bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Electronics and Photonics Division Award) New Directions in GaN Electronic and Photonic Devices Enabled By Electrochemical Processes
Authors: Han Jung 
Published: February 2020

In the past 30 years, GaN has emerged as one of the most important semiconductors that has made real impact to our society. In this talk I will share my perspective regarding the key breakthroughs, major applications, and under-explored opportunities associated with this material system. Especially I will focus on how electrochemistry can help to circumvent impasses and creates new dimensions in the exploration of electronic and photonic devices using GaN. Examples will be given in photonics and flexible electronics.
The research is supported by US Department of Energy, National Science Foundation, and DARPA.
New Avenues Towards Designing Transition Metal Phosphides for Efficient Electrocatalysis
Authors: Das Debanjan , Nanda Karuna Kar 
Published: February 2020

Transition metal phosphides (TMPs) have emerged as an intriguing class of efficient electrocatalysts finding widespread application in hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) etc. Unfortunately, however, currently adopted wet chemistry and solid-gas synthesis techniques rely on the use of surfactants/ toxic organic solvents or toxic gas which restricts facile fabrication of TMPs. Moreover, hybridizing TMPs with suitable carbon support (graphene, carbon nanotubes etc.) which favorably optimizes the electrochemical activity of TMPs is often achieved via post-synthesis modification further complicating the synthesis procedure.
In an attempt to overcome these limitations, we have recently developed a solid state, phosphine free method to fabricate Co2P nanoparticles encapsulated N,P co-doped CNTs. These as prepared catalysts were applied as a bi-functional electrocatalyst for HER and OER. In order to increase the surface area and loading of Co2P nanoparticles, we next designed Co2P encapsulated CNTs grafted N,P co-doped hollow spheres via MOF-templated strategy with superior catalytic activity compared to Co2P@CNTs.
We then introduced sub-2nm IrP2 nanoparticles encapsulated bilayered N, P co-doped graphene as a novel electrocatalyst which exhibits better HER activity than benchmark Pt/C in acid, neutral as well as the alkaline medium. Interestingly, careful tuning of the reaction parameters also enables the synthesis of phase pure Ir2P. Finally, a MOF-templated strategy was adopted to fabricate N, P co-doped hollow carbon nanocages grafted with ~ 2nm Ru2P nanoparticles which exhibited superior bifunctional HER and ORR activity in alkaline medium.
In conclusion, the versatile strategy developed here can be extended to fabricate a variety of TMPs with widely varied applications.
Building Blocks for Symmetric Multielectron Nonaqueous Redox Flow Batteries
Authors: Porath Anthony , Mann Shane C. , Dumitrascu Adina , Henton Daniel R. , Gillmore Jason G. , Guarr Thomas F. 
Published: February 2020

A series of redox active species were synthesized and assessed for their potential use in nonaqueous redox flow batteries (RFBs). The building blocks for these compounds consist of electron donor groups D and electron acceptor groups A, which are capable of undergoing highly reversible electrochemical oxidation and reduction, respectively. Different combinations of donors and acceptors, such as Dx-A­y, and Dx-Ay-Dx, give rise to a myriad of derivatives with distinct electrochemical properties. The donor/acceptor systems exist in at least three stable oxidation states during RFB operation: reduced (anolyte), neutral, and oxidized (catholyte) forms. The scope of this work includes organic heterocyclic donors attached to pyridinium, imide, and thiadiazole accepting groups. Polypyridinium compounds have also been investigated as a possible mulitelectron accepting platform.
Covalently linking the donor and acceptor groups eliminates crossover, and allows one to design an RFB that uses an inexpensive porous separator rather than an ion exchange membrane, reducing overall cost. In addition, multielectron redox processes serve to increase energy density and further reduce costs. The overall goal of this project is development of a durable, efficient, and inexpensive RFB system for large-scale grid storage applications.
The synthesis, characterization and preliminary electrochemical investigation of these molecules will be described.
Modelling of a Light-Weight, Flexible, Air-Breathing PEMFC
Authors: Kiessling Aleksandr , Mayer Matthew , Besser Ronald S. 
Published: February 2020

