bluuebunny/crossref_metadata_2025 huggingface dataset:
Bipolar Membranes for Photoelectrochemical CO2 Conversion
Authors: Cavaliere Sara , Blanchard Pierre-Yves , Spanu Francesco , Nouxet Morgan , Rozière Jacques , Jones Deborah J.
Published: August 2024

CO2 capture and conversion represent one of the most critical challenges of our society. One sustainable approach to tackle it is the development of electrochemical processes coupling a solar-driven carbon dioxide reduction to CO/water oxidation to O2 with reactions leading tohigh-value products. In such photoelectrochemical reactors, (photo)electrocatalysts and membranes play a crucial role to achieve high CO2 conversion with minimum energy.

The aim of this study is developing polymer membranes with high stability, mechanical resistance and ion conductivity, that can work in the broad pH operation range of CO2/H2O co-electrolysis cells. Consistently with the use of KOH at the anode, the used membrane is often an anion exchange membrane (AEM). However, carbonate crossover through AEM occurs during CO2 electrolysis via diffusion and migration. [1] The use of a bipolar membrane (BPM) allows to mitigate this issue, bringing novel challenges of stability and performance.

The BPM consists in a cation exchange layer (CEL) and an anion exchange layer (AEL), with a bipolar junction formed at their interface. Such membrane must guarantee a constant pH level generating H+ and OH- by water dissociation at the junction, avoid product crossover, and optimize mass transfer and reactivity of coupled anodic and cathodic reactions. A crucial point is the control of the electrochemical behavior at the CEL/AEL interface. With this aim, a 3D-structure made of a network of fibers was developed [2, 3] providing a great interfacial area and mechanical interlocking of the anion and cation exchange ionomers preventing delamination and facilitating the exchange of ions and matter at the interface. Furthermore, such fiber webs allow the controlled deposition of inorganic or organic catalysts to enhance the water dissociation rate at the bipolar junction.

The bipolar membrane was prepared interposing a web of electrospun fibers bearing water dissociation nanocatalysts at the interface between anion and cation exchange polymer layers. The prepared BPMs were characterized for their morphology, composition, ion conductivity, and performance.

This work has been performed with the financial support of the European Union’s Horizon 2020 Research and Innovation Action Program under the project SunCoChem (Grant agreement No 862192).

References

[1] B. Eriksson, T. Asset, F. Spanu, F. Lecoeur, M. Dupont, F.A. Garcés-Pineda, J.R. Galán-Mascarós, S. Cavaliere, J. Rozière, F. Jaouen, J. Electrochem. Soc., 2022, 169, 034508.

[2] R. Sood, S. Cavaliere, DJ. Jones, J. Rozière. Nano Energy, 2016, 26, 729–45.

[3] C. Shen, R. Wycisk, PN. Pintauro. Energy Environ Sci, 2017, 10,1435–42
Recent Advancements in Materials for Proton-Conducting Reversible Solid Oxide Cells
Authors: Luo Zheyu , Zhou Yucun , Kane Nicholas , Zhang Weilin , Hu Xueyu , Liu Meilin
Published: August 2024

The escalating threats posed by climate change and environmental issues underscore the need for urgent exploration of clean energy technologies. In this context, proton-conducting reversible solid oxide cells (P-RSOCs) have emerged as promising contenders for large-scale energy storage and conversion. Their efficacy at intermediate temperatures (400 - 600 °C) is a distinctive advantage, attributed to the remarkable ionic conductivity of proton conductors within this temperature range. This feature positions P-RSOCs favorably for the efficient, cost-effective, and enduring conversion between clean electricity and green hydrogen.

However, the successful commercialization of P-RSOCs hinges on the rational design of novel materials and meticulous surface/interface modifications to significantly enhance performance and durability. Achieving prolonged durability during cycling between fuel cell and electrolysis modes while maintaining high Faraday efficiency and roundtrip energy efficiency is of paramount importance. A central challenge involves the development of electrolyte materials exhibiting exceptional stability and a high ionic transference number under operating conditions. Additionally, bifunctional electrodes/catalysts, particularly for the oxygen electrode, must demonstrate elevated activity for efficient dual-mode operation.

To effectively tackle these challenges, it is imperative to devise new protocols for controlling the structure, composition, and morphology of materials across multiple length scales. Equally crucial is gaining a fundamental understanding of degradation mechanisms and electrode processes. This presentation will illuminate the critical scientific challenges inherent in developing a new generation of P-RSOCs, providing insights into the latest advancements in electrolyte materials and bifunctional electrodes/catalysts. Furthermore, it will highlight strategies for enhancing durability and electrode activity through surface/interface modification, along with the latest developments in modeling, simulation, and in situ characterization techniques to deepen our understanding of the underlying mechanisms. The presentation will conclude prospects for achieving low-cost, highly efficient, and durable P-RSOCs through innovative material-based solutions.
Degradation Behavior of Galvanostatic and Galvanodynamic Cells for Hydrogen Production from High Temperature Electrolysis of Water
Authors: Priest Cameron , Kane Nicholas , Wang Lucun , Gomez Joshua , Hartvigsen Jeremy , Ding Dong , Casteel Micah
Published: August 2024

