bluuebunny/crossref_metadata_2025 huggingface dataset:
Catalytic Activities of Ir-Based Pyrochlore-Type Oxides Doped with Divalent Cations for Oxygen Evolution Reaction
Authors: Miyazaki Kohei , Tanaka Kenji , Miyahara Yuto , Lee Changhee , Abe Takeshi
Published: August 2024

Alternative energy sources to fossil fuels are essential for a sustainable society, and hydrogen energy is expected to be a solution to environmental and energy problems. Currently, proton exchange membrane water electrolyzers are becoming widely used for the electrochemical production of hydrogen due to their advantages such as high efficiency. However, the highly acidic conditions and the large overpotentials of oxygen evolution reaction (OER) at the anode are problems, and the development of catalysts that are stable and highly active in acidic aqueous solutions is important for further popularization.

Ir-based oxides with pyrochlore structure (A2B2O7) are known to exhibit high catalytic activities in acidic aqueous solutions. Recently, it has been reported that the improved catalytic activities of Pr2Ir2O7 by Zn doping, which controlled the composition of A-site elements in the pyrochlore structure [1]. In this study, we synthesized Pr2-x
MgxIr2O7 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5), in which a part of trivalent cation Pr3+ was replaced by divalent cation Mg2+ and improved the OER catalytic activity in acidic aqueous solutions.

Pr2-x
MgxIr2O7 was synthesized by the hydrothermal method. The catalyst was mixed with a conductivity aid carbon (Vulcan XC-72) and a cationic conductive ionomer (Nafion) at a weight ratio of 5:1:1 and dispersed in 2-propanol to form a catalyst ink. The catalytic activity was evaluated by cyclic voltammetry (CV) using a glassy carbon rotating disk electrode (RDE) as a working electrode, a reversible hydrogen electrode (RHE) as a reference electrode, and a platinum wire as a counter electrode. The electrolyte was a 0.1 mol dm-3 HClO4 solution saturated with oxygen, and the CV scanning range was 1.1 to 1.7 V with respect to the RHE, scanning speed was 20 mV s-1, and the RDE rotation speed was 1200 rpm. The stability of the catalyst in acidic aqueous solutions was evaluated by chronopotentiometry (CP) using the same cell.

X-ray diffraction and energy-dispersive X-ray analysis measurements of the synthesized materials confirmed that the desired compounds were obtained, and CV measurements showed that the OER activity of Pr2-x
MgxIr2O7 increased in the first 20 cycles for all compositions, and then stabilized over several tens of cycles. The cycle change was similar to that of Pr2Ir2O7, suggesting that the surface rearrangement proceeds in acidic aqueous solutions [2]. Linear sweep voltammogram (LSV) and OER activity normalized by Brunauer-Emmett-Teller (BET) specific surface area were measured at the 20th cycle, and the catalytic activity stabilized at a high value. The OER activity was enhanced by Mg substitution in the catalysts of Pr2-x
Mg
x
Ir2O7.

References

L. Zhu, C. Ma, Z. Wang, X. Gong, L. Cao, and J. Yang, Appl. Surf. Sci., 31, 151840 (2022).

C. Shang, C. Cao, D. Yu, Y. Yan, Y. Lin, H. Li, T. Zheng, X. Yan, W. Yu, S. Zhou, and J. Zeng, Adv. Mater., 31, 1805104 (2018).
(Invited) The Activation of Alkanes at Electrochemical Interfaces Using Real-Time Control of Potentials: Novel Avenues for Energy Storage and Sustainable Chemical Manufacturing
Authors: Schreier Marcel
Published: August 2024

Producing fuels and chemicals using renewable electricity holds the promise to enable a truly sustainable circular economy based on sustainably produced carriers of electrical energy and sustainably produced chemicals. The science which allows us to link electricity to chemical transformations, electrocatalysis, remains chiefly focused on the electricity-driven transformation of small inorganic molecules such as CO2, H2O, N2, as well as the oxidation and reduction of alcohols. However, comprehensive electrification of society will require electrocatalytic reactions that can promote the central processes that sustain today’s society: alkane transformations. In this presentation, I will show how fundamental understanding of the interfacial processes occurring in electrocatalytic reactions, combined with monolayer-sensitive differential electrochemical mass spectrometry, allows us to independently control the elementary steps (adsorption, transformation, desorption) of complex alkane transformation reactions, allowing for the room-temperature fragmentation of ethane into methane, as well as for enabling the extraction of the chemical energy stored in alkanes in the form of electricity. I will show how we can apply these technologies to expand the reaction scope of electrocatalysis, allowing for novel avenues in energy storage, chemical synthesis and plastics recycling.
Gas Diffusion Electrode Operation for High Current Density Electroreduction of Carbon Dioxide to Formate
Authors: Bashir Shahid M. , Gyenge Elod L.
Published: August 2024

In the context of clean energy and green chemical production, the two-phase flow electrochemical carbon dioxide reduction reaction (CO2RR) to formate has gained considerable interest, and efforts are being made to scale up the process[1]. With respect to electrode design, unlike in the simpler single-phase system, which is limited by the solubility of CO2 in the electrolyte and by the mass transport of the dissolved CO2 gas from the bulk of the electrolyte to the cathode surface[2], mixed gas/liquid flow in the trickle bed reactor[3] or segregated flow in the gas diffusion electrode (GDE)[4] reactor provide more efficient gas delivery at the catalyst/electrolyte interface. This enhanced the overall mass transfer coefficient and enabled higher reaction rates per unit geometric area of the electrodes, providing that the electrocatalyst layer's intrinsic activity and selectivity are established. Due to the limitation in retaining the effective electroactive bed thickness in the trickle bed reactor[3], GDEs are preferred for high current density operations (typically above 100 mA cm-2). Despite the continuous gas transport mechanism, the reported performance in the GDE-based system lies around 200 mA cm-2, with occasional reports above 200 mA cm-2 but on a tiny electrode area (typically 1 cm2 or below)[5]. The flooding of the GDE porous structure is believed to be the prime cause that limits electrode durability at high current density. Here, we present the optimization of the two-phase flow dynamics and the GDE (with 20 cm2 geometric area) operating conditions to enable high current density operation up to 500 mA cm-2 using a tin-based catalyst layer and scalable reactor design. The performance was compared with other catalytic materials that were intrinsically active for CO2RR to formate.

