bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Proton Pump for Solar Energy Transformation:from Nano- to Meso-Scale Architectures
Authors: Rozhkova Elena A. 
Published: February 2020

Proton pumps are group of membrane proteins which carry out proton (H+) transfer across a biological membrane via energy-driven conformational changes in their structures. Light-driven proton pumps utilize sunlight energy to fuel ATP-synthase. Light is absorbed by the retinal cofactor that results in photoisomeriazation of the chromophore that leads to proton translocation through a membrane. Earlier we demonstrated that semiconductor nanoparticles can be self-assembled with membrane-proton pump complexes known as purple membranes (PM), wherein PM can be either isolated from microorganism as micron-scale patches [1,2] or synthesized cell-free as nano-sized particles [3]. These bio-inorganic constructs can be used for efficient water splitting systems in photocatalytic hydrogen production half-reaction. Catalytic activity of these assemblies can be boosted via variety of approaches, for example, control and scaling down of the soft material dimensions [3], introduction of a single atomic layer carbon material [2]. Further efforts are directed toward more complex meso-scale artificial systems for sunlight energy transformation to other fuels and useful products.
1.S. Balasubraanian, P. Wang, R. Schaller, T. Rajh, E.A. Rozhkova, NanoLetters 13, 3365−3371 (2013)

P. Wang, N.M. Dimitrijevic, A.Y. Chang, R.D. Schaller, Y. Liu, T. Rajh, E.A. Rozhkova, ACS Nano, 8(8), 7995-8002 (2014)

P. Wang, A. Y. Chang, V. Novosad, V. V. Chupin, R.D. Schaller, E. A. Rozhkova, ACS Nano, 11 (7), pp 6739–6745 (2017)
(Invited) Electrocatalytic Reduction of CO2in Gas-Phase Electrolyzers: Moving Towards a Relevant Use of CO2
Authors: Deutsch Todd G , Chen Yingying , Klein Ellis , Bender Guido , Neyerlin K C 
Published: February 2020

Controlling product selectivity in electrocatalytic CO2 reduction is critical for achieving an economically viable process due to costly downstream separations of valuable products. Thermodynamically, several possible products of CO2 reduction, as well as the undesired (in this case) H+ reduction reaction, reside within a few tenths of a Volt. Thus, product selection cannot be manipulated by controlling the potential but rather must occur via engineering catalyst-intermediate kinetics. Because most CO2 reduction reactions utilize H+ as a reactant, the products are also a strong function of pH. As the local pH varies due to the consumption of protons, the local product changes at a fixed potential. The majority of CO2 electrocatalyst development occurs in a buffered, liquid electrolyte half-cell with a configuration that portrays a misleading parameter set. Aqueous-based cathode systems are limited by minimal water solubility limits of CO2, which at ~30 mM can only support current densities1 around 30 mA/cm2. Such current densities are at least an order of magnitude too low to be considered for an industrially-relevant device. The product selectivity and efficiency of any catalyst measured in aqueous half-cells will undoubtedly be different in high rate (current) devices. A new analytical solution is required for screening materials designed to utilize CO2 at a scale commensurate with which it is currently being produced. In this talk, we will present an overview of our approach for transforming the CO2 reduction reaction from an aqueous environment to an industry-relevant gas-phase environment, where high rates of conversion are possible.
Through a robust fuel cell and electrochemical engineering research program, the National Renewable Energy Laboratory has developed considerable expertise in transforming gas-phase reactions from utilizing material properties to a functioning device level. This expertise is leveraged to develop a CO2 electrolyzer utilizing a gas phase cathode, and alkaline oxidation anode assembly. The electrodes are separated by a bipolar membrane with an engineered 3-D interfacial layer. Accelerating the water dissociation reaction at the interface of the cation and anion exchange layers in the bipolar membrane is necessary for achieving and maintaining high current densities in our advanced CO2 electrolyzer assembly. Initial results of this endeavor will be presented. We will also describe our progress in designing and fabricating new automated test stands, with real-time online reduction product analysis, capable of performing in-situ electrochemical diagnostics on dynamic processes in these complex systems. The ultimate goal of this project is to establish a platform to evaluate and benchmark promising CO2 electrocatalysts subject to conditions relevant for incorporation into a viable solution for efficient industrial reduction of CO2.

