotentials for hydrogen evolution and electrocatalysts are always necessary. Recently, we successfully engineered the surface energetics of p-Si with n-WO3 overlayer and Ni molecular complexes, which gave rise to a great anodic shift of up to 300 mV in onset potential for photocathodic water reduction.
(Invited) Some Observations on the Electrochemical Interface of Hematite in Alkaline Electrolyte during Solar Water Oxidatiob
Authors: Braun Artur
Published: February 2020

Iron oxide, in particular a-Fe2O3 hematite has been investigated as model photoanode for solar water oxidation for many decades. We have investigated this material with soft x-ray spectroscopy methods and found some chemical changes at the surface when the material is operated as photoelectrode. The first observ ation is that the surface is sub-stoichiometric; it contains an Fe2+-enriched surface. Under anodic bias, the Fe2+ becomes converted to Fe3+ with a parabolic growth law. Also, hole doping is observed on the same samples. Additionally, the surface appears to become hydroxylated or oxy-hydroxylated. The relative abundance of the OH or OOH groups increases with increasing bias potential to the point where the water oxidation sets on. At higher potentials, the surface groups disappear gradually. In the same course, the hydrogen bonds which hold water molecules together become increased and decreased. We have also done in situ and operando experiments which show a nice parallel process of photo hole formation and delection depending on the applied bias. We are therefore able to sketch a realistic scenario of physics and chemistry going on at the surface and subsurface during water oxidation.
Functionalization of Gallium Phosphide Surface with an Organic Monolayer for Advanced Photoelectrochemistry
Authors: Hlynchuk Sofiya , Maldonado Stephen
Published: February 2020

This work presents progress in the development of stable gallium phosphide (GaP) interfaces capable of undergoing subsequent reactions by introducing an organic monolayer. The context of this work is the use of p-GaP in a fuel forming photoelectrochemical cell. Semiconductor photoelectrodes require specific bulk and surface properties. Gallium phosphide has a band gap of 2.26 eV that allows for absorption in the visible range while the band edge positions make processes like hydrogen and carbon dioxide reduction possible. However, the surface is susceptible to rapid degradation via formation of a native oxide. Surface functionalization techniques provide means to passivate the semiconductor/liquid interface against degradation. In addition, by introducing organic monolayers on semiconductor surfaces subsequent reactions can be performed to further tailor the semiconductor interface as desired. This work focuses on using Grignard chemistry to chemically passivate the gallium phosphide surface via a formation of a gallium-carbon bond. To further alter the interface, reactive handles consisting of either hydroxyl or amine groups are introduced. These functional groups are used to covalently couple dyes to the gallium phosphide previously shown to photosensitize the semiconductor. The stability of the covalent attachment is investigate as a function of pH. Covalent attachment is showed using X-ray photoelectron spectroscopy while gallium phosphide dye sensitization is probed by analyzing the photoresponse pass the band gap.
(Invited) Gate-All-Around Transistors Based on Vertically Stacked Si Nanowires
Authors: Mertens Hans , Ritzenthaler Romain , Hikavyy Andriy Yakovitch , Kim Min-Soo , Tao Zheng , Wostyn Kurt , Schram Tom , Kunnen Eddy , Ragnarsson Lars-Åke , Dekkers Harold F. W. , Hopf Toby , Devriendt Katia , Tsvetanova Diana , Chew Soon Aik , Kikuchi Yoshiaki , Van Besien Els , Rosseel Erik , Mannaert Geert , De Keersgieter An , Chasin Adrian , Kubicek Stefan , Dangol Anish , Demuynck Steven , Barla Kathy , Mocuta Dan , Horiguchi Naoto
Published: February 2020

Gate-all-around (GAA) transistors based on vertically stacked horizontal nanowires are promising candidates to replace FinFETs in future CMOS technology nodes. First of all, GAA devices provide optimal electrostatic control over semiconducting nanowire channels, which enables downscaling of the gate length to below the FinFET limit, while maintaining low off-state leakage [1]. Besides, horizontally oriented nanowires are an evolutionary extension of FinFETs, as opposed to vertical nanowires which require more disruptive technology and design changes [2]. Finally, stacking of nanowires is relevant for enhancing the drive current per footprint. Based on these considerations, GAA transistors made of vertically stacked horizontal nanowires have been included in the ITRS roadmap to reduce the contacted gate pitch, which is a key figure of merit for CMOS device density, to below ~40 nm in 2019-2021 [3].