References

[1] M.F. Philips, G.M.Gruter, M.T.M. Koper and K.J.P. Schouten, ACS Sustainable Chem. Eng., 2020, 8(41), 15430-15444.

[2] N. Gupta, M. Gattrell and B. Macdougall, J. Appl. Electrochem., 2006, 36(2), 161-172.

[3] I. Hodgson and C. Oloman, Chem. Eng. Sci., 1999. 54(23): p. 5777-5786.

[4] S. Hernandez-Aldave and E. Andreoli, Catalysts, 2020, 10(6), 713

[5] S. Sen, S. M. Brown, M. Leonard and F.R. Brushett, J. Appl. Electrochem.,2019, 49, 917–928
Water-Insoluble Copper Complexes As Electrocatalysts for CO2 Reduction
Authors: Romano Rafael L. , Sasaki Kotaro , Lima Fabio H.B. H.B.
Published: August 2024

The electrochemical reduction of carbon dioxide (CO2R) constitutes a promising CO2 utilization technology, allowing the production of valuable fuels and chemicals by using electrical energy from renewable sources. Nevertheless, poor selectivity and high required overpotentials hamper practical applications of the CO2R, which highlights the need for the development of more efficient electrocatalysts. Different copper-based materials have been extensively studied as electrocatalysts for CO2R. Particularly, copper complexes exhibited interesting properties under operational conditions: many of them undergo structural modifications (e.g. changes in oxidation state and/or coordination number), which potentially affect activity, selectivity and stability. Interestingly, some complexes exhibit reversible restructuring under specific conditions, which can be an interesting property to reach higher stability. In this presentation, we will show the results obtained for the electrocatalysis of water-insoluble copper complexes for the CO2R. The activity, selectivity and stability of both [Cu(bzimpy)Cl2] and [Cu(pyrben)2(NO3)]NO3 were investigated in K2SO4 0.1 mol L-1 (CO2 sat.) under different electrochemical conditions. Here, bzimpy and pyrben stand for 2,6-bis(2-benzimidazolyl)pyridine and 2-(2-pyridyl)benzimidazole, respectively. Qualitative EC-MS (Electrochemistry Coupled to Mass Spectrometry) analysis evidenced that both complexes are active for CO2 reduction and that product distribution changes according to the applied potential. Quantitative gas chromatography measurements revealed that, at -1.24 V vs. RHE, [Cu(bzimpy)Cl2] promotes the formation of H2, CO, CH4 and C2H4 with faradaic efficiencies of 26, 3.4, 9.2 and 31%, respectively. On the other hand, [Cu(pyrben)2(NO3)]NO3 shows FE values of 24, 8.8, 15 and 24% for H2, CO, CH4 and C2H4, respectively. After 1.6 h of electrolysis, the former exhibited stable current and FE of ~42% towards ethylene formation.
Enhancing Direct Eectrochemical CO2 Electrolysis By Introducing a-Site Deficiency for Dual-Phase Pr(Ca)Fe(Ni)O3-Δ Cathode
Authors: Wang Wanhua , Li Haixia , Park Ka-Young , Lee Taehee , Ding Dong , Chen Fanglin (Frank) (Frank)
Published: August 2024

High-temperature CO2 electrolysis via solid oxide electrolysis cells (CO2-SOECs) has drawn special attention due to the high energy convention efficiency, fast electrode kinetics, and great potential in carbon cycling. However, the development of cathode materials with high catalytic activity and chemical stability for pure CO2 electrolysis is still a great challenge. In this work, A-site cation deficient dual-phase material, namely (Pr0.4Ca0.6)xFe0.8Ni0.2O3-
δ (PCFN, x=1, 0.95, and 0.9), has been designed as the fuel electrode for a pure CO2-SOEC which presents superior electrochemical performance. Among all these compositions, (Pr0.4Ca0.6)0.95Fe0.8Ni0.2O3-
δ (PCFN95) exhibited the lowest polarization resistance of 0.458 Ω cm2 at open circuit voltage and 800℃. The application of PCFN95 as the cathode in a single cell yields an impressive electrolysis current density of 1.76 A cm-2 at 1.5 V and 800℃, which is 76% higher than that of single cells with stoichiometric Pr0.4Ca0.6Fe0.8Ni0.2O3-
δ (PCFN100) cathode. The effects of A-site deficiency on materials’ phase structure and physicochemical properties are also systematically investigated. Such an enhancement in electrochemical performance is attributed to the promotion of effective CO2 adsorption, as well as the improved electrode kinetics resulting from A-site deficiency.
Effect of Mechanical Compression on Ionic Conductivity of PEO-LiTFSI Solid Polymer Electrolytes
Authors: Jadhav Aryan , Cao Dang Khoa Minh , Baltazar Jericko Jay , Oh Dahyun , Lee Sang-Joon John
Published: August 2024

In the field of energy storage materials, the development of robust solid polymer electrolytes for lithium-ion batteries necessitates an understanding of ionic conductivity when subjected to mechanical stress. Accurate determination of ionic conductivity requires knowing the electrolyte thickness, which is subject to volumetric changes during charging and discharging of solid-state batteries. However, compressive stress reduces the thickness of the electrolyte by an indeterminate amount.