Acc. Chem. Res. 2018, 51, 910−918
(Invited) Composition Dependent Performance of Au-Pd Core-Shell Nanocatalysts for CO2 Electrochemical Reduction
Authors: Zhu Shangqian , Qin Xueping , Shao Minhua 
Published: February 2020

Electrochemical reduction of CO2 (CO2RR) to produce valuable chemicals is promising in simultaneously controlling the CO2 concentration and storing renewable energy. However, its wide adoption still needs highly selective and reactive catalysts.
In this study, Au-Pd core-shell (CS) nanoparticles consisting of a Au-rich core and Pd-rich shell were synthesized by wet methods. The nanoparticle composition and shell thickness were adjusted to evaluate their impacts on CO2-to-CO electrocatalytic conversion performance. The CS nanoparticles have a uniform morphology with an average size between 7 to 9 nm. As compared to pure Pd and Au nanoparticles with a similar size, all the synthesized CS nanoparticles exhibited a significantly increased CO selectivity (Figure 1). The CS nanoparticles also have superior mass and specific activities, which are highly dependent on the composition and structure. The best catalyst showed an ultrahigh mass activity of 99.8 mA mg-1 at -0.5 V along with a superior CO faradaic efficiency of 94.7%. In situ infrared spectroscopic studies with an attenuated total reflection configuration (ATR) and density functional theory calculations (DFT) were conducted to reveal the combined structure and composition impacts on the activity. It was found that the scaling relation between *COOH and *CO binding strength was broken on the core-shell nanoparticles and led to the high selectivity and activity toward CO production.
The authors acknowledge the support from Hong Kong Research Grant Council (26206115 and 16309418).

Figure 1. Faradaic efficiency of CO measured on synthesized Au-Pd core-shell, Pd and Au nanoparticles.

Figure 1
Life Testing of Ni-YSZ Fuel Electrode Under Electrolysis and Fuel Cell Operation in High Reducing Environment
Authors: Liu Qinyuan , Zhang Qian , Voorhees Peter W , Barnett Scott A 
Published: February 2020

An electrode supported Ni-YSZ/YSZ/Ni-YSZ symmetric cell was studied with direct-current operation, with one electrode operating in electrolysis mode, and another electrode in fuel cell mode. The 1000 h life tests were carried out at different current densities in 97% H2 / 3% H2O. At a current density ≤ 0.4 A/cm2, the cell total resistance value was reasonably constant, with a slight increase in ohmic resistance; no changes in microstructure were observed relative to the as-prepared cell. At current densities ≥ 0.6 A/cm2, there was a steady increase in ohmic resistance that was offset by a decrease in polarization resistance, resulting in a total resistance that was approximately stable. However, these higher current densities resulted in significant damage to the electrolyte microstructure. First, fracture was observed within the electrolyte near the electrolysis operation side. Second, fracture SEM images showed pronounced intergranular fracture that resulted because voids had formed at grain boundaries during the life tests. These changes presumably explain the observed ohmic resistance increase. In addition, nanoparticles formed in the electrode after electrolysis operation, probably explaining the decrease of polarization resistance.
The constant-current results are compared with those from similar cells life tested in reversing-current operation. The critical current density values for onset of signification degradation were similar: between 0.4 and 0.6 A/cm2. At the same values of current densities ≥ 0.6 A/cm2, the rate of increase in ohmic resistance were comparable during direct-current and reversing-current operation, while the rate of decrease in polarization resistance with direct-current operation were less than half of that with reversing-current operation. The microstructure changes after life tests at higher current densities were different: First, reversing-current operation resulted in damage to the electrode/electrolyte interface, but the electrolyte appeared to be intact. Second, highly concentrated Ni and YSZ nanoparticles were observed at both side of electrodes after reversing-current operation.
Numerical analysis was carried out to determine the effective oxygen partial pressure versus position within the electrolyte. The results show that the oxygen partial pressure near the electrolysis operation side decreased with increasing current density. The values may be low enough to reduce zirconia and form a Ni-Zr alloy. Subsequent oxidation of zirconium presumably causes the observed structural changes near the Ni-YSZ/YSZ interface.
The Examination and Characterisation of Water Transport in Metal Gas Diffusion Layers for PEMFC Via EIS and Neutron Imaging.
Authors: Fahy Kieran F. , Lee Chunghyuk , Lee Jason Keonhag , Zhao Benzhong , LaManna Jacob M , Baltic Elias , Hussey Daniel S , Jacobson David L , Bazylak Aimy 
Published: February 2020