Flexible, light-weight and air breathing proton-exchange membrane fuel cells (F-PEMFC) are promising electricity generators for various future applications like drones and small portable devices [1, 2]. However, compared with “classic” fuel cells, such devices have worse performance in terms of power density on the basis of membrane area (W/cm²). Furthermore, reproducible fabrication is a challenge; promising prototypes were hand-fabricated using expensive equipment. For commercial success, F-PEMFCs must improve in terms of performance and manufacturability. However, this requires a good understanding of the respective device details down to the basic level.
For this work, a COMSOL Multiphysics simulation of a F-PEMFC prototype [3] is built. The simulation will be fed with accurate catalytic and physical parameters and used for an interactive process of (A) describing the F-PEMFC’s operating characteristics in detail, (B) finding approaches for performance optimization and (C) comparing experimental with simulation results. Therefore, polarization curves are created, and reactant and current generation distributions are examined.
Although collection of accurate catalytic and physical parameters is ongoing, preliminary results with comparable data [4] showed that it is likely that the F-PEMFC design is limited by oxygen mass transport. Consequently, we will present results of various changes in device configuration which might enhance cell performance, for example, in the cathode’s catalyst layer morphology geometry.
References
[1] S. R. Mahmoodi and R. S. Besser, “Fabrication and Characterization of a Thin, Double-sided Air Breathing Micro Fuel Cell,” Fuel Cells, vol. 18, no. 4, pp. 499–508, 2018.
[2] F. Ning et al., “Flexible and Lightweight Fuel Cell with High Specific Power Density,” (eng), ACS nano, vol. 11, no. 6, pp. 5982–5991, 2017.
[3] R. S. Besser and S. R. Mahmoodi, “FLEXIBLE PLANAR DOUBLE SIDED AIR BREATHING MICROSCALE FUEL CELL,” US 2018 / 0138516 A1 15/814,208, May 17, 2018.
[4] C. Song et al., “PEM fuel cell reaction kinetics in the temperature range of 23–120°C,” Electrochimica Acta, vol. 52, no. 7, pp. 2552–2561, 2007.

Figure 1
CVD Graphene Modified with Au Nanoparticles As Electrocatalysts for Sodium Borohydride and Hydrazine Oxidation
Authors: Tamašauskaitė-Tamašiūnaitė Loreta , Balčiūnaitė Aldona , Zabielaitė Aušrinė , Vaičiūnienė Jūratė , Norkus Eugenijus 
Published: February 2020

In the present study, the commercially available CVD graphene-Ni/SiO2/Si (Graphene-Supermarket) template was used as a substrate for the deposition of gold nanoparticles (AuNPs). The immersion of the CVD graphene into the 1 mM HAuCl4 solution at a temperature of 25 oC for 1 min results in the deposition of AuNPs on the surface of the CVD graphene-Ni/SiO2/Si. The surface morphology and structure as well as composition of the prepared catalysts were characterized by Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The electrocatalytic activity of the AuNPs modified CVD graphene-Ni/SiO2/Si catalyst was evaluated for the oxidation of sodium borohydride and hydrazine using cyclic voltammetry and chrono-techniques.
It was found that the CVD graphene-Ni/SiO2/Si modified with AuNPs exhibits a significantly higher electrocatalytic efficiency for sodium borohydride and hydrazine oxidation as compared with that of pure CVD graphene-Ni/SiO2/Si electrode, and seems to be a promising anode material for direct borohydride and hydrazine fuel cells.
Visualization of Liquid Water in a Metal Foam Flow-Field Based Polymer Electrolyte Fuel Cell Via Neutron Radiography
Authors: WU Yunsong , Brett Daniel J.L. , Shearing Paul R. 
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) have shown significant advances in terms of performance, efficiency and durability for a wide range of applications. Flow-fields are crucial components that affect the water management and performance of PEFCs. The existence of gas channel and land configurations in the conventional flow-field designs render gas and water distribution highly non-uniform. Such issue can lead to a series of events detrimental to PEFC performance and longevity [1].
As an alternative, new type of flow-field such as metal foam has been introduced. In-depth understanding of water management in metal foam flow-field based PEFC is indispensable for the optimisation of performance and durability. Here, liquid water formation and transport across the 25 cm2 metal foam flow-field based PEFC is evaluated using neutron radiography. A nickel foam was put on cathode aluminium plate and a silicone gasket was then placed around the foam to seal in gases. A vertical single-channel serpentine was used for the anode aluminium flow-field, as shown in Fig. 1 (a). All experiments were conducted at the cold neutron radiography (CONRAD) beamline facility at Helmholtz-Zentrum Berlin (HZB). The setup for neutron imaging has been described in [2].
The result showed the enhancement of mass transport and cell performance in the metal foam flow-field compared to the conventional triple-serpentine design. Correlation of performance to neutron radiography reveals that the performance deviation in the mass transport region is likely due to flooding issues. The metal foam flow-field based PEFC exhibits less flooding and better uniformity in the local water distribution compared with that of serpentine flow-field design (Fig. 1 (b)).
[1] Wu, Y., et al. "Effect of serpentine flow-field design on the water management of polymer electrolyte fuel cells: An in-operando neutron radiography study." Journal of Power Sources 399 (2018): 254-263.
[2] Wu, Y., et al. "Effect of compression on the water management of polymer electrolyte fuel cells: An in-operando neutron radiography study." Journal of Power Sources 412 (2019): 597-605.