This work presents experimental measurements of ionic conductivity as a function of compressive stress, using poly(ethylene oxide) and with bis(trifluoromethane) sulfonimide (PEO-LiTFSI). In this study, we not only measure the stress-strain response of the electrolytes directly, but also monitor the extent of compression during electrochemical impedance spectroscopy (EIS). Compression was applied up to 50% strain for three consecutive cycles, and the typical thickness for the fabricated electrolytes was ~50 µm. EIS testing was performed by using an impedance analyzer, with the electrolyte placed between stainless steel blocking electrodes. Bulk resistance was determined by equivalent circuit modeling of impedance between 100 Hz and 2 MHz. Ionic conductivity κ was calculated from bulk resistance Rb
, electrolyte thickness h, and cross-sectional area A, according to the equation κ = h/(Rb·A).

In order to measure both stress and deformation simultaneously, a custom positioning stage was engineered to apply prescribed compression. The apparatus has an in-line load cell for force measurements and a laser triangulation sensor for position tracking with submicron resolution. We found that the bulk resistance at room temperature decreases exponentially, with magnitude reduced by approximately five-fold when subjected to compressive stress up to 10 MPa. Beyond ~7 MPa, bulk resistance values were no longer dependent on the amount of applied compression.

In addition to mechanical measurements, changes in crystalline and amorphous regions were correlated to the magnitude of compressive stress and the measured ionic conductivity of the electrolyte. For optical imaging with simultaneous EIS measurements, glass slides coated with an indium tin oxide (ITO) film were used instead of stainless steel disks. The extent of crystallinity was visualized by optical microscopy of spherulites through a viewing window when compressed between rigid plates.

Figure 1. Apparatus (left) and representative ionic conductivity vs. compressive stress (right) data for a PEO-LiTFSI polymer electrolyte.

Figure 1
Influence of Mechanical Degradation in Polycrystalline NMC Particles on the Electrochemical Performance of Lithium-Ion Batteries
Authors: Nagda Vinit , Kulachenko Artem , Ekström Henrik
Published: August 2024

Lithium-ion batteries (LIBs) have gained widespread popularity for energy storage systems owing to their high coulombic efficiency and energy density. Within the cathode electrode materials of LIBs, the structural integrity of secondary particles, composed of randomly oriented single-crystal primary active particles, is crucial for sustained performance. The fracture of these particles can occur due to both mechanical stress and chemical interactions within the solid. Modeling LIBs presents a multiphysics challenge as it involves addressing the electro-chemo-mechanical phenomena and their interactions across various length scales. During electrochemical cycling, volume changes in active particles induce mechanical stresses, while the mechanical state of the battery influences the diffusion of lithium.

This study proposes a numerical modeling framework to investigate the degradation of active material particles and its impact on electrochemical performance. The model integrates mechanical and electrochemical processes, solving nonlinear equations related to surface charge transfer, lithium diffusion, and mechanical stresses. By incorporating phase field damage, the model tracks crack evolution and mechanical failure of active particles. The coupled equations are solved within a finite element framework using COMSOL Multiphysics.

Notably, the model offers numerical insights into intergranular and transgranular fracture within secondary active material particles. The infiltration of liquid electrolyte into cracks is identified as a positive effect, reducing electrochemical overpotential by increasing electrochemically active surface area from particle cracking. However, prolonged cycling with particle cracking poses a notable threat to battery performance and capacity. This comprehensive numerical modeling approach provides valuable insights into the intricate interplay of mechanical and electrochemical factors governing LIB performance and degradation.
A Multiscale Computational Modeling Framework to Quantify Microstructural Effects on Nucleation of Li Metal on Carbon Scaffold Architectures
Authors: Wang Bo , Li Sichi , Cross Nicholas R. , Freyman Megan C. , Xiao Yiran , Zhu Cheng , Bucci Giovanna , Heo Tae Wook , Wood Marissa
Published: August 2024

Carbon materials with scaffold architecture have been shown to mitigate the non-uniform Li plating/stripping issues during cycling, which is critical for achieving significantly enhanced energy densities and improved safety of Li metal batteries. However, optimal design of the architecture and microstructure of the carbon materials requires fundamental understanding of the Li metal nucleation behavior at different length scales. In this poster, we present a multiscale computational modeling framework to quantify the microstructural effects of carbon materials on the tendency of Li metal nucleation during plating by integrating atomic-scale simulation, mesoscale microstructure-based homogenization, continuum-scale electrochemistry modeling, and classical nucleation theory. We modeled the architecture of the carbon scaffold and the electrochemistry of Li transport across the electrode and electrolyte by finite element simulation to determine boundary conditions for our mesoscale models. We then generated different porous microstructures of various carbon materials by stochastic and physics-based simulations informed from experiments and performed multiphysics-based simulations at mesoscale to identify the electro-chemo-mechanical hotspots which are sensitive to the microstructure morphology. We calculated the energy barriers for Li to form clusters on graphene surfaces as a function of local Li concentrations and electric fields by ab initio molecular dynamics simulations. The synergistic deployment of different models across scales allows us to theoretically estimate the Li metal nucleation tendency based on a modified classical nucleation theory for different microstructures under various electroplating conditions. Comparison of the theoretical predictions and experimental results will be briefly discussed. The insights obtained from this multiscale framework offer new understanding and strategies for the design of carbon scaffold architectures to mitigate the non-uniformity of Li plating and issues in Li metal anode deployment in 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-Mechanical Coupling Experiments on Solid-State Battery Materials and Interfaces
Authors: Albertus Paul , Larson Karl , Bhargava Bhuvsmita , Carmona Eric A , Crofton Lane , Stewart David Murdock , Talin Albert Alec
Published: August 2024