In the context of the industrial relevance described above, we present the fabrication of Si GAA devices on bulk Si substrates. Multiple processing aspects that are relevant for bulk CMOS technology definition are addressed, including stacking of 8-nm-diameter Si wires at 45-nm lateral pitch and 20-nm vertical pitch [4], and nanowire-compatible replacement metal gate processing in combination with threshold voltage tuning by dual work function metal integration [5]. Temperature restrictions for the formation of shallow trench isolation, and the interaction between N- and P-type junction formation on one hand and nanowire release processes on the other hand are discussed as well.

[1] K. J. Kuhn, IEEE Trans. Electron Devices, vol. 59 (7), p.1813, (2012).

[2] L. Liebmann et al., VLSI Tech. Dig., p.112 (2016).

[3] The International Roadmap for Semiconductors (ITRS) 2.0, http://www.itrs2.net/ (2015).

[4] H. Mertens et al., VLSI Tech. Dig., p.158 (2016).

[5] H. Mertens et al., IEDM Tech. Dig., p.524 (2016).

Figure 1
(Invited) Atomic Layer Etching of SiO2 and Other Materials Using Plasma Process Sequences
Authors: Oehrlein Gottlieb S.
Published: February 2020

Angstrom-level precision in etching of SiO2 is possible using steady-state Ar plasma in conjunction with periodic injection of a defined number of C4F8 molecules and synchronized plasma-based Ar+ ion bombardment.1 The physical sputter rate of SiO2 vanishes for Ar+ ion bombardment with a maximum ion energy of 20 eV and lower, whereas for a fluoroccarbon-coated SiO2 surface, chemical modifications of the SiO2 surface are induced by low energy ion bombardment and SiO2 etching is initiated. The question of SiO2:Si3N4 etching selectivity was studied and evaluated with regard to the dependence on maximum ion energy, etching step length (ESL), FC surface coverage, and precursor selection. Since Si3N4 has a lower physical sputtering energy threshold than SiO2, Si3N4 physical sputtering can take place after exhausting the chemical etchant at the end of each cycle for certain ion energies and leads to Si3N4/SiO2 etching selectivity. By optimization of the ALE process parameters, e.g. low ion energies, ESL, and FC film deposition per cycle, highly selective SiO2 to Si3N4 etching can be achieved for conditions where FC selectively accumulates on Si3N4 surfaces.2Mechanism of the observed ALE behaviors will be discussed using real-time and post-plasma surface analysis data. We will also discuss current challenges with the application of these approaches to other materials.

Acknowledgements: I am pleased to acknowledge the essential contributions and collaboration of D. Metzler, C. Li, S. Engelmann, R. Bruce, E. Joseph, C. S. Lai, and E. A. Hudson to this work, and thank National Science Foundation (CBET-1134273), US Department of Energy (DE-SC0001939) and Semiconductor Research Corporation for funding.

