bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Carbon Additives on the Performance of Oxide-Based Cathode for PEFC
Authors: Yusuke Bokkai , Yamamoto Kanta , Takeuchi Yuu , Monden Ryuji , Ishihara Akimitsu , Fukunaga Hiroshi
Published: December 2024

To further advance the adoption of PEFCs, there's a growing need for developing non-Pt catalysts. Among these, oxide catalysts have caught much attention due to their impressive resistance to corrosion in acidic conditions. However, the lack of electronic conductivity is a challenge, and it is considered that new design guidelines for catalyst layers different from existing Pt/C electrodes are needed. In the field of secondary batteries, it has been reported that the shape and amount of carbon materials used as conductive additives affect performance in electrodes using materials with poor conductivity. Based on these reports, the effects of adding carbon to the catalyst layer for PEFC electrode using oxide catalyst were investigated.

Using an oxide catalyst with Zr as the active site[1, 2], we examined the effects of adding carbon of different shapes to oxide catalysts on electrode structure and power generation performance. The catalyst layer was prepared using a drop method. The IV performance was improved with the addition of carbon, and the catalyst layer with KB added showed higher current density at all potentials than CNT. Thus, it was revealed that the shape of conductive additives also affects the performance of electrodes in PEFCs. When the amount of catalyst layer coating was changed, IV performance improved by increasing the coating amount of the catalyst. From SEM images of cross-sections, it was found that catalyst layers with a higher coating amount had larger aggregates of catalyst particles, larger voids in the catalyst layer, and thicker membranes.

To control the structure of the electrode, a spray coating method was used for the preparation of the catalyst layers. The catalyst layers were fabricated by varying the gun distance, discharge amount, and heater temperature during spray application. IV performance was highest under conditions with a large gun distance. From structural observations, it was found that with a large gun distance, the aggregates became smaller.

To investigate the impact of spray coating conditions on catalyst layer structure, titania was used as the catalyst, and layers were produced by varying the discharge amount and heater temperature. Structures with smaller agglomerates were observed when the discharge amount was low. Similarly, smaller agglomerates were observed when the substrate temperature was higher. These results suggest that porous structures with suppressed particle agglomeration are more likely to form under conditions conducive to drying.

References

[1] A.Ishihara et al., J. Phys. Chem. C, 123, 18150 (2019).

[2] Y.Takeuchi et al., Chem. Lett., 51, 927 (2022).
Promoted Electrochemical Performance of Direct Methanol Fuel Cell By Using PtRu Deposited and TiO2 Coated Porous Carbon Nanofibers
Authors: Gao He , Ishitobi Hirokazu , Nakagawa Nobuyoshi
Published: December 2024

Direct methanol fuel cell (DMFC) has drawn much attention as a promising power source due to its high energy density and environmental friendliness characteristic. But the slow kinetics of methanol oxidation reaction (MOR) limit its wild applications. A higher MOR activity electrochemical catalyst with low PtRu loading amount is now desired to act as anode catalyst layer of DMFC.

In our previous studies, PtRu deposited and TiO2 coated carbon nanofibers (PtRu/TCCNFs) prepared by using electrospinning technology shows a better performance than PtRu/C commercial catalyst. In direct methanol fuel cell (DMFC) applications, this fiber-structure catalyst with a diameter of around 500 nm can offer more gaps by overlapping themselves in catalysts layer, which is benefit for mass transfer of methanol oxidation reaction. However, the CL is thicker than other catalysts based on carbon black. To overcome this feature, another CNFs with porous structure (P-CNFs) was prepared by using electrospinning technology with a mixture precursor solution consist of polyacrylonitrile (PAN), polystyrene (PS) and dimethylformamide (DMF). The P-CNFs with meso- and micropores can not only offer more active sites by inner space to deposit PtRu particles but also decrease the thickness of the catalyst layer.

In this study, different PS to PAN ratio and electrospinning condition was investigated to confirm the most suitable fiber diameter, surface area and pore size by using BET and SEM. Subsequently, different PtRu loading and TiO2 coated catalysts were prepared and measured by EDX and XRD to confirm the elements content and PtRu crystal size. After that, electrochemical surface area (ECSA) and MOR mass activity was tested by three-electrode cell to obtain the catalysts performance. Finally, the porous and non-porous catalysts were used for DMFC application with the catalyst loading of 1.0 mg-PtRu/cm2, the maximum current and power density was measured to compare the performance with commercial catalyst.

The results show that the condition of 18 kV and 15 cm for electrospinning with the PS to PAN ratio of 1.00 exhibit the most suitable pore size (≥10 nm), and BET surface area is 249 m2/g. The prepared PtRu/TCCNFs and PtRu/P-TCCNFs show nearly the same PtRu loading and atomic ratio, as well as Ti content, and with the PtRu crystal size of 3.3 nm. The MOR mass activity shows a rank of PtRu/P-TCCNFs> PtRu/TCCNFs > PtRu/C. The figure shows DMFC performance of PtRu/C, PtRu/P-TCCNFs, and PtRu/TCCNFs catalysts. The result exhibits that the porous structure catalyst has the highest maximum current and power density, and PtRu/TCCNFs is also higher than that of PtRu/C commercial catalyst.

The improved DMFC performance of PtRu/P-TCCNFs is attributed to the accelerated mass transportation due to the porous structure, which offers channels to allow reactants and products passing through the layer.