The interaction of mechanical and electrochemical effects in the areas of thermodynamics, kinetics, and transport are known, but accurately measuring those couplings can be complicated by the difficulty of getting a uniform stress at a solid-solid interface where surface roughness, voids and inclusion result in inhomogeneous contacts.1 This is a particular challenge for solid-state batteries where both the active material and electrolyte are in the solid phase. In addition, cycling of metal anodes (e.g., Na and Li) results in processes such as dendrite and void formation in which electrochemical and mechanical can be amplified.2 This talk will focus on two improvements to typical experiments in which electrochemical-mechanical coupling strongly influences results: (1) The use of a solid-state reference electrode for solid Na / solid electrolyte interfacial studies, and (2) the use of a nanoindentation platform to assess electrochemical-mechanical coupling behaviors in thin-film solid-state materials.

For topic (1), we will discuss our use of a solid Na metal reference electrode to inform the cycling of Na metal against a Na-β″-Al2O3 solid electrolyte using cycling protocols of commercial relevance (e.g., 5 mAh/cm2, <5 MPa external pressure).2 Our work identifies the current density at which stripping shifts from stable to unstable, and shows that large (100s of mV) of interfacial overpotential can persist for hours in some stripping test protocols, which, according to models indicates that >80% of the initial electrochemical active interfacial area has been lost. We will also present recent results on how the applied pressure affects the interfacial behavior of Na metal / Na-β″-Al2O3 interfaces, as well as the role of applied pressure and the cycling protocol for an interface that starts as only current collector / Na-β″-Al2O3.

For topic (2), we will present on our electrochemical-mechanical coupling studies of thin-film (i.e., <1 um thick) V2O5 samples on an Ohara Li+-conducting glass ceramic disc. This platform allows us to simultaneously control electrochemical behavior (e.g., Li insertion and removal, current) and the applied force, to study thermodynamic and kinetic electrochemical-mechanical couplings. This platform enables the application of a uniform stress on the thin-film V2O5 sample.

1. Joule 7, 652–674, April 19, 2023.

2. ACS Appl. Mater. Interfaces 2023, 15, 42, 49213–49222
Revealing the Link between Morphological Heterogeneity and Reaction Behavior of Cathode in Solid-State Batteries
Authors: Park Se Hwan , Juarez Yescaz Carlos , Zahiri Beniamin , Luo Yuting , Braun Paul V. , Vishnugopi Bairav Sabarish , Naik Kaustubh Girish , Mukherjee Partha P. , Greer Julia R. , Wang Yingjin , Xiao Xianghui , Hatzell Kelsey
Published: August 2024

Structural heterogeneity within solid-state electrodes can have a significant impact on material utilization and reaction rates. This reaction heterogeneity is greater in solid state systems in comparison to conventional liquid electrolytes because it requires exquisite solid-solid contact between the active energy storage materials and the solid ion conducting phase (e.g. solid electrolyte) [1]. Electrode reaction behaviors encompass electrochemical lithiation and delithiation dynamics and chemo-mechanical processes such as volume change and fracture [2]. Understanding the connection between structural heterogeneity and reaction behavior is crucial for understanding degradation mechanisms and optimizing solid state battery architectures. Herein, we examine the implications of reaction heterogeneity in an additive-free, crystallographically textured electroplated lithium cobalt oxide (LCO) cathode [3]. The electroplated dense cathode alleviates the need for any solid electrolyte material in the cathode. A diverse set of synchrotron-based operando and ex situ experiments are combined with modeling to uncover the relationship between structural heterogeneity and reaction behavior. Operando energy dispersive X-ray diffraction and ex situ 3D XANES are used to identify reaction heterogeneity and X-ray nanotomography is used to probe nano-scale structural heterogeneity. Nanoindentation is utilized to determine the mechanical properties of LCO. To validate the results, we combine these experimental results with transport and mechanics modeling. Through this comprehensive characterization approach, we confirm that the reaction behavior of cathode in our model is mainly determined by the morphological heterogeneity rather than the Li diffusion within the electrode. Structural heterogeneity causes localized high stress and leads to fracture, which in turn limit the full utilization of the cathode.

Reference

[1] Jung, S.H., Kim, U.H., Kim, J.H., Jun, S., Yoon, C.S., Jung, Y.S. and Sun, Y.K., 2020. Ni‐rich layered cathode materials with electrochemo‐mechanically compliant microstructures for all‐solid‐state Li batteries. Advanced Energy Materials, 10(6), p.1903360.

[2] Liu, X., Zheng, B., Zhao, J., Zhao, W., Liang, Z., Su, Y., Xie, C., Zhou, K., Xiang, Y., Zhu, J. and Wang, H., 2021. Electrochemo‐mechanical effects on structural integrity of Ni‐rich cathodes with different microstructures in all solid‐state batteries. Advanced Energy Materials, 11(8), p.2003583.