1 D. Metzler, R. Bruce, S. Engelmann, E. A. Joseph, and G. S. Oehrlein, J. Vac. Sci. Technol. A 32, 020603 (2014).

2 C. Li, D. Metzler, C. S. Lai, E. A. Hudson, and G. S. Oehrlein, J. Vac. Sci. Technol. A 34, 041307 (2016).
(Invited) GaN-on-Diamond Electronics: The Next Generation Microwave Technology
Authors: Kuball Martin
Published: February 2020

GaN-on-SiC microwave devices are limited in power density by the thermal conductivity of the SiC substrate; to increase the potential for GaN microwave devices to increase their power density beyond the typical 10W/mm for reliable device operation, it is important to explore new substrates, in particular diamond substrates as their thermal conductivity can be as high as 2000W/mm allowing at least 3x increase in power density. We review the current state-of-the-art of GaN-on-diamond materials and devices, in the context of material and device reliability, material microstructure and thermal device management.
Effects of Metal-Doping on the Electrochemical Properties of Ptni Octahedral Catalysts for Oxygen Reduction Reaction in PEM Fuel Cells
Authors: Lim Jeonghoon , Kim Minjoong , Cho EunAe
Published: February 2020

Polymer electrolyte membrane fuel cells (PEMFCs) are the most attractive power source for vehicles with zero CO2 emission, low weight and volume, high power density, and high efficiency. However, high cost and low durability of PEMFCs have prevented the highly efficient technologies from being fully implemented and commercialized, mainly due to the use of noble platinum catalyst in the electrodes. To reduce the Pt usage, platinum and nickel (Pt-Ni) alloy catalysts with controlled shapes have been developed over the past years. In particular, PtNi octahedral catalysts exhibited significant enhancement of ORR performance with well-extended (111) facet. Here, we report metal-doped PtNi octahedral nanoparticles on carbon support (M-PtNi/C) for oxygen reduction reaction (ORR) in PEMFCs. M-PtNi/C catalysts showed high mass activity compared with commercial Pt/C and undoped octahedral PtNi/C catalysts. The M-PtNi/C catalysts not only showed remarkable enhancement in an initial ORR performance, but also exhibited a great stability in a voltage-cycling test with keeping the initial Ni concentration in the nanoparticles. They maintained the initial octahedral shape after the durability test, while the PtNi/C catalyst lost its initial octahedral shape and the Ni atoms in the PtNi/C catalyst were dissolved during the first a few cycles. These results demonstrate that M-PtNi/C catalysts can be utilized as a new active and durable ORR catalyst for PEMFCs.
Water Management in Low Temperature Fuel Cells through in-Operando X-Ray Computed Tomography
Authors: Normile Stanley J. , Calzada Osvaldo , Mandal Pratiti , Parkinson Dilworth Y. , Xiao Xianghui , Weber Adam Z , Zenyuk Iryna V.
Published: February 2020

For polymer-electrolyte fuel cells (PEFCs) and anion exchange membrane fuel cells (AEMFCs) optimal water management is essential. During start-up and at low operating temperatures, where water is present in a liquid form, it can block reactant delivery to electrocatalyst sites, resulting in significant mass-transport losses, flooding and low fuel cell power densities. Using synchrotron X-ray computed tomography (CT) we have previously shown how water transport properties depend on porous materials morphology and chemical composition, as well as cell compression.1-3 These ex- and in-situ studies isolate specific porous membrane / electrode assembly (MEA) component’s effect on water management (such as micro-porous (MPL) or gas-diffusion layer (GDL)). To understand water transport under operating conditions we use in-operandoX-ray CT studies, where water distribution is observed under various steady-state conditions.

In-operando single serpentine channel (1x1 mm) fuel cell testing hardware for synchrotron X-ray CT is used with active area of 1 cm2. Steady-state water generation and removal is observed in PEFCs and AEMFCs for temperature of 30oC with chronoamperometric holds at current densities ranges of 20 – 100 mA/cm2. Furthermore, comparison of water distribution in PGM and PGM-free catalysts for both type of fuel-cells will be presented. In all of these systems water pooling is observed at the component interfaces, indicating the importance of interfaces design.