Novel materials for gas diffusion layers (GDLs) in polymer electrolyte membrane fuel cells (PEMFCs) are increasingly under investigation to improve high current performance. Metal gas diffusion layers are of interest as they provide high thermal and electrical conductivity as well as offering the possibility of integration of the flowfield and gas diffusion layer. These properties are all of importance to fuel cells as they should give increased volumetric power density and decrease resistive losses at higher current densities.
Some recent studies have shown that these metal GDLs can outperform commercial carbon GDLs in the high current region [1]–[3]. The water dynamics of these types of GDL are poorly understood however, and there has been little or no research on this topic.
We have performed a study using neutron imaging to study the movement of water in metal mesh GDLs and used EIS to study the consequent effect of mass-transport resistance at a number of current densities and humidities [4]. We have observed a number of interesting phenomena in the water transport in metal-mesh GDLs, which show quite different behavior to that of the normal carbon papers.
When metal mesh is used as the anode and cathode GDL, there appears to be water accumulation in the areas of the channel, which also promotes the back-diffusion of water from the cathode to the anode side of the cell. With a carbon-paper GDL, liquid water accumulates in the land, and there does not appear to be significant back-diffusion compared to the metal mesh GDL. These behaviors also have significant effects on mass-transport and the performance of the cell. The insights provided by the neutron imaging, along with the EIS data will allow us to inform novel and future fuel cell designs.
References
[1] T. Yoshida and K. Kojima, “Toyota MIRAI Fuel Cell Vehicle and Progress Toward a Future Hydrogen Society,” Interface Mag., vol. 24, no. 2, pp. 45–49, Jan. 2015.
[2] K. F. Fahy, J. Lapinski, and A. R. J. Kucernak, “Metal Mesh Gas Diffusion Layers for PEM Fuel Cells,” Meet. Abstr., vol. MA2016-02, no. 38, pp. 2569–2569, Sep. 2016.
[3] N. Hussain, E. Van Steen, S. Tanaka, and P. Levecque, “Metal based gas diffusion layers for enhanced fuel cell performance at high current densities,” J. Power Sources, vol. 337, pp. 18–24, Jan. 2017.
[4] R. S. Fu et al., “An Investigation of Thermally-Induced Water Transport in Polymer Electrolyte Fuel Cells with Neutron Radiography Imaging Technique,” in ECS Transactions, 2009, pp. 543–552.

Figure 1
(Invited) Perspective on Modeling in Proton Exchange Membrane Fuel Cells
Authors: Fuller Thomas F. 
Published: February 2020

Following their use in the Gemini space program (1965-66), proton exchange membrane fuel cell (PEMFC) technology languished. Los Alamos National Laboratory (LANL), and more specifically Shimshon Gottesfeld’s group, was instrumental in the resurgence of PEMFCs. Polymer Electrolyte Fuel Cell Model,[i] has been cited more than 2000 times since 1991 and exemplifies the influence that Gottesfeld’s group had on the community during his roughly two decades at LANL. Remarkable advances have subsequently been made in modeling of PEMFCs, arguable greater than those seen in the lithium-ion battery field. The focus of this presentation is to connect the broader work of Gottesfeld’s group on PEMFCs to the field of modeling of fuel cells and to offer a perspective on the remaining barriers and opportunities, and specifically those for the catalyst layer, nearly 30 years after Springer et al.’s seminal paper.
[i] Springer, T. E., Zawodzinski, T. A. & Gottesfeld, S. Polymer Electrolyte Fuel-Cell Model. J Electrochem Soc
138, 2334-2342 (1991).
(Invited) Fuel Cells Fueled By Sustainable Liquid Fuels
Authors: Soloveichik Grigorii L. 
Published: February 2020

