bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Conversion of CO2 to Fuels and Useful Chemicals over Metal Supported Solid Oxide Electrolyzers
Authors: Hu Boxun , Tucker Mike C , Park Ka-Young , Lee Taehee , Wang Wanhua , Chen Fanglin (Frank) (Frank)
Published: August 2024

Electrochemical conversion of CO2 and H2O to fuels and chemicals provides a promising approach to simultaneously mitigate greenhouse emission and store surplus energy, which reduces electricity network variation due to increased intermittent renewable energy (such as solar and wind) utilization. Metal supported solid oxide electrolyzers (MS-SOEs) developed at Lawrence Berkeley National Laboratory provide advantages of rapid start-up, mechanical ruggedness, redox tolerance, dynamic operation, and low-cost materials. A relatively high operating temperature range of 600 to 750°C promotes energy efficiency and allows utilization of thermal energy such as steam.

In this work, efficient and stable catalysts developed at the University of South Carolina have been infiltrated in the symmetrical and porous MS-SOE architecture. The phase purity has been analyzed by X-day diffraction. The morphologies of these infiltrated and posttest catalysts have been examined by scanning electron microscopy. Optimization of cell structure, processing temperature, cell voltage, and catalyst infiltration cycles for better cell performance will be presented. The stability of MS-SOEs has been evaluated during continuous operation for >200 hours. The cell degradation mechanisms revealed by electrochemical impedance spectroscopy and high-resolution scanning electron microscopy techniques will be presented.

In addition to pure CO2 electrochemical conversion, effects of additional water and hydrogen in CO2 feedstock will be analyzed. Faradic efficiency and chemical selectivity calculated from gas chromatograph and electrochemical analyses will be presented.
Direct Non-Oxidative Methane Conversion and Hydrogen Co-Production in a Proton Conducting Membrane Reactor
Authors: Tang Qiming , Saqib Muhammad , Anjum Aniqa , Duncan Keith , Wachsman Eric D
Published: August 2024

Direct Non-oxidation Methane Conversion (DMNC) has been recognized a promising technology for the upgrading of cheap and abundant methane to higher hydrocarbons (C2+) and H2, but this technology has not been commercialized yet because of the low methane equilibrium conversion and severe carbon deposition.1-3 Here, we present our effort to develop a proton conducting membrane reactor (SrCe0.7Zr0.2Eu0.1O3-
ⴃ) combined with the catalysts (Fe©SiO2) to circumvent the equilibrium limitations of the DMNC reaction and solve the coking (i.e., solid carbon deposition) problem. By coupling the Fe©SiO2 catalysts with H2 permeable membrane reactor, part of produced H2 during the catalytic conversion can be extracted from the effluent gas, which not only provides a one-step hydrogen production without additional separation process, but also shifts the equilibrium of the reaction to the product side and achieves an improved methane conversion and higher C2+ yield when compared to the traditional fixed-bed reactor. In addition, an air sweep outside the reactor results in O-permeation into catalyst to oxidize any deposited carbon to CO thus preventing coking.

The membranes were fabricated using tape casting of the support layer followed by dip coating process to form the dense membrane layer. Using this method, we obtained 25 µm for the thickness of the dense layer and around 700 µm for the thickness of the support layer (see Fig. 1a and 1b). The catalyst was synthesized by a simple sol-gel method followed by fusing process, and then was crushed into 40-80 mesh and loaded inside of membrane reactor to test.

The performance metrics include methane conversion, selectivity, and product yield. Our membrane reactor achieved single-pass methane conversion of 17.5%, and a C2+ yield of 15% (see Fig. 1c) at 1323K.

Finally, our membrane reactors were stable for over 350 hours, which, along with the aforementioned performance metrics, constitutes a major advance in the development of commercial DMNC technology.

References

Guo, X.; Fang, G.; Li, G.; Ma, H.; Fan, H.; Yu, L.; Ma, C.; Wu, X.; Deng, D.; Wei, M.; Tan, D.; Si, R.; Zhang, S.; Li, J.; Sun, L.; Tang, Z.; Pan, X.; Bao, X., Direct Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen. Science
2014,
344 (6184), 616-619.

Thyssen, V. V.; Vilela, V. B.; de Florio, D. Z.; Ferlauto, A. S.; Fonseca, F. C., Direct Conversion of Methane to C2 Hydrocarbons in Solid-State Membrane Reactors at High Temperatures. Chemical Reviews
2022,
122 (3), 3966-3995.

Sakbodin, M.; Schulman, E.; Cheng, S.; Huang, Y.-L.; Pan, Y.; Albertus, P.; Wachsman, E. D.; Liu, D., Direct Nonoxidative Methane Conversion in an Autothermal Hydrogen-Permeable Membrane Reactor. Advanced Energy Materials
2021,
11 (46), 2102782.