Acknowledgment: The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

References:

1. I. V. Zenyuk, D. Y. Parkinson, L. G. Connolly and A. Z. Weber, Journal of Power Sources, 2016, 328, 364-376.

2. I. V. Zenyuk, D. Y. Parkinson, G. Hwang and A. Z. Weber, Electrochemistry Communications, 2015, 53, 24-28.

3. I. V. Zenyuk and A. Z. Weber, ECS Transactions, 2015, 69, 1253-1265.

Figure 1. In-operando cross-section tomograph of serpentine channel AEMFC operating at 30 mA/cm2, 30oC and 100 % RH.

Figure 1
(Invited) Textile-Based Electrochemical Energy Storage Devices
Authors: Zheng Zijian
Published: February 2020

Textiled-based electrochemical energy storage devices including supercapacitors and Li-ion batteries that made use of and/or shaped into textile fibers, yarns, and fabrics, which are promising energy storage devices for wearable electronic applications. To date, the major challenge in the development of wearable energy storage devices is how to improve the electrochemical properties of the device while acquiring high flexibility and durability under wearing conditions. Recently, our laboratory has developed several yarns and fabrics-type devices, which show record­high electrochemical performances of their kinds as well as excellent flexibility. These textile­based devices can be readily integrated into different textile forms by means of weaving, embroidery, and heat pressing for wearable applications.
Effects of Carbon Supports on the Stability of Pt and PtCo Nanoparticles in PEMFC Cathodes
Authors: Yarlagadda Venkata , Padgett Elliot , Kukreja Ratandeep S , Ziegelbauer Joseph M. , Braaten Jonathan , Ogawa Shohei , Komini Babu Siddharth , Arisetty Srikanth , Gu Wenbin , Thompson Levi T , Litster Shawn , Muller David A. , Kongkanand Anusorn
Published: February 2020

The drive to reduce the Pt loading in the PEMFC cathode in order to minimize the overall Pt in the fuel cell system below 10-15 g Pt/vehicle requires a durable and stable catalyst that has desirable characteristics such as high activity and low oxygen and proton transport resistances. The carbon support plays an important role in determining the catalyst nanoparticle distribution and transport properties in the electrodes. Therefore, it is vital to understand the degradation mechanisms of both the Pt and carbon support to develop better PEMFC cathodes for automotive applications.

In this study, we evaluated the performance and morphological changes after voltage-cycling accelerated stability tests for Pt and PtCo catalysts supported on different carbon supports. Among the catalysts with different carbon supports, it was found that although the Pt surface area loss, strongly related to Pt dissolution, was comparable, the losses in oxygen reduction kinetics and fuel cell performance for catalysts with high-surface-area carbon were smaller. We studied and will report changes in electrochemical properties, Pt and Co redistribution, and electrode morphology. Simulation to illustrate the stability differences will also be discussed.

This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271.
A Novel Porous Carbon-Based Non-Metal Catalyst Based on Electrochemical Deposition of Polyaniline: Synthesis, Characterization and Electrochemical Performance
Authors: Zhou Fen
Published: February 2020

Polyaniline-based porous carbon material with high surface area (769.86~1341.12 m2/g) was prepared via electrochemical method combined with high temperature carbonization process. A very clear pore structure can be observed by scanning electron microscope. The ORR activity and the electrochemical stabilities of the porous carbons were compared to the commercial Pt/C by linear potential scan (LSV) and chronoamperometry, respectively. The catalytic activity for oxygen reduction reaction of the porous carbon increases by increasing carbonization temperature. The oxygen reduction reaction for the prepared porous carbon which was carbonized at 850℃ is catalyzed by a four-electron transfer pathway. Furthermore, the current density of oxygen reduction reaction of the synthetic porous carbon decreases by 33%@10 h, which is lower than commercial Pt/C (64%@10 h).
Novel Liquid/Gas Diffusion Layers with Micro/Nano Surface Modifications for High-Efficiency Water Electrolysis
Authors: Zhang Feng-Yuan
Published: February 2020