High temperature electrolysis of water using solid oxide electrochemical cells (SOEC) is a promising technology for hydrogen production with high energy efficiency and may promote decarbonization when coupled with renewable energy sources and excess heat from nuclear reactors. One of the challenges facing the commercial deployment of this technology is improving the cost competitiveness of hydrogen produced by electrolysis, which, among other factors, critically depends on the long-term durability of the SOEC system under relevant duty cycles. To extend the lifetime and optimize hydrogen production costs over projected lifetimes, fundamental knowledge of degradation mechanisms and rates as a function of operating conditions is a critical gap to close. Degradation mechanisms of solid oxide electrolysis cells are often coupled with each other and may vary based on cell overpotential and current, making them difficult to isolate and investigate effectively. Pulse Width Modulation (PWM) can be used to create a low-time scale variation under operating conditions that can identify non-linear degradation mechanisms between current and voltage. The short-term perturbations caused by PWM can help relieve stressors compared to cells running under constant (e.g., galvanostatic) conditions, even if the average current that the cell experiences over time is the same. In this work, water electrolysis cells were operated under dynamic conditions and compared with galvanostatic cells with respect to overall cell lifetime and degradation behavior. Specifically, the increases in overpotential and impedance are analyzed and compared between these two different operating modes to provide insights into the differences between average and instantaneous current.
Electrocatalytic Upgrading of CO2 to Light Olefins in Protonic Ceramic Electrochemical Cells
Authors: Wang Min , Wang Lucun , Ding Dong
Published: August 2024

Light olefins (ethylene, propylene, butylene) are primary building blocks for chemical manufacturing of large volume products including organic chemicals, plastics, and even sustainable aviation fuels. Currently, the dominant commercial process for olefin production is steam cracking of naphtha or ethane, which is highly energy intensive and accounts for a large fraction of global CO2 emissions. To decarbonize olefin production processes, electrochemical CO2-to-olefin conversion coupled with renewable or low-emission energy sources including electricity and heat offers an attractive alternative. Previously, extensive research efforts have been devoted to low temperature electrochemical CO2 reduction in aqueous media, i.e., occurring below 100 °C. This approach, however, still faces enormous scientific and technological challenges in improving CO2 utilization, energy efficiency, and product selectivity. In this work, we have developed a new electrochemical process for direct conversion of CO2 to ethylene at intermediate temperatures (350-500°C) in an electrochemical membrane reactor. This process is based on high-performance protonic ceramic electrochemical cells (PCECs) that integrate CO2 hydrogenation reaction to produce olefins in the cathode and concurrent hydrogen generation reaction in the anode to provide hydrogen for CO2 conversion. Highly active and selective catalysts for CO2-to-olefin conversion have been identified and integrated into the PCECs. Both the catalytic and electrochemical performances of the integrated reactor system are evaluated and optimized. In contrast to the use of molecular H2 in conventional thermal catalytic pathways, the active hydrogen in PCECs could be sourced from different feedstocks including H2O, light alkanes, and ammonia, etc. This work also provides valuable insights into the selection and design of efficient catalysts for electrochemical CO2 conversion at elevated temperatures.
Advancements in Additive Manufacturing of Protonic Ceramic Fuel Cells
Authors: Asghar Muhammad Imran
Published: August 2024

Protonic ceramic fuel cells (PCFCs), also known as proton conducting solid oxide fuel cells, are a promising low-temperature (400-600oC) fuel cell technology. Compared to conventional oxygen-ion conducting ceramic materials, proton conducting ceramic electrolyte materials have lower activation energy (< 50 eV), which can enhance fuel cell efficiency and power output. Additive manufacturing has the potential to revolutionize PCFC manufacturing, as it enables fabrication of both dense and porous structures with desirable mechanical and electrochemical properties. In this study, we employed extrusion-based 3D printing to fabricate PCFCs using BaZr0.3Ce0.5Y0.15O3-δ and BaZr0.4Ce0.4Y0.1Yb0.1O3-δ as electrolytes, NiO as anode, and BaCo0.4Fe0.4Zr0.1Y0.1O3-δ and Ba0.5Sr0.5Co0.8Fe0.2O3-δ as cathode. For comparison, we also printed oxide conducting ceramic fuel cells using gadolinium-doped-ceria (GDC ) as electrolyte. We investigated the printable pastes' rheological properties using dynamic light scattering, viscometer, tensiometry, differential scanning calorimetry, and thermal gravimetric analysis. We also characterized the cells using current-voltage measurements, electrochemical impedance spectroscopy, and various spectroscopic and microscopic techniques (HR-TEM-EELS, SEM-EDX) to understand the underlying mechanisms. Finally, we conducted a systematic study to optimize the sintering temperature for optimal fuel cell performance and investigate degradation mechanisms to improve stability. The best printed fuel cells produced 926 mW/cm2 with 3-layer structure and 426 mW/cm2 with 1-layer structure at 550oC.
Understanding Electrochemical and Mechanical Durability of Bipolar Membranes Used in Electrodialysis
Authors: Crow Allison M , Deutsch Todd G , Smith Wilson A
Published: August 2024

Using renewable energy to drive direct carbon capture systems is a powerful way to contribute to net negative emissions. When using liquid alkaline sorbents for CO2 direct air capture, it is critical to reduce the energy demand for CO2 concentration and sorbent regeneration. Electrodialysis is an ideal candidate technology to integrate renewable energy into this process, however, to enable this ion-exchange membrane separators that can operate at high ion flux and low voltage are needed. Bipolar membranes (BPMs), that generate protons and hydroxide ions from the dissociation of water when operated in reverse bias, are the enabling component to generate acid and base in electrodialysis systems. Bipolar membrane electrodialysis (BPMED) uses a BPM to create acidifying and basifying chambers which are well suited to concentrate and release CO2 and concentrate the remaining alkaline effluent to cycle back to the capture process. Current BPM durability, however, sufferers at high current density (ion flux) and physical scale. BPMs have several known degradation mechanisms including chemical breakdown of ion exchange polymers, loss of junction adhesion, or physical breakdown due to shearing force and pressure swings in an electrodialysis cell.