Figure 1
Integrated Experiment-Theory Framework for Studying Mass Transport Effects in Electrochemical CO2 Reduction on Copper
Authors: Matthews Jesse E , Govindarajan Nitish , Varley Joel , Guo Jack , Ehlinger Victoria Marie , Roy Thomas , Chu An , Cho Ara , Pedersen Frank Abild , Bajdich Michal , Lee Dong Un (Daniel) , Lin Tiras Y , Hahn Christopher , Jaramillo Thomas F.
Published: August 2024

Electrochemical carbon dioxide reduction (eCO2R) has emerged as a promising approach to produce high-value fuels and chemicals using renewable energy sources. In particular, Cu catalysts can convert CO2 to a wide range of hydrocarbon and oxygenate products, including CO, formate, ethanol and ethylene. However, the activity and selectivity of eCO2R is highly dependent on mass transport and the corresponding reaction microenvironment present under operating conditions. In this talk, we present an integrated framework that combines experiments with computational fluid dynamics (CFD) and density functional theory (DFT) based microkinetic modeling to predict the effect of varying mass transport on eCO2R in a custom-designed flow cell. The flow cell is designed with multiple electrolyte jets impinging onto the electrocatalyst surface for rapid and homogeneous reactant transport. We first demonstrate the effect of mass transport in a flow cell architecture by controlling the flow rate of CO2-saturated 0.1 M KHCO3 to a Cu electrocatalyst. Significant increases in the production rates of formate and CO are observed with increasing flow rate, as well as an enhancement in multi-carbon products at high overpotentials. Increasing flow rate promotes hydrogen evolution at low overpotentials but has little effect at large overpotentials, suggesting a transition from HCO3
- to water as the dominant proton donor with increasing overpotential. CFD simulations are employed to model the distribution of boundary layer thicknesses within the flow cell, which subsequently set the boundary conditions for the coupled 1D transport-microkinetic model. The calculated boundary layer thickness values are corroborated by experimentally measured transport-limited currents. Our model successfully predicts experimentally observed trends in selectivity with mass transport, such as an increase in the production of ethylene and ethanol at high flow rates due to enhanced CO2 transport. The slight suppression of hydrogen reduction at higher flow rates due to an increase in *CO coverage is also predicted and supported by experimental results. This work demonstrates the importance of incorporating transport processes in the CFD-DFT coupled modeling of device performance for electrochemical CO2 reduction.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL release number: LLNL-ABS-857566.
How Mechanical Challenges Affect the Performance of Industrial Scale Carbon Dioxide Electrolyzer Cells?
Authors: Kecsenovity Egon , Hursán Dorottya , Janáky Csaba
Published: August 2024

One of the most important challenge of humanity in the mid-21st century is to maintain economic growth in an environmentally sustainable way. The European Green Deal addresses this issue, and it aims at making Europe climate neutral by 2050. To reach this aim, a promising technology is to convert a greenhouse gas, carbon dioxide into valuable chemicals (produce e.g., energy carriers, fine chemicals, pharmaceuticals) in an environmentally and economically sustainable manner, such as the utilization of renewable energy sources.

The direct electrochemical reduction of carbon dioxide into carbon-monoxide (a high-value product which can be readily used in the chemical value chain) is a promising waste-to-wealth approach among the developed technologies and it can be easily coupled with carbon-free electricity sources to make the process completely sustainable. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance, as well as finding technological solutions that enable scale-up to reach industrially relevant dimensions.

Zero-gap electrolyzer cell technology operates with high reaction rates and good efficiencies under ambient and near ambient conditions. In addition, its operation is simpler compared to other types of carbon-dioxide electrolyzer cell technologies (just one example: there is no need very precisely pressure control because no flowing catholyte inside the cell), and this allows the scale up of such architectures. Exploring the fundamentals and understanding of the chemistry in zero-gap electrochemical cells is carried out by many research groups, usually with small experimental test cells. These results provide a good scientific basis (e.g., to select the right catalysts, components, or to study long-term degradation, etc.), however, compared to the size of an industrial-scale electrolyzer, these experimental cells only measure a "one point" chemistry. The results cannot be transferred without careful consideration during scale-up, due to several additional challenges. These challenges are mainly of mechanical origin, and all of these create uneven conditions that can significantly affect the chemistry of the on given sections of the cells.

Over the past several years, we have gone through the steps of scaling up electrochemical cells (for CO2-to-CO conversion) from a small experimental test cell (8 cm2) to an industrial-sized cell stack (2500 cm2 / cell). During the development journey we encountered many of the challenges outlined above. In this talk, I am going to present some of these challenges, their origins, what affects them and by them, and what principles can be used to find solutions.
(Invited) Scaling CO2 to MeOH Conversion in an Electrolyzer
Authors: Henckel Danielle Alexia , Smith Wilson A
Published: August 2024

Methanol is a desirable, value-added product from CO2 electroreduction, but is difficult to obtain in high Faradaic efficiencies. Promising results have emerged from a catalyst system comprised of cobalt pthalocyanine adsorbed onto carbon nanotubes (CoPc/CNT) in batch cell reactors, reaching Faradaic efficiencies of 40-50%.(1) In this talk, we will present our work on scaling this reaction in a 25 cm2 flow reactor with a gas diffusion electrode. We discuss the differences in the two geometries (electrolyzer vs. batch reactor) and the effect of different process conditions, such as pH, electrolyte identity and CO2 partial pressure on product selectivities.

