bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward a Fundamental Understanding of Strain Generation and Strain Tuning for the Fuel Cell Applications
Authors: Zeng Zhenhua , Liu Guangdong , Shih Arthur J , Deng Huiqiu , Steinbach Andrew , Koper Marc T. M. , Greeley Jeffrey
Published: July 2022

The development of industrial electrocatalysts with excellent performance in fuel cells strongly relies on the fundamental understanding of governing principles of catalysis from fundamental research on well-defined model systems. One particularly successful strategy has been to tune surface strain and thereby modulate the surface electronic structure and energetics of reaction intermediates, leading to a fundamental understanding and identification of catalysts with improved activity. For the well-known example of the oxygen reduction reaction (ORR) on platinum in fuel cells, previous studies indicated that a 1% compressive strain could improve the activity by more than 300%.

While the concept of tailoring the reactivity of metal catalysts through surface strain has been discussed over two decades, fundamental challenges remain regarding both strain generation and strain tuning. In the present contribution, We will share our recent progress on these topics, including [1] tunable intrinsic strain in two-dimensional transition metal electrocatalysts, [2] tunable intrinsic strain in stepped transition metal electrocatalysts, and [3] strain tuning of supported transition metal overlayers. We will demonstrate [1] how these fundamental understanding can be used to understand terrace-width dependent ORR activity of stepped Pt surfaces that have puzzled the community over a decade; and [2] how they pave the way toward developing both model electrocatalysts and industrial electrocatalysts with significantly improved performance toward the oxygen reduction reaction.

References

Wang, Z. Zeng*†, W. Gao, T. Maxson, D. Raciti, M. Giroux, X. Pan, C. Wang, J. Greeley,. Science 2019, 363, 870-874.

Wang, W. Gao, Z. Liu, Z. Zeng, Y. Liu, M. Giroux, M. Chi, G. Wang, J. Greeley, X. Pan, C. Wang, ACS Catal. 2018, 8, 35-42.

J. Steinbach, C. Duru, A. T. Haug, A. E. Hester, M. Kuznia, K. A. Lewinski, S. M. Luopa, J. T. Petrin, G. M. Thoma, A. J. Kropf, D. J. Myers, D. Yang, D. A. Cullen, J. Greeley, Z. Zeng, ECS Transactions 2017, 80, 659-676.

Zeng, J. Greeley, Nano Energy 2016, 29, 369.
Synthesis and Characterization of Efficient Nitrogen-Doped Carbon Materials for Supercapacitors Application
Authors: Norkus Eugenijus , Jablonskiene Jolita , Urbanas Davyd , Jasulaitiene Vitalija , Niaura Gediminas , Drabavicius Audrius , Plavniece Ance , Volperts Aleksandrs , Dobele Galina , Zhurinsh Aivars , Tamasauskaite-Tamasiunaite Loreta
Published: July 2022

N-doped carbons are widely used in the energy storage and conversion field because of their excellent electrical conductivity, high specific surface area, and superb electrochemical stability. Herein, high-efficiency carbon material has been derived using the kraft pulping residues – black liquor as the carbon source. The carbon material was prepared from black liquor through a two-step process, including chemical activation with NaOH at high temperature and doping with nitrogen using dicyandiamide (DCDA). The synthesized catalyst's morphology, structure, and composition were characterized using TEM, XPS, Raman Spectroscopy, and ICP-OES. The electrochemical performance has been evaluated using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques.

The synthesized nitrogen-doped carbon material had a high specific surface area of 2481 m2 g−1. Moreover, this catalyst had a high nitrogen content of 4.33 at%. Most of the nitrogen was in the pyridinic-N (66.58 at%) and graphitic-N forms (33.42 at%). It was found that the specific capacitance of catalysts depends on the catalyst loading. The specific capacitance of ca. 50 F g-1 was achieved in the 1 M Na2SO4 aqueous solution at the scan rate of 5 mV s-1. Besides, the specific capacitance retention was 99% after 100 cycles indicating good electrochemical stability. Our present results demonstrated that kraft pulping residue, such as black liquor, can be employed as a promising carbon precursor to synthesize low-cost and efficient catalysts for supercapacitors.

Acknowledgment

This project has received funding under the Baltic Research Programme project “Sustainably produced nanomaterials for energy applications (SuNaMa)” (No. S-BMT-21-12, LT08-2-LMT-K-01-055).
Characterisation of Novel Nitrogen Doped Reduced Graphene Oxide
Authors: Nerut Jaak , Teppor Patrick , Palm Rasmus , Jäger Rutha , Thomberg Thomas , Tuul Kenneth , Koppel Miriam , Aruväli Jaan , Kikas Arvo , Mondal Jay , Iakimov Valentino , Lust Enn
Published: July 2022

The utilisation of fuel cells in everyday life is of critical importance for the introduction of clean energy and departure from carbon-based economy. The oxygen reduction reaction (ORR) rate on the cathode is the key factor for effective polymer electrolyte membrane fuel cells. Therefore, novel cathode catalysts have to be designed to reduce the ORR over voltage. One of the most efficient ways to increase the ORR rate is to use nitrogen doping of carbon materials.1 Such materials are also promising for applications in supercapacitors and other energy storage devices.2

In this work, experimental results based on a nitrogen-doped reduced graphene oxide are presented. The nitrogen-doped reduced graphene oxide has been produced by Sea Further SARL using a biological micro-organisms and non-toxic chemicals.3

The material has been characterised by several physical methods: particle size distribution analysis, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis, gas adsorption method, and electrical conductivity measurements. X-ray diffraction data reveal the presence of peaks characteristic to reduced graphene oxide. The specific surface area of the bulk material is around 2.4 m2 g−
1 based on the nitrogen adsorption method. The bulk sample, in powder form, exhibited considerable specific conductance under pressure.