To assess the electrochemical and mechanical durability of BPMs under operational conditions, we investigated how fabrication conditions (including preconditioning, hot pressing, and catalyst loading) impact the adhesion of custom made BPMs. T-peel studies were performed ex-situ to quantify adhesive forces of BPMs made of different compositions and prepared under different conditions, and BPMED experiments were performed to assess the electrochemical performance of the corresponding BPMs. The BPMED results show that, while adhesion is necessary to physically maintain the BPM junction, mechanical adhesion alone cannot overcome poor ion and water transport management at the water dissociation junction. The results of this systematic comparison indicate that in order for BPMs to operate at high current densities, high adhesion forces made during fabrication of BPMs will need to be balanced with water dissociation kinetics and ion/water transport through the individual membrane layers.
Impact of Mechanical Stimuli on PEO-Litfsi Stiffness and Ionic Conductivity
Authors: Garcia ThomasJae , Elcombe Gregory , Lee Min Hwan
Published: August 2024

Recently a large emphasis has been placed on developing safer electrolytes for lithium-ion batteries as a response to an increase in battery demand. Solid polymer electrolytes, such as those based on polyethylene oxide (PEO) show good resistance to mechanical loading, and when coupled with ceramic fillers demonstrate enhance ionic conductivity as well. Prior to this work, efforts have been made to determine the effects mechanical stimuli have on the stiffness and ionic conductivity of the electrolyte.1–3 However, while previous research has primarily focused on bulk EIS measurements of the electrolyte, here we leverage atomic force microscopy (AFM) to modulate the tip-substrate contact force from a few piconewtons to tens of millinewtons to study the correlation between mechanical loading and ionic conductivity, along with measuring the evolution of the substrate stiffness as a function of mechanical cycling.

In this study, we contact the PEO-LiTFSI surface with an electrically conductive Pt-coated tip and mechanically cycle the sample by applying a pre-determined contact force a set number of times. By keeping the contact force and time constant, we extracted the cycle-dependent evolution of the sample stiffness. Results show that stiffness is reduced 30% within the first ten cycles, and then minimally changes with subsequent cycling, matching the results from bulk measurements. Changes in ionic conductivity as a function of mechanical cycling are then measured using electrical characterization techniques. To gain a better understanding of how conductivity and stiffness are evolving, we conducted a parametric study by varying tip size, contact force, and number of mechanical cycles. From early results, we found that electrical resistance increases by ~3% (from 2985 Ohm to 3075 Ohm) after 100 cycles of mechanical force ranging between ~ 0 nN to 450 nN with a 5 µm radius tip. The change in the electrical resistance is believed to originate from the local amorphization of PEO-LiTFSI induced by the mechanical stimuli and resulting change of the local conductivity. These results can be leveraged to further understand how mechanical stimuli affects the mechanical and electrical characteristics of solid electrolytes and help establish a model to predict long-term stability and performance of batteries.

This work was supported by the National Science Foundation (#2125640).

(1) Yoon, D. et al., ACS Appl. Energy Mater, 6 (18), 9400, 2023

(2) Li, X. et al., ACS Appl. Mater. Interfaces, 11 (25), 22745, 2019

(3) Liu, L. et al., Nano Energy, 69, 104398, 2020
Characterization of Proton Exchange in Protonic Ceramic Electrochemical Cells Using Operando Drifts
Authors: Meng Yuqing , Zhang Qian , Zhao Haiyan , Ding Dong
Published: August 2024

The protonic ceramic electrochemical cells (PCECs) have attracted tremendous attention for their fast hydrogen production at intermediate temperatures. This work applied in situ Diffuse reflectance infrared Fourier transform infrared spectroscopy (DRIFTS) together with electrochemical impedance spectroscopy (EIS), to characterizes transport and hydration properties of the state-of-the-art electrolyte materials. The adsorption of water molecules and formation of surface hydroxyl groups on the electrolyte surface as a function of temperature, steam concentration, and electrical potential were systematically investigated by DRIFTS under operando conditions. The quantitative information on the concentration of hydroxyl species on the electrolyte materials before and after exposure to steam were obtained. The determination of OH intensity leads to the direct determination of the proton exchange coefficient k, at different steam concentrations and biases. The results are unique and should be able to provide valuable insights into the mechanisms of proton formation, migration, and evolution under various operating conditions, which is critical to design better electrolyte compositions and optimize the operation conditions for next-generation PCECs.
(Invited) The Electrochemical-Mechanical Coupled Interface Contacts during Lithium Plating and Stripping
Authors: Qi Yue , Feng Min , Liu Xing
Published: August 2024

The current density during battery operation is often assumed uniform across the entire electrode surface. This may be valid for conformal solid/liquid interfaces; however, solid/solid interfaces generally have imperfect contacts. By introducing the contact area ratio, γ, to the electrochemical model, it can be demonstrated clearly that the effective current density scales linearly with the 1/γ and the overpotential scales exponentially with contact area loss, 1-γ.