[3] Zahiri, B., Patra, A., Kiggins, C., Yong, A.X.B., Ertekin, E., Cook, J.B. and Braun, P.V., 2021. Revealing the role of the cathode–electrolyte interface on solid-state batteries. Nature Materials, 20(10), pp.1392-1400.

Figure 1
Improving the Catalytic Efficiency of Electrochemical Nitrogen Reduction Reaction (NRR) through Surface Modification and Nanostructured Bimetallic Catalysts
Authors: Stem David , Akter Tania , Barile Christopher J.
Published: August 2024

Electrochemical nitrogen reduction is recognized as a promising and sustainable alternative to the conventional Haber-Bosch method to produce ammonia. However, there are many challenges that pose significant barriers to the practical application of the nitrogen reduction reaction (NRR). These challenges are primarily attributed to the strong triple bond in the N2 molecule and the competing hydrogen evolution reaction (HER). This work investigates the synergy between alloys and nanostructured bimetallic systems and the application of molecular overlayers to improve efficiency and production rate of ammonia on the catalyst surface. We studied the combination of a noble metal catalyst scaffold modified with active metals (Li/Mg) that is known to cleave the N-N bond. Solvent effects were also tested in both aqueous and non-aqueous media to see changes in catalyst effects. Additionally, various experimental controls were performed including argon controls, isotope labeling, and assessing NOX contaminants to ensure that the reaction was interacting with our catalyst. Overall, this work demonstrates the use of molecular overlayers on nanostructured bimetallic systems to control hydrophobicity of catalyst surface and improve faradaic efficiency, ammonia production rate, catalyst durability and current density. Relationships between these parameters helped understand NRR mechanism and will help guide future NRR catalyst design.
(Invited) Breaking the Bottlenecks in Electrochemical Nitrogen Reduction
Authors: Stephens Ifan
Published: August 2024

There is a burgeoning interest in the development of a green method of ammonia synthesis; ammonia, already critical for fertilisers in the agricultural industry, is also being touted as a possible future energy vector or carbon-free fuel. The current method of production - the Haber Bosch process - is environmentally damaging and energy intensive but to date no viable alternative has been demonstrated. An electrochemical method operating under ambient conditions would be particularly attractive, as it would enable ammonia to be produced on a decentralised basis on-site and on-demand.1

Thus far, amongst solid electrodes, only lithium and calcium based electrodes in organic electrolytes can unequivocally reduce nitrogen to ammonia.2-4 Even so, at present, there is ample room for improvement.

To investigate this reaction, we use a combination of electrochemical experiments, cryo-microscopy, infrared spectroscopy, electrochemistry mass spectrometry, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy and density functional theory. By drawing from the adjacent fields of enzymatic nitrogen reduction and battery science, we will aim to build a holistic picture of the factors controlling nitrogen reduction.

I will explore the role of the individual electrolyte components, including the cation, the salt, solvent and proton carrier.5-
7 On the basis of the insight, I will propose avenues towards higher rates and higher efficiencies in electrochemical nitrogen reduction.

1 Westhead, O., Barrio, J., Bagger, A., Murray, J. W., Rossmeisl, J., Titirici, M.-M., Jervis, R., Fantuzzi, A., Ashley, A. & Stephens, I. E. L.
Nature Reviews Chemistry
7, 184, (2023).

2 Andersen, S. Z., Colic, V., Yang, S., Schwalbe, J. A., Nielander, A. C., McEnaney, J. M., Enemark-Rasmussen, K., Baker, J. G., Singh, A. R., Rohr, B. A., Statt, M. J., Blair, S. J., Mezzavilla, S., Kibsgaard, J., Vesborg, P. C. K., Cargnello, M., Bent, S. F., Jaramillo, T. F., Stephens, I. E. L., Norskov, J. K. & Chorkendorff, I.
Nature
570, 504, (2019).

3 Westhead, O., Jervis, R. & Stephens, I. E. L.
Science
372, 1149, (2021).

4 Fu, X., Niemann, V. A., Zhou, Y., Li, S., Zhang, K., Pedersen, J. B., Saccoccio, M., Andersen, S. Z., Enemark-Rasmussen, K., Benedek, P., Xu, A., Deissler, N. H., Mygind, J. B. V., Nielander, A. C., Kibsgaard, J., Vesborg, P. C. K., Nørskov, J. K., Jaramillo, T. F. & Chorkendorff, I.
Nature Materials
, (2023).

5 Bagger, A., Wan, H., Stephens, I. E. L. & Rossmeisl, J.
ACS Catalysis
11, 6596, (2021).

6 Spry, M., Westhead, O., Tort, R., Moss, B., Katayama, Y., Titirici, M.-M., Stephens, I. E. L. & Bagger, A.
ACS Energy Letters
, 1230, (2023).

7 Westhead, O., Spry, M., Bagger, A., Shen, Z., Yadegari, H., Favero, S., Tort, R., Titirici, M., Ryan, M. P., Jervis, R., Katayama, Y., Aguadero, A., Regoutz, A., Grimaud, A. & Stephens, I. E. L.
Journal of Materials Chemistry A
, (2023).
A Durable Vanadium Disulfide-Based Catalyst for Nitrate Reduction and Insights on in-Line Ammonia Detection By Mass Spectrometry
Authors: Wilder Logan , Balogun Kabirat , Gerke Carter , Klein Walter , Young James L. , Miller-Link Elisa
Published: August 2024

