bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasma Treatment As an Effective Way of Modifying Carbon-Based Electrocatalysts for an Enhanced Oxygen Reduction Reaction
Authors: Schechter Alex , Mohan Roopathy , Modak Arindam 
Published: May 2020

Oxygen reduction reaction (ORR) is pivotal in renewable energy technologies such as in fuel cells and metal-air batteries. Precious metal-free electrochemical ORR is a critical component in designing cost-effective electrochemical energy conversion devices. In this report we demonstrate an efficient surface modification of carbon nanotubes (CNT) through one-step oxygen plasma irradiation that induces doping and charge redistribution around the doped heteroatom oxygen that promotes ORR activity. The defect sites generated owing to oxygen dopant in CNTs were confirmed by Raman spectra, X-ray photoelectron spectroscopy (XPS) surface composition and CHNO elemental analysis. The O-doped CNTs were thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) measurements. Our research shows that plasma-treated single-walled carbon nanotubes (SWCNT) are more effective ORR catalyst compared to multi-walled carbon nanotubes (MWCNT) due to the inherent structure of SWCNT that can access more defects and surface functional groups than MWCNT.
In the following study, plasma modification approach was implemented in the synthesis of a highly active robust Metal-Nitrogen-Carbon (M-N-C) catalysts through NH3-plasma pretreatment on high surface area black pearl carbon. Pre-treated FeNC/NH3-C contains Fe3C and Fe-Nx as catalytically active sites. XPS confirms the presence of a high surface concentration of pyrrolic to pyridinic nitrogen and ferrous sites on FeNC/NH3-C that promotes low oxygen reduction overpotential (0.80 V vs RHE in 0.5 M H2SO4 and 0.96 V vs RHE in 0.1 M KOH). Hence plasma activates the surface and incorporates nitrogen which forms stable Fe-N coordination for accelerating oxygen reduction. Importantly, FeNC/NH3-C shows lower peroxide yield at 0.6V/RHE (<20% in 0.5 M H2SO4 and <2 % in 0.1 M KOH) that can reduce the detrimental effect of H2O2 on the catalysts support and exhibits high stability, seen from thousands of potential cycling stability tests of FeNC/NH3-C in acid solutions. Thereby this plasma-based new synthetic approach can promote more active and stable non-precious metal catalysts.
Application of Au Nanoparticles Supported Nitrogen-Doped Carbon for Direct Ethanol Fuel Cells
Authors: Tamašauskaitė-Tamašiūnaitė Loreta , Upskuvienė Daina , Balčiūnaitė Aldona , Šimkūnaitė Dijana , Vaičiūnienė Jūratė , Niaura Gediminas , Kruusenberg Ivar , Kaare Kätlin , Volperts Aleksandrs , Dobele Galina , Zurins Aivars , Norkus Eugenijus 
Published: May 2020

In this study, the synthesis of gold nanoparticles (AuNPs) supported nitrogen-doped activated carbon (N-doped C) nanocomposites and their application for the electro-oxidation of ethanol in an alkaline medium is presented. The AuNPs have been deposited on the N-doped C material using chemical reduction with glucose and ascorbic acid as reducing agents and microwave-assisted synthesis. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, X-ray diffraction (XRD) and inductively coupled plasma optical emission spectroscopy (ICP-OES) were used for the characterization of morphology, structure and composition of the resulting nanocomposites, whereas, the electrocatalytic activity of the ones for the electro-oxidation of ethanol in an alkaline medium has been investigated using cyclic voltammetry and chrono-techniques.
It has been determined that the AuNPs/N-doped C nanocomposites have a higher electrocatalytic activity for the electro-oxidation of ethanol than the pure Au or N-doped carbon alone, indicating the synergistic effect of AuNPs and N-doped carbon material. The obtained N-doped carbon supported AuNPs catalyst seems to be an efficient anode material for direct ethanol fuel cells (DEFCs).
Irreversible Structural Dynamics in Bimetallic Pt-Ni Alloy Catalyst Under Alternating Redox Environments
Authors: Khalakhan Ivan , Vega Lorena , Viñes Francesc , Vorokhta Mykhailo , Skála Tomáš , Yakovlev Yurii , Neyman Konstantin , Matolínová Iva 
Published: May 2020