The calculation of surface contact area must consider the multi-length-scale nature of surface roughness. Assuming surface roughness is self-affine, Bo Persson’s multiscale contact mechanics model for elastic materials can be used for the cathode/solid electrolyte interface to predict the necessary pressure to maintain the original contact area. [1]

However, the most challenging process is Li-stripping, as the vacancy generated by each Li atom removed from the interfaces can accumulate and generate voids, reducing the contact area. However, under an applied stack pressure, the self-affine property will reach a steady state interface contact ratio (γo.) in different length scales. Thus, we proposed a coupled atomistic-and-continuum model, which will capture Li striping and vacancy hopping and accumulation near the Li/SE interface with Density Functional Theory (DFT) informed Kinetic Monte Carlo (KMC) simulations and predict the macroscopic contact area evolution according to the macroscopic creep law with finite element simulations (FEM). The creep rate will be mapped to preferred forward hopping rates for all the Li atoms at the atomic scale. Solving these models iteratively leads to a steady contact area ratio (γo.). Generally, lithiophilic interface requires less stack pressure to maintain a flat surface while a higher stack pressure is needed at lithiophobic interfaces to accelerate Li vacancy diffusion into the bulk and maintain a flat surface. This critical stack pressure needs to be high enough to alter the Li forward-and-backward hopping barriers at the interface. This predictive multiscale simulation scheme was able to combine multiple chemical-mechanical effects during Li stripping morphology evolution. [2,3]

[1] Hong-Kang Tian and Yue Qi, Electrochem. Soc. 2017, 164, E3512

[2] T. Yang and Y. Qi, Chem. Mat. 2021, 33, 2814-2823

[3] Feng, C.T. Yang, and Y. Qi, J. Electrochem. Soc. 2022, 169, 090526
Residual Compressive Stress to Prevent Dendrite Penetration through Solid Electrolytes
Authors: Harris Stephen J , Morris Sydney , Jagad Harsh , Qi Yue , Sheldon Brian W.
Published: August 2024

The use of lithium (Li) or sodium (Na) metal anodes together with highly ion-conductive solid electrolytes (SEs) could provide batteries with a step improvement in volumetric and gravimetric energy densities. Unfortunately, these SEs face significant technical challenges, in large part because Li and Na dendrites can penetrate through SEs, leading to short circuits. We discuss our proposed concept for preventing penetration of lithium dendrites through SEs by putting the SE surfaces into a state of residual compressive stress. We describe quantum and MD calculations, together with ion exchange experiments to demonstrate our progress.
Microstructure-Aware Mesoscale Modeling of Chemomechanical Stress Evolution during Cycling in Solid Electrolyte-Cathode Composite
Authors: Wang Bo , Feng Longsheng , Kim Kwangnam , Wood Marissa , Wan Liwen , Wood Brandon C. , Heo Tae Wook
Published: August 2024

The volume change of cathode active materials during charge-discharge cycling is responsible for the capacity fading of all-solid-state Li batteries due to mechanical degradation in the cathode such as delamination and crack formation. Many strategies to alleviate the chemomechanical stress buildup have been proposed in experiments but rationale of the stress release mechanisms at the mesoscale remain elusive. In this presentation, we present a microstructure-aware mesoscale model to quantitatively predict the stress distribution during cycling in a secondary particle agglomerate of the cathode active material embedded within a solid electrolyte matrix, taking the LiCoO2-Li7La3Zr2O12 (LCO-LLZO) as a model system. We find that the mechanical stress hotspots develop at different stages within the grain boundaries of the LCO agglomerate and the LCO-LLZO interfaces. We investigate the influences of microstructural morphology (columnar versus equiaxial), grain orientations (textured versus random), mechanical properties at the grain boundaries and heterogeneous interfaces, and anisotropy of chemical expansion on the stress hotspot evolution and provide optimal mitigation strategies. The theoretical results can help gain mechanistic understanding on cathode degradation and inform guidelines for experimental design of mechanically optimized cathode materials for long-life solid-state batteries.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and 22-ERD-043.
Electrochemical Embrittlement Accelerates Dendrite Growth in Ceramic Electrolytes
Authors: Fincher Cole D. , Gilgenbach Colin , Roach Christian , Osmundsen Rachel , Sheldon Brian W. , Carter W. Craig , LeBeau James , Chiang Yet-Ming
Published: August 2024

Although solid-state batteries with metal anodes promise to enable safer, higher energy density batteries, metal protrusions (dendrites) grow when charging faster than a critical current density[1,2]. It is generally believed that dendrites grow when plating-induced stresses exceed that required for fracture of the solid-electrolyte[2–4]. Although the electrolyte's fracture toughness is commonly taken as a constant[2–4], here we show that the effective fracture toughness depends markedly upon the metal deposition current density. Based upon operando birefringence microscopy[5], we directly measure dendrite-induced stresses and obtain the mechanical driving force for failure, as well as the electrolyte fracture toughness. We find that increasing current densities embrittle the solid electrolyte—diminishing the fracture toughness by as much as 70%. Cryogenic Scanning Transmission Electron Microscopy (Cryo-STEM) reveals decomposed electrolyte phases at the dendrite tip. This decomposition is associated with a volume contraction consistent with embrittlement of the electrolyte. All experiments were conducted on the most electrochemically stable Li-ion conducting solid electrolyte (tantalum-doped lithium lanthanum zirconium oxide); the fracture toughness of less stable electrolytes (e.g., agryodites) may be even more susceptible to such embrittlement. The collective results indicate that “electrochemical embrittlement” markedly weakens the electrolyte, enabling dendrite growth—even when such degradation has negligible effect on bulk electrochemical properties.