Ammonia is critical to agriculture worldwide and is a renewable fuel. The dominant process for ammonia synthesis, Haber-Bosch, is fossil-fuel dependent, energy intensive and highly centralized. Electrochemical N2 or NO3
- reduction promises to provide a decentralized and environmentally friendly route to ammonia synthesis. Electrochemical ammonia synthesis research is challenging due to typically low amounts of ammonia produced relative to environmental levels. In this two-part presentation, a VS2-based nitrate reduction catalyst, which has shown exceptional activity, selectivity, and durability, will be discussed. The proposed mechanism of nitrate reduction on VS2 will be discussed along with thorough characterization of the catalyst material, and we will present density functional theory mechanistic insight of nitrate reduction on VS2. Various experimental controls used in the VS2 nitrate reduction experiments, including Ar purge and NMR characterization experiments will also be detailed. Additionally, a test platform for nitrogen or nitrate reduction catalysts in a gas-diffusion electrode architecture with in-line NH3 and 15NH3 monitoring by multi-turn TOF-MS will be discussed. This part of the presentation will detail some advantages of our analytical approach that stem from the low limit of detection and high mass resolution. Finally, we will address areas of opportunity in electrochemical ammonia generation.
Green Ammonia Electrosynthesis from Nitrate-Polluted Waters
Authors: Garcia Ballesteros Sara , Pirrone Noemi , Hernandez Simelys , Bella Federico
Published: August 2024

Ammonia (NH3) is the basis of all nitrogen fertilisers constituting one of the pillars of modern society, without which nearly half of the population would not be present on Earth.1 Moreover, due to its high energy content and density, it has recently emerged as a potential fuel on the route to decarbonisation.2 However, contemporary NH3 is mainly produced via the energy-intensive and fossil fuel-dependent Haber-Bosch process so to meet the future NH3 demand, the development of new green synthesis techniques is crucial.3 Conversely, due to its high solubility, nitrate (NO3
-) is considered one of the most widespread pollutants in groundwaters.4 Increasing NO3
- concentrations in water sources represent an environmental concern and a risk to human health, requiring the development of novel and efficient techniques to remove them5,6

To this end, electrochemical nitrate reduction reaction (E-NO3RR) has received considerable attention since, among other advantages, it permits the utilization of electricity from renewables. Besides, taking into account that molybdenum and sulphur play key roles in nitrogenase-based nitrogen fixation, molybdenum disulphide (MoS2) is expected to be active toward E-NO3RR, even if it has already demonstrated good catalytic activity toward hydrogen evolution reaction (HER, the main competitor of E-NO3RR).6

In this work, MoS2 has been tested for E-NO3RR in combination with K2SO4 0.1 M as electrolyte. Experiments have been performed employing a flow cell with a gas diffusion electrode (GDE), on which the catalyst is immobilized through air-brushing technique. The design of the experiment and surface response methodology (DoE/RSM) were used to gain further insight onto the influence of three operational variables (i.e. operating potential, catalyst loading and salt concentration in the electrolyte) on the Faradaic efficiency and NH3 yield of the NO3RR, as well as the possible interaction between those variables. Concretely a 3-factors Doehlert design with 3 replicates of the central point was employed. To select the proper range for every variable, screening experiments were first performed. Results reveal operational potential and salt concentration at the electrolyte as main parameter controlling the efficacy of the process

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Electrofiltration-Enabled Nitrate Reduction Reactivity of Carbon Nanotube Electrified Membrane for Drinking Water Treatment
Authors: Fan Yingzheng , Winter Lea R
Published: August 2024

Electrocatalytic nitrate reduction could enable nitrate removal in drinking water without generating concentrated waste streams. However, current processes heavily rely upon metal catalysts with high activity to achieve sufficient nitrate removal, which increases treatment costs and can inevitably lead to leaching of metals into treated water. In this study, we elucidate how electrified filtration enables sufficient nitrate conversion to meet drinking water standards in metal-free defective CNTs by tunable matching of mass transport and reaction timescales. The metal-free carbon nanotube (CNT)-based electrified membrane (EM) was employed as a porous flow-through cathode to decrease the diffusion boundary layer. Computational fluid dynamics simulations revealed that the flow-through mode mitigates diffusion limitations to enhance overall reaction activity, as compared to the conventional flow-by mode at the same flow rate. Additionally, the nitrate reduction rate could be tuned by controlling the nitrate advection rate using permeate flux (0 to 60 L h-1 m-2). A maximum removal efficiency of 86.9% was reached when the mass transport rate matched the reaction rate across a range of applied potentials. Furthermore, defects in CNTs were identified as the catalytic active sites. We employed density functional theory and molecular dynamics simulations to gain insight into CNT defect-catalyzed nitrate reduction under electrofiltration. Finally, the long-term stability, tolerance of environmental interferences, and sufficient nitrate removal and N2 selectivity to meet drinking water standards were demonstrated in synthetic surface water, suggesting that the CNT-EM and flow-through reactor may provide a promising solution for decentralized nitrate destruction in drinking water.
(Invited) Selective Ammonia Separation Using Prussian Blue Analogues
Authors: Kim Taeyoung
Published: August 2024