Figure 1
Impact of Surface Functionalization of Pt/Graphitized Carbon on Catalyst Layer Structure and PEMFC Performance
Authors: Taning Ahmad Zulfikri , Woo Seunghee , Park Seok-Hee , Yim Sung-Dae 
Published: February 2020

The understanding of catalyst layers (CL) structure is of great importance to reduce Pt loading in a MEA of PEM fuel cell. Recent studies have shown that the CL structure is largely dependent on ionomer microstructure, affecting Pt utilization by controlling reactant transport [1]. The ionomer microstructure such as the distribution of ionomer thin film in the CL can be controlled by introducing functional groups on the carbon support to tune the interaction between PFSA ionomers and carbon supports, which was demonstrated by MD calculation [2] as well as experimental MEA study [3].
We have tried to introduce the surface functional groups to the Pt loaded highly graphitized carbon supports using non-covalent approaches [4] to resolve the non-uniform ionomer distribution issue, particularly in highly graphitized carbon-based catalysts. The pyrene aromatic compounds with different functional groups to form different surface charge were applied to the Pt/C commercial catalyst, and the surface modified catalysts were fabricated to cathode CL of MEAs through decal process. The MEA performance evaluated in a single cell showed that the Pt/C catalyst modified with amine groups performs better than the catalyst modified with other functional groups and non-functionalized reference catalyst. The reason of better MEA performance of the surface modified Pt/C catalyst will be discussed in terms of better ionomer distribution in the CL. In addition, the issues affecting the MEA performance such as the Pt poisoning by the functional groups during the non-covalent functionalization of Pt/C will also be presented.
[1] F. C. Cetinbas, R. K. Ahluwalia, N. Kariuki, V. D. Andrade, D. Fongalland, L. Smith, J. Sharman, P. Ferreira, S. Rasouli, D. J. Myers, J. Power Sources 344 (2017) 62.
[2] T. Mashio, A. Ohma, T. Tokumasu, Electrochim. Acta 202 (2016) 14.
[3] A. Orfanidi, P. Madkikar, H. A. El-Sayed, G. S. Harzer, T. Kratky, H. A. Gasteiger, J. Electrochem. Soc. 164 (2017) F418.
[4] H.-S. Oh, H. Kim, Adv. Funct. Mater 21 (2011) 3954.
Electrodeposition of Silver Metavanadate (AgVO3) As a Visible Light-Active P-Type Semiconductor
Authors: Vali Abbas , Firouzan Farinaz , Rajeshwar Krishnan 
Published: February 2020

The silver-based ternary oxides are promising candidates to use as a visible light active semiconductor because their band gaps are decreased due to the presence of the Ag 4d with O 2p orbitals in the valence band. Silver metavanadate (AgVO3), one of myriad silver-based ternary oxides, is a visible light active semiconductor because of its small band gap (2.5 eV).1