Additionally, electrochemical measurements have been conducted in 0.1 M HClO₄ and 0.1 M KOH solutions. The electrochemical stability, capacitive behaviour, and ORR activity of nitrogen-doped reduced graphene oxide have been determined using cyclic voltammetry, rotating disc electrode and electrochemical impedance spectroscopy methods. The material under discussion has a good electrochemical stability within the investigated potential region in both media. The measurement data show that the ORR kinetics in alkaline media is much faster than in acidic media. Surprisingly, this material has a high gravimetric capacitance. Therefore, nitrogen-doped reduced graphene oxide has high potential for energy storage devices and is promising co-catalyst material in fuel cell.

Acknowledgements

This work was supported by the EU through the European Regional Development Fund under project TK 141 “Advanced materials and high-technology devices for energy recuperation systems” (grant number 2014 2020.4.01.15 0011); and by the Estonian Research Council (grant number PUT PRG 676).

References

N. Daems, X. Sheng, I.F.J. Vankelecom, and P.P. Pescarmona, J. Mater. Chem. A, 2, 4085 (2014).

N.A. Elessawy, J.E. Nady, W. Wazeer, and A.B. Kashyout, Sci. Rep., 9, 1129 (2019).

V. Iakimov, International Patent Application No. WO2021/059152, WIPO, April 1st 2021.
Metal Fluoride Particles to Enhance Durability of Composite Membranes at MT-PEM Fuel Cell Operating Temperatures
Authors: Kutter Maximilian , Hilgert Annika , Hagemeier Wiebke , Rosin Andreas , Gerdes Thorsten , Roth Christina
Published: July 2022

Fuel cells, as a local, emission-free and versatile system, promise to overcome our dependence on fossil fuels.[1] Polymer electrolyte membrane fuel cells (PEMFCs) are considered one of the most promising technologies among the various kinds of existing fuel cells and offer an attractive alternative for automotive and stationary energy applications. Especially PEMFCs operating at an increased temperature range (MT-PEM) offer an enhanced performance. Operating temperatures between 100 – 130 °C lead to better reaction kinetics, higher tolerance to fuel impurities and to an improved heat, water and power management of the system.[2] However, some issues regarding durability and performance, such as low proton conductivity of PFSA-based membranes, higher membrane degradation and lower long-term stability at increased temperatures, are still unsolved.[3]

In previous works we have shown that various metal fluorides implemented into perfluorosulfonic acid (PFSA)-membranes have a positive impact on performance and mechanical stability at operating temperatures above 100 °C.[4] In this work, we describe the modification of lithium fluoride nanoparticles, their influence on membrane durability in single cell tests at enhanced PEMFC operating temperatures and the morphology of the composite membranes, at different temperatures and degree of hydration, by in-situ small-angle X-ray scattering (SAXS). The lithium fluoride modified membrane showed increased cell performance under both standard and harsher cell conditions as well as in various long-term stability tests, such as accelerated OCV tests, load cycles and on-off cycles.One explanation for the performance boost, in addition to the increased mechanical stability of the membrane, would be an increased water uptake and storage capability, especially at low humidity levels during cell operation. We assume that the nanoparticles adsorb water molecules by hydrogen bond formation, which leads to an enhanced proton conductivity even at high temperatures. To confirm this assumption, we applied in-situ SAXS to analyze the water uptake of the modified membranes at various relative humidity and temperatures to understand the structural changes. In addition, we hope to connect different nanoparticle shapes to their influence on water uptake and retention.

[1] I. Staffell, D. Scamman, A. Velazquez Abad, P. Balcombe, P. E. Dodds, P. Ekins, N. Shah, K. R. Ward, Energy Environ. Sci.
2019, 12, 463–491.

[2] R. E. Rosli, A. B. Sulong, W. R. W. Daud, M. A. Zulkifley, T. Husaini, M. I. Rosli, E. H. Majlan, M. A. Haque, Int. J. Hydrogen Energy
2017, 42, 9293–9314.

[3] L. Mazzapioda, S. Panero, M. A. Navarra, Polymers
2019, 11, 914.

[4] A. Moszczynska, H. Wolf, M. A. Willert-Porada, Patent WO/2009/014930, 2009.
Anode Defects’ Propagation to the Electrolyte and Catalyst Layers in Polymer Electrolyte Membrane Fuel Cells
Authors: Salah Touhami , Crouillere Marie , Mainka Julia , Dillet Jérôme , Nayoze-Coynel Christine , Bas Corine , Dubau Laetitia , El Kaddouri Assma , Dubelley Florence , Micoud Fabrice , Chatenet Marian , Bultel Yann , Lottin Olivier
Published: July 2022

Defects known to shorten the lifetime of polymer electrolyte membrane fuel cells (PEMFC) can appear on different membrane electrode assembly (MEA) components and under different forms due to manufacturing processes or operational aging of the fuel cell [1, 2]. Defects-propagation in polymer electrolyte membrane fuel cells membrane electrode assemblies (MEA) is investigated via Accelerated Stress Tests (AST) combining load (hence potential) cycling, load-driven humidity cycling, and open-circuit voltage. Customized MEA with lack of anode catalyst layer at two different locations -near the hydrogen inlet or outlet- are fabricated and subjected to the AST. Periodical electrochemical characterizations are performed using a segmented and instrumented cell, enabling to track the cell performance and anode/cathode electrochemical surface area (ECSA) over the test period with a spatial resolution along the gas channels. These observations are completed by post mortem analyses of the MEA.