Y. Wu, Z. Jiang, X. Lu, Y. Liang, H. Wang, Nature. 575, 639–642 (2019).
Electrodes Modified with Overlayers for Enhanced CO2 Reduction Selectivity
Authors: Barile Christopher J.
Published: August 2024

Like many electrocatalytic reactions involving the transfer of multiple protons and electrons, the CO2 reduction reaction frequently exhibits poor selectivity among many possible products. In this presentation, I will describe our laboratory’s efforts to design electrochemical platforms that enable the control over proton transfer dynamics to electrocatalysts using molecular and polymeric overlayers with the goal of increasing product selectivity and understanding reaction mechanism. This platform is generally applicable to both molecular and metallic systems, and we demonstrate how it can be used to improve the selectivity of nonprecious metal O2 reduction and NO3
- reduction catalysts.

For the CO2 reduction reaction, this strategy as applied to metal electrodes is also broadly germane and is used to modulate catalyst reactivity such that it results in the selective production of ethylene, ethanol, methanol, carbon monoxide, and methane, with examples for each with Faradaic efficiencies in excess of 70%. A common theme is that the hydrophobicity of the metal-overlayer interface frequently controls product selectivity and can steer the site of protonation events at intermediates. In this manner, for example, the selectivity of catalysts between the C2 products ethanol and ethylene can be dictated. To aid in mechanistic understanding and catalyst characterization, the majority of these studies are conducted on nominally flat metal electrodes. However, we will also describe ongoing efforts to nanostructure these CO2 reduction systems to develop selective catalysts that operate at high current densities.
Impact of Pulsed Currents on Zero-Gap Cu-Reduction of CO2 to Ethylene
Authors: Marufu Michell , Goldman Maxwell , Prajapati Aditya , Baker Sarah , Clemens Auston L. , Krall Eric , Hahn Christopher , Duoss Eric B
Published: August 2024

The electrochemical reduction of CO2 provides a sustainable route to produce key building blocks in the petrochemical and manufacturing industries, thereby reducing carbon emissions and dependence on non-renewable sources. Zero gap electrolyzers are more energy efficient compared to traditional electrolyzers due to significant reduction in ohmic losses. However, the challenge of salting out limits the lifetimes of high performance zero gap electrolyzers to a few hours, hindering their adoption into industry.

Pulsed currents have been shown to increase the electrochemical stability of copper-based electrodes during the electrochemical CO2 reduction reaction (CO2RR). High operating current provides favorable CO2RR product efficiencies, but also increases the salt crossover from the anolyte to the cathode where the salt precipitation may lead to blocking the CO2 flow fields causing the electrolyzer to fail. We demonstrate an operating protocol that incorporates a short period of lower current which reduces CO2 consumption and allows for dissolution of carbonate salt on the cathode surface by reducing cation crossover. This is followed by a higher current to maximize CO2RR products. Intermittent pulsing reverses some of the carbonate salt production at the cathode, which allows the electrolyzer cell to restore itself, thereby increasing lifetime. The method is demonstrated in a 5cm2 zero-gap cell, with KOH, CsOH and CsHCO3 to establish the extent of this method’s utility with different cations and the effect of solubility limits on this salting behavior. By employing this pulsing protocol, we observe significantly increased cell lifetimes at a high current density of 200mA/cm2.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore

National Laboratory under Contract DE-AC52-07NA27344.

LLNL-ABS-847304
Electrochemical Conversion of Bicarbonate Using Proton Exchange Membrane-Based Electrolyzer
Authors: Jeong Hui-Yun , Hahn Christopher
Published: August 2024

Direct electrochemical conversion of captured carbon dioxide (CO2) is gaining interest as an efficient method for capturing and utilizing CO2, eliminating the need for energy-intensive CO2 separation process.[1] The integrated electrolyzer with bicarbonate feed operates on the principle of spontaneous reduction of CO2 released from bicarbonate within the electrolyzer. The key to the on-site decomposition of bicarbonate into CO2 is to acidify the bicarbonate within the electrolyzer through the deliberately generated pH gradient. Bipolar membrane has been extensively used to generate pH gradient and acidify the bicarbonate feed.[2] However, the high ionic resistivity of bipolar membrane and slow kinetic of water dissociation reaction can result in a high operation cell voltage.

In this study, we demonstrate proton exchange membrane based-bicarbonate electrolyzer which produces carbon monoxide from bicarbonate feedstock with high CO production selectivity and low cell voltage that are comparable to the conventional gas fed CO2 electrolyzer. To achieve highly selective CO production selectivity, a nickel single atom catalyst (Ni SAC) where the atomically dispersed nickel active sites decorated on the nitrogen doped carbon was prepared and utilized. Ni-SAC showed high CO production selectivity even in bicarbonate feed electrolyzer. To further improve the performance of this integrated electrolyzer, significant attention was given to the optimization of electrode structures. Due to the complexity of the reaction environment within the integrated electrolzyer, the performance of the electrolyzer is heavily dependent on the porosity of electrodes and distribution of catalyst on the electrodes. By optimizing the fabrication of electrodes with Ni-SACs, the optimal catalyst coated electrode showed high CO production selectivity over 90% with current density of 100 mA/cm2 at low operating cell potential of 3 V.

References

[1] M. C. Freyman, Z. Huang, D. Ravikumar, E. B. Duoss, Y. Li, S. E. Baker, S. H. Pang and J. A. Schaidle, Joule, 2023, 7, 631-651.