The Advanced Research Projects Agency (ARPA-E) funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency across all economic sectors, and ensure US technological lead in advanced energy technologies, including electrochemical technologies for energy transformation and storage for distributed, grid scale and automotive applications.
Recently hydrogen PEM fuel cells (FC) made great progress in performance, durability and cost that reflected in the emerging of multiple commercial vehicles powered by FCs. However their market penetration is hampered mostly by the absence of hydrogen infrastructure including transportation and storage, and high cost of its implementation. On the other side, carbon-neutral liquid fuels (CNLFs) have energy density higher than of liquid hydrogen, better safety, low footprint and cost of transportation and storage. Easily liquefied ammonia and dimethyl ether as well as more traditional lower alcohols are the most promising CNLFs. They can be used with or without internal reforming in direct liquid fuel cells (DLFCs) or as a hydrogen carrier for PEM fuel cells thus allowing the use of existing liquid fuels infrastructure. History of DLFCs started in 1960s from first GE attempts to use diesel fuel in a FC and continued with development of direct methanol fuel cells (DMFCs). In spite intensive research, the latter found very limited application because of low efficiency and power density. As conventional low temperature PEMs and AEMs content a lot of water to support high H+ or OH- conductivity, high crossover rate of most CNLFs is inevitable and leads to low cell voltage and energy efficiency. In addition, traditional platinum group metal catalysts are easily poisoned by CNLFs or by intermediate oxidation products. Therefore, to realize high energy density of CNLFs and provide high FC power density, it is necessary to increase operation temperature of DLFCs, develop more active and less expensive electrocatalysts, develop selective ion conducting membranes and design electrodes and cells for using liquid fuels.
Recent advances in the development of novel DLFCs that is being funded by ARPA-E via REFUEL and OPEN 2018 programs will be presented. Possible future ARPA-E program targeting the use of such fuel cells for transportation (in hybrids, range extenders, APUs for aviation and ground transportation) will be also discussed.
(Invited) Effects of an Alkyl Spacer and the Cationic Group on the Hydrated Morphology of Anion Exchange Membranes
Authors: Paddison Stephen J. , Luo Xubo , Zhu Zhenghao 
Published: February 2020

Anion exchange membranes (AEMs) are increasingly of interest as the electrolyte in energy and conversion devices. Challenges for their use in these devices are the low chemical stability under alkali conditions and only meager ionic conductivity. A promising strategy to enhance the conductivity of these materials may be through tailoring of the phase segregation of the polymer. Hence, the hydrated morphology of an AEM polymer may be a strategy to achieving high performance. Recently, AEMs based on the triblock copolymer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS), and functionalized with various cationic groups have shown satisfactory chemical stability.
We have recently undertaken an extensive investigation to understand how various molecular features (placement of an alkyl spacer on the side chain, choice of the cationic group, and the associated anion) determine the hydrated morphology of functionalized SEBS systems. DPD, a meso-scale simulation technique, enables relatively large time and length scales to be examined and therefore permits the elucidation of the morphology of the polymer system in acceptable time and computational expenses. The optimized structure and the interaction parameters used in these DPD simulations were calculated using a recently developed methodology employing DFT based electronic structure calculations. The morphology was determined over a broad range of hydration and our results underscore the complexity of effects of these parameters.
(Invited) Ten Years on: Evolution, Status and Future of Alkaline Exchange Membrane Fuel Cell Systems
Authors: Page Miles , Amel Alina , Azra Charly , Kitayev Anna , Ben-Yehuda Chaya 
Published: February 2020