Figure 1
Effect of Pore-Forming Agent on Concentration Overpotential of Carbon-free Pt Electrodes for PEFC
Authors: Segawa Haruki , Sasaki Takaaki , Shimada Iori , Osada Mitsumasa , Takahashi Nobuhide , Fukunaga Hiroshi
Published: December 2024

Platinum is widely recognized for its high reactivity and is commonly used in the cathodes of polymer electrolyte fuel cells (PEFCs). However, due to its high cost and limited availability, there is a pressing need to reduce the amount of platinum used. Conventional low-platinum electrodes, comprised of Pt-supported carbon (Pt/C) and ionomer, face challenges such as catalyst dissolution and redeposition, carbon support corrosion, and platinum poisoning by the ionomer. This study focuses on Pt nanosheets (Pt(ns)) [1] as a novel catalyst with high activity and durability. These electrodes are considered to be a novel low-platinum electrode with high durability. In our previous research electrodes fabricated using Pt(ns) observed significant overvoltage in high-current density regions, attributed to hindered gas diffusion caused by catalyst stacking. Therefore, we aimed to reduce overvoltage by increasing the porosity of the electrode through the addition of a pore-forming agent. Inspired by reports on utilizing urea (Ur) to enhance electrode porosity [2], electrodes were prepared by incorporating Ur into the ink, followed by dissolution and removal to create voids. The resulting cathode catalyst layer was then hot-pressed to assemble the membrane-electrode assembly (MEA). I-V measurements demonstrated that the addition of Ur suppressed concentration overvoltage. Scanning electron microscopy (SEM) observations revealed increased electrode porosity compared to non-additive electrodes. Furthermore, despite a similar electrochemical surface area (ECSA) compared to non-additive electrodes, the mass activity (MA) in the low-current density region significantly improved.

Acknowledgement

Part of this paper is based on results obtained from a project, JPNP20003, subsidized by the New Energy and Industrial Technology Development Organization (NEDO).

References

[1] S. Takenaka et al.,
J. Phys. Chem.,
119, 12445(2015)

[2] T. Suter et al., Nanomaterials.,
11, 2530(2021)
Effect of Oxygen Content on Free-Sulfur Defects in Sodium Phosphosilicate Oxy-Sulfide Glasses
Authors: Maier Keaton , Wakefield Alec , Tader Nick , Martin Steve
Published: December 2024

Sodium glassy solid electrolytes (GSEs) are an attractive option for the future of grid-scale energy storage. This is primarily because sodium is far more abundant than lithium, driving down material cost and allowing for large-scale implementation. Additionally, GSEs do not pose the same risk of fire as organic liquid electrolytes that are found in most batteries on the market today. However, the presence of free-sulfur defects in these glasses has been shown to make them cathodically unstable and undermine their usefulness as GSEs. Previous work suggests that increased oxygen content contributes to an increase in free-sulfur defects in these glasses, but the mechanism is unknown. To investigate further, samples of NaPSiSO from the series (1-y)Na2S + y{(1-z)[(1-a)SiS2 + aPS5/2] + zNaPO3} were synthesized with oxygen content (O/[O+S]) ranging from 0.0 to 0.3 while glass former ratio and R-value were held constant. These glasses were characterized using Raman spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and x-ray photoelectron spectroscopy to investigate the mechanism of formation for free-sulfur defects.
(Invited) Designing Redox-Active Organic Molecules (ROMs) for Fast-Charging Battery Electrodes with High Stability
Authors: Kwon Ji Eon
Published: December 2024

Redox-active organic molecules (ROMs) are drawing significant attention as promising alternatives to conventional transition metal oxide electrodes. Their appeal stems from numerous benefits including abundance, sustainability, biocompatibility, cost-effectiveness, and ease of chemical tunability. Notably, their flexible nature with large free volume, owing to loosely packed intermolecular structures, is expected to facilitate fast diffusion of charge-carrying ions – a key attribute for enhancing the high-rate performance of electrode materials. Yet, the practical application of ROMs is hindered by their slow rate capability with limited capacity utilization, a consequence of their intrinsically electron insulating properties. Furthermore, the high solubility of ROMs in organic electrolytes has caused rapid capacity fading within the first few cycles, compelling one to prepare polymers via complicated synthesis and/or to fabricate composites with expensive nanocarbons. These factors increase production costs and significantly deteriorate processability in the electrode fabrication process.

In this talk, we introduce novel molecular design strategies to improve both cycle stability and rate performance in simple small molecule ROMs, paving the way for the development of fast charging batteries.
(Invited) In Situ Crosslinked Gel Polymer Electrolytes for Li-Ion Capacitors with Improved Safety and Stability at High Temperature Operation
Authors: Ajuria Jon , Lindberg Simon , Martinez-Ibañez María , Arnaiz María , Canal Rodríguez María
Published: December 2024

Li-ion capacitors (LICs) are considered a promising option for high-power application with a relatively high energy content compared to traditional supercapacitors1. There are however some issues with LICs: The anode needs to be pre-lithiated, which adds extra processing steps and increases the cost of assembly and/or material, and the stability at elevated temperatures and flammability of organic electrolytes often used in LICs. Recent progress regarding the pre-lithiation has been made by researchers at CIC energiGUNE, by using as a sacrificial salt together with hard carbon as anode2. Regarding novel electrolytes, polymer electrolytes (PEs) are considered a promising route to improve stability and increase the safety in battery research. However, the low ionic conductivity at room temperature limits high-power performance. Overall, important properties of electrolytes for LICs are a wide electrochemical stability window, high conductivity, and a low viscosity. For a PE to fulfil these demands, a liquid component is added to the polymer, forming a gel polymer electrolyte (GPE). In this work, we have investigated a mixture of two monomers, PETEA and PEGDMA, as polymer components in a standard 1M LiFSI EC:DMC liquid electrolyte. This polymer mixture enables the formation of a GPE in situ, at very low concentrations, through a mild heat treatment. Results have been shown in slightly different systems to provide a high conductivity and wide electrochemical stability windows3. In this work we show that the GPE is compatible with the sacrificial salt and that the addition of a polymer component reduces evaporation and improves stability and performance at 70 and 80ºC compared to the liquid electrolyte alone.