[2] T. Li, E. W. Lees, M. Goldman, D. A. Salvatore, D. M. Weekes and C. P. Berlinguette, Joule, 2019, 3, 1487-1497.
The Role of Surface Roughening in Improving the Selectivity of Copper for CO2 Electroreduction
Authors: Halldin Stenlid Joakim , Gauthier Joseph , Head-Gordon Martin , Bell Alexis T. , Ablid-Pedersen Frank
Published: August 2024

Electroreduction of CO2 (eCO2RR) has emerged as a promising alternative for production of renewable fuels and important commodity chemicals such as ethylene and ethanol. Simultaneously, it opens an economically attractive path to mitigate point sources of CO2, a potent greenhouse gas. Despite decades of research efforts, Cu remains the only catalyst capable of producing significant amounts of desirable C2+ products, containing more than one carbon atom. However, further improvement is needed for industrial applications. It is known that roughened copper-based electrocatalysts surfaces exhibit enhanced selectivity towards C2+ products during electroreduction of CO2. This poses a challenge for modeling efforts aiming to find a rationale for the enhanced selectivity. In this work, we use an innovative modeling approach to investigate roughened copper surfaces derived from cuprous oxide on structures of 100x100 nm2 size with atomic resolution and accuracy compared to density functional theory (DFT). We combine semilocal DFT (RPBE) in VASP, effective medium theory (EMT), and linear scaling relationships via the recently proposed alpha parameter scheme to investigate the site-resolved catalytic selectivity of copper sites. Electrode potential-dependence is included via the use of the VASPsol implicit solvation and a grand canonical potential approach. The approach allows us to investigate the effect of varied macroscopic roughness on the intrinsic catalytic activity of copper by comparing surfaces exposed to simulated sputtering and electropolishing, respectively. The study highlights i) the challenge for designing improved copper catalysts for CO2RR with monodisperse active site selectivity, ii) the need for careful experimentation when comparing to theory, and iii) the limitations of macroscopic roughness in controlling atomic scale activity.
CO Residence Time Modulates Multi-Carbon Formation Rates in a Copper Based Zero Gap CO2 Electrolyzer
Authors: Subramanian Siddhartha , Burdyny Thomas
Published: August 2024

Carbon dioxide (CO2) electrolysis on copper (Cu) catalysts has attracted interest for its direct production of C2+ feedstocks. Using the knowledge that CO2 reduction on copper is primarily a tandem reaction of CO2 to CO and CO to C2+ products, we show that modulating CO concentrations within the liquid catalyst layer allows for C2+ selectivity of > 80 % at 200 mA cm-2 in a membrane electrode assembly over broad conversion conditions. The importance of CO pooling is demonstrated through residence time distribution curves, varying flow fields (serpentine/parallel/interdigitated), and flow rate. While serpentine flow fields require high conversions to limit CO selectivity and maximize C2+ selectivity, the longer CO residence times of parallel flow fields reach similar selectivity over broad flow rates. Critically, we show that parts of the catalyst area are predominantly reducing CO instead of CO2 as supported by CO reduction experiments and transport modelling of the reactor. In addition, higher cation crossover from the anolyte is shown to maximize C2
+ selectivity providing further evidence of cation effect on C-C coupling rates.
(Invited) Streamlined Production of Protonic Ceramic Electrochemical Cells Via Ultrasonic Spray Coating
Authors: Wu Wei , Ding Dong , Zhao Zeyu
Published: August 2024

Thin solid oxide films are crucial for developing high-performance solid oxide-based electrochemical devices aimed at decarbonizing the global energy system. This presentation introduces ultrasonic spray coating technique (USC) for producing <10 µm thin electrolyte films, as well as uniform 4×4 cm2 oxygen electrode films, with a systematic process optimization considering solid loading rates, spray passes, and annealing temperature etc. Notably, the integrated approach highlights the versatility of USC in addressing both oxygen electrode and electrolyte fabrication challenges. The resulting protonic ceramic electrochemical cells, fabricated with these optimized parameters, exhibit remarkable electrochemical performance, structural integrity, and stability in both fuel cell and electrolysis modes. This presentation provides a holistic perspective on scalable production techniques, showcasing the potential of ultrasonic spray coating for advancing large-sized solid oxide electrochemical cells.
(Invited) Novel High Entropy Perovskite Oxides for High-Performance Protonic Ceramic Electrochemical Cells
Authors: Tong Jianhua , Zou Minda
Published: August 2024

Due to the intermediate operating temperatures (400-600oC), protonic ceramic electrochemical cells have attracted significant attention in the last 10 years because of the demonstration of potential applications of fuel-flexible fuel cells, water electrolysis to produce hydrogen, solid-state ammonia synthesis, electrochemical reduction of carbon dioxide to fuels, and fuel processing (e.g., natural gas to liquids). In addition to developing specific fuel electrodes for different electrocatalytic reactions, we need to discover new electrolyte and oxygen electrode materials generically for all the protonic ceramic electrochemical cells to further decrease the operating temperatures, increase performance, and prolong the long-term stability. The recently emerging materials of high entropy perovskite oxides have been reported to be able to serve as promising electrolyte and oxygen electrode materials. In this talk, we will summarize what Clemson University has done about developing, characterizing, understanding, and demonstrating high entropy perovskite oxides as high-performance and stable electrolyte and oxygen electrode materials for protonic ceramic electrochemical cells.
Scale-up of PTFE-Based Gas Diffusion Electrodes from Lab Scale to Stack Level Using Polymer-Coated Current Collectors
Authors: Filippi Michael , Möller Tim , Pastusiak Remigiusz , Magori Erhard , Paul Benjamin , Strasser Peter
Published: August 2024

