bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited, Digital Presentation) Doping Gallium Oxide and Competing Ultra-Wide Bandgap Oxides
Authors: Lyons JOHN L 
Published: July 2022

Although Ga2O3 is widely believed to be the among most promising ultrawide-bandgap semiconductors, its inability to be p-type doped hampers future applications. Moreover, alloying with aluminum increases the Ga2O3 band gap, but it is unclear if electrical conductivity of AlGO alloys can be controlled. The properties of group-IV (C, Si, Ge, and Sn) and transition metal (Hf, Zr, and Ta) substitutional dopants in AlGO alloys are systematically explored here using first-principles hybrid functional calculations. In Ga2O3, all dopants act as shallow donors. However, in Al2O3 all are deep defects, characterized by DX behavior or the emergence of positive-U (+/0) levels. Combining our calculations of dopant charge-state transition levels with information of the AlGO alloy band structure, the critical Al composition at which each dopant transitions from being a shallow to a deep donor is estimated. Si is identified as being the most efficient dopant to achieve n-type conductivity in high Al-content AlGO alloys, acting as a shallow donor over the entire predicted stability range for AlGO solid solutions. Compensation by other unintentional impurities (such as H and C) is also assessed.
Other oxide materials have also emerged as potential competitors to Ga2O3, but their propensity for hole conductivity is less well known. Here the stability of hole polarons in a set of ultrawide-bandgap oxides (Ga2O3, Al2O3, ZnGa2O4, MgGa2O4, LiGaO2 and GeO2) is examined and compared, both in pristine material and in the presence of acceptor impurities. Holes spontaneously self-trap in all oxides investigated, with varying stabilities. Acceptor impurities further stabilize these trapped holes, leading to large acceptor ionization energies. Hole trapping also leads to characteristic distortions and distinct optical transitions, which may explain some experimentally-observed signals. These results indicate that achieving p-type conductivity in any of these oxides is unlikely, with the possible exception of GeO2.
This work was performed in collaboration with Darshana Wickramaratne (NRL), Joel Varley (LLNL), Sai Mu (UCSB), Mengen Wang (UCSB) and Chris Van de Walle (UCSB), and was supported by the ONR/NRL 6.1 Basic Research Program.
Catalyst Dissolution Analysis in PEM Water Electrolyzers during Intermittent Operation
Authors: Milosevic Maja , Knöppel Julius , Ehelebe Konrad , Abbas Dunia , Escalera López Daniel , Thiele Simon , Cherevko Serhiy 
Published: July 2022

Sustainable development of the global energy sector requires a transition from fossil fuels to renewable energies. Considering the continuously increasing energy demand, effective utilization of intermittent output from the renewable sources will depend on the efficiency of energy storage and utilization processes. Low chemical complexity and high energy density and efficiency make hydrogen produced via proton exchange membrane water electrolysis (PEMWE) a prominent solution for the mentioned challenges.
Acidic conditions and high potentials at the anode side of PEM water electrolyzers, where the oxygen evolution reaction (OER) takes place, demand for materials with high catalytic activity and corrosion stability. The state-of-the-art platinum and iridium (oxide) catalysts in the cathode and anode catalyst layers (CLs), respectively, demonstrate relatively good activity and stability during steady operation at low and moderate electrical loads. Indeed, it is anticipated that a significant decrease in the noble metal amount may be achieved without sacrificing the cell performance [1]. An intermittent operation of PEMWE, however, represents a considerable risk factor as both CLs may degrade with time. The extent of such degradation, especially at low catalyst loadings and high current densities, alternated with numerous off cycles is still not well understood and hence, difficult to predict and mitigate.
Recent results from our group indicate a severe discrepancy between OER catalyst dissolution in aqueous model systems (AMS) and membrane electrode assemblies (MEA), with the main reasons being a suggested discrepancy between estimated and real pH in MEA and stabilization occurring over time [2]. In this work, CLs degradation during dynamic electrolyzer operation in a specially designed PEMWE test station was studied via ex-situ inductively coupled mass spectrometry analysis (ICP-MS) and its influence on the cell’s overall performance was analyzed. The S number, a new metric for OER catalyst lifetime estimation [3], was also used to compare catalyst stability properties within the two systems.