The better understanding on the structural dynamics of a bimetallic catalyst during its interaction with reactive environments is a prerequisite for the development of an efficient catalyst for proton exchange membrane fuel cells (PEMFCs). The main focus should be given to the outermost layers of catalytically active material which are directly involved in catalysis.
Herein, we applied the synchrotron radiation photoelectron spectroscopy (SRPES) and X-ray photoelectron spectroscopy (XPS) techniques to investigate surface chemistry aspects in a PtNi alloy catalyst under alternating oxidation (O2) and reduction (H2) atmospheres at different temperatures that simulate its behavior as a cathode catalyst in PEMFCs. The experimental results are substantiated by theoretical calculations on model PtNi nanoalloys.
We showed that PtNi alloy does not maintain its chemical integrity and undergoes surface reconstruction during the switching between oxidizing and reducing conditions in terms of relative surface nickel enrichment. Along with compositional changes catalyst coarsening was observed by atomic force microscopy (AFM).
The revealed behavior of the PtNi alloy provides valuable fundamental insights that help to gain advanced understanding of PtNi alloy catalytic activity in real conditions.

Figure 1
Interface Engineering: On the Impact of Micro-Porous Layers on Polymer Electrolyte Water Electrolysis Performance
Authors: Schuler Tobias , Schmidt Thomas J. , Büchi Felix N. 
Published: May 2020

In polymer electrolyte water electrolysis (PEWE), operational cost represents the main cost fraction. Losses induced by kinetic, ohmic as well as mass transport overpotentials limit cell efficiency and in turn lead to lower volumetric power density and higher energy consumption.
The interplay of porous transport layer bulk/surface properties1,2, providing thermal and electrical conductivity as well as fluid management between bipolar plates and catalyst layer, and cell efficiency is a disputed question in literature. Governing design parameters for porous transport layers, as well as fundamental limiting process haven’t been addressed so far. This study aims to close the gap between fundamentals and highly efficient PTL microstructure design. A novel class of hierarchically structured porous transport layers is fabricated based on sintering of economically viable Ti powder, see Figure 1..
A series of four different PTL materials including three different MPL types was analysed. Structural properties, characterized by laboratory and synchrotron based X-ray tomographic microscopy (XTM) were correlated to in-depth electrochemical analysis. Performance of the novel PTLs was probed by comparison to state-of-the-art PTL materials and stack technology. The superior surface properties of the microporous-layer enabled the use of ultra-thin membranes with Ti PTLs for the first time. To elucidate the MPL effect and reveal the mechanism of partial catalyst utilization3,4, the catalyst layer conductivity was studied as function of hydration state and ionomer content.
Reference
1 S. A. Grigoriev, P. Millet, S. A. Volobuev and V. N. Fateev, International Journal of Hydrogen Energy, 2009, 34, 4968-4973.
2 T. Schuler, R. De Bruycker, T. J. Schmidt and F. N. Büchi, Journal of The Electrochemical Society, 2019, 166, F270-F281.
3 Z. Kang, J. Mo, G. Yang, S. Retterer, D. Cullen, T. Toops, J. Green Jr, M. Mench and F.-Y. Zhang, Energy and environmental science, 2017, 10, 166-175.
4 T. Schuler, T. J. Schmidt and F. N. Büchi, Journal of The Electrochemical Society, 2019, 166, F555-F565.
Figure 1. XTM rendering of hierarchically structured porous transport layer.

Figure 1
Understanding the Mechanisms for Recoverable Vs. Unrecoverable AEMFC Degradation
Authors: Ul Hassan Noor , Adabi Firouzjaie Horie , Mustain William E. 
Published: May 2020

In recent years there has been significant improvement in the achievable current and peak power densities [1 - 3] as well as the longevity of operating AEMFCs [4]. However, cell performance degradation remains an area of concern for the technology and a key to reducing performance decline is understanding mechanisms at work – which includes both recoverable and irrecoverable (irreversible) losses. To date, very few studies have been done that aim to understand and counter performance degradation mechanisms, while those that have generally focused only on irrecoverable performance degradation [5,6] The present study highlights recoverable (mainly associated with water management) and unrecoverable degradation mechanisms (AEM and Ionomer degradation, catalyst loss etc.) and propose solutions for these problems. Rigorous experiments have been performed to understand the degradation processes and fundamental factors have been explored responsible for AEMFC in-situ degradation.
References
[1] Huang et al., “Composite Poly (norbornene) Anion Conducting Membranes for Achieving Durability, Water Management and High Power (3.4 W/cm2) in Hydrogen/Oxygen Alkaline Fuel Cells”, J. Electrochem. Soc. 2019 volume 166, issue 10, F637-F644.
[2] Mandal et al., “The Importance of Water Transport in High Conductivity and High-Power Alkaline Fuel Cells”, J. Electrochem. Soc. 2020 volume 167, issue 5, 054501.
[3] Kohl et al., “High Conductivity, Stable Anion Conducting Membranes Based on Poly(norbornene)”. 235th ECS Meeting.
[4] Peng et al., “Improving the Long-Term Operational Stability (>1000h) of AEMFCS By Understanding Water Dynamics through in-Situ Neutron Imaging and X-Ray Computed Tomography”, 236th ECS Meeting.
[5] Dekel et al., “Predicting performance stability of anion exchange membrane fuel cells”, Journal of Power Sources, Volume 420, 30 April 2019, Pages 118-123.
[6] Charles E.Diesendruck and Dario R.Dekel, “Water – A key parameter in the stability of anion exchange membrane fuel cells”, Current Opinion in Electrochemistry, Volume 9, June 2018, Pages 173-178.
Using Impedance to Quantify Transport Losses in Alkaline Water Electrolysis Electrode Catalyst Layers
Authors: Reumert Alexander Kappel 
Published: May 2020