The MEA accelerated degradation is obvious, with multiple impacts on the cell performance and materials. More specifically, the results brought first evidence of defects propagation in terms of membrane thinning and anode ECSA loss: significant membrane thinning is observed for the defective segments, while anode ECSA loss is measured downstream in the direction of the hydrogen flow. The cathode degradation is poorly affected by the presence of the anode defects. In addition, membrane degradation also appears to propagate downstream the channels when the AST is prolonged for a long period of time. Anode and cathode local potential monitoring during the AST reveals the absence of cathode high-potential excursion, in both the segments with/without initial defects. However, oxygen crossover -toward the hydrogen compartment- is probably detected through slight variations in the anode local potential: this lead to the conclusion that the membrane and anode accelerated degradations are seemingly governed by chemical mechanisms like gas crossover rather than electrochemical mechanisms induced by high-potential excursions.

Guilminot, E. et al. Membrane and Active Layer Degradation upon PEMFC Steady-State Operation. J. Electrochem. Soc. 154, B1106 (2007).

Dubau, L. et al. A review of PEM fuel cell durability: Materials degradation, local heterogeneities of aging and possible mitigation strategies. Wiley Interdiscip. Rev. Energy Environ. 3, 540–560 (2014).

Figure 1
(Digital Presentation) Achieving High Selectivity for the Nitrogen Reduction Reaction through the Mars-Van Krevelen Mechanism
Authors: Johnson Denis , Djire Abdoulaye
Published: July 2022

Electrochemical nitrogen reduction reaction (NRR) technology is a viable alternative to reducing the energy and greenhouse gas footprint from the current ammonia (NH3) production technology. Most NRR catalysts suffer from low selectivity towards NH3 because they operate by using an associative or dissociative mechanism, during which the NRR competes with the hydrogen evolution reaction (HER). In this presentation, we report on a new catalyst and untapped mechanism for NRR to increase the selectivity towards NH3. This untapped Mars-van Krevelen (MvK) mechanism reduces the competition between NRR and HER by eliminating the sluggish hydrogenation reactions of the dissolved N2 molecule. The new catalyst, two-dimensional (2D) Ti2N nitride MXene, was synthesized via an oxygen-assisted molten salt fluoride etching technique. We confirmed its phase purity and stability in aqueous electrolytes using various characterization techniques, including x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and cyclic voltammetry (CV). Through an MvK mechanism, the Ti2N nitride MXene catalyst achieved a high Faradaic efficiency (FE) of 19.85% towards NH3 at an applied potential of –250 mV vs. RHE with a yield of 11.33 μg/cm2/hr in a 0.1M hydrochloric acid (HCl) N2-saturated electrolyte. These results constitute the foundation of NRR technology based on MXenes and can be expanded to a broad class of systems evoking the MvK mechanism.
(Invited, Digital Presentation) Chalcopyrite-Based Devices for Photoelectrochemical Water Splitting: Challenges and Opportunities
Authors: Gaillard Nicolas
Published: July 2022

Photoelectrochemical (PEC) water splitting has the potential to become an efficient method for renewable hydrogen production. However, the efficiency, projected cost, and durability of lab-scale systems are not yet at the level required to make this technology economically feasible. Amongst all materials studied to date, the chalcopyrite class is arguably one of the most promising classes for PEC water splitting, as it has already demonstrated low-cost and high photoconversion capabilities as a photovoltaic material. In the context of PEC, our group has shown that co-evaporated 1.65 eV bandgap (EG) CuGaSe2 is capable of evolving hydrogen with Faradaic efficiency greater than 85% and generate photocurrent densities over 15 mA.cm-2, as measured in a 3-electrode configuration in 0.5M H2SO4 under simulated AM1.5G illumination. Unfortunately, CuGaSe2’s narrow EG limits its integration as top absorber into a dual junction stacked PEC device (also known as hybrid photoelectrode, HPE). In the present communication, we report on our latest efforts to synthesize wide-EG (1.8-2.0 eV) chalcopyrites, compatible with the HPE integration scheme, and capable of generating saturated photocurrent densities greater than 10 mA/cm2. We present specifically results on EG tunable Cu(In,Ga)(S,Se)2, Cu(In,Ga)S2, CuGa(S,Se)2 and CuGa3Se5. We also discuss some of the strategies developed to improve their surface energetics for the hydrogen evolution reaction, including the use of bandgap tunable MgZnO n-type buffer layers. Finally, we introduce the concept of semi-monolithic tandems, a new integration scheme where wide- and narrow-bandgap chalcopyrites are first integrated on separate substrates and then exfoliated, and finally bonded to create fully functional tandem device.
(Energy Technology Division Supramaniam Srinivasan Young Investigator Award) Materials and Capability Development in Photo- and Electro-chemical Electrons-to-Molecules (E2M) Device Research
Authors: Young James L.
Published: July 2022

In this talk, I will first give an overview of some recent work in photoelectrochemical (PEC) materials and device development as part of the HydroGEN Consortium. Within this consortium, I serve as the NREL lead and a capability expert for the PEC water splitting technology. Our group supports several, university-led seedling projects in developing various PEC materials and plays the central role in a national laboratory collaboration focused on improving PEC device durability. I will highlight the development and demonstration of our flagship capability for PEC device benchmarking and on-sun testing.