References:

1Y. Shao et al., Chemical Reviews, 2018, 118(18), 9233–9280

2M. Arnaiz et al., Energy & Environmental Science, 2020, 13(8), 2441–2449

3Y.-H. Su et al., Journal of Power Sources, 2021, 481, 228869

Figure 1. Showing the different steps in preparation/pre-treatment of the LIC concept investigated: from a) liquid phase infiltration of the electrodes, b) crosslinking the electrolyte, c) pre-lithiation of the anode and finally d) normal operation of the LIC.

Figure 1
(Invited) The Tortuous History of Photoelectrochemistry and Photocatalysis after the Fujishima Discoveries
Authors: Rajeshwar Krishnan
Published: December 2024

In this talk, I will attempt to chart the numerous twists and turns the twin fields of photoelectrochemistry and photocatalysis have undergone since the momentous discovery by Fujishima and Honda that anodic films of titania could split water into hydrogen and oxygen under sunlight. Interestingly, these authors did not discover this phenomenon, nor did they pioneer the fact that irradiated titania (or other oxide semiconductor) films could promote the photocatalytic degradation of environmental pollutants to mineralized products. There are also question marks on whether in the original Nature paper, these authors (and their junior collaborators) truly demonstrated that water was being split into hydrogen and oxygen. Instead, claims have been made that what they reported was a regenerative cell involving the generation and subsequent reduction of dioxygen instead of the photoinduced reduction of protons into hydrogen. (However, these authors did demonstrate, in a subsequent paper in the J. Electrochem. Soc., that hydrogen gas indeed was evolved in the correct stochiometric ratio with oxygen.) Nonetheless, it must be said that the Fujishima-Honda reports truly sparked intense interest in this solar conversion strategy and spawned a veritable, bonanza for the field, and indeed for the parent disciplines of photochemistry and electrochemistry. Other twists and turns that affected the evolution and growth of these twin fields including the discovery that most narrow bandgap semiconductors were photoelectrochemically unstable, and subsequent attempts to tackle this issue, will be discussed. Finally, the field of solar water splitting is truly at a pivotal point right now and its very future is murky. Avenues that may instead prove to be more profitable will be identified.

Acknowledgements

.
The author thanks his numerous collaborators over the years. This work was primarily supported by the National Science Foundation UTA/NU Partnership for Research and Education in Materials (NSF DMR-2122128).
(Invited) Control of Magnetic and Electric Polarization via Electron Transfer in Molecular Crystals
Authors: Sato Osamu
Published: December 2024

The design and synthesis of novel molecular compounds with physical properties that can be controlled via external stimuli have attracted considerable attention. We have synthesized several functional compounds, of which the electric polarization can be switched via electron transfer or spin transition process.1-3 A typical example is the [CoGa] heterometallic dinuclear complexes.1 The [CoGa] complex exhibits thermally-induced electron transfer between the metal and ligands, CoIII-LS–dhbq3-–GaIII DCoII-HS–dhbq2-–GaIII, which involves changes in the molecule’s dipole moment. Since the [CoGa] complexes are designed to be oriented in the same direction within the crystal via chiral ligands, intramolecular electron transfer causes the polarization to switch at the crystal level. This polarization switching could also be induced by incident photons. Changes in polarization are normally mediated by ion displacement and molecular reorientation, whereas the polarization switching in the [CoGa] complex is realized via electron transfer. Another example is the [FeCo] heterometallic dinuclear complexes, the mechanism of which is the spin transition.2The [FeCo] dinuclear complex exhibits a magnetic field-induced spin crossover process, resulting in a significant polarization change of 0.45 μC cm–2. Mössbauer spectroscopy and theoretical calculations suggest that the spin transition coupled with electron redistribution between ligand and metal leads to the observed polarization change.

Reference

P. Sadhukhan, O. Sato
*
et al., “Energy conversion and storage via photoinduced polarization change in non-ferroelectric molecular [CoGa] crystals”, Nature Commun., 2023, 14, 3394.

X. Zhang, O. Sato
*
et al., “Magnetoelectricity Enhanced by Electron Redistribution in a Spin Crossover [FeCo] Complex”, J. Am. Chem. Soc., 2023, 145, 15467.

S.-Q. Su, O. Sato
*
et al., “Control of Electronic Polarization via Charge Ordering and Electron Transfer: Electronic Ferroelectrics and Electronic Pyroelectrics”, Chem. Sci., 2023, 14, 10631-10643.
(Invited) Rapid Photochemical Control of Surface Chemical Properties and Molecular Assembly Formation Using Novel Amphiphilic Lophine Dimers
Authors: Sakai Hideki , Sakai Kenichi , Akamatsu Masaaki
Published: December 2024

Photo-induced rapid control of molecular assemblies formed by amphiphilic molecules, such as micelles and vesicles, enables effective and on-demand release of drugs or active components, with applications such as drug delivery systems (DDS) and cosmetics1). Thus far, no attempts to optimize the responsiveness of photoresponsive molecular assemblies have been reported. We previously reported photoresponsive surfactants bearing a lophine dimer moiety that exhibit fast photochromism in confined spaces, such as inside a molecular assembly. However, rapid control of the micelle structures and solubilization capacity have not yet been demonstrated.