Anthropogenic climate change has brought on a global climate crisis and emergency. Increased levels of atmospheric carbon dioxide levels has brought with it undesirable changes to the world’s climate. To halt and eventually stop this trend the world needs to move to zero-carbon sources of electricity, transport and chemical production.
To offset the variability in zero-carbon electricity sources storage or usage of the excess energy is necessary. One of several technologies to achieve this is water electrolysis. A promising candidate of this field of study is Alkaline Water Electrolysis
The field of alkaline electrolysis have recently moved from a gap-based macro-material approach to a nanomaterials based membrane cell architecture.
Due to recent advances in membrane technology both ion-conduction and electrolyte solvating membranes allow for a zero-gap architecture. With this approach comes new engineering challenges. Bubble formation, -diffusion, -suppresion, and –transport are all phenomena that are recently unexplored in the context of nanopowder-based electrode in flooded KOH systems.
One of the ways of exploring this is the use of Galvanostactic Electrochemical Impedance Spectroscopy (GEIS)..
Through GEIS investigations and Distribution of Relaxation Times of the electrochemical response of nano-powder based cathodes a Gerischer-like response indicating transport issues and a way of quantifying this.
Spray Pyrolysis Strategy for Preparation of Cathode-Supported Protonic Ceramic Fuel Cells
Authors: Tsimekas Georgios , Irvine John T. S. 
Published: May 2020

Since the discovery of proton conducting ceramic materials many research efforts have been focused into overcoming processing difficulties that hinder long-term stability and high performance of protonic ceramic fuel cells (PCFCs). Notably, high processing temperatures exceeding 1600 °C are often required to meet the microstructural demand of a dense proton conducting electrolyte membrane [1-2]. At this temperature range most potential electrode materials are chemically incompatible and therefore preclude the fabrication of electrode supported structures. In addition, for barium-based electrolytes (e.g. BaZr1-xYxO3-d) barium loss is anticipated resulting in lower conductivities and formation of structural defects. To overcome this major challenge thin film deposition techniques can be employed[3-4].
Spray pyrolysis is a cost effective and simple deposition technique for preparation of ultra-thin films (i.e.<5μm) enabling the reduction of operating and processing temperatures of fuel cells [5]. Microstructures and electrochemical performance of multi-layered thin film PCFCs fabricated at exceptional low temperatures of 950 °C, are investigated. Large area 5x5cm2 cathode substrates of (La0.8Sr0.2)0.95MnO3-d prepared by tape casting were used for mechanical support of the cells. To modify and reduce the surface porosity of the substrate Ce0.9Gd0.1O3-d was coated to facilitate the deposition of the BaZr0.9Y0.1O3-d (BZY) thin electrolyte. Subsequently, the anode electrode was sprayed in two stages comprised by a nano-porous layer of BZY and infiltrated Ni particles. Characterization of the cathode-supported PCFCs was performed by electrical measurements operating up to 600°C and scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) techniques.
[1] Shanwen Tao and John T.S. Irvine, Adv. Mater., 18, 1581-1584, (2006).
[2] Peter Babilo and Sossina M. Haile, J. Am. Ceram. Soc., 88 2362-2368, (2005).
[3] Kiho Bae et al., Adv. Energy Mater., 8, 1801315, (2018).
[4] Georgios Tsimekas et al., ECS J. Solid State Sci. Technol.,6(8), P553-P560, (2017).
[5] Georgios Tsimekas et al., ECS Trans., 70(1), 205-212, (2015).
Designing the Ideal Catalyst Layer in PEMFCs
Authors: Lamb James , Andrei Petru 
Published: May 2020