In the second part of this talk, I will present some efforts in low-temperature electrolysis (LTE) research as part of the H2NEW Consortium and a Technology Commercialization Fund project. My work focuses on ex-situ characterization of membrane electrode assembly (MEA) performance and development of porous transport layer (PTL) materials and surface modifications. The ex-situ characterization approaches are used in concert with in-situ testing to understand and improve LTE materials and interface properties.

Finally, I will give an overview of NREL’s recent E2M electrochemical device testbed development for CO2 and N2 reduction research. This includes powerful, inline product analysis systems and custom hardware to study electrocatalyst integration, evaluate cell architectures, and conduct spatial and combinatorial studies.
(Invited, Digital Presentation) Neutral pH Water Electrolyzer: Can It Become a Disruptive Technology for Green Hydrogen Production?
Authors: Takanabe Kazuhiro
Published: July 2022

Cost reduction for green hydrogen production is urgently needed to realize the carbon neutral society. Low temperature water electrolysis is operated in extreme pH conditions; polymer electrolyte membrane (PEM) electrolyzer (acidic) or alkaline electrolyzer. In such electrolyzer, substantial cost must be spent for electrode materials, system corrosion tolerance, ion conductive membrane and/or securing safety operation. Water electrolyzer using near-neutral pH environment may become a disruptive technology to produce green hydrogen driven by renewable electricity. This is essentially because a variety of materials can be applied to the electrolysis system in electrode and substance, and most significantly the electrolyte is naturally unharmful to human beings. In the past, the study on neutral pH electrolyzer was limited due to inevitable low efficiency compared to abovementioned counterparts. To identify the limiting factors associated with near neutral pH electrolysis, a rigorous microkinetic analysis of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) was performed in various electrolyte conditions. The electrocatalytic performance is dependent substantially on the buffered conditions, which involves the kinetics of the local H+/OH− supply by the buffering action, mitigating the local pH shift observed in unbuffered conditions. Our study herein demonstrated thorough “electrolyte engineering” approach that can maximize the efficiency by maximizing reactant flux, mitigating pH gradient, reducing solution resistance, and regulating the crossover of gaseous molecules. Specifically suppressing the crossover of gaseous molecules by regulating their diffusion flux can be achieved. A simple hydrophilized mechanically stable glass-filter was sufficient to suppress the permeation of gas bubbles. We also found that a trade-off between the exchange current density and the Tafel slope with respect to the pKa and pH of the electrolyte disclosed the optimal pKa(=pH) and buffer identity to minimize the HER/OER overpotential at a given current density. Our preliminary results show that overall performance for water splitting under near neutral pH is already competitive with the performance to those operated at extreme pH conditions. High current density and excellent stability are achieved by the inexpensive electrolyzer system at near neutral pH.
(Invited) In Situ Time-Resolved Probe of Charge Carrier Dynamics at Planar Semiconductor Photoelectrode/Liquid Interface
Authors: Lian Tianquan
Published: July 2022

Photoelectrochemistry is a promising approach for converting solar energy to storable chemical energy in chemical fuels. The efficiency of photoelectrochemcial devices depends critically on efficient transfer of charge carrier across the electrode liquid interface and the efficiency and selectivity of the catalytic reaction on electrode surface. Although transient absorption spectroscopy is a powerful tool for probing interfacial dynamics in high surface area electrodes, it is often not applicable on planar electrodes because the observed signal is often dominated by carrier dynamics in the bulk. In this talk, we discuss our recent effort in developing in situ time-resolved linear and nonlinear spectroscopic tools that can be used to probe carrier dynamics and reactions at planar electrode/liquid interfaces, focusing on transient reflection spectroscopy and electric field induced second harmonic generation (EFISH) spectroscopy. Compared to transient absorption, transient reflection spectroscopy is more sensitive to surface carrier density that can be more directly correlated to catalysis. We showed that transient reflectance change can be used to follow charge carrier dynamics and their amplitude can be directly correlated to efficiency of initial interfacial charge separation on p-GaP single crystals protected by TiO2 ALD layer. Our finding suggests that IPCE is determined by the product of the efficiency of initial ultrafast (< hundreds of ps) charge separation across the GaP/TiO2 interface and the efficiency of water reduction reaction on the slower time scale. Key loss pathways that limit these efficiencies are discussed. In a second approach, we showed the EFISH signal in a n-doped single crystal TiO2 can be used to probe the accumulation of photogenerated carriers at surface states and these trapped carriers are responsible for the water oxidation reaction.
Ternary-Oxides CuWO4/BiVO4/FeCoOx Films for Photoelectrochemical Water Oxidation: Insights into the Photoinduced Charge Transfer Pathway
Authors: Goncalves Renato Vitalino , Rabelo Lucas Gabriel , Santa Rosa Washington , Zampaulo Luis
Published: July 2022