In this work, we will present a novel current collector concept that allows the scale-up of PTFE-based gas diffusion electrodes (GDEs) from an initial 5 cm2 to 300 cm2 geometric area. It is very well known that PTFE-based GDEs are very good solutions to circumvent flooding, however, due to the insulating nature of PTFE, scale-up was so far not addressed. Our novel current collector concept was first demonstrated in the so-called "grid" current collector design and was later transferred into a so-called "monopolar design". We show the importance of an insulating polymer coating on the surfaces of the current collector that are in contact with the bulk electrolyte to suppress hydrogen evolution. Later on, our new concept was transferred and optimized for the operation of 100 cm2 PTFE-based GDEs. The GDEs plus current collector were finally transferred into a stack comprising 5 electrodes with a total cathode surface area of 1500 cm2. Overall, we will demonstrate our new concept from the lab scale to the stack level and will talk about future use-case scenarios of our new technology.
Using Atomic Layer Deposition to Create Mixed Metal Oxide Electrodes for H2O2 Generation through Water Oxidation
Authors: Kupferberg Jacob Eric , Messias Igor , Rozyyev Vepa , Jones Jessica Catharine , Papa Lopes Pietro Papa , Elam Jeffrey W. , Martinson Alex B. F.
Published: August 2024

The electrochemical synthesis of H2O2 through water oxidation provides a means of producing a useful chemical and potential fuel without the input of fossil fuels. Highly stable metal oxides like TiO2 and SnO2 surfaces have shown activity as electrocatalysts for oxidative H2O2 generation, but often require high overpotentials that result in parasitic side reactions. Using atomic layer deposition (ALD) to introduce well-distributed layers of MnOx dopant one can lower the required overpotential of TiO2 and SnO2 surfaces for H2O2 production. Even a single sub-surface layer of MnOx can alter the redox behavior of a 5 nm thick oxide film. While the doped films maintained reversible Mn redox peaks and prevent the total dissolution of the deposited Mn, in-situ inductively coupled mass spectrometry did reveal loss of Mn from the film at applied potentials close to the expected onset potential of the 2e- water oxidation reaction. The depth of sub-surface MnOx was varied to determine the effect on both electrode activity, selectivity, and stability. In addition, the use of either inert and oxidizing annealing atmospheres was used to control both the distribution and the charge-state of the Mn species. This work provides some indication of how manganese-doped metal oxide electrodes degrade during operation and how controlling the surface can improve the activity and stability of the device. This study may also provide a framework of how other redox active species can be embedded within more stable oxide matrices using ALD methods to maximize stability and activity.
Thin Film Based Membrane Electrode Assemblies for Solid-State Ammonia Synthesis
Authors: Wallis Jan , Ravkina Olga , Surkus Annette-Enrica , von Mallinckrodt Robin , Mewafy Basma , Wartmann Jens , Kruth Angela
Published: August 2024

Ammonia is the of the most crucial chemicals and currently primarily produced through the Haber-Bosch process causing the industrial ammonia production to emit more CO2 than any other chemical-making reaction. While the current primary function of ammonia lies within the fertilizer production, it can also be directly used as a fuel for power generation or in the maritime industry. Compared to hydrogen, ammonia has superior storage and transportation capabilities due to its greater volumetric energy density and mild conditions for liquefication. Given the need of reducing global carbon emissions, ammonia could be synthesized electrochemically using air, water and electricity by the Solid-State Ammonia Synthesis (SSAS). Protonic ceramic cells operate within an intermediate temperature regime of around 450 - 550 °C which is well suited for this process. Within our work, we present a tubular membrane electrode unit entirely made of ceramic components based on a barium zirconate thin film electrolyte. An ammonia production rate of 9.06 × 10-10 mol s-1 cm-2 and a Faradaicefficiency of 6.58% were achieved using a NiO-BaZr0.7Ce0.2Y0.1O3-
δ
| BaZr0.8Y0.2O3-
δ
| Ru@Ba0.5Sr0.5TiO3-δ cell.

A key innovation lies in the production of dense BaZr0.8Y0.2O3-δ electrolyte layers, ranging from 1 to 5 µm in thickness, utilizing a Closed-Field Unbalanced Magnetron Sputtering (CFUMS) process. This technique allows precise adjustments of stoichiometric ratios within the perovskite structure, offering improved sputtering yields compared to conventional methods. Furthermore, the crystallinity, phase purity, and microstructure of sputter-deposited thin films are enhanced through selective laser annealing (SLA), resulting in high-density films composed of single-phase BaZr0.8Y0.2O3-δ with average crystallite sizes of 200 nm while avoiding substrate damage from thermal stress. Electrochemical performance was evaluated through impedance spectroscopy, half-cell tests and full cell tests providing insights into the efficacy of the developed tubular membrane reactor for the electrochemical synthesis of ammonia. The results demonstrate the feasibility of utilizing ceramic proton conductors in SSAS, particularly highlighting the potential of high-pressure operation up to 80 bars in tubular cells at relatively low temperatures around 450 °C, thereby achieving attractive NH3 production rates.