In the present study, photo-induced morphological changes in micelles were monitored using in-situ small-angle neutron scattering (SANS) and UV/Vis absorption spectroscopy2,3). An amphiphilic lophine dimer (3TEG-LPD) formed elliptical micelles. These were rapidly elongated by ultraviolet light irradiation, which could be reversed by dark treatment, both within 60 s (Fig. 1). For a solution of 3TEG-LPD micelles solubilizing calcein as a model drug molecule, fluorescence and SANS measurements indicated rapid release of the incorporated calcein into the bulk solvent under UV irradiation. Building on these results, we investigated rapid controlled release via hierarchical chemical processes: photoisomerization, morphological changes in the micelles, and drug release. This rapid controlled release system allows for effective and on-demand DDS.

References

1) M. Akamatsu, K Sakai, H Sakai, Chemistry Letters, 52 (7), 573 (2023). (Highlight Review)

2) M. Akamatsu, K. Kobayashi, H. Iwase, Y. Sakaguchi, R. Tanaka, K. Sakai, H. Sakai, Scientific Reports, 11:10754 (2021).

3) H. Iwase, M. Akamatsu, Y. Inamura, Y. Sakaguchi, K. Kobayashi, H.Sakai, Langmuir 39 (35), 12357 (2023).

Figure 1
(Invited) Influence of Hydrogen Bond Networks on Hydrogen Evolution Reaction in Aqueous Systems
Authors: Ikeda Katsuyoshi
Published: December 2024

Hydrogen evolution reaction (HER) is one of the key issues to achieve “carbon neutrality”. Driving the electrocatalytic HER in aqueous solutions with solar-energy cells is considered as a green and sustainable way to produce hydrogen molecules (H2). To achieve effective H2 production, it is required to reduce HER overpotential using appropriate heterogeneous electrocatalysts such as Pt. The HER activities of catalytic metals have a strong correlation with the hydrogen adsorption free energies on their surfaces, which is known as a so-called volcano-like relation. Because the optimum adsorption energy and hence maximum HER activity are found at the top of the volcano, most of the studies to develop electrocatalysts focus on tuning of the adsorption energy. However, the hydrogen adsorption step, i.e., discharge reaction of proton, at the surface is strongly influenced by hydrogen bonding with the bulk phase of liquid water. Recently, we have developed a surface-selective THz-vibrational spectroscopy based on surface-enhanced Raman scattering, which can obtain dynamical and structural information on hydrogen bond networks of water at interfaces with the frequency range of 10 - 100 cm-1 (0.3 – 3 THz) [1-6]. Using this technique, we have examined the potential-induced behavior of interfacial hydrogen bonds under the HER process on various metal surfaces with different HER activities and found that there is a correlation between the HER activities and hydrogen bond structures at interface. The details will be discussed in the presentation. We will also present a new strategy to produce hydrogen gas more efficiently using a non-traditional electrochemical cell structure.

[1] M. Inagaki, K. Motobayashi, K. Ikeda, J. Phys. Chem. Lett., 8, 4236-4240 (2017).

[2] M. Inagaki, T. Isogai, K. Motobayashi, K. -Q. Lin, B. Ren, K. Ikeda, Chem. Sci., 11, 9807-9717 (2020).

[3] M. Inagaki, K. Motobayashi, K. Ikeda, Nanoscale, 12, 22988-22994 (2020).

[4] R. Kamimura, T. Kondo, K. Motobayashi, K. Ikeda, Phys. Status Solidi B, 259, 2100589 (2022).

[5] T. Kondo, M. Inagaki, K. Motobayashi, K. Ikeda, Catal. Sci. Technol., 12, 2670-2676 (2022).

[6] T. Isogai, M. Inagaki, M. Uranagase, K. Motobayashi, S. Ogata, K. Ikeda, Chem. Sci. 14, 6531-6537 (2023).
Unique Photothermal Materials for Cutting-Edge Interfacial Solar Desalination and Wastewater Purification
Authors: Tatachari Santhanagopalan Shridharan , Ho Lee , Tan Runfa , Sivanantham Arumugam , Cho In Sun
Published: December 2024

Harnessing renewable solar energy for solar desalination shows great promise for addressing freshwater scarcity. However, conventional solar desalination suffers from low photothermal conversion and excessive heat dissipation, limiting its practicality for meeting water demand. Interfacial solar steam generation (ISSG) has emerged to address these limitations, leveraging advances in photothermal absorber materials, structural design, and thermal management. The photothermal material (PTM) plays a crucial role as it facilitates the conversion of solar energy into localized heat energy, leading to water evaporation within a localized high-temperature zone.1 In this talk, we present unique photothermal absorber materials that are not common for ISSG, such as bismuth copper oxysulfide (BiCuSO; BCSO), silicon (Si), and red phosphorus (RP), exhibiting broad light absorption, low thermal conductivity, and high heat localization. 2–5 We employed a mechanochemical activation method to regulate particle size and surface defects simultaneously, thus enhancing the optical, thermal, and photothermal properties. Utilizing the 1D water path architecture, we achieved an outstanding water evaporation rate of 2.2 (photothermal efficiency: 107.9%), 1.77 (96%), and 1.75 kg/m2·h (94.0%) using Si, BCSO, and RP absorber materials, respectively, under 1 sun illumination (100 mW/cm2). Furthermore, our photothermal absorbers demonstrated excellent ion rejection capabilities when subjected to continuous measurement for 50 h with both seawater and industrial wastewater. The emerging interface solar-driven steam generation technology promises to meet future human needs for freshwater, energy, and environmental sustainability.

Keywords: Photothermal materials; Mechanochemical activation; Defect control; Interfacial solar desalination; Wastewater purification.