References:

Sudworth, J. L., Hames, M. D., Storey, M. A., Azim, M. F. & Tilley, A. R. An analysis and laboratory assessment of Two Sodium Sulfur Cell Designs. Power Sources 4, 1–18 (1972).

Sharafi, A., Meyer, H. M., Nanda, J., Wolfenstine, J. & Sakamoto, J. Characterizing the Li–Li7La3Zr2O12 interface stability and kinetics as a function of temperature and current density. J. Power Sources 302, 135–139 (2016).

Fincher, C. D. et al. Controlling dendrite propagation in solid-state batteries with engineered stress. Joule 6, 2794-2809 (2022).

Porz, L. et al. Mechanism of lithium metal penetration through inorganic solid electrolytes. Adv. Energy Mater. 7, 1701003 (2017).

Athanasiou†, C. E., Fincher†, C. D. et al. Operando measurements of dendrite-induced stresses in ceramic electrolytes using photoelasticity. Matter (2023).
(Invited) Multiscale Contact Mechanics and Electrochemistry of Li-SE Interfaces with a SE-Reinforced Polymer Interfacial Coating, Using Machine Learning to Optimize the Coating and Stack Pressure Conditions
Authors: Harris Stephen J , Zhang Xin
Published: August 2024

We describe a multi-scale three-dimensional time-dependent contact model for the interface between Li and a solid electrolyte, with and without a SE-reinforced polymer interface coating. Our simulation without an interface coating considers the surface roughness of the Li and SEs, Li elastoplasticity, Li creep, and the Li metal plating/stripping process to predict the time-evolution during plating. When we also have an interface coating, we consider its viscoelasticity as well as the effect of the reinforcement on the polymer’s modulus and on its conductivity. Machine learning allows us to optimize values for thickness, stack pressure, and coating material properties (modulus, conductivity, etc). We describe the technique used to solve the multiscale problem.
Multiple Strategies for Producing and Utilizing Ammonia Using Electrochemical Methods Using Transition Metal Based Electrocatalysts
Authors: Kim Jeehye , Jang Ji Hee , Doucet Mathieu , Wang Hanyu , Browning Jim , Jang Youn Jeong , Lee Jae Sung
Published: August 2024

Ammonia is one of the most important chemicals in fertilizer and industrial chemical production, stands as the world’s second-largest synthetic chemical (> 200 million tons). Additionally, its potential as a clean energy source is gaining attentions due to its carbon neutrality, high energy density, and ease of transport. Electrochemical ammonia production emerges as a 'green' method which minimize the carbon footprint. However, the development of effective systems to produce and utilize 'green' ammonia remains a significant challenge [1,2].

To enhance the efficiency of electrochemical systems, modifications in both catalyst and system design are mandatory. This presentation will introduce the electrochemical nitrogen reduction reaction (eNRR) using Cu-based catalysts [3]. For catalyst modification, we addressed copper’s challenge of its low affinity and activation potential for stable dinitrogen (N2) molecules. This was achieved through phosphorus activation, which enhance the adsorption and activation of N2 by creating electron-deficient Cu sites on the catalyst surface. System-wise, the poor solubility of nitrogen in aqueous electrolytes limits it’s the performance of the system. Addressing this, we applied a gas diffusion electrode (GDE) coated with polytetrafluoroethylene (PTFE) into the eNRR system. This setup establishes an efficient three-phase boundary among liquid water, gaseous N2, and the solid catalyst, thus facilitating nitrogen access to the catalytic sites. Our novel catalyst in a flow-type cell attains a Faradaic efficiency of 13.15% and an ammonia production rate of 7.69 μg h-1 cm-2 at -0.2 VRHE. These figures represent 3.56- and 59.2-times improvements, respectively, over a pristine Cu electrode in a conventional electrolytic cell.

Additionally, the presentation will provide a brief introduction to the amorphous Ni-Cu electrocatalyst for electrochemical ammonia oxidation, which is an essential reaction for ammonia utilization [4]. We highlight its doubled ammonia removal efficiency compared to the Ni-Cu LDH electrocatalyst, underlining the potential of these developments.

[1] Y. Zeng, C. Priest, G. Wang, G. Wu, Restoring the Nitrogen Cycle by Electrochemical Reduction of Nitrate: Progress and Prospects, Small Methods, 4 (2020) 2000672.

[2] B. Yang, W. Ding, H. Zhang, S. Zhang, Recent Progress in Electrochemical Synthesis of Ammonia from Nitrogen: Strategies to Improve the Catalytic Activity and Selectivity, Energy Environ. Sci., 14 (2021) 672-687.

[3] J. Kim, C.H. Lee, Y.H. Moon, M.H. Lee, E.H. Kim, S.H. Choi, Y.J. Jang, J.S. Lee, Enhancing Ammonia Production Rates from Electrochemical Nitrogen Reduction by Engineering Three-Phase Boundary with Phosphorus-Activated Cu Catalysts, J. Energy Chem., 84 (2023) 394-401.