References:

Bernt, A. Siebel, H. Gasteiger, J. Electrochem. Soc. 165 (5), F305-F314 (2018)

Knöppel, M. Möckl, D. Escalera-Lopez, K. Stojanovski, M. Bierling, T. Böhm, S, Thiele, M. Rzepka, S. Cherevko, Nat. Commun. 12, 2231 (2021)

Geiger, O. Kasian, M. Ledendecker, E. Pizzutilo, A. M. Mingers, W. T. Fu, O. Diaz-Morales, Z. Li, T. Oellers, L. Fruchter, A. Ludwig, K. J. J. Mayrhofer, M. T. M. Koper, Serhiy Cherevko, Nat. Cat. 1, 508 (2018)

Figure 1. Longterm stability of IrOx in AMS and MEA environment. a) Loading-normalized total dissolved iridium amount at current densities of 0.2 A mgIr
-1 and 2 A mgIr
-1 in AMS and MEA respectively; b) S-numbers calculated from the amount of dissolved iridium.

Figure 1
Exploring the Effectiveness of Carbon Cloth Electrodes for All-Vanadium Redox Flow Batteries
Authors: Caiado Ashley A. , Aravamuthan Sundar Rajan , Goulart James , Gallaway Joshua W , Agar Ertan 
Published: July 2022

Redox flow batteries (RFBs) have proven to be a promising technology for the integration of intermittent renewable energy sources into the existing electrical grid due to their ability to decouple energy and power ratings, and the associated cost-effectiveness in long-duration energy storage [1]. Among various flow battery chemistries, vanadium redox flow battery (VRFB) is one of the most prominently studied flow battery system [2]. In comparison to other chemistries, four soluble oxidation states of vanadium are available and accessible. This characteristic of VRFBs eliminates cross-contamination between the positive and negative half-cells that would otherwise deteriorate the life and durability of the battery [3]. In a flow battery cell, porous electrode is the key component that determines the performance of the system by delivering liquid electrolytes, facilitating ion/charge transfer, and providing sites for electrochemical reactions [4]. Recently, it has been found that significant performance improvements can be achieved with fabric (carbon cloth) electrodes when coupled with a wetting electrolyte [5].
In this talk, we will report our experimental approach to evaluate the short- and long-term effectiveness of various carbon cloth electrode samples for use in VRFBs. Results generated from symmetric flow cell cycling coupled with electrochemical impedance spectroscopy and polarization curve measurements will be discussed. The key physico-chemical properties and their evolution during cycling will be elucidated.

References:

[1] Z. Li, M. S. Pan, L. Su, P.-C. Tsai, A. F. Badel, J. M. Valle, S. L. Eiler, K. Xiang, F. R. Brushett, Y.-M. Chiang, Joule, 1, 306-327 (2017).
[2] M. Nourani, C. R. Dennison, X. Jin, F. Liu, E. Agar, J. Electrochem. Soc.,
166, A3844-A3851 (2019).
[3] M. Nourani, B. I. Zackin, D. C. Sabarirajan, R. Taspinar, K. Artyushkova, F. Liu, I. V. Zenyuk, E. Agar, J. Electrochem. Soc.,
166, A353-A363 (2019).
[4] A. Forner-Cuenca, F. R. Brushett, Curr. Opin. Electrochem., 18, 113-122 (2019)
[5] K. M. Tenny, A. Forner-Cuenca, Y.-M. Chiang, and F. R. Brushett, J. Electrochem. Energy Convers. Storage, 17, 041010 (2020).
Nonaqueous Redox Flow Batteries Incorporating Novel Pyridinium Anolytes
Authors: Hengesbach Charley , Scott Jessica , Samaroo Sharmila , Bruggeman Chase , Hickey David , Guarr Thomas F. 
Published: July 2022

While the use of nonaqueous solvents in redox flow batteries (RFBs) offers the promise of higher cell voltages than can typically be obtained in aqueous electrolytes, suitable compounds that are sufficiently soluble and stable to permit extended operation has proven challenging. Viologen anolytes have been successfully employed in aqueous systems, but their first reduction occurs at very modest potentials, thus limiting their advantage in nonaqueous systems. We have previously reported flow battery chemistry employing a series of extended bis(pyridinium) species with reduction potentials ca. 300-400 mV more negative than viologens and very long-lived, durable reduced states. However, these materials were difficult to access via common synthetic routes and often exhibited limited solubility.
In this presentation, we describe an extension of those studies to new pyridinium compounds that provide still more negative reduction potentials (ca. -1.6 to -1.7 V vs Fc/Fc+). Moreover, these compounds are readily synthesized in good yield from inexpensive raw materials, are highly soluble, display excellent electrochemical kinetics, and are extremely persistent in the reduced state. The synthesis and electrochemical characterization of compounds incorporating these groups will be presented, along with preliminary RFB cycling results.
(Digital Presentation) Development of a Bio-Inspired Non-Aqueous Redox Flow Battery Utilizing Anionic Active Materials
Authors: Pahari Shyam Kumar , Visayas Benjoe Rey B. , Brown Ross S , Gokoglan Barut Tugba Ceren , Golen James A , Agar Ertan , Mayes Maricris L. , Cappillino Patrick J. 
Published: July 2022