This research contributes to the evolving landscape of sustainable ammonia synthesis by presenting a novel approach that integrates advanced materials and manufacturing techniques. Electrification and decentralization of the ammonia supply chain will expand the market by supporting its current use as fertilizer source and enable a new route as green energy carrier paving the way for an ammonia-based economy.

Figure 1
Atomic Layer Deposition of Cu Catalysts on Gas Diffusion Electrodes for Electrochemical CO2 Reduction
Authors: Lee Si Young , Lenef Julia D. , Fuelling Kalyn M. , Rivera Cruz Kevin Enrique , Prajapati Aditya , Delgado Cornejo Daniel O. , Cho Tae H. , Sun Kai , Alvarado Eugenio , Arthur Timothy Sean , Roberts Charles , Hahn Christopher , McCrory Charles , Dasgupta Neil P.
Published: August 2024

Electrochemical CO2 conversion is gaining attention as an important process for carbon fixation through the use of renewable electricity to address the climate change crisis. Copper is a unique single-element catalyst that can induce C-C coupling reactions to generate high-value-added compounds. The triple phase boundary has been successfully controlled at the catalyst interface using gas diffusion electrodes (GDEs) over the past few years, resulting in high C-C coupling performance. Therefore, methods to engineer the catalyst interface on the 3D structure of GDE are of significant importance. Generally, the catalyst on the GDE is introduced through physical vaper deposition (PVD) using sputtering or E-beam evaporation, or through solution methods such as spray coating and drop-casting of nano-particles. However, the porous and tortuous 3D structure of the GDE often result in limited conformality and difficulty in obtaining a uniform and controlled infiltration of the catalyst into the support structure.

In this study, we synthesized Cu catalysts directly onto GDE surfaces using plasma-enhanced atomic layer deposition (PE-ALD), which allowed for precise tuning of the catalyst size and loading at the nanoscale [1]. The synthesized catalysts were confirmed to be polycrystalline Cu nanoparticles using grazing incidence X-ray diffraction. To demonstrate the advantages of the conformal and tunable control of PE-ALD deposition, we deposited the same areal mass loading of Cu catalyst onto the GDE substrates using PVD, and compared the CO2 reduction activity in an H-cell environment. The PE-ALD Cu catalyst showed more than 3 times higher current density than the PVD catalyst at the same electrode potential, a low (~10%) Faradaic efficiency (FE) for the hydrogen evolution reaction (HER), and greater than 75% FE for C-C coupling to form C2+ products including ethylene and ethanol, which is comparable to the highest performances reported to date for metallic Cu catalysts in a H-cell environment. Furthermore, stable operation was observed for a duration of 15 hours, with minimal changes in activity and selectivity. In conclusion, the introduction of catalysts using PE-ALD on GDE electrodes represents a powerful new synthesis method that can increase both C-C coupling performance and selectivity compared to PVD deposition, due to its adjustable Cu nanoparticle size and high conformality.

Reference

1) J. D. Lenef, S.Y. Lee, K. M. Fuelling, K. E. Rivera Cruz, A. Prajapati, D. O. D. Cornejo, T. H. Cho, K. Sun, E. Alvarado, T. S. Arthur, C. A. Roberts, C. Hahn, C. C. L. McCrory, N. P. Dasgupta, Nano Lett. 23, 10779-10787 (2023)
Mass Transport Regimes in a CO2R Gas Diffusion Electrode Pore with Coupled Microkinetics Model
Authors: Antimes Aymeric , Euzenat Florian , Roy Thomas , Ehlinger Victoria Marie , Govindarajan Nitish , Lin Tiras Y , Sarkar Amitava
Published: August 2024

Gas Diffusion Electrodes (GDEs) have arisen as a popular CO2 electrolyser configuration due to the improved mass transfer properties and higher current densities possible in comparison to a liquid-fed system. In this work, we aim to understand the mass transport regimes in a single liquid-filled pore of a GDE, i.e., an idealized model of the porous catalyst layer. In previous work, Butler-Volmer (BV) expressions have been used to model the CO evolution reaction and the Hydrogen Evolution Reaction (HER). In this study, we extend that in a few ways: (1) a MicroKinetic Model (MKM) of Au at the surface of the electrode is used instead of the BV expressions, (2) volume/steric effects are incorporated through the Generalized Modified Poisson-Nerst-Planck (GMPNP) equation, and (3) more reactions are considered in the electrolyte. By analyzing pores of varying sizes, following the size distribution measured by Focused Ion Beam Scanning Electron Microscopy (FIB/SEM) in a GDE from the literature, we assess conditions where concentration profiles are no longer effectively one-dimensional in the pore axis. We discuss how these three-dimensional mass transfer effects impact CO2 conversion efficiency. In such regimes, we describe why special treatment is required when calling BV expressions in macroscale pore-averaged models.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL release number: LLNL-ABS-858384.
pH Effects in the Electrochemical Reduction of CO at Cu Electrocatalysts in an MEA Cell Configuration
Authors: Bello Mustapha , Hendershot John C , Dauda Monsuru Olatunji , Park Junghyun , Flake John C.
Published: August 2024

We explore the impact of pH and buffer on the electrochemical reduction of CO at Cu electrocatalysts in a membrane electrode assembly (MEA) cell. Anolytes included alkaline KOH solution with potassium hydrogen phosphate and potassium dihydrogen phosphate buffers with pH values ranging from 8 to 14. Results show near-neutral pH electrolytes enhance acetate selectivity. Figure 1 shows Faradaic efficiencies to acetate over 85% at a current density of 300 mA/cm². More alkaline electrolytes resulted in increasing HER along with coproduction of ethanol and n-propanol.