Many design parameters affect the performance of PEMFCs, including catalyst density, porosity, nafion distribution, agglomerate size, etc. The ideal values of these parameters vary not only from layer to layer (for instance from catalyst layer to gas diffusion layer or from anode catalyst layer to cathode catalyst layer) but also from location to location inside the same layer, resulting in non-uniform 3-dimensional spatial distributions of the platinum, nafion, and pore and agglomerate sizes. Furthermore, the optimal values of these parameters also depends on the operating conditions, such as electrical current density, pressure, and temperature, which increases the complexity of the problem even more. To design the ideal catalyst layer, the designer must determine the optimum distributions of the above parameters within each layer. In this work, we focus on estimating the ideal structure of the catalyst layer in PEMFCs, in particular on determining the optimum spatial distributions of the platinum, porosity, nafion, and agglomerate size.
To solve the above problem, we apply the adjoint method to compute the optimum parameters for the microstructure of the catalyst layer. We start by computing the sensitivity functions (which are related to the Gâteaux derivatives) of the cell voltage or current in the direction of the design parameter variation. The sensitivity functions are then applied to adjust the parameters of the entire catalyst layer in a point-by-point fashion. The process is repeated until convergence is obtained.
Numerical results will be presented showing the non-optimized and optimized distributions at different values of the operating current density, temperature, and pressure for a 25 μm membrane PEMFC, as well as the polarization curves for non-optimized and optimized configurations.
References
[1] M. Secanell, K. Karan, A. Suleman and N. Djilali, Jour of the Electrochemical Society, 155, B125 (2008).
[2] F. C. Cetinbas, S. G. Advani and A. K. Prasad, Jour of Power Sources, 250, 110 (2014).
[3] J. Lamb, G. Mixon and P. Andrei, Jour of the ECS, 164, E3232 (2017).
[4] P. Andrei and L. Oniciuc, Jour of Appl. Physics, 104, Art. No. 104508 (2008).
[5] P. Andrei and L. Oniciuc, Jour of Comp. Elec., 7, 111 (2008).
Enhancing the Stability and Performance of Mo-Doped Titanium Suboxide Fuel Cell Catalyst Supports
Authors: Alipour Moghadam Esfahani Reza , Easton E. Bradley 
Published: May 2020

Polymer electrolyte membrane fuel cells (PEMFCs) are a near-commercial clean energy technology with potential application in automotive and station power systems. However, the high cost of Pt catalyst and long-term durability of electrode materials still represents barriers towards that hinder market gains for the technology. The catalyst support material greatly influences electrocatalytic activity and durability of the catalytic Pt nanoparticles. Carbon black has been the primary catalyst support in fuel cells over the last 30 years due to its high surface area and electrical conductivity. However, carbon corrosion occurs readily during start-up/shutdown conditions. Therefore, more advanced support materials are need in order to overcome these problems.
Metal oxides supports have improved corrosion resistance over carbon black supports, but they typically lack the required electrical conductivity for high performance. Titanium suboxides, specifically those doped with Mo (TOM) and other metals, have been shown to have acceptable electronic conductivity and strong affinity for Pt nanoparticles, to enhance their activity and stability in fuel cells. However, doping with only Mo still creates materials with a sizable band bandgap of 2.6 eV. Furthermore, the long term stability of the Mo dopant is a potential concern.
Our group has taken a two-pronged approach to improving TOM materials. The first approach has been to add a second dopant. Specifically, we have a new material doped with both Mo and Si, Ti3O5-Mo-Si (hereafter referred to as TOMS) support. Remarkably, this support has a band gap of only 0.31 eV, approaching the conductivity of a metal. Furthermore, the TOMS material are highly durable and corrosion resistant, showing no signs of dopant loss under extremely corrosive conditions.
Our second approach to improving TOM has been to convert it into a nanotube structure (TNTS-Mo) and from there covalently attach a monolayer of a nitrogen-rich terpyridine (tpy) ligand to the surface of the support (hereafter referred to as TPY/TNTS-Mo). The tpy ligand serves as a protective barrier that stabilizes the TNTS-Mo support. Furthermore, the nitrogen groups also have an electronic interaction with Pt catalyst nanoparticles that enhances their stability under harsh operating conditions.
In this presentation, we will give an overview of support modification methods as well as detailed discussion of catalyst durability.