Energy storage is an indispensable part of future electrical grids as they increasingly shift toward renewable energy sources.1 Although many other energy storage technologies have shown potential, redox flow batteries are especially promising because of advantages arising from their decoupled power and energy capacity, wide range of possible electroactive materials, wider potential window (in non-aqueous solvents) and safety. 2 However, the nascent non-aqueous redox flow battery (NRFB) technology currently faces key challenges that need to be addressed to ensure their reliability and widespread implementation. Low stability of active material during deep cycling is one such challenge that needs to be addressed while low solubility of active material in organic solvent is another main hurdle that greatly limits energy density.
Herein, we present a cost-effective, experimental-theoretical approach 3
,
4 to improve the solubility of a vanadium-based, highly stable, anionic active material known as vanadium-bis-hydroxyiminodiacetate (VBH). This is accomplished by tuning the key thermodynamic quantities of free energy of solvation and free energy of the lattice. We also demonstrate that the lattice free energy, which has been largely ignored in theoretical solubility models, is vital to obtain a meaningful prediction of solubility, and cannot be overlooked. Finally, we report the full cell cycling of the highly soluble VBH, coupled with an anthraquinone, exhibiting excellent cyclability and a reliable spectroscopic method to characterize pre- and post-cycled electrolytes.
References
(1) IEA. Renewable Energy Market Update 2021
; Paris, 2021.
(2) Dunn, B.; Kamath, H.; Tarascon, J.-M. Electrical Energy Storage for the Grid: A Battery of Choices. Science
2011, 334 (6058), 928-935. DOI: 10.1126/science.1212741.
(3) Pahari, S. K.; Gokoglan, T. C.; Visayas, B. R. B.; Woehl, J.; Golen, J. A.; Howland, R.; Mayes, M. L.; Agar, E.; Cappillino, P. J. Designing high energy density flow batteries by tuning active-material thermodynamics. RSC Advances
2021, 11 (10), 5432-5443, 10.1039/D0RA10913D. DOI: 10.1039/D0RA10913D.
(4) Visayas, B. R. B.; Pahari, S. K.; Gokoglan, T. C.; Golen, J. A.; Agar, E.; Cappillino, P. J.; Mayes, M. L. Computational and experimental investigation of the effect of cation structure on the solubility of anionic flow battery active-materials. Chemical Science
2021, 12 (48), 15892-15907, 10.1039/D1SC04990A. DOI: 10.1039/D1SC04990A.
Incorporating ALD Based Pt Alloy Catalysts into Gas Diffusion Electrodes for Proton Exchange Membrane Fuel Cells
Authors: Tan Shunquan , Xu Shicheng , Dull Samuel , Jaramillo Thomas F , Prinz Fritz 
Published: July 2022

Atom layer deposition is a promising method to fabricate gas diffusion electrodes (GDE) with platinum catalysts for high-power-density Proton Exchange Membrane Fuel Cells (PEMFCs). Alloying Pt with transition metals can further improve the intrinsic activity for oxygen reduction reaction due to the ligand and strain effects. Nevertheless, incorporating alloy catalysts into GDE posts more challenges.
In this study, we systematically explore and optimize alloy-based catalysts via ALD deposition on gas diffusion layers (GDL). While GDE tolerates 200 oC annealing for alloys that can form under low temperature (e.g.PtxZny) and present high ORR performance, GDE for PtxTiy alloy presents inferior performance after high-temperature annealing.
To circumvent this temperature compatibility issue, we successfully developed a modified high-temperature ALD method for PtxTiy alloy by taking advantage of a porous metal felt. With this, ALD-based high temperature annealed PtxTiy series alloy can maintain its atomic structure, and the GDL can keep its high hydrophobicity. Further Membrane Electrode Assembly (MEA) testing results and insights into active site areas and activation energy for different alloys and fabrication methods provide the in-depth elucidation of the relationship between reaction kinetics and GDE structures.
Platinum-Based Nanoparticle Fuel Cell Catalysts Synthesized By Sputtering Onto Liquid Substrates
Authors: Lönn Björn , Brown Rosemary , Pfeiffer Robin , Frederiksen Henrik , Wickman Björn 
Published: July 2022