References:

1 X. Cui, Q. Ruan, X. Zhuo, X. Xia, J. Hu, R. Fu, Y. Li, J. Wang and H. Xu, Chem. Rev., 2023, 123, 6891–6952.

2 T. S. Shridharan, M. J. Kang, A. Sivanantham, S. Kim and I. S. Cho, Desalination, 2022, 540, 115984.

3 T. S. Shridharan, A. Sivanantham, R. Tan, S. Y. Hong, D. H. Kim and I. S. Cho, Desalination, 2023, 561, 116700.

4 T. S. Shridharan, A. Sivanantham, J. H. Lee, S. Y. Hong, Y. J. Jeong, S. S. Shin and I. S. Cho, Chem. Eng. J., 2024, 486, 150247.

5 T. S. Shridharan, J. H. Lee, R. Tan, A. Sivanantham, H. S. Han, H. S. Jung and I. S. Cho, Desalination, 2024, 579, 117464.

Figure 1
(Invited) Synthesis, Arrangement, and Applications of 2D Oxide Nanosheets
Authors: Sakai Nobuyuki , Sasaki Takayoshi
Published: December 2024

2D oxide nanosheets, with their unique molecularly thin thickness and large lateral dimension, have attracted considerable attention in recent decades due to their intriguing physicochemical properties. These nanosheets can be obtained by delaminating precursor crystals of layered metal oxides into single elementary layers, and exhibit a wide range of functionalities, making them promising candidates for various applications in nanotechnology. Among the various types of nanosheets developed so far, titania nanosheets stand out as wide bandgap semiconductors, showing remarkable potential as photoelectrodes and photocatalysts, while manganese oxide nanosheets exhibit notable redox activity, serving as excellent candidates for anodes in lithium-ion batteries. The controlled arrangement of nanosheets on substrate surfaces to form laterally packed monolayer films, characterized by minimal gaps and overlaps, represents a critical step in the advancement of nanosheet-based nanodevices. Achieving this precise organization facilitates optimal functionality and performance. Since nanosheets are typically obtained as colloidal suspensions, a variety of solution-based assembly techniques have been developed to fabricate monolayer and multilayer films of nanosheets. These techniques include electrostatic self-assembly, the Langmuir-Blodgett method, spin coating, and others, each of which offers unique advantages in terms of control and scalability. In addition, these methods allow the construction of artificial layered structures in which different nanosheets are stacked in a designed sequence. This approach not only enhances the structural integrity of the nanosheet films, but also unlocks a wealth of sophisticated functionalities that arise from the interactions between the individual constituent nanosheets. In this talk, we would like to review the progress of our research on 2D oxide nanosheets.
(Invited) Cleaning Coastal Environments through Electrocatalysis and Electromicrobiology
Authors: Nakamura Ryuhei
Published: December 2024

Coastal environments play an increasingly important role in the world's food supply. However, excessive inputs of carbon and nitrogen compounds to the seafloor are severely damaging the benthic ecosystem, causing eutrophication, algal blooms and red tides. Therefore, the development of new technologies to maintain the health of the benthic ecosystem is essential for sustainable use of marine resources. In this study, we investigated the redox homeostasis of benthic ecosystems using a marine oligochaete as a model benthic organism to assess the ecological resilience of aquafarms to nutrient influx. Real-time monitoring of the redox potential of a model benthic ecosystem allowed assessment of the homeostatic response of the system to nutrient addition. We also found that the movement and metabolic activity of benthic animals can be controlled by artificially manipulating the redox potential of the sediments. Further, we have developed electrocatalysts for nitrification, denitrification, and anaerobic ammonium oxidation to alleviate the nitrogen nutrient imbalance in marine environments. Given the importance of benthic animals in maintaining coastal ecosystems, electrochemical monitoring, and physiological regulation of marine oligochaetes, together with the electrocatalytic control of nitrogen cycling, could provide an intriguing approach towards sustainable use of marine resources.

Reference

Shono, M. Ito, A. Umezawa, K. Sakata, A. Li, J. Kikuchi, K. Ito, R. Nakamura, Tracing and regulating redox homeostasis of model benthic ecosystems for sustainable aquaculture in coastal environments, Front. Microbiol., 13:907703. DOI: 10.3389/fmicb.2022.907703

He, H. Ooka, Y. Li, Y. Kim, A. Yamaguchi, K. Adachi, D. Hashizume, N. Yoshida, S. Toyoda, S. H. Kim, R. Nakamura, Regulation of the electrocatalytic nitrogen cycle based on sequential proton–electron transfer, Nat. Catal., 2022, 5, 798-806.

He, K. Adachi, D. Hashizume, R. Nakamura, Copper sulfide mineral performs nonenzymatic anaerobic ammonium oxidation through a hydrazine intermediate. Nat.Chem (in press)
(Invited) Human-AI-Robotics Collaboration for Catalysts Discovery in Electrochemical Reactions
Authors: Zhang Zhen , Ren Zhichu , Li Ju
Published: December 2024

The exploration and discovery of materials for electrochemical reactions have traditionally been a tedious and time-intensive process. The complexity inherent in the design of materials with high-dimensional parameters and the exhaustive nature of data acquisition are the primary causes of this bottleneck [1]. To overcome this challenge, we introduce the Copilot for Real-world Experimental Scientist (CRESt). CRESt employs a large multimodal model (LMM) to guide a robotic system that is adept at active learning (driven by the Gaussian process-Bayesian optimization process), thereby streamlining the entire workflow—ranging from the selection of composition through to the high-throughput synthesis of materials, electrochemical screening, materials characterization, and device testing—for the optimization of electrocatalysts (see video demonstrations in [2-4]). Through this method, we have been able to rapidly screen thousands of catalysts with minimal human intervention. Our development of high entropy alloy catalysts, which comprise more than five elements, have demonstrated exceptional performance in applications such as direct formate fuel cells and alkaline water electrolyzers. This strategy holds the promise of broad implementation across a spectrum of electrochemical systems.