Novel Liquid/Gas Diffusion Layers with Micro/nano Surface Modifications for High-efficiency Water Electrolysis

Zhenye Kang[1], Jingke Mo1, Gaoqiang Yang1, Scott T. Retterer[2], David A. Cullen2, and Feng-Yuan Zhang*1

Abstract

Proton exchange membrane (PEM) water electrolysis coupled with renewable sources is considered one of the most practical and high-efficiency methods to produce pure hydrogen. The liquid/gas diffusion layers (LGDLs), which located between the catalyst layer (CL) and bipolar plate, are expected to transport electrons, heat, and reactants/products with minimum losses. Due to the harsh environment at anode of PEMECs, most materials, including carbon and stainless steel, can be easily corroded, which significantly affects the performance and durability of PEMECs. Titanium based thin/well-tunable LGDLs have many advantages, such as high corrosion resistance, small thickness (25 µm), well-controlled pore shape, pore size and pore distribution. Most importantly, it can achieve superior multifunctional performance in low temperature PEMECs, which significantly improves the PEMEC efficiency. In this study, the novel thin/well-tunable LGDLs with different pore morphologies and surface modifications are comprehensively investigated in order to enhance the PEMEC performance. Gold (Au) is deposited on the surface of the thin/well-tunable LGDLs by different micro/nano surface modification methods, and the surfaces of the LGDLs are both ex-situ characterized and in-situ investigated. In addition, the performance and electrochemical impedance spectroscopy (EIS) of the PEMECs with different LGDLs are experimentally investigated and analyzed.

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

[2] Oak Ridge National Lab, USA

* Contacting Author: E-mail: fzhang@utk.edu; Tel: +1-(931)-393-7428
New High Potential Membrane Material (For Electrochemical Hydrogen Compression)
Authors: Koeman Menno , Bouwman Peter Jaime , Sikkema Doetze , Mulder Martijn J.J. , Raymakers Leonard F.J.M. , Dalhuijsen Wouter , Semerel Daniel , Konink Jonne , Bosch Melissa , Bleekman Joris J. M.
Published: February 2020

The company HyET has been working since 2008 on electro chemical hydrogen compression technology. Previously HyET demonstrated as one of the first companies a compression record showing pressures as high as 100MPa in one single stage using EHC.

When using commercial membranes the energy demand for reaching higher pressures has been unfavourable considering the proton conductivity, back diffusion and mechanical properties. From the start HyET has been involved in the membrane development to better understand the requirements in EHC environment and have an angle how to achieve the best performance and durability.

Now a new, fully aromatic hydrocarbon, membrane has been developed which was tested at HyET facilities, and results indicate that compared to commercial reference materials this seems to have game-changing properties. More efficient compression was achieved enabling higher throughput and minimising parasitic losses (back diffusion), thus reducing the operation cost significantly for hydrogen compression. Besides its use in the electrochemical compressor, the newly developed membrane may also prove to have merit in other electrochemical applications, such as electrolysers and fuel cells.

This presentation will show results on the enhanced performance, providing insight in the solutions/benefits for EHC technology and show a method for characterisation of new membrane materials that bring great potential to the future of EHC technology.

Figure 1
(Invited) Novel Nanomaterials, Structures and Interfaces for Solar Fuel Production
Authors: Yang Shihe
Published: February 2020

Bottom-up strategies for the fabrication of nanomaterials have the advantage of scalability, cost-effective and sustainability, and thus hold great potential to solve the current critical energy and environmental issues facing humanity. Current challenges consist of assembly of the nanomaterials into, for example, various forms of films, which are immensely useful in realistic applications of the nanomaterials. The key is to understand the interplay between the material components. In this contribution, I will present some of our recent results in interfacing and assembling different nanostructures at different length scales by solution processes. The resulting architectures have been explored for the efficient conversion of sunlight to chemical fuels. It has proved promising to use earth-abundant materials and low-cost processes to fabricate solar fuel devices for artificial photosynthesis.
Selective Electrocatalytic CO2 Reduction to CO on Solid Nickel-Nitrogen-Doped Carbon Catalysts
Authors: Leonard Nathaniel , Ju Wen , Varela Ana Sofia , Steinberg Julian , Strasser Peter
Published: February 2020