Previous works have shown that ethylene production is enhanced at near-neutral pH values and other works have demonstrated that acetate is more favored in alkaline conditions, with ketene identified as a key intermediate. This study highlights the role of phosphate buffers in acetate selectivity at near-neutral pH. SEM, XPS, and XRD analyses show morphological and compositional changes in the Cu catalyst under different pH conditions. We propose that the phosphate buffers stabilize acetate precursors.

Figure 1: Electrochemical performance measurement at different anolyte pH; Faradaic Efficiency of H2, C2H4, CH4, Ethanol, Acetate, and n-Propanol during CO electroreduction in a zero-gap MEA configuration at 300 mA*cm−2.

Figure 1
Impact of Local Environment on Selectivity of Ag and Cu Gas Diffusion Electrodes with Strong Hydrophobic Substrate during the Electrochemical Reduction of CO2
Authors: Bernasconi Francesco , Senocrate Alessandro , Plainpan Nukorn , Battaglia Corsin
Published: August 2024

Electrochemical CO2 reduction (CO2RR) is a promising pathway to convert detrimental CO2 emissions into sustainable fuels and chemicals, and close the carbon loop1. To ensure the industrial applicability of this technology, electrocatalysts need to be highly active, selective towards a desired product, and offer long-term stability. High activity can be achieved with gas diffusion electrodes (GDEs), in which the CO2 reactant is supplied directly from the gas phase, however reaching high selectivity toward a single product over time remains a challenge. Recently, the control of the local environment around the catalyst has been identified to be a key factor to ensure high selectivity and stability2.

In this work, we show that the local environment around the catalyst drives the selectivity of the catalyst depending on the pore size and hydrophobicity of the GDE. GDEs with large pores and weak hydrophobicity lead to poor selectivity toward carbon products, while GDEs with small pore and strong hydrophobicity yield a greatly improved Faradaic efficiency (FE) towards CO in the case of Ag (FE > 70%)2 and towards C2H4 in the case of Cu (FE > 50%) 3 at 200 mA/cm2 for several hours. The further increase of current density is detrimental to the performance of the GDEs, which points to a limitation of the transport of CO2 to the electrocatalyst. Additionally, CO reduction experiments show a qualitatively similar behavior but at much lower current densities. These findings are consistent with the presence of an electrolyte layer wetting the electrocatalyst that forces the electrocatalytic reaction to take place at double phase boundaries. Finally, we provide evidence for the correlation between the loss of selectivity towards carbon products over time and the precipitation of carbonates by operando synchrotron X-rays diffraction experiments4.

In summary, our results highlight the importance of controlling the local environment near the catalyst to enhance the selectivity towards carbon products during CO2RR.

References

1A. Senocrate, C. Battaglia, J. Energy Storage
2021, 36, 102373

2A. Senocrate, F. Bernasconi, D. Rentsch, K. Kraft, M. Trottmann, A. Wichser, D. Bleiner, C. Battaglia, ACS Appl.
Energy Mater.
2022, 5, 14504

3F. Bernasconi, A. Senocrate, P. Kraus, C. Battaglia, Energy & Environ.
Science Catalysis, 2023, 1, 1009

4F. Bernasconi, A. Senocrate, N. Plainpan, M. Mirolo, Q. Wang, C. Battaglia, submitted
Active Electrode for Ammonia Direct Utilization and the Reactivity of Metal Component in High-Temperature SOFCs
Authors: Horita Teruhisa , Bagarinao Katherine Develos , Kishimoto Haruo , Matsui Toshiaki , Muroyama Hiroki
Published: August 2024

We have been conducting the international collaboration study on “Green ammonia synthesis and utilization by solid electrolysis cells for maritime application” between Germany and Japan (term:2022-2024) under the SICORP program of Japan Science and Technology Agency (JST). The contributors of this project are AIST, Kyoto University, and Morimura SOFC Technology from Japan side and Fraunhofer IKTS and EDL from German side.

The purpose of this project is to establish a new concept for energy loop based on the ammonia synthesis and utilization with maritime application. The task of Japan side is to make a new anode material for direct utilization of ammonia (cracking and oxidation of NH3 component) and degradation mechanism at anode. Addition of BaO into Ni/YSZ anode improved the decomposition rates of NH3 and anode performance in NH3 fuels. We have succeeded the decomposition rate of NH3 over 99.9 % with an optimum addition amounts of BaO into Ni-YSZ electrode. An excellent performance of BaO-added Ni-YSZ cermet electrode was observed with a stable performance over 80 hours operation.

Preliminary analysis using secondary ion mass spectrometry (SIMS) indicated possible nickel nitride (NiN) formation in the Ni/YSZ substrate of commercial cells exposed to NH3 and possible degradation mechanisms are considered taking into account the thermodynamics and electrochemical oxidation.