Photoelectrochemical (PEC) water oxidation using semiconductor oxide films as a working electrode is an essential approach for investigating the effective utilization of sunlight and the production of green fuel. Herein, we report a ternary-oxides-based CuWO4/BiVO4/FeCoOx film deposited entirely by RF-magnetron sputtering using homemade ceramic targets. Our CuWO4/BiVO4 photoanode exhibits a significant photocurrent density of 0.82 mA/cm² at 1.23 V vs. RHE under AM 1.5G illumination, corresponding to a record > 380% increase to that of pure CuWO4 photoanode. To further boost the PEC performance, we deposited an ultrathin layer of amorphous FeCoOx cocatalyst, resulting in a triple CuWO4/BiVO4/FeCoOx heterojunction with a significant reduction in onset potential and a 500% increase in photocurrent density of pure CuWO4. Experimental studies and numeric computations were used to provide insights into the photoinduced charge carrier pathway across heterojunctions. Our results reveal noticeable interface potential barriers for charge carriers at the CuWO4/BiVO4 heterojunction, potentially lowering PEC efficiency without external potentials. Conversely, the deposition of the FeCoOx ultrathin layer over the CuWO4/BiVO4 heterojunction induces a - junction on the BiVO4/FeCoOx interface, which, when combined with the abundant FeCoOx oxygen vacancies, results in improved charge separation and transport, as well as enhanced photoelectrochemical stability. Our study provides a feasible strategy for producing photocatalytic heterojunctions systems and novel tools for investigating interface effects on photoinduced charge carrier pathways for PEC water splitting.
(Invited) (Photo)Electrochemical Cells for Hydrogen Production and Carbon Dioxide Utilization
Authors: Minegishi Tsutomu
Published: July 2022

Photoelectrochemical (PEC) and electrochemical cells can produce hydrogen from water and/or can produce useful chemicals from carbon dioxide, and, thus, are the key technologies for construction of carbon neutral society.

Direct water splitting using photoelectrochemical cell is one of the promising means to produce hydrogen utilizing solar energy. The most important issue for photoelectrode the central of photoelectrochemical cell is narrow bandgap combined with large reaction driving force. Cu(In,Ga)Se2 (CIGS) which is employed as an absorber material in photovoltaic devices is one of the promising photocathode materials because of its long absorption edge of >1000 nm. [1] However, its driving force for water splitting is limited because of relatively shallow valence band maximum (VBM). The solid solution between ZnSe and CIGS (ZnSe-CIGS) is one of the promising candidates of photocathode material for water splitting because of its long absorption edge, ~900 nm, and large driving force, ~1.0 V. [2] In the present study, we investigated introduction of tellurium during ZnSe-CIGS thin films, and found the tellurium introduction increase grain size of ZnSe-CIGS film. The sequential deposition of Ga-rich layer and In-rich layer resulted in formation of composition gradient which facilitate charge separation thorough conduction band minimum (CBM) gradient. The ZnSe-CIGS base photocathode prepared with employing tellurium introduction and composition gradient showed significantly increased incident photon-to-current conversion efficiencies (IPCEs), close to unity. [3]

The electrochemical cell with gas diffusion electrode (GDE) for carbon dioxide reduction reaction (CO2RR) can produce useful chemicals efficiently. Copper species are the catalysts with capable of producing C2 products such as C2H5OH and C2H4. In the present study, Cu2O was examined as an electrocatalyst for CO2RR. A GDE composed of carbon paper coated with Cu2O by electroplating method showed C2H4 production with faradaic efficiency (FE) of >50% and C2H5OH production with FE of >20% under the optimized conditions for >10 hours.

References

H. Kumagai, T. Minegishi, N. Sato, T. Yamada, J. Kubota, K. Domen, J. Mater. Chem. A, 3, 8300 (2015).

H. Kaneko, T. Minegishi, M. Nakabayashi, N. Shibata, K. Domen, Angew.Chem. Int. Ed. 55,15329 (2016).

T. Minegishi, S. Yamaguchi, M. Sugiyama, Appl. Phys. Lett. 119, 123905 (2021).
(Invited, Digital Presentation) Relevant Production of Fuels Via Unifying Electrocatalytic Processes of Carbon Dioxide and Ammonia
Authors: Lee Jaeyoung
Published: July 2022

At the beginning of the 21st century our world is facing serious problems with regards to environment, climate, energy conversion, raw materials and food. All these global problems are seeking scientific solutions, especially from chemistry, and in this connection electrochemistry and catalysis are of tremendous importance, in particular for energy conversion and pollution control such as i) how to supply future energy alternatives (hydrogen) and ii) create valuable chemicals or fuels from greenhouse gas, i.e., carbon dioxide (CO2). In this presentation, I shall intend to introduce very efficient co-electrocatalytic processes for hydrogen production from ammonia and fuels from CO2 by applying a near zero-gap cell, which consists of a membrane electrode assembly.
(Invited) Influence of Fermi Level Engineering in Multi-Interface Photoelectrodes on Photoelectrochemical CO2 Reduction
Authors: Solarska Renata , Bienkowski Krzysztof
Published: July 2022

Heterojunction engineering enables more versatile and higher-performance systems than single components. In parallel with heterojunction engineering, defect engineering has emerged as a means of tailoring the optoelectronic properties of photoelectrodes. However, constructing effective, visible-light responding, and stable hybrid semiconductor heterojunctions is a challenging task under the strict requirements of band alignment, vacancy characteristics, and interface properties. In this study, the photoelectrochemical (PEC) reduction of CO 2 to methanol is augmented by a novel approach explored by modeling the Fermi level in a multi-interface architecture.
Cu As Co-Catalyst for the Photo-Electrochemical CO Reduction on Multi-Junction Photoabsorbers
Authors: Naumann Kathrin , Tichter Tim , Hansen Ole , Seger Brian , Chorkendorff Ib , Vesborg Peter
Published: July 2022