Reference:

[1] Ren, Z., Ren, Z., Zhang, Z. et al. Autonomous experiments using active learning and AI. Nat. Rev. Mater.
8, 563–564 (2023).

[2] https://www.youtube.com/watch?v=iRauT95ECmo&t=82s

[3] https://www.youtube.com/watch?v=POPPVtGueb0&t=340s

[4] https://www.youtube.com/watch?v=sibCICesrEY
(Invited) Mechanical Suppression of Electron Transfer in Subnanometer Confinement between MXene Layers
Authors: Zhang Yuan , Zhang Danzhen , Bi Lingyi , Lei Ming , Jiang De-en , Gogotsi Yury
Published: December 2024

Ion adsorption and electron transfer are the primary charge storage mechanisms in porous electrodes. Desolvation/solvation of ions in subnanometer confinement may alter the balance between those two processes. For 2D materials like MXenes, there is a continuous change in interlayer spacing as ions are transported and stored between the layers. However, little is known about the effect of the mechanical constraint (pressure) on electrochemistry in confinement. In this work, the ion transportation process in between mechanically constrained MXene layers is monitored by combining in-situ UV-vis spectroscopy, in-situ optical spectroscopy, and in-situ XRD characterization. Compared with spray-coated Ti3C2Tx films, physically constrained Ti3C2Tx film with a constant interlayer spacing exhibited exceptional capabilities in suppressing redox reactions. Notably, this property of faradaic suppression under mechanical strain led to the application of MXene-based electrochemical cells as high-pressure electrochemical sensors.
(Invited) Ferrofluid Lithography: Advances in Cu(In,Ga)Se2 Alkaline Electroplating
Authors: Piccinni Marco , Carrea Davide , Peddis Davide , Friedman Gary , Colombara Diego
Published: December 2024

Ferrofluid lithography allows to economically obtain sub-micron patterns by externally guiding ferrofluid droplets onto a desired substrate via external magnetic fields produced by arrays of permanent or electromagnets1. The main advantage of this approach is the complete recovery of the lithographic mask, providing environmental and economic benefits. Here, we present the formulation of smart electrolytes2 for the fabrication of CuIn1-xGaxSe2 (CIGS) micropatterned solar cells3 by sequential electrodeposition/selenization, a route compatible with world-record industrial processing4. In this work, we stack thin films of metallic Cu, In, and Ga on top of each other by means of potentiostatic electrodeposition. We tune the formulation of Cu2+, In3+ and Ga3+ electrolytes to be mutually compatible in terms of pH. Moreover, by operating under alkaline conditions, we minimize the hydrogen evolution reaction during plating. Lastly, to ensure the stability of the alkaline electrolytes, we carefully choose environmentally friendly complexing agents that also yield flat and smooth metallic deposits.

Acknowledgements

This work was supported in part by the Italian Ministry of Foreign Affairs and International Cooperation, grant number US23GR17 and in part by the European Commission PathFinder Open programme under grant agreement No. 101046909 (REMAP)5. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or European Innovation Council and SME Executive Agency (EISMEA). Neither the European Union nor the granting authority can be held responsible for them.

References

B. B. Yellen, G. Fridman, and G. Friedman, Nanotechnology, 15, S562–S565 (2004).

Diego Colombara, (2020) https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2020136057

D. Correia et al., Results Phys, 12, 2136–2140 (2019).

M. Nakamura et al., IEEE J Photovolt, 9, 1863–1867 (2019).

https://re-map.eu/
(Invited) Insights from Cyclic Voltammetry into Active Sites on Carbon Electrodes and Their Importance in Vanadium Flow Batteries and Other Electrochemical Applications
Authors: Al Hajji Safi Maria , Bourke Andrea , Buckley D. Noel , Lynch Robert P.
Published: December 2024

Flow battery technology is uniquely positioned to fill the niche of long duration energy storage that will be needed to enhance grid reliability and power quality. Vanadium Flow Batteries (VFBs) and other flow battery technologies use carbon as their electrodes. The behaviour of carbon as an electrode is complex and there is considerable variation in the literature regarding the kinetics of flow battery reactions at carbon electrodes.

The electrochemical response of a carbon electrode towards redox reactions is known to be improved after electrochemical treatments. For the past decade we have investigated the effect of electrochemical treatment on the electrode activity of carbon towards vanadium redox reactions. We have reported that cathodic treatment in acidic solution enhances the kinetics of the positive (VIV-VV) electrode in VFBs but inhibits the kinetics of the negative (VII-VIII) electrode, while anodic treatment inhibits the kinetics of the positive electrode but enhances the kinetics of the negative electrode1-3. We also showed that the activity of carbon-based material is strongly dependent on the surface history, and in particular on the most positive and the most negative potential used to treat an electrode4.

In this presentation, we report some interesting results from our investigations of carbon electrode pretreatment in H2SO4. The cyclic voltammetry behavior which we observe shows a remarkable correlation with kinetics measurements in vanadium-containing electrolytes. We believe that our results provide a novel method of investigating the behavior of active sites on carbon electrodes. This is particularly important in the context of flow battery electrodes but may also, in a much broader context, provide a route to understanding the electrocatalytic behavior of carbon electrodes in many other applications.

References.

A. Bourke, M. A. Miller, R. P. Lynch, X. Gao, J. Landon, J. S. Wainright, R. F. Savinell and D. N. Buckley, J. Electrochem. Soc.
163, A5097 (2016).