Prussian blue analogues (PBAs) are a three-dimensional coordination polymer with iron and transition metals bridged with cyanide ligands, creating open-framework structures for hosting guest ions into interstitial sites. These sites can be occupied by cations via adsorption/desorption or intercalation/deintercalation, which has been widely utilized in developing separation processes and energy storage devices. Additionally, it has been well established that the size of the channel provides selectivity between monovalent cations based on their hydrated radii. Using these unique functionalities allows for selective ammonia recovery from wastewater. The feasibility of selective separation has been demonstrated using PBA-based electrodes that showed reversible and selective intercalation/deintercalation of NH4
+ by cyclic operation. To enable continuous separation, we recently developed an electrochemically driven membrane process, where PBAs provided selective ion-conducting channels. An improved selectivity for NH4
+ relative to Na+ was achieved using synthetic and domestic wastewaters, which was attributed to a thin layer of PBA created on the surface of a cation exchange membrane. These results collectively show that the use of PBAs for selective ammonia separation could lead to the development of efficient electrochemical processes for nutrient recovery.
Tetrazole-Containing Polyelectrolytes: A New Class of Ion-Solvating Membranes for Alkaline Water Electrolysis
Authors: Serhiichuk Dmytro , Rajappan Sinu Charamchirail , Krishnan Yogeshwaran , Xia Yifan , Kraglund Mikkel Rykær , Hansen Heine Anton , Jensen Jens Oluf Oluf , Aili David
Published: August 2024

Alkaline ion-solvating membranes, such as those based on polybenzimidazole (PBI), offer high ion conductivity and good gas barrier properties, making them promising for next-generation alkaline water electrolyzers.1 However, the stability of commonly used PBI derivatives is limited due to gradual backbone degradation. Consequently, alternative PBI chemistries and other polymer options like poly(vinyl alcohol),2 and carboxylate functionalized styrene-ethylene-butylene copolymers are being explored to address this inherent stability issue.3

In this study, we present the synthesis and characterization of a novel type of ion-solvating membranes for alkaline water electrolyzers. These membranes are based on tetrazole functionalized polymers derived from poly(styrene-co-acrylonitrile). A one-step click-type [3+2] cycloaddition reaction was utilized to introduce tetrazole pendants by converting acrylonitrile groups in poly(styrene-co-acrylonitrile). The degree of functionalization was controlled by adjusting the content of acrylonitrile units in the polymer. Subsequent treatment in aqueous KOH solution led to the formation of negatively charged tetrazolide pendants with high ionization degrees.

The alkaline stability of the tetrazolides was evaluated using both DFT simulations and model compound studies, demonstrating remarkable stability with no degradation observed for over 3000 hours in 25 wt.% KOH at 80 °C. Physicochemical properties such as electrolyte uptake, swelling behavior, thermal stability, and ion conductivity were assessed for the synthesized polymers. The electrolyte-imbibed membranes exhibited high ion conductivity, reaching up to 90 mS cm-1 in 15 wt% KOH at 80 °C. Electrolysis operation using these membranes showed stable performance for 600 hours with no signs of degradation.

1 D. Aili, M. R. Kraglund, S. C. Rajappan, D. Serhiichuk, Y. Xia, V. Deimede, J. Kallitsis, C. Bae, P. Jannasch, D. Henkensmeier, J. O. Jensen, ACS Energy Letters, 2023, 1900–1910.

2 Y. Xia, S. C. Rajappan, D. Serhiichuk, M. R. Kraglund, J. O. Jensen, D. Aili, J Memb Sci 2023, 680, 121719.

3 D. Serhiichuk, D. Tian, M. R. Almind, Z. Ma, Y. Xia, M. R. Kraglund, C. Bae, J. O. Jensen, D. Aili ACS Applied Energy Materials 2024 7 (3), 1080-1091

Figure 1 Tetrazolation of poly(styrene-co-acrylonitrile) and formation of corresponding potassium tetrazolide following equilibration in aqueous KOH.

Figure 1
AEM Water Electrolysis with Ni-Based Catalysts and Tailored Poly(arylene piperidinium) Materials for Improved Stability
Authors: Hagner Luis , Metzler Lukas , Koch Susanne , Klingenhof Malte , Strasser Peter , Weber Richard , Landrock Michelle , Sommer Michael , Vierrath Severin
Published: August 2024

Anion-exchange membrane water electrolysis (AEMWE) is a promising low-temperature technology for hydrogen production. It leverages the advantages of the currently dominant technologies (alkaline water electrolysis and proton-exchange membrane water electrolysis) by using transition metal group based catalysts and a zero-gap configuration, enabling high efficiency. However, current AEMWE systems show a limited stability and efficiency.

In this work, commercial and non-commercial polymers are used to fabricate catalyst-coated membranes with a production method oriented towards scalable production (1). A tailored poly(arylene piperidinium) polymer (PAP) shows enhanced stability compared to commercial Aemion+TM during 100 h operation at 1 A/cm2 and 60 °C in 1 M KOH electrolyte (Figure 1) (2). Additionally, different anode catalysts are employed and measured in a reference electrode setup to separate the cell voltage into contributions from the anode and cathode (3). Here, the overpotential of Ni(OH)2 is higher compared to the more active NiFe-layered-double-hydroxide(LDH) and iridium oxide. Employing this setup to measure individual degradation of cathode and anode is part of ongoing research.

Figure 1. a) Tailored PAP material compared to Aemion+TM based systems operated at 1 A/cm2 showing a linear degradation of ca. 400 µV/h. b) Polarization curves of AEMWE single cells with different anode catalysts, measured with an integrated reference electrode setup, which allows to distinguish anode and cathode contribution to the cell voltage. Measured at 60 °C in 1 M KOH electrolyte, 5 cm2 cell area.

References

Koch, S.; Metzler, L.; Kilian, S. K.; Heizmann, P. A.; Lombeck, F.; Breitwieser, M.; Vierrath, S. Toward Scalable Production: Catalyst‐Coated Membranes (CCMs) for Anion‐Exchange Membrane Water Electrolysis via Direct Bar Coating. Advanced Sustainable Systems
2023,
7 (2). DOI: 10.1002/adsu.202200332.