In 2009, CellEra Technologies began work on an Alkaline Exchange Membrane Fuel Cell (AEMFC) stack. Shortly thereafter, at a time when there was relatively little interest in the technology, a stack with 100 cm2 active area, yielding slightly under 100 mW/cm2, running on H2 and O2 was achieved. This result was the first demonstration of an AEMFC stack in operation and generated significant market interest. The membrane-electrode assemblies (MEA’s) used therein yielded up to 200 mW/cm2 in single-cell tests, a comfortably world-leading AEMFC power density at the time. Nevertheless, critical and potentially insurmountable obstacles were also in sharp focus: Low performance vs PEM fuel cells, low durability arising from chemical instability of ionomer in alkaline conditions, sensitivity to atmospheric CO2 and more.
There exists in addition a special challenge of water management in the AEMFC. Though not traditionally assigned the same weight as the above obstacles in general AEMFC mythology, it was flagged as critical early on in our development program, and has since remained thematic, as it was determined to be a root cause in a large proportion, if not the majority, of identified device technology limitations. Active water consumption in the cathode electrode,
½O2 + H2O + 2e- → 2OH- (1)
balanced by double the overall water generation rate at the anode,
H2 + 2OH- → 2H2O + 2e- (2)
leads to a wide variety of mutually reinforcing detrimental phenomena that must be mitigated holistically to achieve sustained high performance and durability.
The existence of the additional reactant – water – in the cathode (Eq 1) is especially significant, with strong multi-scaled implications, from requirements for the chemistry of the component materials, to the design of catalyst layers, structural aspects of the MEA, optimization of operating conditions, design of flow fields and stack engineering. Even today, ten years on, this remains the core engineering and materials science challenge of the technology in spite of impressive progress made in the research field as a whole.
In this talk we review the developments in, and understanding of, the PO-CellTech (formerly CellEra) MEA, stack and fuel cell system that have by now resolved all the fundamental questions of AEMFC viability as a technology, and allow us to target the nascent consumer automotive “FCEV” market: Ultra-low Platinum Group Metal (PGM) loadings, next-generation membrane technology, high areal (MEA) and volumetric (stack) power density, CO2 tolerance, and significant room for continued improvement. We will analyze the status and limitations of AEMFC power density, as well as the major outstanding challenge of device durability, with special reference to the ever-present water management imperative as well as increasingly stringent demands that need to be met, in order successfully to address a rapidly maturing exchange membrane fuel cell market.
Protein Film, and Diffusion–Controlled Voltammetry of Hemeproteins on a Single Surface
Authors: Gerroll Benjamin , Peters Dennis G 
Published: February 2020

Protein film voltammetry has made possible electrochemical studies of complex protein reactions, such as redox-induced conformational dynamics1 and enzyme kinetics.2 However, without diffusion-controlled experiments as a reference, one cannot be sure of the extent to which the protein–electrode interaction affects conformational dynamics or enzyme kinetics. Diffusion-controlled voltammetric experiments can provide an alternate view into these processes. Previously, semiconductor electrodes have been successfully employed for diffusion-controlled experiments.3

Herein, we report novel application of electrochemically deposited cadmium oxide (CdO) as a working electrode for both diffusion-controlled voltammetry as well as protein-film voltammetry (PFV). The hydrophilic CdO surface allows transient protein interactions for diffusion-controlled measurements, as well as a suitable surface for drop casting protein films. Polycrystalline CdO electrodes were electrodeposited onto a fluorine-doped tin oxide (FTO) working electrode held at –0.7 V vs. SCE for 15 min in aqueous solutions of CdCl2, then annealed at 450 °C for 2 h. CdO surfaces were characterized by means of x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and scanning electron microscopy (SEM). XPS and XRD confirm formation of polycrystalline CdO. Electron micrographs confirm complete coverage of the FTO by CdO. To generate protein films, 10 mg/mL solutions of either cytochrome c or hemoglobin were drop cast onto CdO electrodes and left for 2 h. Cyclic voltammograms recorded for both hemoglobin and cytochrome c display nearly reversible electron transfer, with redox potentials similar to those previously reported.4

1 A. El Kasmi, M. C. Leopold, R. Galligan, R. T. Robertson, S. S. Saavedra, K. El Kacemi, E. F. Bowden, Electrochem. Commun. 2002, 4, 177–181.
2 H. Liu, G. Zou, J. Biochem. Biophys. Methods.
2006, 68, 87–99.
3 G. Valincius, V. Reipa, M. P. Mayhew, V. L. Walker, Electrochem. Commun.
2002, 4, 314–317.
4 G. Battistuzzi, M. Bosari, M. Sola, F. Francia, Biochemistry, 1997, 36, 16247–16258.