A. Bourke, M. A. Miller, R. P. Lynch, J. S. Wainright, R. F. Savinell and D. N. Buckley, J. Electrochem. Soc., 162, A1547 (2015).

M. A. Miller, A. Bourke, N. Quill, J. S. Wainright, R. P. Lynch, D. N. Buckley and R. F. Savinell, J. Electrochem.
Soc., 163, A2095 (2016).

M. Al Hajji Safi, A. Bourke, D. N. Buckley, R. P. Lynch, ECS Trans., 109, 67-84 (2022).
Direct Surface Sulfidation of Layered Metal Hydroxides Using Bis(trimethylsilyl) Sulfide
Authors: Muramatsu Keisuke , Sugimoto Wataru
Published: December 2024

Layered transition metal hydroxides have been extensively researched for applications such as electrodes and electrocatalysts owing to their tunable redox properties based on various cation compositions. To control critical physical properties such as chemical adsorption and conductivity in these applications, topochemical control of anion compositions will be effective. While many reports have demonstrated the synthesis of nitrides and sulfides by reacting layered metal hydroxides with different anion sources, the existing methods often result in the formation of microcrystalline aggregates.1 Even under mild conditions, core-shell structures are formed through dissolution and reprecipitation.2 Hence, it is necessary to develop a new approach that allows direct reaction of anionic species with metal species in the crystal framework. In this study, we propose a reaction using bis(trimethylsilyl) sulfide ((Me3Si)2S), commonly used for preparation of metal sulfide nanoparticles,3 as a sulfur source for the direct sulfidation of layered metal hydroxides.

Layered nickel hydroxide nanocrystals (Ni(OH)2nc) were reacted in a liquid phase with a desired amount of (Me3Si)2S. The product is denoted as S_Ni(OH)2nc. X-ray diffraction (XRD) patterns of S_Ni(OH)2nc shows that all peaks corresponded to β-Ni(OH)2, and no new peaks appeared. The original Ni(OH)2nc was an aggregate of hexagonal plate-shaped nanocrystals with sizes of 80 to 200 nm and thicknesses of 15 to 25 nm, and no significant changes in crystal morphology after the reaction were observed after the reaction. In contrast to the blue-green color of Ni(OH)2nc, S_Ni(OH)2nc was obtained as a blue-gray powder. X-ray photoelectron spectroscopy (XPS) spectra of S_Ni(OH)2nc revealed new photoelectron peaks attributed to S2p, which were within the range of sulfide compounds. Scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM-EDS) mapping detected sulfur species at locations corresponding to plate-like crystals. Furthermore, quantitative analysis by EDS estimated the atomic ratio of sulfur to nickel in S_Ni(OH)2nc to be 5.0%, which corresponded well to the proportion of anion sites on the outer surface of Ni(OH)2nc. These results suggest that (Me3Si)2S reacts with Ni on the outer crystal surface of Ni(OH)2nc to form nickel sulfide compounds. Thus, sulfidation of layered metal hydroxides by (Me3Si)2S is effective in controlling the anion composition on crystal surfaces.

(1) Y. Guo, T. Park, J.W. Yi, J. Henzie, J. Kim, Z. Wang, B. Jiang, Y. Bando, Y. Sugahara, J. Tang, and Y. Yamauchi, Adv. Mater., 2019, 31, 1807134. (2) B. Wang, C. Tang, H.-F. Wang, X. Chen, R. Cao, Q. Zhang, Adv. Mater., 2019, 31, 1805658. (3) R. García-Rodríguez, M. P. Hendricks, B. M. Cossairt, H. Liu, and J. S. Owen, Chem. Mater., 2013, 25,1233.
Evolution of Cu-Co-Fe Prussian Blue Analogues with Open Nanoframe Architectures for Enhanced Electrochemical Capacitive Deionization
Authors: Guo Yanna , Chen Zeqiu , Jiang Dong , Li Yulin , Zhang Wenyang , Kozumi Kazuya , Kang Yunqing , Yusuke Yamauchi , Sugahara Yoshiyuki
Published: December 2024

Water scarcity is one of the most severe global challenges in our generation. Electrochemical capacitive deionization (CDI), a green water desalination system, has emerged as a promising technology for producing clean water due to its low energy consumption and environmentally friendly. Prussian blue analogues (PBAs), a class of coordination compounds which can accommodate Na+ ions into their nanoscale interspaces of skeleton frameworks, promise their extraordinary functionalities in CDI technology. Volume expansion that occurs during the ion-insertion/extraction process and inherent low conductivity of PBA electrodes, however, still inevitably lead to their sluggish desalination kinetics and capacity fading. Herein, preparation of trimetallic PBA containing copper, cobalt, and iron with nanoframe superstructures (CuCoFe-PBA NFs) via a multi-step in-situ structural conversion is reported. Comparable experiments indicate that successful conversion via this route is attributable to a self-templated epitaxial growth triggered by the additional introduction of Cu ions into the reaction system. The optimal composition and three-dimensional (3D) opened nanoframe structure of CuCoFe-PBA NFs offer the electrode with rich redox active species, abundant accessible adsorption sites, and fast ion transport that enhance its capacitive deionization (CDI) performance. As a result, the CuCoFe-PBA NFs demonstrate an exceptional CDI performance with a desalination capacity of 46.8 mg g-1 at an applied potential of 1.4 V and superior cyclability with negligible decay on the desalination capacity even after 100 cycle tests.