Electrochemical reduction represents a potential solution for converting carbon dioxide into more valuable products. One application for the carbon dioxide reduction reaction (CO2RR) would be carbon monoxide production, which is a valuable fuel and chemical precursor. An important challenge for commercialization of this process has been finding inexpensive catalysts with a high selectivity to carbon monoxide production. The selectivity towards carbon monoxide production is limited both by the competing hydrogen evolution reaction and poisoning caused by strong binding of carbon monoxide[1-2]. Initial work on non-precious metal CO2RR catalysts was based on iron-based metal-nitrogen-carbon (MNC) catalysts that were originally developed for the oxygen reduction reaction but have also shown strong CO generation performance [1, 3-5]. In the present work a Nickel based MNC catalyst is shown to have higher CO-production rates and less CO-poisoning in comparison to the iron-based MNC catalysts.

In order to make this comparison, a family of catalysts is synthesized by the polymerization of nitrogen precursors around a carbon support and metal precursor [1, 6-7]. Upon heat treatment at 900 °C and subsequent acid washes, a nitrogen-rich, metal-nitrogen-carbon matrix is synthesized. These catalysts are characterized physically and electrochemically. In this work the nickel-based MNC catalyst is shown to be a significant improvement over the Fe-based catalysts and other non-precious metal alternatives. Although the iron-based catalyst shows lower onset overpotential, the nickel-based catalyst has higher peak currents and a longer lifetime.

In this work it is found that the higher current densities and longer lifetime are a result of increased resistance to CO-poisoning. Furthermore, the CO-poisoning allows in situ confirmation of active site quantification via carbon monoxide adsorption techniques. Ultimately, these findings allow optimization of MNC catalysts resulting in high performance non-precious metal catalysts for CO2RR.

References:

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2015,
54 (37), 10758-10762.

[2.] Tripkovic, V.; Vanin, M.; Karamad, M.; Bjorketun, M. E.; Jacobsen, K. W.; Thygesen, K. S.; Rossmeisl, J., J Phys Chem C
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[3.] Sahraie, N. R.; Paraknowitsch, J. P.; Gobel, C.; Thomas, A.; Strasser, P., J Am Chem Soc
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136 (41), 14486-14497.

[4.] Hao, G. P.; Sahraie, N. R.; Zhang, Q.; Krause, S.; Oschatz, M.; Bachmatiuk, A.; Strasser, P.; Kaskel, S., Chem Commun
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51 (97), 17285-17288.

[5.] Gong, X.; Liu, S. S.; Ouyang, C. Y.; Strasser, P.; Yang, R. Z., Acs Catal
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[6.] Gang Wu, K. L. M., Christina M. Johnston, Piotr Zelenay, Science
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(Invited) The Importance of the Cathode Catalyst Support in the Pursuit of Low-Cost PEM Fuel Cells
Authors: Gu Wenbin , Kongkanand Anusorn , Yarlagadda Venkata , Yu Paul Taichiang , Mathias Mark
Published: February 2020

Because fuel cells are sized based on their high-power requirement, improvements in the high-power capability (W/cm2) can directly be translated to reduced active area and thus reduced cost. For proton-exchange-membrane (PEM) fuel cells, state-of-the-art PtCo catalysts on several different carbon supports have exhibited impressive and similar kinetic (low-current-density) activity. However, it is now becoming clear that the carbon-support selection can be important in determining their high-power performance. At beginning of life, we have recently observed that active nanoparticles reside predominantly within some porous carbon support particles and are apparently shielded from direct contact with the solid ionomer electrolyte as shown in the second illustration in Figure 1. This raises questions involving O2 and proton transport mechanisms and possible rate limitations within these primary carbon particles.