Substantial research effort has been dedicated to the electrochemical reduction of CO2 (CO2R) to higher carbon products throughout the recent years, baring the promise of a production pathway for green fuels and chemicals.1 However, only little progress has been achieved in the light driven heterogeneous CO2R catalysis, especially considering selective processes towards C2+ products. This arises from the additional complexity of photo-electrochemical reactions, which means that not only the sluggish reaction kinetics, high overpotentials and low selectivity of CO2R, but also the insufficient voltage and sensitivity towards harsh electrolyte conditions of photoabsorbers have to be encountered. Considering CO2R as multi-step process with CO as intermediate mitigates some issues of the process, e.g. the necessary overpotential is reduced and a higher selectivity towards valuable products can be achieved.2

Multi-junction solar stacks can provide operating voltages >2 V, which is sufficient for reducing CO2 to CO with high efficiencies or even produce multi-carbon products from CO while oxidizing water as anode reaction.3

In this work, we designed a process for photo-electrochemical CO reduction with multi-junction photoabsorbers. We start out by showing photo-electrochemical modelling of tandem photoabsorbers that emphasizes the advantages of CO as reactant compared to CO2. Further, we focus on the preparation of a nano-structured Cu catalyst, the most common material for reducing CO to C2+. Therefore, the electrochemical deposition and surface characterization using SEM, EDX and XPS of the catalyst on a dark model electrode coated with a sputter deposited TiO2 protection layer will be presented. Moreover, the CO reduction performance of the model at different potentials are characterized. In addition, the light transmission of the model electrode is reported, baring the possibility of illuminating the photoelectrode from the catalyst front side in mind. Lastly, the transfer of the model catalyst to a photoabsorber as well as the design of a photo-electrochemical flow-cell are discussed.

Nitopi, S. et al. Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte. Rev.
119, 7610–7672 (2019)1.

Wang, L. et al. Electrochemical Carbon Monoxide Reduction on Polycrystalline Copper: Effects of Potential, Pressure, and pH on Selectivity toward Multicarbon and Oxygenated Products. ACS Catal.
8, 7445–7454 (2018)

Seger, B., Hansen, O. & Vesborg, P. C. K. A Flexible Web-Based Approach to Modeling Tandem Photocatalytic Devices. RRL
1, e201600013 (2017).

Figure 1
Pt Current Collectors Artificially Boosting Si-Contaminated Praseodymium Doped Ceria Oxygen Surface Exchange Coefficients
Authors: Ma Yuxi , Burye Theodore , Nicholas Jason
Published: July 2022

The chemical oxygen surface exchange coefficient (kchem
) values used to quantify and rank oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalyst performance for high-temperature, oxygen-exchange-enabled devices (such as Solid Oxide Fuel Cells, Solid Oxide Electrolysis Cells, oxygen sensors, etc.) are often determined electrically, with the aid of precious metal current collectors. In addition, due to ease of introducing siliceous contaminants during the manufacturing and operation of these devices, the performance of their oxygen exchange catalysts are often impacted by Si surface contaminants.

Here, Curvature Relaxation (KR), Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and X-Ray Photoelectron Spectroscopy (XPS) analyses performed on Pulsed Laser Deposited thin films of the oxygen exchange catalyst Pr0.1Ce0.9O2-x (PCO) show that siliceous surface phases only a few nanometers thick are capable of 1) reducing the PCO chemical oxygen surface exchange coefficient by approximately 3 orders of magnitude and 2) approximately doubling the activation energy for oxygen incorporation and removal. Further, the results show that unpolarized platinum current collectors dramatically improve the kchem
of Si-contaminated PCO by reducing the Si concentration at the PCO surface and/or diffusing into the PCO; even for PCO thin films only exposed to mild temperatures of 500 oC. This suggests that precious metal current collectors are likely responsible for some of the large kchem
variation reported in the literature for “identical” materials tested under “identical” conditions.

Figure 1
(Invited) Electro-Chemo-Mechanical Effects in Mixed Ionic–Electronic Conductors
Authors: Chen Chia-Chin
Published: July 2022

Performance and reliability of energy harvesting, storage and conversion devices are closely connected to mechanics as large stress gradients are usually intrinsic. In addition to causing mechanical failure, large stress is suspected to lead to anomalous experimental observations in a wide range of electrochemical cells. However, the standard framework for mixed ion-electron conductors does not capture this electro-chemo-mechanical coupling in stressed solids; it remains a challenge to theoretically predict how external stress would influence the reaction kinetics or electrical transport of solids.