Weber, R.; Klingenhof, M.; Koch, S.; Metzler, L.; Merzdorf, T.; Meier-Haack, J.; Strasser, P.; Vierrath, S.; Sommer, M. Meta -kinks are key to binder performance of poly(arylene piperidinium) ionomers for alkaline membrane water electrolysis using non-noble metal catalysts. J. Mater. Chem. A [Online]
2024,
12 (13), 7826–7836.

Xu, Q.; Oener, S. Z.; Lindquist, G.; Jiang, H.; Li, C.; Boettcher, S. W. Integrated Reference Electrodes in Anion-Exchange-Membrane Electrolyzers: Impact of Stainless-Steel Gas-Diffusion Layers and Internal Mechanical Pressure. ACS Energy Lett. [Online]
2021,
6 (2), 305–312.

Figure 1
Analysis and Improvement of Characterisation Methods for Transport Properties of Gas Diffusion Layers (GDL) for Pemfcs
Authors: Uhlemayr Theresa , Messerschmidt Matthias
Published: August 2024

Target of the presented work is to determine absolute values of GDL parameters with high accuracy, analysing and avoiding error sources caused by both test equipment and measurement methodology to the highest possible extent. The focus is on electrical, thermal and gas transport. Error sources are examined and identified. Specific attention is paid to identify inherent, inevitable measurement uncertainties. As an example, stacking of GDLs as a method to separate the contact and bulk through-plane electrical resistance of the material under compression will be reviewed in detail. In addition, the influence of the sample dimension, the sample orientation and the sample preparation is shown in examples.

The results presented are acquired within the project QM-GDL (GDL quality assurance for the market run-up), which is funded by the German Federal Ministry for Digital and Transport under grant agreement number 03B11016C.
Voltammetric Investigations of Low-Coordinate Manganese As an Electrocatalyst for Organic Coupling and Functionalization
Authors: Legaspi Kristine , Tang Tianhua , Minteer Shelley , Sigman Matthew , Gustafson Jeffrey , Smith Diane
Published: August 2024

Earth-abundant, first row, low coordinate transition metal complexes are considered promising candidates for the electrocatalysis of many organic reactions. The use of transition metal catalysts is no stranger to the field of synthetic organic chemistry; however, many of the existing catalysts require the use of rare and expensive metals such as platinum, palladium, ruthenium, and iridium. In this study, we seek to identify and understand the mechanism by which an Mn(I) complex may act as an electrocatalyst for simple organic coupling and C-H functionalization reactions, beginning with the radicalization of benzyl bromide and benzyl chloride as representative organic halide substrates. The careful design and evaluation of this manganese complex has the potential to offer an effective non-toxic 3d metal electrocatalyst, provided that common transition metal behaviors, such as disproportionation or carbon-metal bond formation, are avoided. Initial characterization of the complex by cyclic voltammetry (CV) demonstrates general reversibility of the catalyst, while additions of benzyl halide exhibit the execution of the electron transfer and catalytic step. Electrochemical simulations run in parallel with CV experiments provide supplementary guidance into the relationship between the substrate and catalyst. Additional studies conducted using bulk electrolysis, mass spectrometry, nuclear magnetic resonance, and density functional theory (DFT) calculation will help to further characterize the mechanism and supporting details. Elucidation of the catalytic mechanism will allow us to use this electrocatalyst in a series of synthetic organic conditions and aid in our advancement toward sustainable organometallic catalysis.
Electrocatalytic Radical Cation Diels-Alder Reactions Using Enol Ethers As Dienophiles
Authors: Morizumi Haruka , Nakayama Kaii , Kitano Yoshikazu , Okada Yohei
Published: August 2024

Single-electron oxidation enables the conversion of electron-rich alkenes such as styrene derivatives to radical cation species. We have been developing various cycloaddition reactions of radical cations produced by single-electron oxidation using electrochemical and TiO2 photochemical methods. Introducing an electron-rich aryl group which we call a redox tag is a critical part of the process to control the reactivity of the radical cations. During carbon-carbon bonds formation the motif functions as both electron donor and electron acceptor. In addition to styrene derivatives, enol ethers can also be readily oxidized by single electron transfer (SET) electrochemically or photochemically to generate the radical cations. For instance, enol ethers tethered redox tag serves efficient radical cation precursors for [2+2] cycloadditions.[1] The cycloadditions are net redox-neutral reactions and are initiated by the formation of a radical cation by single-electron oxidation and completed by reduction after ring formation.

Herein, we present [4+2] cycloadditions using enol ethers as dienophiles by electrochemical oxidation in lithium perchlorate (LiClO4)/nitromethane (MeNO2) system. In the case of disubstituted enol ethers prepared from aldehydes, the approach involving redox tag was successful in obtaining the corresponding cycloadducts, while the desired products were not obtained when the substrates without redox tag were subjected.[2] This result suggests that intramolecular electron transfer from the redox tag is crucial for the formation of the cyclohexene ring systems. In contrast, the trisubstituted enol ethers prepared from ketones allowed the cycloaddition reaction to proceed without the involvement of redox tag. It is expected that the methyl group significantly stabilizes the cyclohexene radical cations to have enough lifetime to be reduced by intermolecular SET. Furthermore, since the cycloaddition reaction of enol ether was completed with a catalytic amount of electricity (0.4 F/mol), a radical cation chain mechanism is proposed in which electron acts as a catalyst.

References

[1] Okada, Y.; Maeta, N.; Nakayama, K.; Kamiya, H. J. Org. Chem.
2018, 83, 4948−4962.

[2] Synlett
2023, accepted.

Figure 1