In this work, we will present a mathematical model that includes the cathode-reactant-transport processes within a porous carbon support, allowing estimation of Pt utilization as a function of material parameters and operating conditions. We will also report recent experimental work that we are bringing alongside the model in attempts to validate and develop it further. Finally, we will discuss the implications for optimizing the support and the active-material location within it.

References

1) E. Padgett et al., Proceeding of Microscopy & Microanalysis 2015 Volume 21, Issue S3, August 2015, pp. 799-800.

This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271.

Figure 1
(Invited) Membrane Electrode Assembly for Alkaline Anion Exchange Membrane Fuel Cell
Authors: Yu Hongmei
Published: February 2020

Anion exchange membrane fuel cell (AEMFC) is expected as a promising power source candidate as it may enables the adoption of non-precious metal catalysts; therfore, it exhibits great advantages over proton exchange membrane fuel cell (PEMFC) using precious metal catalysts . However, AEMFCs are much less understood than PEMFCs. As a key component, the membrane electrode assembly plays an important role in AEMFCs. The electrode fabrication and resulting microstructure largely determinates the performance of AEMFCs.

In this work, the electrode microstructure of a AEMFC was investigated. The ionomer content in catalyst layers as well as the dispersion solvents for catalyst inks have shown a strong impact on the active, ohmic and mass-diffusion polarization losses of a AEMFC. Performance measurements of a single cell, as well as a stack, were implemented to evaluate the feasibility of AEMFC applications. Pt-free AEMFC stack was assembled and tested in DICP.

In addition, a novel cathode architecture is also developed., which uses vertically aligned nanoneedle arrays as an oriented catalyst support for the AEMFC Without ionomer, the oriented catalyst layer shows its potential application in AEMFCs.
Four-in-One Electrode for Micro Polymer Electrolyte Membrane Fuel Cells
Authors: Li Yinshi
Published: February 2020

The miniaturization of the µPEMFC can be readily achieved by scaling down the size of the cell components, it, however, strongly depends on the development of the micro-scaled tailoring, fabricating and assembling technologies [1, 2]. Therefore, designing a novel architecture that integrates the different components will be a more effective way to miniaturize the cell system. This work presents an efficient strategy by developing a four-in-one electrode, in which the functions of the flow field, backing layer, micro-porous layer, and catalyst layer are brought together. This integrated design facilitates the mass and charge transport as well as extends the three-phase boundary, thereby enabling to miniaturize the cell system while enhance the power output [3, 4]. It has been demonstrated that when applying a pair of the four-in-one electrode (the height, length and width respective 500 µm, 4 mm and 4 mm) to the liquid-feed µPEMFC, the peak power density goes up to 123 mW cm-2 even at room temperature. This four-in-one electrode makes it possible to develop a simple-structure and high-performance liquid-feed µPEMFC for lab-on-a-chip applications.

References

[1] J.P. Esquivel, M. Castellarnau, T. Senn, B. Lochel, J. Samitier, N. Sabat, Lab. Chip, 2012, 12: 74-79.

[2] Y. S. Li, Int. J. Hydrogen Energy, 2016, 41: 3600-3604.

[3] Y.S. Li, J.H. Lv, Y.L. He, J. Electrochem. Soc., 2016, 163: F424-F427.

[4] Y.S. Li, Y.L. He, J. Electrochem. Soc., 2016, 163: F663-F667.
(Invited) The Fuel Cell Solution for Automobile Industry
Authors: Hou Zhongjun , Shi Weiyu , Wang Keyong , Xing Danmin , Liang Dong , Wang Renfang , Ming Pingwen
Published: February 2020

Proton exchange membrane fuel cell (PEMFC) has been considered as an ideal power source of electric vehicle propulsion due to its high power and energy density, particularly when combined with high pressure hydrogen storage technology. After decades of R&D, the PEMFC technology has been improved to a commercially viable level. In the next five years, the automobile industry in China will invest substantially more efforts on fuel cell vehicles, and Chinese government has launched an attractive subsidy policy towards commercialization of fuel cell vehicles.