The quest of finding cheaper and better fuel cell catalyst materials has been long ongoing and remains a crucial step in making fuel cells a commercially viable technology. Platinum (Pt) is still the conventional catalyst used in proton exchange membrane (PEM) fuel cells, however, with slow cathode kinetics and high material cost. Platinum-rare earth (RE) and lanthanide alloys have been found to greatly enhance the catalytic activity towards the oxygen reduction reaction (ORR).1 Increases in ORR activity of up to one order of magnitude compared to pure platinum has been observed for these alloys, but high oxygen affinity of the RE alloying agents considerably complicates their synthesis. Sputter deposition into low vapor pressure liquid substrates, such as ionic liquids and certain polymers enables fabrication of clean nanoparticles, without the presence of air and other contaminates, making it a potential technique for Pt-RE nanoparticle synthesis.
Here, we will present our recent work on magnetron sputtering of Pt 2 and Pt-alloys into different liquid substrates, including polyethylene glycol and three imidazolium-based ionic liquids. We have investigated the influence of substrate temperature on Pt nanoparticle growth during sputtering, and in post-sputtering heat treatment.2 We show that whilst substrate temperature influences the Pt nanoparticle size, the effect is not as great as for other materials. Better understanding the growth processes of Pt nanoparticles sputtered into liquids is an important step towards tunable sizes and catalytic activities of Pt-RE nanocatalysts.

Escudero-Escribano, María, et al. "Tuning the activity of Pt alloy electrocatalysts by means of the lanthanide contraction." Science 352.6281 (2016): 73-76.

Brown, Rosemary, et al. "Plasma-Induced Heating Effects on Platinum Nanoparticle Size During Sputter Deposition Synthesis in Polymer and Ionic Liquid Substrates." Langmuir 37.29 (2021): 8821-8828.
Bifunctional Platinum-Free Mixed Metal Oxygen Electrocatalysts Based on Naturally Abundant Peat
Authors: Teppor Patrick , Jäger Rutha , Härmas Meelis , Aruväli Jaan , Volobujeva Olga , Koppel Miriam , Lust Enn 
Published: July 2022

A functioning hydrogen economy requires efficient ways of producing and utilizing hydrogen via electrolyzers and fuel cells. The commercialization of these devices is well underway but their considerable capital costs still inhibit faster adoption by society1,2. One pathway towards more inexpensive devices is by tackling their respective bottlenecks, the oxygen evolution and reduction reactions, which currently require catalyst materials comprised of scarce precious metals. Intensive research is being conducted to introduce and develop suitable replacements for these catalysts. In this field, non-platinum group metal (NPGM) type catalysts have gained significant attention2,3.
We present several NPGM-type oxygen electrocatalysts synthesized by modifying peat-derived carbon with nitrogen and different combinations of transition metals (Fe, Co, Ni). The obtained catalysts were characterized with various methods to elucidate their structure-reactivity relations. Namely, SEM-EDS was used to confirm that the modification of peat-derived carbon was successful. Additionally, the various metal alloy species found in the catalysts were identified via X-ray diffraction analysis. The excellent bifunctional electrocatalytic activity of the peat-based materials towards oxygen evolution and reduction was confirmed with rotating disc electrode measurements conducted in a 0.1 M KOH solution. Correlations between the physical and electrochemical properties of the catalysts were established and analyzed.

Acknowledgments

This work was supported by the EU through the European Regional Development Fund under projects TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), NAMUR “Nanomaterials - research and applications” (3.2.0304.12-0397), PRG676 “Development of express analysis methods for micro-mesoporous materials for Estonian peat derived carbon supercapacitors” (01.01.2020–31.12.2024) and PUT1581 (1.01.2017–31.12.2020).

References

E4tech, 2021, The Fuel Cell Industry Review 2020.

C. Lei, S. Lyu, J. Si, B. Yang, Z. Li, L. Lei, Z. Wen, G. Wu, Y. Hou, ChemCatChem 2019, 11, 5855.

L. Osmieri, J. Park, D. Cullen, P. Zelenay, D. Myers, K. Neyerlin, Curr Opin Electrochem 2021, 25, 100627.

Figure 1
Investigation of Oxygen Reduction on Platinum Nanoparticles Deposited Onto Peat-Derived Carbon Carrier
Authors: Lobjakas Wiljar , Nerut Jaak , Kasuk Heili , Adamson Anu , Thomberg Thomas , Aruväli Jaan , Valk Peeter , Teppor Patrick , Koppel Miriam , Mikli Valdek , Volobujeva Olga , Lust Enn 
Published: July 2022