[4] J.H. Jang, S.Y. Park, D.H. Youn, Y.J. Jang. Recent Advances in Electrocatalysts for Ammonia Oxidation Reaction.Catalysts., 13 (2023) 803.
(Invited) Understanding Potential Losses and pH Distribution in Electrochemical Nitrate Reduction Reaction to Ammonia
Authors: Nazemi Mohammadreza (Reza) , Ahmadi Maryam , Boppella Rami Reddy
Published: August 2024

Electrochemical nitrate reduction reaction (NO3
-RR) to ammonia is a promising route to eliminate one of the major pollutants in surface and groundwater. When powered by renewable electricity, electrolysis provides a sustainable method to generate ammonia from nitrate ions, facilitating the transition from a linear to a circular economy. Optimizing the physical and chemical properties of electrolysis cells is crucial to make this process economically viable for widespread implementation. Here, we explore how the choice of current density, conductivity, pH, inter-electrode distance, membrane, catalyst, and buffer solution affect nitrate removal performance and efficiency. We develop a modeling framework to investigate the cell characteristics and fluid dynamics during electrochemical NO3-RR using both laminar and bubbly flows. To obtain more precise results, we employed the bubbly flow model (i.e., Multi-phase Fluid) to take into account how gas production near the electrode surface affects liquid velocity, pH distribution, and, ultimately, potential losses. We exploit mass transfer theory to include the current density effect on migration and diffusion. In the absence of a buffer solution, the Nernstian loss became a significant portion of the polarization loss, which increased with current density. We identified the positive effect of the membrane on energy efficiency to be more significant at smaller inter-electrode distances. This study provides insights into the origin of potential losses and pH distribution, enabling electrochemical cell optimization for renewable fuel synthesis. Next, we will discuss our recent work on designing single atom alloys (SAAs) for selective conversion of low concentration nitrate ions in natural wastewater streams from Dairy farm into ammonia. We benchmarked the catalyst's selectivity, activity, and stability following standard protocols established in the field of nitrogen fixation, including control experiments by using an electrolyte that does not contain nitrate ions and performing experiments under the same operating conditions using nitrogen isotopes (i.e.,
14NO3
-, 15NO3
-).
Design and Fabrication of Electrolyzers for the Production of Green H2 & O2 and Reduction of CO2 to Value-Added Chemicals
Authors: Kharwar Yashwant Pratap , Dutta Arnab
Published: August 2024

The electrochemical cells generate electrical energy from chemical reactions (i.e., Galvanic cells) or use electricity to conduct chemical reactions and produce chemicals (i.e., Electrolytic cells).1,2 Electrolyzers are the electrolytic cells, where water (H2O) electrolyzes to produce Hydrogen (H2) and Oxygen (O2), and CO2 electrolyzes to produce various chemicals (such as CO, HCOOH, CH3OH, C2H5OH, etc.), depending upon the selectivity and efficiency of the electrocatalysts.3–5 Though various electrocatalysts for electrolyzers are developed but without well-designed, portable, and cost-effective electrolyzers, the overall commercialization is still limited. Herein, we are working to design new types of electrolytic cells to solve electrochemical problems and improve the overall performance of cells on a laboratory-to-industry scale.6,7

We have designed a three-electrodes system cell where we can study electrochemical properties by variation in temperature of selectively working electrodes only (i.e., electrode materials), keeping all other systems at a constant temperature. In the second problem, we solved the ion migration issue from one compartment to another by minimizing the conventional H-cell's bar length (l).8,9 We are developing stack electrolyzers that can be used as both H2O and CO2 electrolysis (Fig.1a-c).

Figure 1
Refining Mn(III) Active Sites in MnO2-Based Self-Assembled Electrodes Via Oxygen Vacancy Induction to Enhance Oxygen Reaction Performance in Zinc-Air Batteries
Authors: He Zizhou , Xu Nengneng , Wang Yudong , Zhou Xiao-Dong
Published: August 2024

Rechargeable zinc-air batteries are considered as a promising candidate for next-generation electrochemical energy conversion devices due to their safety, low cost, and high theoretical capacity/ energy density. Over the past few decades, α-MnO2-based electrodes have demonstrated their excellent performance and competitiveness in oxygen catalytic reactions. (1) According to eg filling theory, Mn(III) (t2g3eg1) sites in [MnO6] octahedral unit deliver superior bifunctional activity compared to Mn(II) (t2g3eg2) and Mn(IV) (t2g3eg0) sites.(2) However, the presence of unpaired single electrons of the Mn(III) site leads to low thermodynamic stability. Introducing oxygen vacancies to promote the electron rearrangement of the [MnO6] unit is a promising approach for enhancing the durability of Mn(III) active sites. Herein, we construct an oxygen-vacancy-enhanced MnO2-based electrode via a self-assembly process (NiCo2O4-MnO2@Ni foam). The intrinsic oxygen catalytic activity of NiCo2O4-MnO2@Ni foam is significantly improved by forming abundant highly stable Mn(III) active sites, which accelerate the mass transfer ability. As expected, the NiCo2O4-MnO2@Ni foam shows good bifunctional activity with a low overpotential of 0.69 V. The zinc-air battery assembled by NiCo2O4-MnO2@Ni foam exhibits a high peak power density of 576 mW cm-2, surpassing that of the Pt/C-Ir/C electrode. Additionally, benefiting from its stable flower-shaped hierarchical structure, the self-assembled electrode demonstrates long-term charge-discharge cycling stability, which lasts over 800 hours. This work provides innovative insights into enhancing MnO2-based electrodes by oxygen vacancy introduction.