This presentation will show the recent progress of this research.
Selectivity and Durability in the Electrochemical Reduction of CO2 to C2 Products Using Cu-P, Cu-Sn and Cu-Se Electrocatalysts
Authors: Dauda Monsuru Olatunji , Hendershot John C , Bello Mustapha , Agbadan Ignace , Tasnim Soundarzo , Plaisance Craig , Flake John C.
Published: August 2024

Ethylene is typically reported as the primary product from CO2 reduction at copper electrocatalysts in MEA-type cell configurations with alkaline anolytes. In this work, we evaluate CO2 reduction selectivity at Cu-P, Cu-Sn, and Cu2Se electrocatalysts that were synthesized via a common one-pot approach. Electron microscopy, X-ray diffraction and inductively coupled plasma optical emission spectrometry show 100-110 nm nanoparticles with uniform distributions of P, Sn, or Se. When using neutral (0.1 M KHCO3) anolytes, electrocatalysts with P-doping yield increases in ethylene Faradaic efficiency (up to 52 % at 150 mA cm-2) while Cu-Sn and Cu-Se electrocatalysts result in increased oxygenate selectivity. Cu-Sn electrocatalysts yield an FE of 24 % ethanol at 150 mAcm-2 and Cu2Se electrocatalysts yield an FE of 32 % to acetate at 150 mAcm-2. More alkaline anolytes (1 M KOH) further increased oxygenate formation, with 48 % ethanol Faradaic efficiency on Cu-Sn and 40 % acetate Faradaic efficiency on Cu2Se at 350 mA cm-2. Galvanostatic experiments were conducted at 150 mA cm-2 in 0.1 M KHCO3 electrolyte for over 200 h for the three electrocatalysts. Figure 1 shows the slow losses in FEs to C2 products (0.02 % per h) and increasing cell potentials (1 mV per h). In this talk, we consider the mechanisms for selectivity and the nature of durability improvements.

Figure 1
Membrane Electrode Assembly Development for Industrial CO2 Electrolysis
Authors: Hursán Dorottya , Kecsenovity Egon , Danyi Antal , Piszmán Rita , Kovács Anita , Janáky Csaba
Published: August 2024

Membrane electrode assemblies (MEAs) are the key components of zero-gap CO2 electrolyzers, having various functions in the electrolysis process. The catalyst layers serve as the reaction interface, the porous transport layers ensure reactant and product transport to and from the catalysts, while the membrane is responsible for the ion transport between the two half cells. Thus, the structure of the MEA has a determining role on the electrolyzer operation. Industrial application requires large surface area electrolyzers and / or assembly of stacks. The scale-up, however, imposes different challenges on MEA preparation and on electrolyzer operation, therefore the optimal operating conditions can not necessarily be translated from small-scale (< 10 cm2) experiments.

With the aim to scale-up the CO2 electrolysis to an industrially relevant level (>2500 cm2 active area), we thoroughly study the MEA components in a test electrolyzer cell having 100 cm2 active area. Currently we focus mainly on the optimization of the catalyst layers and the porous transport layers. The used electrolyzer size is already large enough that we can draw relevant conclusions for the operation of the large-scale electrolyzer, however, still offers possibility to screen a wide range of parameters.

I will present selected results on how the improvement of the quality of the catalyst layers - through the optimization of the catalyst ink and the coating process- results in enhanced CO2 reduction performance. We also focus on the screening of different porous transport layers on the anode side with the long-term goal to reduce the precious metal consumption of the CO2 electrolysis. In the second part of my presentation, I will show how the operational parameters (e.g. cell temperature, humidity) affect the stability of the electrolysis. We have thoroughly investigated one of the biggest issues of the anion exchange membrane CO2 electrolysis: the carbonate precipitate formation and the related flooding phenomenon. We identified the pressure drop at the cathode side as a key test output parameter, which can serve as an early warning for the start of the undesired precipitation. When it is recognized in time, and the adequate preventive measures are applied, the lifetime of the electrolyzers can be greatly improved.
Magnetically Enhanced Electroconversion of CO2 to Valuable Products at High Current Densities
Authors: Gutierrez-Carballo Alejandro , Wilson Nathan W. , Gonzalez-Fernandez Cristina , Botte Gerardine G , Gomez-Pastora Jenifer
Published: August 2024

Carbon dioxide reduction has emerged as a highly promising area of focus, particularly considering the perpetual CO2 emissions from the industrial sector. The electrochemical reduction pathway stands out as one of the most auspicious methodologies for CO2 utilization, owing to its compelling attributes. These include, but are not limited to, operation under mild conditions, the ability to tailor CO2 conversion towards desired products, and the potential for seamless integration with renewable electricity sources (e.g., derived from solar and wind), thus offsetting the associated carbon footprint. Moreover, the application of magnetic fields has demonstrated effectiveness in numerous electrocatalytic reduction processes. Presently, there is a paucity of literature addressing the utilization of magnetic fields for CO2 reduction, as it represents a recently introduced concept. This presentation aims to contribute to the advancement of this novel idea, paving the way for its scalability in the near future. Our focus is on addressing mass transfer limitations and optimizing the process to handle high current density, thereby rendering it viable for large-scale CO2 reduction.