In this contribution, we will present a generalized thermodynamic theory to explain how and mechanics are coupled to ionic and electronic carriers in the presence of stress field. We categorize the carriers into physically-meaningful four types, based on the signs of the charge number (i.e., polarity) and the partial molar volume (i.e., expansion coefficient). Beyond the electrostatic effects discussed in the literature, our work reveals the importance of elastic effects, as demonstrated by simulations of a composite beam bending experiment. The proposed framework not only provides a deeper understanding of stress-driven phenomena in electrochemical materials, but also suggests an unconventional approach to mechanically tune the interfacial electrical properties of mixed-conducting solids.
(Invited, Digital Presentation) Chemo-Mechanics in Lithium Metal Solid State Batteries
Authors: Hatzell Kelsey
Published: July 2022

Transportation accounts for 23% of energy-related carbon dioxide emissions and electrification is a pathway toward ameliorating these growing challenges. All solid state batteries could potentially address the safety and driving range requirements necessary for widespread adoption of electric vehicles. However, the power densities of all-solid state batteries are limited because of ineffective ion transport at solid|solid interfaces. New insight into the governing physics that occur at intrinsic and extrinsic interfaces are critical for developing engineering strategies for the next generation of energy dense batteries. However, buried solid|solid interfaces are notoriously difficult to observe with traditional bench-top and lab-scale experiments. Understanding material transformations within these interfaces is critical for assessing failure onset and growth mechanisms in solid electrolytes is necessary for high performance solid-state batteries. While phenomenological understanding of failure mechanisms in garnet solid electrolytes exist, limited experimental validation is available. Herein, we examine the two predominant failure mechanisms observed in lithium metal solid state batteries: (1) filament formation, and (2) isolated lithium plating. We combine a suite of ex situ diagnostic techniques with in situ x-ray imaging to probe material transformation and chemo-mechanics and lithium metal-solid-electrolyte interfaces. Operating conditions as well as material processing conditions are discussed.
Optimizing The Hot-Press Procedure Of High-Temperature Proton Exchange Membrane Fuel Cells For Adhesion Strength And Conductivity
Authors: Leader Jared O , Walluk Mark R , Waller Michael G , Trabold Thomas A
Published: July 2022

As society considers alternatives to energy systems based on fossil fuel combustion, high-temperature proton exchange membrane (HT-PEM) fuel cells may play an important role in our future energy and transportation portfolio. When compared to low-temperature proton exchange membrane (LT-PEM) fuel cells, HT-PEM technology offers enhanced electrode kinetics, simplified water management, and most notably increased tolerance to fuel impurities such as carbon monoxide. However, compared to more conventional LT-PEM systems, less is known about the durability, performance, and fabrication of HT-PEM materials. Comprised of multiple layers, the membrane electrode assembly (MEA) is a fuel cell’s central component. In a fabrication process similar to LT-PEM MEAs, the proton-conducting membrane, electrodes, gas diffusion layers and sub gaskets are usually hot-pressed together. The parameters surrounding the hot-pressing operation can have a significant impact on the ultimate performance of the fuel cell, in addition to influencing process reliability and repeatability. In the current research, measurements of MEA thickness, impedance, and adhesion strength were obtained for samples over a range of conditions to optimize for the most suitable processing parameters. Testing in this study quantified the effects of hot-press time, temperature and pressure, within ranges of 1-10 minutes, 140 – 200oC, and 7.72 – 92.67 MPa (1120 - 13440 psi), respectively. After hot pressing, the MEA samples were tested for resistance with a 1260a Solartron impedance gain phase analyzer in tandem with a Solartron Ametek 12962a sample holder, and with a Scott internal bond tester for adhesion strength. Based on the results of these tests the optimal hot-press parameters were established, four 25 cm2 MEA were built and tested for performance with post-mortem analysis conducted utilizing scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). These measurements enabled interrogation of potential sources of conductivity loss associated with material layer delamination and/or dehydration of phosphoric acid in the polybenzimidazole (PBI) membrane. In this case, all tests were conducted at 140oC and the resulting material assembly was allowed to cool to room temperature in a nitrogen glove box prior to executing conductivity measurements (i.e., inverse of resistance). Our results have demonstrated that the optimal conditions for MEA hot-pressing for the HT-PEM system are around 170oC and 23.1 MPa for 5 minutes. Each curve in Figure 1 represents the performance of in-house MEAs, prepared using the optimized hot-pressing condition, with variation of platinum-on-carbon content (Pt/C) and total Pt loading. The data presented in Figure 1 demonstrate the effect of varying electrode thickness on MEA performance.

Figure 1
(Invited) Self-Absorption Correction in X-Ray Fluorescence Imaging
Authors: Ge Mingyuan , Huang Xiaojing , Yan Hanfei , Gursoy Doga , Meng Yuqing , Zhang Jiayong , Ghose Sanjit , Chiu Wilson , Brinkman Kyle , Chu Yong
Published: July 2022

The self-absorption problem in the x-ray fluorescence (XRF) imaging community is a long-lasting and grand challenge to achieve quantitative analysis. Accurate correction is of broad interest in many disciplines, including material science, environmental science, and biology. The researchers desire to obtain a 3D structure with accurate material compositions or trace element distributions from complex 3D specimens with multi-components. We will present a generalized absorption correction method, which works broadly for 2D and 3D imaging. With the developed method, we reveal internal 3D elemental composition in a mixed ionic-electronic conductor (MIEC), which has important applications in energy conversion and catalysis, whose material functionality is intimately tied to diffusion and phase-separation at grain boundaries. By performing accurate quantification of 3D concentration over an unprecedented number of grains (i.e. a total of 340 grains), we unveil deep insights on the complex phase transformation at the grain boundaries and the mechanistic model for producing the so-called emergent phases, which plays a critical role in achieving high transport properties of the MIEC material system.
(Invited, Digital Presentation) Impedance Analysis of Porous Electrodes in Solid Oxide and Polymer Electrolyte Fuel Cells
Authors: Weber Andre
Published: July 2022

Technical electrodes in fuel cells rely on complex multiphase microstructures that facilitate electronic, ionic and gas transport to active reaction sites distributed in the electrode volume. In such electrodes, material and microstructural properties of the porous electrode likewise determine the cell performance and different losses related to gas diffusion, electronic / ionic transport or the charge transfer at the active reaction sites might dominate the electrode resistance.