References

N. Xu, Q. Nie, L. Luo, C. Z. Yao, Q. Gong, Y. Liu, X. Zhou, and J. Qiao, ACS applied materials & interfaces (2018).

Z. Yin, R. He, H. Xue, J.-M. Chen, Y. Wang, X. Ye, N. Xu, J. Qiao and H. Huang, Energy Materials (2022).
Reinforced Poly (dibenzyl-co-terphenyl piperidinium) Membranes for Highly Durable Anion-Exchange Membrane Water Electrolysis
Authors: Lee Ju Yeon , Lee So Young
Published: August 2024

Low-cost anion exchange membrane water electrolysis (AEMWE) is an attractive technology to solve global energy shortage and environmental problems. However, AEMWE suffers from poor performance and durability, leading to problems associated with the lack of qualified anion exchange membranes (AEMs). In this study, a reinforced membrane using PDTP (Poly(dibenzyl-co-terphenyl Piperidinium)) and PE (Polyethylen) was developed to improve performance and durability. Additionally, the effects of support layer and polymer membrane thickness on water electrolysis were observed. Due to the excellent electrochemical properties of filled PDTP, the prepared reinforced membranes exhibit excellent mechanical properties with tensile strength > 112 MPa, elongation at break > 84%, conductivity (96.3 mS cm−1), and dimensional stability (swelling). ratio < 50% at 80°C). More importantly, the AEMWE based on the reinforced membrane exhibits an outstanding current density of 4.86 A cm−2@2.0 V at 2.0 V and voltage decay rate, while simultaneously exhibiting in-situ durability of less than 1 and 2 A cm−2 for 1000 hours at 60°C. That it can be achieved. 0.02 mV h−1 and 0.1 mV h−1, respectively. This study shows that PDTP reinforced composite membrane can effectively improve AEMWE performance and durability.
(Invited) Analyzing Cyclic Voltammetry to Understand (Bio)Electrocatalysis for Electrosynthesis
Authors: Minteer Shelley D.
Published: August 2024

After meeting Diane Smith 25 years ago as a graduate student, I quickly learned the importance of careful voltammetric studies in quantitatively understanding all types of electrocatalysis. The Smith Group provided a wealth of protocols for studying all types of redox systems that have been used across the electrosynthesis field by my group and many others. This paper will discuss the use of cyclic voltammetry for studying homogeneous, heterogeneous, and biological electrocatalysis. This talk will discuss the use of fundamental electroanalysis for improving electrosynthesis.
Novel Electrocatalytic Hydrogenation Using a Solid Polymer Electrolyte (SPE) Reactor
Authors: Atobe Mahito , Shida Naoki
Published: August 2024

Organic electrosynthetic reactions, which are driven by electricity, can generally be carried out under mild conditions (room temperature and ambient pressure). In addition, they do not require any hazardous reagents and produce less waste than other conventional chemical syntheses. Therefore, electrosynthesis is known to be a mild and clean method for organic synthesis and there has recently been renewed interest in its development. However, electrosynthesis also has some disadvantages. Ordinary chemical reactions are homogeneous, while the reaction field of electrolysis is a heterogeneous interface, therefore electrosynthesis has a productive drawback. In addition, a large amount of supporting electrolyte is usually required. Therefore, the availability of solvents is limited by the necessity for dissolution of a supporting electrolyte. The presence of the supporting electrolyte might also cause separation problems in the reaction workup. Moreover, in an ordinary electrolysis system, solution resistance is generated between the working and counter electrodes, resulting in a decrease in energy efficiency. To overcome these problems, we focused on a solid polymer electrolyte (SPE) reactor which was originally developed for fuel cell technologies and demonstrated various electrocatalytic hydrogenations in a SPE reactor (Figure 1) [1-5].

As shown in Figure 1, a SPE membrane such as a proton exchange membrane (PEM) is integrated into the central part of the reactor, and is sandwiched between a pair of catalyst layers on the anode and cathode sides. For this reason, the substrate solution does not require a supporting electrolyte and the cell resistance can be minimized. The anode and cathode have highly porous 3D structures in order to conduct an efficient electrochemical reaction. Moreover, the reaction can be carried out in a flow operation. Thus, the SPE reactor system possesses many characteristics designed to overcome the disadvantages of conventional electrosynthetic processes.

In a series of studies we have conducted, in this presentation, we will discuss two topics such as diastereoselective reduction of cyclic ketones and electrocatalytic hydrogenation of pyridines.

The authors gratefully acknowledged support by JST CREST Grant No. 18070940, Japan.

[1] A. Fukazawa, M. Atobe, et al. ACS Susutain. Chem. Eng.
2019, 7, 11050.

[2] S. Nogami, M. Atobe, et al. J. Electrochem. Soc.
2020, 167, 155506.

[3] A. Fukazawa, M. Atobe, et al. Org. Biomol. Chem.
2021, 19,7363.

[4] S. Nogami, M. Atobe, et al. ACS Catalysis,
2022, 12, 5430.

[5] Y. Shimizu, M. Atobe, et al. ACS Energy Lett.,
2023, 8, 1010.