Figure 1
The g-C3N4 @Cdo/ZnO Ternary Composite: Photocatalysis, Kinetics and Acute Toxicity Studies
Authors: Berhanu Sintayehu Berhanu
Published: December 2024

Binary and ternary nanocomposites (NCs) were synthesized by precipitation and through facile one-pot ultrasonic

assisted methods to serve as photocatalysts for treatment of wastewater as well as their toxicity toward aquatic

organism (Nile tilapia). The crystalline structure, band gap energy and functional groups of these materials were

characterized by XRD, UV-Vis, and FT-IR instrumental techniques. Based on the UV-Vis study, the band gap of

ZnO/CdO (ZC) to hybrid g-C3N4@ZnO/CdO (GZC) nanocomposite was reduced from 3.41 eV to 3.21 eV, sug-

gesting good charge carrier mobility. Photocatalytic degradation performances of ZC and GZC were further

assessed by conducting methyl red (MR) photodegradation reaction using UV light. The highest degradation

efficiency was achieved for GZC NCs (97.78%) than ZC (89.41%) in 2 h. The values of free energy, and enthalpy

were negative; showing spontaneous photodegradation of MR. The kinetics of photodegradation follows pseudo-

first-order reaction with rate order of 0.0713 min1 . The HO* and O2 * were main active species for the photo-

degradation of MR. The toxicity of NCs calculated and the lethal concentration (LC50 ) was 113 ppm after 12 h.
Structural Origins of High Performance in Partially Disordered Li- and Mn-Rich Cathodes
Authors: Anand Shashwat , Mishra Tara , Zhong Peichen , Jadidi Zinab , Chen Tina , Ceder Gerbrand
Published: December 2024

The discovery of Li-excess cation-disordered rocksalt (DRX) cathodes lifts the restriction on a specific Li-TM ordering to enable the exploration of cathode materials in a chemical space of earth abundant materials. Recently, phase transformation in disordered Li- and Mn-rich rock-salts (Li1.05Mn0.85Ti0.1O2) have been shown to form high energy density, capacity retention and rate capability cathode materials (named delta) with partial Spinel-like ordering at short coherence lengths.1 However, atomic scale structural features of the material which determine its high performance such as extent of disordering and Li-transport pathways are not well-understood yet. We first perform symmetry analysis to reveal aspects of the transformation which are central to the nanoscale domain formation in the delta phase and crucial for characterizing its structure. We develop a simple structural order parameter to distinguish the Spinel-like ordering from the disordered rocksalt (DRX) structure, characterizing the extent of disordering, sizes and spatial location of the domains as the transformation proceeds. We perform multi time-scale Kinetic Monte Carlo Simulations for understanding the DRX-to-delta transformation. Our results reveal both thermodynamic and kinetic factors causing the formation of spinel-like nano domains and spatial distribution of Ti and Li-excess in the delta phase of Li1.05Mn0.85Ti0.1O2, providing key insights into its high rate capability. Our simulations reveal principles for designing the structure at nanoscale and electrochemical performance through changes in composition.

Cai, Z.; Ouyang, B.; Hau, H.-M.; Chen, T.; Giovine, R.; Koirala, K. P.; Li, L.; Ji, H.; Ha, Y.; Sun, Y.; Huang, J.; Chen, Y.; Wu, V.; Yang, W.; Wang, C.; Clément, R. J.; Lun, Z.; Ceder, G. In Situ Formed Partially Disordered Phases as Earth-Abundant Mn-Rich Cathode Materials. Nat. Energy 2023, 1–10. https://doi.org/10.1038/s41560-023-01375-9.
Understanding High Voltage Electrolyte Reactivity on Cation-Disordered Rock Salt Cathodes
Authors: Rastinejad Justin , McCloskey Bryan D.
Published: December 2024

Li-ion battery demand is expected to increase dramatically to meet rapidly increasing energy storage demands. To address the expense and scarcity of cobalt and nickel used in current layered oxide cathodes, alternative cathode materials that rely on earth-abundant transition metals must be explored. Promising such materials are cation-disordered rocksalt (DRX) oxides, particularly those that are comprised of manganese and titanium, along with lithium excess to allow for high reversible capacities (>300 mAh/g). A substantial fraction of extractable lithium capacity in DRX materials occurs at high voltages, creating high energy density, but also leading to deleterious degradation processes. Recent studies have observed reactivity of the DRX surface when cycled to high voltages: >25% of transition metals migrating out of the cathode and continuous evolution of CO2 after 150 cycles [1]. 13C labeling has identified the carbonate electrolyte as the primary source of the CO2 after the first cycle [2]. This reactivity leads to a sharp increase in impedance and rapid capacity fade [1]. However, the exact cause of high voltage reactivity is still not fully understood for the electrolyte – DRX interface.

In this study, we quantify the surface reactivity of select electrolyte – DRX systems using operando gas measurements and inductively coupled plasma – optimal emission spectrometry (ICP-OES). Through this method, we can identify what electrolyte and DRX properties have the largest influence on surface reactivity. To monitor surface reactivity of the electrolyte, differential electrochemical mass spectrometry (DEMS) was used to quantify evolution of CO2 and other gaseous products during cycling. To track the surface reactivity of the DRX, ICP-OES was used to quantify transition metal dissolution. We show that ethylene carbonate oxidation is particularly problematic above 4.4 V, and that processes involving the conductive carbon, as well as Mn and O redox are culpable. The results of this study provide insight into the primary causes of capacity fade in DRX-based batteries, informing future designs of the electrolyte, DRX, and other cathode materials.

[1]: Matthew J. Crafton et al 2024 J. Electrochem. Soc.
171 020530

[2]: Manuscript in Preparation: Tzu-Yang Huang et al
2024. Chem. Of Mat. (Manuscript ID: cm-2024-007563)