Impedance spectroscopy is a powerful tool to evaluate and quantify the losses within a porous electrode. In this contribution it will be shown how impedance spectroscopy, an impedance data analysis by the distribution of relaxation times (DRT) (1,2) and a subsequent transmission line modeling (TLM) can provide physicochemically meaningful information about technical electrodes applied in solid oxide cells (SOC) (3-7) and polymer electrolyte fuel cells (PEFC) (4,5). Limitations in TLM will be discussed and it will be shown that the well-established straight-forward approach of CNLS-fitting might lead to physicochemically incorrect results. Possible countermeasures as a pre-identification of TLM-parameters by means of separate electrical measurements and microstructural analysis or an appropriate selection of operating parameters during impedance analysis will be presented.

An example for the application of TLM in electrode development and microstructural design of the multiphase microstructure will be discussed and examples how the TLM-approach can be used to optimize an electrode in consideration of available materials and producible microstructures will be shown.

(1) S. Dierickx, A. Weber and E. Ivers-Tiffée, Electrochim Acta, 355, p. 136764 (2020).

(2) A. Weber, tm - Technisches Messen, 88 (1), p. 1 (2021).

(3) C. Endler-Schuck, J. Joos, C. Niedrig, A. Weber and E. Ivers-Tiffée, Solid State Ionics, 269, p. 67 (2015).

(4) M. Heinzmann, A. Weber and E. Ivers-Tiffée, J. Power Sources, 402, p. 24 (2018).

(5) M. Heinzmann, A. Weber and E. Ivers-Tiffée, J. Power Sources, 444, p. 227279 (2019).

(6) S. Dierickx, J. Joos, A. Weber and E. Ivers-Tiffée, Electrochim Acta, 265, p. 736 (2018).

(7) S. Dierickx, T. Mundloch, A. Weber and E. Ivers-Tiffée, J. Power Sources, 415, p. 69 (2019).
(Keynote, Digital Presentation) Mixed Electronic-Ionic Conduction in Spinel-Structured Solid Electrolyte-Electrodes for Li-Ion Batteries
Authors: Allen Jan L
Published: July 2022

Solid Li-ion conducting electrolytes are one pathway towards future, energy-dense, intrinsically-safe solid-state batteries. Thus, it is of interest to study novel fast Li-ion solid electrolyte materials. Here we report the synthesis and characterization of a family of spinel structured oxide solid electrolytes[1]. Further, we will report on the interface and mixed electronic-ionic conductivity of the spinel structured solid solution which is formed upon reaction with spinel structured Li-ion battery electrode materials. We detail the compositions that were explored and give the results of the synthesis, densification and the structural, physical and electrochemical characterization. The properties of the new materials will be compared and contrasted to well-known solid Li electrolytes such as garnet and NASICON structured materials.

References

1. Allen, J.L.; Crear, B.A.; Choudhury, R.; Wang, M.J.; Tran, D.T.; Ma, L.; Piccoli, P.M.; Sakamoto, J.; Wolfenstine, J. Fast Li-Ion Conduction in Spinel-Structured Solids. Molecules
2021, 26, 2625. https://doi.org/10.3390/molecules26092625

Figure 1
(Invited, Digital Presentation) Detailed Chemical Modeling of Solid Electrolyte Interphase Growth and Evolution
Authors: DeCaluwe Steven C.
Published: July 2022

The solid electrolyte interphase (SEI) is a layer that forms at the anode-electrolyte interphase in lithium ion batteries. The layer forms due to voltage instability of the electrolyte at low anode potentials, but serves to passivate the electrolyte to protect against further uncontrolled decomposition. In theory, the SEI is self-limiting, but in reality, continued growth over the battery’s lifetime leads to capacity fade, poor rate capability, and eventually cell death. Though significant progress in recent years has improved the SEI’s function and stability, poor understanding of its most basic chemistry impedes “rational design” of SEI layers for advanced battery applications. Understanding and quantifying the elementary chemistry of the SEI is made challenging by the layer’s thickness (10s to ~100 nm), chemical sensitivity, mechanical fragility, and complex chemistry (upwards of 100 reactions have been proposed). For these reasons, These factors combine to make studying the fundamental chemistry of SEI growth and evolution a significant challenge. Both the computational tools to model the SEI’s complex chemistry and the experimental data required to validate such models are all too rare.

This talk will provide an overview of recent efforts to model the fundamental electrochemistry of SEI growth and evolution. The simulations are based on a continuum-scale, finite-volume framework, and leverage the open-source software package Cantera to enable efficient simulation of arbitrarily complex electrochemical mechanisms. Simulation results, as in Figure 1, are validated against two operando measurements of the SEI grown on a non-intercalating tungsten anode: depth profiling via neutron reflectometry (NR), and SEI mass uptake data via quartz crystal microbalance with dissipation (QCM-D) taken during cyclic voltammetry cycling. Interrogation of the detailed model results provide insights into the complex phenomena controlling initial SEI growth, and validation against NR and QCM-D data identify prominent reaction pathways and key chemical species present in the SEI. Finally, we will conclude by discussing future steps, includuing transferring mechanistic insights to new scales, geometries, and chemistries, and coupling models with inputs from atomistic simulations.

Figure 1