This paper describes the electrodeposition and characterization of electrodeposition of AgVO3. Electrodeposition is a fast and low temperature method which can be used to make thin films of a given semiconductor. In addition, the optical parameters (e.g., photocurrent, flat band potential) of the thin film semiconductors prepared by electrodeposition can be measured easily without any more processing steps.
A two-step electrodeposition strategy was demonstrated for ternary oxides2 and was applied in this study, to prepare AgVO3 thin films on FTO substrate. In the first step, a silver thin film was deposited cathodically from silver nitrate solution. In the second step, the silver thin film was stripped anodically in ammonium metavanadate solution to generate Ag+ and subsequent in situ precipitation with VO3
- to yield AgVO3 thin film on the substrate. The electrochemical crystal micro balance (EQCM) analysis confirmed one electron transfer in both steps.
The XRD pattern of the as-prepared sample confirmed that the as-prepared thin film was in α-AgVO3 form. Energy-dispersive X-ray analyses of the as-prepared sample gave the composition: Ag0.94±0.02V1.02±0.01O2.90±0.07 for the as-prepared thin film. β-AgVO3 was prepared by thermally annealing the as-prepared sample at 300 oC for 30 min. The energy band gaps of α-AgVO3 and β-AgVO3 thin films were measured by diffuse reflectance spectroscopy (DRS) and found to be 2.46 and 2.12 eV respectively. Atmospheric photoemission spectroscopy (APS) showed the valence band positions of α-AgVO3 and β-AgVO3 to be -5.65 and -5.41 eV respectively. By combining the DRS and APS results, the calculated conduction band edge positions of α-AgVO3 and β-AgVO3 were -3.19 and -3.29 eV respectively. These results will be discussed in the context of the application of these compounds for photoelectrochemical reduction processes such as hydrogen evolution or CO2 reduction.

References

R Konta, H. Kato, H. Kobayashib, and A.Kudo , Chem. Chem. Phys., 2003, 5, 3061–3065.

H. Antonia, N. R. Tacconi, W. Chanmanee, H., N. Myung, and K. Rajeshwar, Electrochem. Solid-State Lett., 2010, 13, D29-D32.
(Invited) Red TiO2 and Ferroelectric Photocatalysts
Authors: Liu Gang 
Published: February 2020

The strong band-to-band absorption of photocatalysts spanning the whole visible light region (400-700 nm) is critically important for solar-driven photocatalysis. Although it is actively and widely used as photocatalyst for various reactions in the past four decades, TiO2 has a very poor ability to capture the whole-spectrum visible light. Here, by controlling the spatially homogeneous distribution of boron and nitrogen heteroatoms in anatase TiO2 microspheres with a predominance of high-energy {001} facets, a strong visible light absorption spectrum with a sharp edge beyond 680 nm is achieved. The red TiO2 with the homogeneous doping of boron and nitrogen obtained shows no increase in defects like Ti3+ that are commonly observed in doped TiO2. More importantly, it has the ability to induce photocatalytic water oxidation to produce oxygen under the irradiation of visible light beyond 550 nm and also photocatalytic reducing water to produce hydrogen under visible light.
Integrating a semiconducting light absorber with an appropriate co-catalyst appears almost indispensable for photocatalytic solar fuel generation. Although ferroelectric materials with spontaneous electrical polarization are considered promising light absorbers with the ability to induce oppositely directed transport of photogenerated electrons and holes in the bulk, their applications are intrinsically restricted by the large Schottky barrier at the interface of the ferroelectric material and the co-catalyst, which has a larger work function. Here, we demonstrate that, by selective chemical epitaxial growth of anatase TiO2 islands on the positively poled (00-1) facet of PbTiO3 single-crystal particles to form an atomically smooth interface with a small potential difference, the material shows significantly improved photocatalytic hydrogen and oxygen generation under both UV-visible and visible light, while the island-free PbTiO3 is inactive in visible light.
(Invited) Mixed-Metal-Oxide Based Electrocatalysts for Efficient Reduction of Carbon Dioxide
Authors: Rutkowska Iwona Agnieszka , Kulesza Pawel J. 
Published: February 2020

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of catalytic sites (metal and metal oxide nanostructures, their stabilization and intentional activation, as well as organization into two-dimensional arrays, ultra-thin films or three-dimensional networks (e.g. through sequential deposition) on electrode surfaces. They can form nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties (e.g. toward reduction of CO2). We explore here the ability of polynuclear inorganic metal oxo systems to stabilize and functionalize metal (e.g. copper) nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, zinc or tungsten have been demonstrated to influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ag, Au, Pd, Ru) thus affecting their chemisorptive and catalytic properties. Metal oxide nanospecies can generate –OH groups at low potentials that induce proton mobility at the electrochemical interface.
Our research interests concern development of systems for the electrocatalytic reduction of carbon dioxide not only in neutral but also in acid media. For example, nanosized Cu or Ru naoparticles immobilized within ultra-thin films of tungsten oxide or zirconia have been considered. Selectivity of the catalytic systems largely depends on the activing adsorptive (CO2) phenomena and the affinity of catalytic centers to the adsorbed carbon monoxide (CO) type intermediates leading to their protonation or hydrogenation. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities relative to the competitive hydrogen evolution.
(Invited) High Conductivity, Stable Anion Conducting Membranes Based on Poly(norbornene)
Authors: Kohl Paul A , Huang Garrett , Mandal Mrinmay 
Published: February 2020

Alkaline exchange membranes (AEM) fuel cells and electrolyzers are potentially cost-saving alternatives to traditional proton exchange membrane (PEM) devices. Recently, anion conducting polymer membranes have achieved ionic conductivity and chemical stability comparable to Nafion, the current state of the art in PEM technology. Phase segregation is an effective way to achieving high hydroxide mobility. An all-carbon backbone with light cross-linking and a long, alkyl tether for the cation head-group are effective means of achieving chemical stability and limiting unwanted water hydration.
In this study, a series of tetrablock copolymers containing an all-hydrocarbon backbone and tethered quaternary ammonium groups were synthesized based on vinyl addition polymerization of norbornene. Several variations of block copolymer AEMs with different ion exchange capacities (IEC) were made by adjusting the ratio of hydrophilic to hydrophobic blocks. Correlations were found between the ionic conductivity and mechanical properties to the polymer structure, channel size, and degree of phase separation. Furthermore, it was found that light crosslinking of the membranes allows for high IEC materials to be used while maintaining acceptable water uptake. The crosslinked AEMs have demonstrated record-high hydroxide conductivities (198 mS/cm) for a chemically stable polymer. The chemical degradation at 80oC in 1 M KOH was <1% degradation in 1,200 hours. The AEMs were also used to construct MEAs for alkaline fuel cells.
Microstructure and Transport Analyses in Polymer Electrolyte Membrane Fuel Cells: Comparing Modeling Approaches
Authors: Randall Corey R. , DeCaluwe Steven C. 
Published: February 2020

Despite the recent entrance of proton exchange membrane fuel cells (PEMFC) into the automotive industry, performance under low platinum loading is still hampered by prohibitive and poorly understood transport losses inside the heterogeneous catalyst layer (CL). Predictive models do not yet sufficiently capture the transport of oxygen, water, and protons in the CL ionomer phase, due to the complexity of the CL microstructure. These transport rates are highly dependent on the substrate, film thickness, and relative humidity. Confinement effects limit water uptake and transport rates below roughly 100 nm thickness, and substrate effects can induce ionomer structures (i.e. lamellae) that further impact transport rates. Implementing these complexities into computational models allows for the microstructural and transport effects on PEMFC performance to be studied and better understood, especially in devices with low platinum loading.
Research presented here examines two pseudo-2d, Newman-type model approaches for examining microstructure and transport in PEMFC functional layers: particle-shell and flooded-agglomerate. Figures 1 and 2 show the differences in model domains for these two approaches, respectively. The particle-shell approach approximates a physically realistic structure by simulating a carbon particle at the center of a thin shell of Nafion. This thin shell is discretized to resolve the complex transport that takes place within it. At each vertical discretization, a single Nafion-wrapped carbon particle is taken to be representative of others at that same functional layer depth. The flooded-agglomerate model also simulates a representative spherical domain for each vertical discretization; however, the domain is made up of a cluster of Nafion-wrapped carbon particles enclosed in an additional layer of electrolyte.
The models predict cell polarization to examine the effect of CL microstructure as a function of RH- and thickness-dependent transport properties. Figure 3 shows an example overpotential curve from the flooded-agglomerate model in which interesting behavior can be seen with respect to the Nafion thickness. It shows that the CL overpotentials decrease with decreasing ionomer thickness down to 7 nm. Below 7 nm thickness, decreased proton conductivity limits transport, leading to increasing overpotentials at higher currents. The trends indicate that the balance between proton and oxygen transport rates in the CL Nafion can lead to possible trade-offs in optimizing CL design. These and other results will be presented and discussed, to demonstrate the coupled impacts of Nafion thickness and transport on PEMFC performance, and the impact of modeling approach on CL microstructure design.

Keywords
– Nafion, Transport, PEM, Fuel Cell, Modeling, Electrochemistry, Flooded Agglomerate

Figure 1