Carbon supported platinum catalysts for proton exchange membrane fuel cell (PEMFC) applications have been studied intensively in the scientific community.1,2 The catalytic activity of the catalyst depends on the characteristics of the carbon support material3 and on the Pt depositing method4,5. The aim of the study was to investigate the oxygen reduction reaction (ORR) on Pt nanoparticles deposited on peat-derived carbon. The Pt nanoparticles were deposited on the carbon support material by three different methods using NaBH4 (NBH), ethylene glycol (EG) and isopropyl alcohol (IA) as a reducing agent.
The studied materials were characterized using N2 sorption, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Structure of the platinum nanocatalyst on carbon support was also studied using scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). For electrochemical characterization, the electrochemically active surface area (ECA) of the materials were measured in a three-electrode system (0,1 M HClO4) and in a completed PEMFC. The ORR kinetics of the materials were studied by the rotating disk electrode (RDE) method as well as in a PEMFC configuration.
As a result, it was found that the higher the ECA of the material, the higher the catalytic activity. The catalytic activity of the synthesized materials increases in order: IA < NBH < EG. ECA of the materials increases in the same order. Also, the special surface area of the materials increases in the same order. The catalytic activities of the synthesized materials were compared to a commercial catalyst material, 60% Pt on HSA Ketjenblack.

References

O. Z. Sharaf and M. F. Orhan, Renew. sust. energ. rev., 32, 810–853 (2014).

Y. Wang, K. S. Chen, J. Mishler, S. C. Cho, and X. C. Adroher, Appl. Energ., 88, 981–1007 (2011).

S. Sharma and B. G. Pollet, J. Power Sources, 208, 96–119 (2012).

S. Sepp et al., Electrochim. Acta, 203, 221–229 (2016).

P. Valk et al., J. Electrochem. Soc., 165, F315–F323 (2018).

Acknowledgements

The author thanks the European Union Regional Development Fund for the financial support of the project TK141 “Innovative materials and high-tech equipment for energy recovery systems” (2014-2020.4.01.15-0011); the Estonian Research Agency project (personal research support group grant project No. PRG676) and the Estonian Energy Technology Program: SLOKT10209T “. Nanomaterials – research and applications (NAMUR)” project 3.2.0304.12-0397. The author also thanks the private limited company AuVe Tech.
3D Structured Pt(Cu-Ni)/Ti Catalysts for the Oxidation of Sodium Borohydride
Authors: Balciunaite Aldona , Činčienė Žana , Tamasiunaite Loreta , Vaičiūnienė Jūratė , Norkus Eugenijus 
Published: July 2022

Currently, one of the renewable energy sources is fuel cells, namely chemical energy is directly converted into electricity. Designing new or enhancing the existing fuel cells, much attention is devoted to the search of new effective catalysts, which would allow increasing the effectiveness of fuel cells and creating the background for designing new technologies for catalysts formation.
The aim of the work is to form efficient and inexpensive nanostructured catalysts by electroplating 3D structure metal copper-nickel (Cu-Ni) foams on titanium (Ti) surface and decorating them with low amounts of platinum nanoparticles (PtNP) for the electrooxidation of sodium borohydride (NaBH4). The Cu-Ni foam was prepared by electrochemical deposition (I
deposition=1.5 Acm-2, t
deposition= 3,6 and 9 min) on Ti surface. The electrolyte contained 0.5 M Ni2+ ions, and the concentrations of Cu2+ ions ranged from 0.01 to 0.02 M.
PtNP particles were deposited on Cu-Ni foam (noted (Pt(Cu-Ni)/Ti)) by immersion of Cu-Ni foam into 1 mM H2PtCl6 solution at 25 °C for 1 minute. The morphology and composition of the prepared catalysts were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The electrocatalytic activity of the 3D catalysts was evaluated towards the oxidation of borohydride by cyclic voltammetry method in 0.05 M NaBH4 solution in an alkaline media in the potential range from -1.2 to 0.6 V (vs. Ag/AgCl) and with an electrode potential scan rate of 10 mVs-1.
The study showed that the prepared 3D Cu-Ni foam and Pt(Cu-Ni)/Ti have good electrochemical stability in alkaline NaBH4 solution. It was also observed that immersion of Cu-Ni foam in a platinum-containing solution for 1 min increased the electrocatalytic activity of the prepared Pt(Cu-Ni)/Ti catalysts for NaBH4 oxidation compared to Cu-Ni foam.

Acknowledgment

This project has received funding from European Social Fund (project No 09.3.3-LMT-K-712-19-0138) under a grant agreement with the Research Council of Lithuania (LMTLT).