Figure 1
Isopropyl Alcohol Effects on the Electro-Catalytic Hydrogenation of Guaiacol
Authors: Setiawan Felix Arie , Shen Beini , Smith Kevin J. , Kim Chang Soo , Gyenge Elod Lajos
Published: August 2024

The complete electrocatalytic hydrogenation-hydrodeoxygenation of guaiacol to produce cyclohexane is demonstrated for the first time using isopropyl alcohol as a polar protic solvent in a stirred slurry electrocatalytic slurry reactor with Pt/C as a catalyst. The addition of 25% IPA on 0.1 M guaiacol reduction with the presence of 1.0 M methanesulfonic acid and 0.25 M sodium chloride both for catholyte and anolyte was most effective for electrocatalytic guaiacol hydrogenation-hydrodeoxygenation at -66 mA.cm-2 current density and 60 °C for 4 h using 0.5 g 5% Pt/C catalyst. In terms of the separation process, the addition of IPA is very compatible with the system, as the chemical produced, cyclohexane, can later be introduced into the separation process as an entraining agent.
Chiral Bioelectrocatalytic Oxidations Driven By Electrocatalytic Oxygen Reduction and Horseradish Peroxidase or Cytochrome P450
Authors: Hena Jr John , Weerasuriya D. Randil K. , Kankanamage Rumasha N.T. , He Jie , Rusling James F.
Published: August 2024

Biocatalysis, the use of enzymes for synthesis, has emerged as a powerful tool for synthesis of chiral molecules in pharmaceutical and fine chemical industries. Natural enzymes offer inherent stereoselectivity, making them attractive catalysts for this purpose. Peroxidases and cytochrome P450s enzymes utilize an iron-heme cofactor to perform a diverse array of chemical transformations including CH2 hydroxylation, epoxidations, and sulfur-oxidations. Here, we report chiral biocatalytic oxidations in microemulsion media driven by horseradish peroxidase (HRP) coupled with a synthetic Cu2+-polymer electrocatalyst to convert O2 to H2O2. This tandem system uses crosslinked layer-by-layer (LBL) films of polyelectrolytes with Cu2+- poly(2-hydroxy-3-dipicolylamino) propyl methacrylate (Py-PGMADPA) to drive O2 reduction. Peroxide in turn activates HRP crosslinked in LbL films on magnetic beads (MB) to biocatalytically oxidize styrene, ethylbenzene, and methyl phenylacetate to chiral products. R-stereoisomers of these reactants were selectively formed with a high enantiomeric excess of > 80%. Conductive microemulsion reaction media are used to provide solubility to the non-polar reactants and water to hydrate the enzymes to function. The enzyme films show high thermal stability and high chiral selectivity up to 90 °C. A second synthetic goal was to compare chiral products of reactions catalyzed by cyt P450’s natural catalytic pathway mimicked by electrocatalysis versus via electrochemical generation of H2O2. We immobilized baculosome-P450s in LBL films with polystyrene sulfonate for the natural catalytic pathway, and for peroxide activation crosslinked P450 LbL on magnetic beads. These synthetic hybrid approaches open new doors to designing biocatalytic syntheses using an electrochemical driving force.

Keywords: Biocatalysis, organic syntheses, cytochrome P450, horseradish peroxidase, regioselective and stereoselective oxidation
Electroauxiliary-Assisted C-C Bond Formations in Lithium Perchlorate / Nitromethane Solution
Authors: Akahane Shinnosuke , Kitano Yoshikazu , Okada Yohei
Published: August 2024

C-nucleosides have C-C bonds between ribosyl moiety and nucleobase at anomeric carbon. This substitution of covalent bond gives hydrolysis resistance to C-nucleosides. Therefore, C-nucleosides are good candidates for antiviral or antitumor drugs as mimic building blocks of oligonucleotide.

To synthesize nucleosides, cation intermediate is used for installing nucleobase on ribosyl moiety. When it comes to generation of cation intermediate, electrochemical methodology is one of the useful tools. In electrochemical method, 1’-arylthioriboses are used as glycosyl donors. They have thioether group as electroauxiliary at anomeric carbon forging O,S-acetal that are activated with anodic oxidation to generate corresponding cation intermediate. Since electrochemically generated cation intermediates have high reactivity enough to react with carbon nucleophiles, this method can be adopted to C-nucleoside synthesis.

Previously, electrochemical nucleoside synthesis was reported using cation pool method in combination with electroauxiliary. To avoid undesired oxidation of nucleophile, it is important to pool the cation and/or to lower the oxidation potential of ribose. The low temperature condition such as -78 ~ -50 oC is necessary to pool cation intermediates.

In this research, we aimed to achieve electrochemical C-C bond formation at anomeric carbon with ambient temperature condition. In this strategy, we use glycosyl donors with lowered oxidation potential to avoid competitive oxidation with carbon nucleophiles. We also adapt lithium perchlorate/nitromethane system for electrolysis.

Figure 1
Using Electroanalytical Techniques to Study Inhibition Mechanisms in Enzymes
Authors: Minteer Shelley D.
Published: August 2024

Spectroscopic assays are typically utilized to study oxidoreductase enzyme kinetics, mechanisms, and inhibition. This talk will discuss the use of mediated and direct bioelectrocatalysis for studying kinetics followed by a thorough study of the effect of mediators in studying inhibition mechanisms. This will be followed up with strategies for studying mechanisms via direct bioelectrocatalysis. The talk will conclude with a discussion of the applications of these electroanalytical techniques in the fields of energy, sensing, and sustainable manufacturing.