Sunrise Power has focused on achieving fuel cell technology targets for automobile industry over fifteen years. Three generations of PEMFC power systems has been developed to enhance the power density, durability, and to reduce the cost.The 1st generation of PEMFC power system was developed for fuel cell vehicle demonstration during “2008 Beijing Olympic Games” and “2010 Shanghai EXPO” in China. And the fuel cell lifetime between 1000~2000 hours was demonstrated. The 2nd generation optimized the system and stack design following a fuel cell failure mode, which was disclosed via the degradation research on the 1st generation fuel cell systems. And it has been validated that the fuel cell lifetime can be improved to about 5000 hours. The 3rd generation eliminated air humidification via the adoption of a water management strategy to achieve higher power density and lower cost. Basing on the research, Sunrise Power has launched fuel cell product portfolio of HyMOD, HyMOD+ and HySYS to support the application of the fuel cell vehicle industry.
(Invited) Chemcatbio: Chemical Catalysis for Bioenergy
Authors: Fitzgerald Nichole
Published: February 2020

Catalytic materials significantly contribute to the cost of making advanced biofuels. ChemCatBio will leverage unique capabilities and experts within the DOE National Laboratories to bring new catalytic materials to commercial bioenergy applications at least two times faster and at half the cost. ChemCatBio is part of the Energy Materials Network.
Photoredox Catalyst Based on an Arylimidazole Oxidative Electrochemical Mediator
Authors: Lam Chiu Marco , Little R. Daniel
Published: February 2020

Photocatalysis [1] and electrosynthesis [2] have been recognized as environmentally friendly methodologies for redox reactions, as they obviate the need for toxic or dangerous reagents. These approaches also allow for unstable reagents to be produced in situ, thereby permitting mild conditions. The reactive intermediates can be generated by the photoexcitation [1], or ionization of a mediator [2] at an electrode. The reagent can then perform redox chemistry with the substrate, and return to its original form to complete the catalytic cycle.

A class of oxidative electrochemical mediators based on the triarylimidazole framework has recently been investigated by Little, Zeng and Francke [2-5]. These mediators undergo one electron oxidation at the anode to form a radical cation that serves as an oxidative catalyst.

Recently, we have explored the potential of imidazole and phenanthroimidazole mediators to serve as photocatalysts. With an amine playing the role of a sacrificial reductant, the excited state serves as a reducing agent suitable for dehalogenation of aromatics, 5- and 6-exo,trig cyclizations of allyloxy and homoallyloxy iodo aromatics, as well as the photoredox equivalent of electrohydrocyclization [6].

Reference

[1] Tucker, J. W.; Stephenson, R. J. J. Org. Chem., 2012, 77, 1617-1622.

[2] Francke, R.; Little, R. D. Chem. Soc. Rev., 2014, 43, 2492-2521.

[3] Francke, R.; Little, R. D. J. Am. Chem. Soc., 2014, 136, 427-435.

[4] Zhang, N.-T.; Zeng, C.-C.; Lam, C. M.; Gbur, R. K.; Little, R. D. J. Org. Chem.
 
2013, 78, 2104–2110.

[5] Zeng, C.-C.; Zhang, N.-T.; Lam, C. M.; Little, R. D. Org. Lett., 2012, 14, 1314-1317.

[6a] Miranda, J. A.; Wade, C. J.; Little, R. D. J. Org. Chem. 2005, 70, 8017-8026.

[6b] Moëns, L.; Baizer, M. M.; Little, R. D. J. Org. Chem. 1986, 51, 4497-4498.