Figure 1
Synthesis of Au Nanoparticles Attached to Large-Area Cu-Oxide Nanowires By Thermal Treatment for Artificial Photosynthesis Process
Authors: Canto-Olvera Jose Fernando , Cigarroa-Mayorga Oscar E. , Guillen-Cervantes Angel 
Published: May 2020

Developing materials for fuels based on solar utilization is a current need to solve the energy problem in the world society [1]. The proposal of heterostructures conformed by nanowires and nanoparticles has been suggested for solar energy recovery application [2] focused on the artificial photosynthesis process.
In this work, heterostructures of copper oxide nanowires (CuO-Nw) and Gold nanoparticles (Au-Np) were achieved by thermal treatment. To grow the nanowires array, a Cu foil (99.99 % in purity) of 1 cm x 1 cm was chemically etched with 1 M nitric acid solution for 10 seconds, then it was isothermally heated in a horizontal furnace. The Oxygen atmosphere inside the furnace was controlled within 21 wt. % ± 1 wt. % content and a 20 L/min flux rate was used. The effect of temperature and time on density, diameter, and length of CuO-Nw was studied. The experiments were carried out at 400, 500 and 600 °C for 1h, 3h, and 5h. Afterward, Cu-O Nw were Au-coated by sputtering. Au films with 10 nm and 60 nm in thickness were deposited. In order to synthetize the Au-Np a thermal treatment was isothermally performed under Nitrogen atmosphere at 450 °C for 15 min. To guaranty reproducibility, the experiments were performed by triplicate in separated experiments.
Field emission scanning electron microscopy images proved the achievement of heterostructures consisting of Au-Np attached to CuO-Nw walls. The average diameter of Au-Np was obtained about 60 nm and 80 nm. No organic contaminants were identified by Raman spectroscopy, thus, the proposed methodology is a clean and environment friendly process. Cyclovoltammetry curves were recorded by potentiometer chamber in alkaline medium to characterize the electrochemical response of samples. It was found that Au-coated heterostructures exhibit an enhancement in efficiency for oxygen evolution reaction against those containing CuO-Nw array alone.

Acknowledgments

The authors acknowledge the Secretaría de Investigación y Posgrado of the IPN for the economic support to this work. The authors have no conflict of interest to disclosure.

References

[1] Beck, Fiona J., ACS Applied Energy Materials (2019), doi: 10.1021/acsaem.9b01030

[2] Cigarroa-Mayorga, O., Neri, E., Calderon, H., & Kisielowski, C. Microscopy and Microanalysis (2017), doi:10.1017/S143192761701100X

Figure 1
(Invited) Engineering Hematite Interfaces By Dual Modification for Sunlight Driven Water Oxidation Reaction
Authors: Freitas Andre L. M , Souza Flavio L 
Published: May 2020

The present study describes the role of different modifiers on the overall hematite photocurrent response, which allowed a dual material insertion increasing the charge separation without compromise the surface catalysis. The pristine and Sn-hematite electrodes were obtained with two different morphologies (columnar, CN, and ellipsoid (EN) nanostructure) by low-cost aqueous chemical method. The following step was the addition at the Sn-hematite surface of a spinel cocatalyst that was also synthesized via chemical method. Sn-hematite-cocatalyst (Ni2FeOx) electrodes were submitted to additional thermal treatment under nitrogen atmosphere to activate the material surface. The pristine hematite electrode showed considerable enhancement on photocurrent density J, in comparison with previous work in our group for both method from a range of ~ 30 µA.cm-2 up to 0.2 mA.cm-2 and 1.0 mA.cm-2 to 2.0 mA.cm-2 at 1.23 VRHE, for CN and EN photoelectrodes respectively. Sn-addition onto hematite electrodes clearly increased flat band potential promoting a good charge separation and shifts the onset to a higher potential, attributed to the surface state created by this modification. Notoriously, Sn-hematite electrode loaded with FeNiOx exhibited the highest photocurrent density suggesting a partially passivation of surface states created during the electrode designing. The well-known co-catalyst acted majoritypassivating the surface states instead of improving surface for catalysis. The dual modification contributes to understand the role of different modifiers that is possible to satisfactorily improve charge separation maintaining the conductivity attributed to intermetallic ions. In summary, the synergy of Sn+4 and Ni2FeOX addition enables us to promote a shift on the onset towards a lower potential and enhancing the photocurrent density.
The authors gratefully acknowledge support from FAPESP (Grant 2017/11986-5) and Shell and the strategic importance of the support given by ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation.