bluuebunny/crossref_metadata_2025 huggingface dataset:
Maximizing Energy Efficiency of Porous Electrodes Via Topology Optimization
Authors: Roy Thomas , Salazar de Troya Miguel A , Worsley Marcus Andre , Beck Victor A
Published: July 2022

Conventional porous electrodes normally consist of homogeneous, unorganized collections of small-scale particles that offer little opportunity in terms of designing higher performance electrochemical devices. Indeed, simply increasing the surface area to maximize activity is usually detrimental to electrochemical transport because of increased tortuosity. Luckily, modern advanced and additive manufacturing methods present an opportunity for porous electrode structures that span length scales. In this presentation, we consider topology optimization as a tool to inform the design of porous electrodes. We introduce an optimization framework for a generic porous electrode model and apply it to two applications: an electrode driving a steady Faradaic reaction, and a transiently operated electrode in a supercapacitor. In each case, computationally designed electrodes that maximize energy efficiency are shown to outperform monolithic, homogeneous electrodes. For low effective ionic conductivity materials, the optimized designs exhibit hierarchical features with macropores that facilitate ionic transport.
(Invited) Composite Lithium-Conductive Latp+Pvdf Membranes: Development, Optimization, and Applicability for Li-Hybrid Redox Flow Batteries
Authors: Stevenson Keith J , Romadina Elena , Akhmetov Nikita , Ovsyannikov Nikolay , Gvozdik Nataliya , Pogosova Mariam
Published: July 2022

Lithium metal hybrid flow batteries (Li-HFBs) represent a very promising type of RFBs distinguished by improved energy and power density and simplified set-up. Unfortunately, the absence of a highly conductive and stable membrane hinders Li-HFBs evolution. This talk will describe the development of Li1.3Al0.3Ti1.7(PO4)3-poly(vinylidene fluoride) composite membranes and will demonstrate their applicability for Li-HFBs. The easily fabricated membranes demonstrate high ionic conductivity of 3.4 ∙ 10-4 S cm-1 (in contrast with 0.74 and 0.16 ∙ 10-4 S cm-1 of commercially available Nafion and Neosepta, correspondingly) and improved stability towards metallic lithium. The hybrid Li-TEMPO cell with composite membrane shows stable coulombic and energy efficiency (over 95 and 73%, respectively), moderate capacity decay from 2.5 to 1.4 Ah L-1 (preliminarily associated with membrane’s permeability), and no membrane degradation after 100 charge/discharge cycles. The combination of functional features established for the proposed composite membranes makes them promising for Li-HFBs, as well as for other energy storage devices, and can potentially accelerate their introduction to the energy storage market.
Numerical Investigation of Supporting Electrolyte Using in a Vanadium Redox Flow Battery
Authors: Alphonse Phil-Jacques , Tas Mert , Elden Gülşah
Published: July 2022

The vanadium redox flow battery (VRFB) store chemical energy and generate electricity by redox reactions between vanadium ions dissolved in electrolytes. The main components of VRFB are positive and negative porous electrodes, membrane, current collectors, electrolyte, and pumps. The electrolyte is composed of vanadium species and supporting electrolytes. The supporting electrolyte has two main functions: 1) to increase the electrolyte's ionic conductivity, and 2) to deliver hydrogen ions to the positive electrode reaction. The supporting electrolytes are many kinds of an acid such as sulfuric acid, hydrochloric acid, methane sulfonic acid, etc. Some study has been done to improve the performance of VRFB a mixed electrolyte supporting. Zhang et al. proved that the stabilities of vanadium ions in sulfuric acid solution could be improved marginally by adding some additives as stabilizing agents 1. Sha et al studied the effect of organic additives on positive electrolyte for vanadium redox battery They found that the energy efficiency for the electrolyte with D-sorbitol was higher than that electrolyte without additives 2. Chang et al investigated coulter dispersant IIIA additive into the positive electrolyte 3. The obtained result showed that the coulter dispersant IIIA increased the stability of the positive electrolyte in VRFB.

According to the authors' knowledge, there is no a numeric study that comparing, the supporting electrolyte used in a VRFB. The aim of this study is to perform comparatively a numerical analyze of the supporting electrolyte of H2SO4 and HCl in the negative and positive electrodes. To achieve these objectives a two-dimensional model is developed with COMSOL Multiphysics under some assumptions and boundary conditions. The electrolyte potential is deeply investigated through the state of charge (SOC).

The simulation result shows that the difference in the electrolyte potential between the supporting electrolyte of H2SO4 and HCl, the supporting electrolyte of H2SO4 possesses a higher potential compared to the HCl. This phenomenon is strongly related to the number of hydrogen protons delivered by the supporting electrolyte of H2SO4 which is more compared to that of HCl 4.

Acknowledgement

The authors would like to thank the Scientific Research Projects Unit of Erciyes University for funding under the contract no: FDK-2019-9340.

Reference

1. J. Zhang et al., J. Appl. Electrochem., 41, 1215–1221 (2011).

2. S. Li et al., Electrochim. Acta, 56, 5483–5487 (2011).

3. F. Chang, C. Hu, X. Liu, L. Liu, and J. Zhang, Electrochim. Acta, 60, 334–338 (2012).

4. H. Yan et al., Membranes (Basel)., 10, 1–15 (2020).

Figure 1
Surface Properties of Graphite for Electrocatalysis of Vanadium Redox Reactions
Authors: Radinger Hannes , Scheiba Frieder , Hansen Heine Anton , Ehrenberg Helmut
Published: July 2022

The interfacial processes controlling charge transfer in vanadium redox reactions at graphite electrodes are still poorly understood. Accurate knowledge of the underlying mechanism is mandatory to improve the efficiency of conversion from electrical to chemical energy and vice versa. Various surface modifications are known to improve the catalytic activity of graphite by introducing active sites. Differentiating between influences on structural properties by activation processes is difficult due to the heterogeneity of the material and the interplay of microstructural changes and surface chemistry. This requires the application of multiple analytical tools and the systematic correlation with electrochemical results. In this way, our group has recently demonstrated that the 30-year-old mechanism involving surface oxygen does not stand up to thorough investigation. Instead, we primarily identified lattice defects such as edges and carbon vacancies as the actual origin of enhanced electron transfer kinetics. We have studied these defects on various scales and introduced an onion-like model to explain why thermal treatment is effective but care must be taken to remove the material from the oxidizing atmosphere at the right time. Otherwise abundant oxygen groups and dull pore edges will counteract the intended activation. Special attention was subsequently paid to the interaction of microstructure and electronic states, establishing a relationship of catalytic activity and the schematic band structure. Whereas edges decrease the work function of graphite, vacancies increase the density of states close to the Fermi level. Using real and model electrodes, we distinguished between the architecture of structural disorder and found zigzag edges to provide superior kinetics over armchair edges. Our experimental studies were complemented by theoretical density functional theory calculations to learn about the adsorption properties of electrolyte species with regard to the orientation of graphite. The potential-dependent structural changes and coordination spheres of the electrode and the near-electrode electrolyte were investigated by operando Raman spectroscopy to elucidate the interaction between vanadium and carbon.
(Keynote) Spectroscopic and Theoretical Studies of HOR/HER Electrochemical Interfaces
Authors: Shao Minhua , Zhu Shangqian , Qin Xueping
Published: July 2022

Hydrogen fuel cells and water splitting electrolyzers are clean electrochemical devices toward the sustainable utilization of H2 as an energy carrier to replace traditional fossil fuels, in which hydrogen oxidation and evolution (HOR/HER) are two key reactions. Regardless of the apparent simplicity of these two reactions that involve *H as the only surface intermediates, the reaction mechanisms are still under intensive debate.

It has been well reported that the HOR/HER kinetics in alkaline media is about two orders of magnitude slower than that in acid environment on Pt-group metals, while the reasons are not fully revealed. In this work, power surface-enhanced infrared absorption spectroscopy (SEIRAS) is utilized to directly monitoring the structures of HOR/HER electrochemical interfaces in a wide pH range. Through the changes of vibrational wavenumbers of Pt-H and O-H stretching, we find both the weakened *H and H2O binding strength on Pt as the solution pH increases, which are important contributions to the lowered reaction kinetics. Through constructing density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulation models that contain various interfacial parameters, HER activation energy barriers as a function of pH are further elaborated.

In addition, Ru adatoms have been found to significantly accelerate HER/HOR kinetics on Pt in alkaline media. However, the promotion mechanism is unclear. Through directly monitoring the vibrational features of Pt-H and Ru-H on Ru-modified Pt thin films, we find that the HER/HOR kinetics is proportional to the Ru coverage, which unambiguously demonstrates Ru overlayer as the true active sites, instead of an auxiliary to Pt through the oxophilicity or alloying effects as proposed previously. DFT calculations illustrate that the strain and electronic effects of the Pt substrate lead to the more suitable binding energies of *H and *OH on the Ru overlayer, which lower the activation barrier of the rate-determining Volmer step.

The authors acknowledge the support from Hong Kong Research Grant Council (16308420, 16310419, C6011-20G, and HKUST PDFS2021-6S08), Hong Kong Branch of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (SMSEGL20SC01), and Hong Kong Innovation and Technology Commission (ITC-CNERC14EG03).
(Keynote) Effect of the Surface Charge on the Oxygen and Hydrogen Peroxide Reduction Reactions
Authors: Herrero Enrique , Feliu Juan , Briega Valentin
Published: July 2022

The electrochemical behavior of hydrogen peroxide, which is a possible intermediate of the oxygen reduction reaction (ORR), has been investigated on platinum single crystal electrodes containing terraces with (111) symmetry separated by monoatomic steps with either (110) or (100) symmetry in different pH solutions [1]. On these electrodes, a decrease, in absolute value, of the reduction current at low potentials is observed. The potential at which the decrease is observed, can be correlated with the potential of maximum entropy (pme) of the double layer formation on the terraces. In addition, it is possible to relate the peak appearing at potentials below 0.3 V (RHE) to the local pme in the steps.

By performing experiments at different pH values, up to pH ≈ 5, it is observed that the inhibition potential on the terraces shifts 59 mV per pH unit towards more positive potentials, in line with what was observed for the pme in laser-induced temperature jump experiments. For the possible explanation of this phenomenon, it must be taken into account that OH adsorption may influence this trend when the pme values are close to the potentials corresponding to OH adsorption. From results obtained in alkaline medium, it is clear that the surface charge plays an important role in this inhibition of the limiting diffusion current.

Finally, the comparison of the results obtained under similar conditions for the hydrogen peroxide and oxygen reduction reactions suggests that the formation of hydrogen peroxide as an ORR intermediate is less favored with increasing pH. As a consequence, there must be a bifurcation in the ORR mechanism prior to peroxide formation. These results agree with previous results [2], which indicate that ORR involves different steps in which several bifurcation points may exist. Depending on the experimental conditions, the reaction may follow a different reaction pathway [3].

References.

(1) Briega-Martos, V.; Herrero, E.; Feliu, J.M. Electrochimica Acta
2020
, 334, 135452.

(2) Gomez-Marin, A.M.; Feliu, J.M. ChemSusChem
2013, 6, 172-176.

(3) Briega-Martos, V.; Herrero, E.; Feliu, J.M. Chinese J. Catal.
2020, 41, 732-738.
(Invited) Correlation between the Porosimetric Features, Morphology, “Ex-Situ” and “in-Situ” electrochemical Performance of Hierarchical “Core-Shell” Carbon Nitride Pt-Alloy ORR Electrocatalysts
Authors: Negro Enrico , Vezzu Keti , Lorandi Francesca , Pagot Gioele , Zuliani Giacomo , Bang Yannick , Kulesza Pawel J. , Rutkowska Iwona A. , Di Noto Vito
Published: July 2022

The widespread commercialization of proton-exchange membrane fuel cells (PEMFCs) is still bottlenecked by the high loading of platinum-group elements (PGMs), typically platinum, in the cathodic electrocatalytic layer. One strategy to overcome the sluggish kinetics of the oxygen reduction reaction (ORR) taking place at the PEMFC cathode is to increase the mass activity of Pt by implementing Pt-alloy electrocatalysts (ECs) [1]. This strategy allows to decrease the overall Pt loading in the membrane electrode assembly (MEA), the crucial functional component at the heart of the PEMFC.

This contribution discusses “core-shell” hierarchical ECs (H-ECs) consisting of: (i) a hierarchical “core” comprising a blend of nanostructured carbons, that are covered by (ii) a carbon nitride (CN) “shell” wherein Pt-alloy active sites are stabilized by C- and N- ligands in “coordination nests” [2]. The active sites are based on Pt together with Ni and Cu as “co-catalysts” to enhance the ORR kinetics [3]. The bulk of the support of the H-ECs is minimized to promote mass transport phenomena.

The morphology of the H-ECs is probed by ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM), and is discussed in relation to the synthetic parameters and chemical composition. In a second step, nitrogen physisorption techniques are used to evaluate the porosimetric features of the H-ECs, including the specific surface area and the size distribution of the pores. The porosimetric and morphological features are correlated with the electrochemical performance of the H-ECs as measured: (i) “ex-situ”, via cyclic voltammetry with the thin-film rotating ring-disk electrode method (CV-TF-RRDE); and (ii) in single PEMFC under operating conditions as a function of the partial pressure of oxygen in the cathodic feed. A new framework is finally proposed to rationalize and quantify the porosity-morphology-performance correlation for the H-ECs.

References

[1] Y. Sun, S. Polani, F. Luo, S. Ott, P. Strasser, F. Dionigi. Nature Commun. 12, 5984 (2021).

[2] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn. Electrochem. Soc. Interface, 24, Summer 2015, 59-64 (2015).

[3] V. Di Noto, E. Negro, A. Bach Delpeuch, F. Bertasi, G. Pagot, K. Vezzù, Patent application PCT/EP2017/084801 (2017).

Acknowledgements

The described research has received funding from: (a) the European Union's Horizon 2020 research and innovation programme under grant agreement 881603; (b) the project "Advanced Low-Platinum hierarchical Electrocatalysts for low-T fuel cells" funded by EIT Raw Materials; and (c) the project "Hierarchical electrocatalysts with a low platinum loading for low-temperature fuel cells e HELPER" funded by the University of Padova.
Unravelling the Influence of Oxygen on the Degradation Mechanisms of Fe-N-C Oxygen Reduction Reaction Catalysts
Authors: Kumar Kavita , Asset Tristan , Atanassov Plamen , Jaouen Frederic , Dubau Laetitia , Maillard Frederic
Published: July 2022

Pyrolyzed iron-nitrogen-carbon materials (Fe-N-C) comprising mostly atomic Fe-Nx moieties are the most mature class of noble metal free catalysts for the oxygen reduction reaction (ORR) in acidic media. Such catalysts show excellent performance in proton exchange membrane fuel cell (PEMFC), approaching that of platinum-based catalysts. [1] However, an important performance loss is observed during operation, in conditions mimicking those of a PEMFC. [2] To shed fundamental light onto the degradation mechanisms at stake, two different Fe-N-C materials were prepared, one using a metal organic framework (MOF) and the other a sacrificial support method (SSM), and are labelled Fe-N-C_MOF and Fe-N-C_SSM, respectively. These materials were characterized before and after two different accelerated stress tests (ASTs: 10 k cycles, 0.6-1.0 V vs. RHE, 3s-3s, 0.1 M H2SO4, 80°C) under Ar or O2 atmosphere. Stronger degradation and higher ORR mass activity loss were observed when the AST is performed in O2
vs. Ar-saturated acidic electrolyte. For AST under Ar condition, physicochemical characterisations revealed a demetallation process and the eventual occurrence of a clustering mechanism whereas for AST performed in O2 atmosphere, a decrease of the Fe content and the formation of Fe oxide particles was observed (Figure 1).

Keywords: Electrocatalysis, Fe-N-C, Oxygen Reduction Reaction, Durability, PEMFC

Acknowledgements

These studies were financed by the French National Research Agency in the frame of the CAT2CAT (grant number n°ANR-16-CE05-0007) and the ANIMA (grant number n°ANR-19-CE05-0039) projects. References

[1] E. Proietti, F. Jaouen, M. Lefèvre, N. Larouche, J. Tian, J. Herranz, J. P. Dodelet, Nat. Commun.
2011, 2, 416.

[2] Y. Shao, J. P. Dodelet, G. Wu, P. Zelenay, Adv.
Mater.
2019, 21, 1807615.

[3] K. Kumar, T. Asset, X. Li, Y. Liu, X. Yan, Y. Chen, M. Mermoux, X. Pan, P. Atanassov, F. Maillard, L. Dubau, ACS Catal.
2021, 11, 484-494.

[4] K. Kumar, P. Gairola, M. Lions, N. Ranjbar-Sahraie, M. Mermoux, L. Dubau, A. Zitolo, F. Jaouen, F. Maillard, ACS Catal.
2018, 8, 11264-11276.

[5] K. Kumar, L. Dubau, M. Mermoux, J. Li, A. Zitolo, J. Nelayah, F. Jaouen, F. Maillard, Angew.
Chem.
2020, 132, 3261-3269.

Figure 1
(Keynote) Roles of Oxygen Vacancies in Metal Oxide Photocatalysts and Electrocatalysts
Authors: Wu Nianqiang
Published: July 2022

This talk concerns with the roles of oxygen vacancies in various metal oxide photocatalysts and electrocatalysts. A low level of oxygen vacancies in titanium oxide can induce shallow and deep sub-band gap Ti(III) states below the conduction band, which increases light absorption but not enhance photocatalytic activity. A high level of oxygen vacancies in metal oxides may generate an abundance of states near Fermi level and induce surface plasmon resonance.
(Digital Presentation) Catalytic Interruption Mitigates Edge Effects in the Characterization of Heterogeneous, Insulating Nanoparticles
Authors: Chung Julia , Hertler Phoebe , Plaxco Kevin , Sepunaru Lior
Published: July 2022

Single entity electrochemistry encompasses a broad collection of techniques that are used to detect and characterize single, freely diffusing analytes in solution1,2. A particular scheme in this field, “blocking” nanoimpacts, has expanded the scope of electrochemistry to the study of redox-inert materials. Here, as a particle adsorbs, it prevents charge exchange between the microelectrode with a freely diffusing electroactive redox mediator. The interpretation of these blocking results, however, is often complicated by “edge effects,” in which enhanced mass transport to the edges of microelectrodes leads to uneven current distributions3,4. To overcome this problem we introduce here the use of electrochemical amplification5. That is, we employ electrocatalytic amplification to drive a current increase, moving the rate limiting step in current generation away from the electrode surface, reducing the geometric impact of the electrode’s edges. Finite element simulations indicate that the rapid chemical kinetics introduced by this approach contributes to the amplification of the electronic signal to restore analytical precision and reliability detect and characterize the heterogeneity of nanoscale electro-inactive materials. Using this approach, which we have termed “electrocatalytic interruption,” we achieve significantly improved precision in the determination of particle size distributions.6

References

Quinn, B. M.; van’t Hof, P. G.; Lemay, S. G. Time-Resolved Elec-trochemical Detection of Discrete Adsorption Events. J. Am. Chem. Soc. 2004, 126 (27), 8360–8361. https://doi.org/10.1021/ja0478577.

Bard, A. J.; Faulkner, L. R. Electrochemical Methods: Fundamentals and Applications, 2nd ed.; Wiley: New York, 2001.

Compton, R. G.; Banks, C. E. Understanding Voltammetry (Third Edition); World Scientific, 2018.

Deng, Z.; Elattar, R.; Maroun, F.; Renault, C. In Situ Measurement of the Size Distribution and Concentration of Insulating Particles by Electrochemical Collision on Hemispherical Ultramicroelectrodes. Anal. Chem. 2018, 90 (21), 12923–12929. https://doi.org/10.1021/acs.analchem.8b03550.

Bonezzi, J.; Boika, A. Deciphering the Magnitude of Current Steps in Electrochemical Blocking Collision Experiments and Its Implica-tions. Electrochimica Acta 2017, 236, 252–259. https://doi.org/10.1016/j.electacta.2017.03.090.

Chung, J.; Hertler, P.; Plaxco, K.W.; Sepunaru, L. J. Am. Chem. Soc. 2021, https://doi.org/10.1021/jacs.1c04971.

Figure 1
Nanometric Amorphous TiO2 As an Extrinsic Pseudo-Capacitive Electrode for All-Solid-State Asymmetric Hybrid Micro-Supercapacitors: Effects on the Electrochemical Performance
Authors: Sallaz Valentin , Poulet Sylvain , Rouchou Jouhaiz , Boissel Jean-Marc , Chevalier Isabelle , Secouard Christophe , Bedjaoui Messaoud , Voiron Frederic , Lamy Yann , Oukassi Sami
Published: July 2022

On-chip solid-state micro-supercapacitors (MSCs) have gained widespread attention owing to their versatile benefits, including high power density and long cycle life1,2. Recently asymmetric hybrid microsupercapacitors (AsHMSCs) introducing a charge storage mechanism based on both faradaic reaction and electric double-layer phenomena have been considered to increase the energy density. Within this context, the selection of electrode materials and their interaction at the interface with the electrolyte is a key issue to optimize the AsHMSC electrochemical performance.

In this work, nanometric (5-20 nm thick) amorphous TiO2 films have been elaborated and characterized in liquid and solid-state electrolyte (LiPON) half-cell configurations. Interestingly, TiO2 films after LiPON deposition exhibited a constant initial amount of intercalated lithium ions for all considered thicknesses and did not require a first activation process, in comparison to the liquid electrolyte configuration. For all considered configurations, the specific capacity extracted from cyclic voltammetry and galvanostatic cycling within [0.5-3V] potential range correspond to the theoretical value expected for the Lix=1TiO2 phase at low current density. Furthermore, the cooperative effects of high Li ion intercalation kinetics and Low interfacial charge transfer resistance for 5nm TiO2 electrode (extracted from electrochemical impedance spectroscopy analysis) exhibit an outstanding specific capacity of 2mC.cm-2 at 1µA.cm-2, and high rate performance with 60% capacity holding ratio at 100µA.cm-2, thus highlighting the extrinsic pseudo-capacitive behavior of the sub 10nm electrodes.

A TiO2 5nm/LiPON 100nm/Pt AsHMSC is successfully fabricated, which achieves an operating voltage window of 3V and a specific capacity of 0.3mC.cm-2 at 1mA.cm-2.In addition, the device also exhibited a 100% coulombic efficiency even after cycling for 6000 continuous charge-discharge cycles. This work offers an approach to tune the Li ion storage properties of TiO2 by nano-engineering and gives insights into the enhancement of pseudocapacitance-assisted lithium-storage capacity.

References

Kyeremateng et al., Nature Nanotech 12, 7–15 (2017). https://doi.org/10.1038/nnano.2016.196

Sallaz et al., J. Power Sources 451, 227786 (2020), doi: 10.1016/j.jpowsour.2020.227786.

Figure 1
Evolution of Selective Contacts in Photoelectrochemical Devices
Authors: Kaufman Aaron James , Boettcher Shannon W.
Published: July 2022

The presence of a carrier selective contact is fundamental for photoelectrochemical (PEC) optoelectronic devices which convert solar energy to chemical/electrical energy. For example, during the overall water splitting (OWS) reaction in an acidic electrolyte, the generated electrons and holes must selectively transport to their respective contacts where they reduce protons and oxidize water, forming H2(g) and O2(g) respectively. Often, bare semiconductor (SEM) absorbers are poor catalysts and metals (or metal oxides) (CAT) are alternatively used, although forming a new junction with the underlying SEM. In some cases, the CAT/SEM junction does not theoretically form the required carrier selective junction. A real photocathode consisting of a p-InP and Pt junction should theoretically form an ohmic or non-selective junction, however, this photocathode efficiently reduces protons in operation. In extension, many single OWS particles decorated with cocatalysts theoretically would not form selective contacts producing sufficient open-circuit voltages required to split water (by simple thermionic-emission theory alone). This is further debated in the mechanism for carrier separation during photoelectrodeposition of catalyst in such OWS particles. Here, we exploited conductive probe microscopies and surface-sensitive spectroscopies to reveal the underlying mechanism driving carrier separation towards selective contacts such as alloying transformation and heterojunction formation in the Pt/p-InP system. Additionally, I will demonstrate the unique behavior of nanoscopic electrical contacts by individual characterization (operando and in-situ), demonstrating selectivity by a manifestation of the pinch-off effect. On the Pt/p-InP model system, individual contact selectivity, by the pinch-off effect, on a chemically controlled surface seen in Figure 1.a later evolves due to the formation of an InOx/p-InP heterojunction after operation (after CV). Furthermore, we investigate SrTiO3 as a planar model system proxy to OWS particles and show only small variation in the oxygen evolution reaction (OER) current in macroscopic cyclic voltammograms of <100> and <110> terminated surfaces (Figure 1.b). By revealing the underlying mechanisms and the degree that they play, PEC devices can be engineered utilizing an optimal absorber and catalyst whilst their pristine junction would theoretically be non-selective or producing an insufficient photovoltage.

Figure 1
(Digital Presentation) In-Situ Growth of Core@Shell Ni@Fe Doped Ni(Oxy)Hydroxide Nanoarrays on Commercial Nickel Mesh to Promote Oxygen Evolution Reaction
Authors: Jiang Tao , Razmjooei Fatemeh , Liao Hanlin , Asif Ansar
Published: July 2022

Oxygen evolution reaction (OER) is a rate-determining step in water electrolysis. Herein, we report a novel one-step oxidation-electrodeposition (OSOE) approach to generate core@shell (CS) Ni@Fe doped Ni(Oxy)Hydroxide nanoarrays based alkaline water electrolysis electrode with an outstanding OER performance that is, an overpotential of 245 mV is obtained reaching 10 mA cm–
2. The corresponding Tafel slope is 36.8 mV dec–
1. Strikingly, it delivers a Ni-based mass activity of 1336 A g–
1 and a high turnover frequency of 0.285 s–
1, over 7-fold higher than state-of-the-art IrO2. Moreover, the electrode can also survive at 500 mA cm–2 for over 500 h without apparent degradation under industrial conditions. The proficient catalysis was driven by the Fe doped Ni(Oxy)Hydroxide shell that serves as the intrinsically active site over an equally important electrically conductive metallic Ni core array. This is the first report by using OSOE to construct high performance practical catalytic electrode for alkaline water electrolysis.
Impact of Flushing Agents in Broadband Dielectric Spectroscopy (BDS) Study of Ethanol Detection By HKUST-1 Metal-Organic Frameworks
Authors: Amoah Papa K. , Redel Engelbert , Baumgart Helmut , Obeng Yaw
Published: July 2022

Traditional volatile organic compounds (VOC) detection with metal semiconductor oxide (MOS) sensing elements depends on chemical resistivity measurements which require electrical contact to the sensing materials [1]. These measurement contacts / probes are inadequate because they tend to introduce parasitic electrical errors which result in misleading reported resistivity values [2]. On the other hand, contactless broadband dielectric spectroscopy (BDS) is a potential alternative metrology [3]. In this paper, we will demonstrate that by using contactless broadband dielectric spectroscopy (BDS)-based metrology, in combination with a metal-organic framework (HKUST-1 SMOF) sensing element, we can avoid distortions in the reported resistivity values in gas monitoring, as well as develop new and unique mechanistic insights into the VOC detection. Specifically, we show that the experimental ambient influences the detection mechanism. The microwave insertion loss data (S21) shows that we lose resolution when N2 was used as the flushing agent, as compared to air, during the measurements. This suggests a possible competition between the ethanol and the N2 for the unsaturated copper centers inside the MOF. Therefore, we opted to use air as a flushing agent in the subsequent experiments. Additionally, the use of BDS enables stable VOC sensing in air at temperatures below 100 °C, which are well below the 200-300C normally used for VOC detection [1, 2].

1) Huaping Wang et al 2021 J. Phys.: Condens. Matter 33 303001

2) Chem. Soc. Rev., 2020,49, 6364-6401, https://doi.org/10.1039/C9CS00778D

3) Papa K Amoah et al 2021 J. Phys. D: Appl. Phys. 54 135104
(Invited) Flock -Flare Clock: Passive Sweat-Based Eczematous Flare Detection System
Authors: Prasad Shalini
Published: July 2022

Point-of-need platforms that work with sweat offer the advantage of self-monitoring for chronic diseases. Sweat based platform offer benefits in areas like comfort, functionality, and provide real time analysis of biomarker fluctuations in the body. For chronic conditions like Atopic Dermatitis, evaluating the severity of the disease on a case-by-case basis can help with providing an effective treatment plan. Sweat contains biomarkers like interleukin-31 and cortisol, which are biomarkers for atopic dermatitis (AD) and circadian disruption that is associated with the itching symptom of the disease. This portable detection technology is aimed at bridging the gap between assessing the severity of the disease and providing a patient-centric treatment plan. The research is envisioned to work as a wearable that can predict flares based on the biomarker levels and help with management of severe cases of AD, especially in pediatric populations.

FLOCK (flare clock) system is a novel platform that comprises of a nanoporous membrane based multilayer stack that works with passively secreted sweat. It is designed to capture eczema severity and circadian disruption caused due to its symptoms. This is aimed to be a wearable designed for efficient management of the flaring associated with Atopic Dermatitis (AD). The work presents the development of an eczematous flare tracker that detects IL-31 and cortisol levels to create an AD management platform. The platform uses electrochemical detection for tracking these biomarkers in sweat. It is sensitive to IL-31 levels in various flare-based formulations tested through simulated sweating with a detection limit of 50 pg/mL and range 50-1000 pg/mL. On-body study highlights the ability of the wearable platform to track the rise and fall in the biomarkers’ levels. These levels are well correlated to salivary levels and commercial gold standard techniques (r>0.8, R2 >0.95).
(Invited) Development of New Strategies for Bringing Photoelectrochemical Biosensing to the Point-of-Need
Authors: Soleymani Leyla , Saha Sudip , Victorious Amanda , Sakib Sadman , Zhitomirsky Igor
Published: July 2022

Photoelectrochemistry combines light excitation with electrochemical readout for lowering the bias voltage needed for performing electrochemical reactions. As a result, when used in biosensing, photoelectrochemical signal readout reduces the background signals, lowering the limit-of-detection of such biosensors. To enable photoelectrochemical (PEC) signal readout to be applied to point-of-need biosensing, we have taken a three tiered approach focused on improving the understanding of signal transduction in PEC Biosensing, developing label-free assays, and creating handheld readout platforms.

In this work, we developed a system using DNA as a nano-ruler to control the distance between plasmonic nanoparticles and PEC electrodes. This system was used to rationally-design PEC material systems for signal-on biosensing. Using this materials architecture, we developed a signal-on biosensor without target labeling for detecting DNA hybridization. This assay uses sequential DNA hybridization to generate a PEC signal. First, the DNA target is captured on probe-modified photoelectrodes. This is followed by hybridization of the unbound probes with DNA strands modified with plasmonic labels. The plasmonic label modulates the PEC signal, increasing the measured PEC current at low target concentrations. To enable biosensing at the point-of-need, we also developed a handheld PEC reader. The integration of plasmonic nanoparticles with PEC electrodes, label-free DNA assays, and handheld PEC readout paves the way toward bringing point-of-need PEC Biosensing.
Structure and Property Changes in Sulfide Solid Electrolytes with Lithiation: A First-Principles Study
Authors: Hao Wei , Hwang Gyeong S.
Published: July 2022

Sulfide-based lithium-ion conductors such as Li3PS4 (LPS) and Li10GeP2S12 (LGPS) have received considerable attention for use as solid electrolytes for rechargeable batteries because of their high ionic conductivity, wide electrochemical window, and appropriate mechanical properties. However, their wide application in all-solid-state lithium batteries is hindered by spontaneous decomposition and solid electrolyte interphase layer formation when in contact with Li metal. To better understand the structure and property changes of LPS and LGPS with lithiation, we have systematically analyzed lithiated LPS/LGPS with varying Li contents by calculating their structural, electronic, and mechanical properties with density functional theory. The variation of Li-ion conductivity in these materials with the lithiation degree is also evaluated using ab initio molecular dynamic simulations. Our results unequivocally show that Li incorporation leads to decomposition of PS4
3- and GeS4
4- tetrahedra, resulting in the formation of small P and GeP clusters, along with Li2S production. The P and GeP clusters are eventually converted to Li3P and Li15Ge4 when LPS and LGPS are fully lithiated. The structural evolution gives rise to volume expansion and band gap narrowing. Over-lithiated LPS/LGPS tends to show metallic character, which could be partly responsible for the electrolyte failure. Despite the significant structural changes, the Li ion diffusivity and conductivity in both LPS and LGPS remain at the same order of the magnitude. This work provides a better understanding of the reaction behavior of LPS and LGPS with Li metal and also insight into how to analyze the reaction at the Li metal/sulfide electrolyte interface leading to an inorganic interphase layer.
Elucidating in-Situ Lithiation Pathway of Si-C Composite Anode in Lithium Ion Battery
Authors: Lee Hyun-Jeong , Kim Hong-Kyu , Byeon Young-Woon , Ahn Jae-Pyoung
Published: July 2022

Lithiation kinetics of a Si-C composite anode for high-capacity lithium-ion batteries were investigated through in-situ lithiation with electrochemical C-V measurements using a focused ion beam. Here, we found in the lithiation procedure that Li migrates sequentially into carbon (C), nanopores, and silicon (Si) in the Si-C composite. In the first lithiation step, Li was intercalated inside C particles while spreading over the surface of the C particles. The second lithiation process occurred through the filling of nanopores existing between electrode particles that consisted of the Si-C composite. The nanopores acted as a Li reservoir during the pore-filling process. Finally, the Si particles were litheated with a volume expansion of 173%, corresponding to a 400% volume expansion of 25wt.% Si particles included in the composite anode. The nanopores did not accommodate a large volume expansion of ~400% in Si particles, because pore-filling lithiation occurred before the Si lithiation in the charging process.
Unveiling the Effects of the Diffusivity and Exchange Current Density on the Electrochemical Modeling of Lithium-Ion Battery
Authors: Lee Hyobin , Yang Seungwon , Kim Suhwan , Song Jihun , Park Joonam , Doh Chil-Hoon , Ha Yoon-Cheol , Kwon Tae-Soon , Lee Yong Min
Published: July 2022

The diffusivity and exchange current density are the two main parameters that determine both ionics and electrodics in the Newman’s battery model. Nonetheless, the values of both parameters are normally selected from eminent literatures or experimental data measured under specific conditions, furthermore, and they are occasionally overfitted to coincide with real electrochemical behaviors without sufficient consideration. Herein, the diffusivities and exchange current densities of a LiNi0.4Mn0.3Co0.3O2/Li half-cell are measured and applied to the electrochemical model using four different electrochemical techniques: galvanostatic intermittent titration technique (GITT), potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The model adopting the diffusivity and exchange current density measured in PITT and EIS, respectively, simulates the actual voltage and capacity profiles well with low errors without any fitting. Therefore, this case study helps us understand the effects of the essential parameters on the electrochemical behavior and the pros and cons of each measurement technique.
Robust Cycling of Ultrathin Li-Metal Enabled By Nitrate-Preplanted Li Powder Electrode
Authors: Jin Dahee , Roh Youngjoon , Ryou Myung-Hyun , Lee Hongkyung , Lee Yong Min
Published: July 2022

The Li metal anode has been spotlighted for large-scale battery systems such as electric vehicles (EVs) and energy storage systems (ESSs) because of its high theoretical energy density and lowest potential. However, the Li metal anode still has the several challenging issues like Li dendrite growth and many side reactions. Our strategy to this problem is to utilize Li metal powder (LMP), which has superior advantages in reducing local current and utilizing slurry-based coating process for wide-width electrodes. Nevertheless, the spherical shape of LMP with the imperfect protection layer can be lost during the long-term cycling, which leads to dead particles formation and ununiform Li distribution.

In this work, we present a LMP electrode having pre-planted nitrates (LN-LMP). The LiNO3 additive in the LMP electrode can chemically replace the native layer with the uniform Li3N-rich passivation layer on the surface during the simple slurry mixing process. Furthermore, residual LiNO3 was continuously released toward electrolyte, thereby repairing the SEI during cycling. As a result, the 20 µm‐thick LN‐LMP electrodes exhibited the robust cycling performances compared to control cells with conventional LMPs and LiNO3‐containing electrolytes.
3D Modeling on Diffusion-Dependent Graphite-Silicon Electrode for All-Solid-State Batteries
Authors: Jung Seungwon , Kim Ju Young , Park Joonam , Song Jihun , Lee Yong Min
Published: July 2022

The novel electrode design, which is a diffusion-dependent electrode structure composed only of active materials, can theoretically realize high energy density. The diffusion-dependent electrode structure can transport lithium ions in the entire electrode through lithium-ion diffusion between the active material particles unless the connectivity between the active material particles is cut off. However, since the electrode structure transfers ions through diffusion, if the thickness of the electrode is too thick, there is a possibility that the performance may have deteriorated. For this purpose, by using not only graphite but also silicon particles, it is possible to have a thin electrode structure compared to the same capacity.

In this study, graphite-silicon diffusion-dependent electrode according to the silicon particle size is formed into a digital three-dimensional electrode structure and based on this, electrochemical simulation and analysis of an all-solid-state battery having a diffusion-dependent electrode are performed. The importance and cause of the size of silicon particles in the graphite-silicon diffusion-dependent electrode will be investigated.

Reference

Diffusion-dependent graphite electrode for all-solid-state batteries with extremely high energy density,
ACS Energy Letters
, 5(9) (2020) 2995-3004

Revisiting TiS2 as a diffusion-dependent cathode with promising energy density for all-solid-state lithium secondary batteries,
Energy Storage Materials
, 41 (2021) 289-296
A Low-Cost and Green Si-Based Anode Material for Lithium-Ion Batteries
Authors: Heitz Alexandre , Vanpeene Victor , Herkendaal Natalie , Soucy Patrick , Douillard Thierry , Roué Lionel
Published: July 2022

The conception of cheaper and greener electrode materials is critical for Li-ion battery manufacturers. In this study, it is shown that a by-product of the carbothermic reduction of SiO2 to Si, containing Si, SiC and C materials, can be valorized as a low-cost and high-capacity anode material for Li-ion batteries after an appropriate high-energy ball milling treatment. The latter results in the production of a micrometric powder (D50 ~1 mm) in which submicrometric SiC inclusions are embedded in a nanocrystalline/amorphous Si matrix. Such a microstructure prevents the deleterious formation of c-Li15Si4 phase, which is well known to accentuate particle cracking. As a result, the electrode is able to maintain a capacity >1000 mAh g-1 (>3 mAh cm-2) over 100 cycles. Moreover, calendering has no negative impact on the electrode performance. However, a significant and irreversible increase of the electrode mass and thickness was observed over cycling, which is mainly attributed to the accumulation of SEI products.

In order to have deeper insights into the microstructural evolution of the electrode during cycling, a focused ion beam (FIB) milled microcavity (45×20×50 µm3) was created in the center of the pristine electrode. This cavity was observed by SEM at different cycling periods of a single electrode (Fig. 1a). This investigation method allows following the same electrode along different steps of its cycling, nearly as for an in-situ method. Additionally, backscattered-electron (BSE) imaging was performed on broad ion beam (BIB) polished cross-section of the electrode after different periods of cycling (Fig. 1b). The morphological change is characterized at the electrode and particle scales by monitoring the thickness, mass, porosity and macrocracking of the electrode, SEI layer thickness and particle morphology. On the basis of these investigations, a more comprehensive view of the degradation phenomena of the electrode is established.

Figure 1
A Novel Electrochemical Method to Extract Lithium from Aqueous Solutions
Authors: Brabson Logan , Huang Po-Wei , Filippas Alexandros , Liu Nian
Published: July 2022

Increasing demand for lithium has been largely spurred by the rapid growth of lithium-ion batteries, most notably in electric vehicles. The need for lithium will continue to increase as demand for safe, reliable, and sustainable energy grows. Global lithium production more than tripled between 1995 and 2008 to nearly 140,000 tons, and lithium demand is projected to reach as high as 1.6 million tons by 2030 with the rise of electric vehicles. Unfortunately, the global land-based lithium supply is maldistributed. A scalable electrochemical route to lithium extraction from brines and seawater is investigated. The oceans represent a nearly infinite lithium supply, containing approximately 230 billion tons of lithium compared to just 14 million tons on land, albeit at very low concentrations of approximately 0.17 ppm.

A four-step electrochemical lithium extraction method is presented. The working lithium iron phosphate (LFP) electrode is first inserted into the lithium-containing brine or seawater, and a negative current is applied to the system. During discharge, lithium ions intercalate into the working electrode. Next, the electrode is placed in a recovery solution, and the system is charged to release the lithium on the electrode surface. The lithium-free working electrode is then reused in another cycle. Once a substantial lithium concentration is achieved in the recovery solution following several cycles, soda ash is added to precipitate the lithium ions as lithium carbonate, the working form of lithium in many battery applications. The working electrode is surface treated with a lithium-selective polymer (LSP) coating to exclude larger, more concentrated metal ions such as sodium from intercalating to the electrode surface. This work explores the effectiveness of crown ethers such as Dibenzyl-14-crown-4 as LSPs.

The combination of our electrochemical extraction process and a focus on enhancing selectivity shortens the lithium production time from years to days and presents a promising image for the future of lithium mining. The ability to extract lithium from the oceans with nominal energy requirements and environmental impacts could revolutionize the lithium mining and battery industries.
Single Crystal Copper and Gold Alloys for the Plasmonically Enhanced CO2 Reduction Reaction
Authors: Adserias Albert , Leach Gary W.
Published: July 2022

Chemical fixation of carbon dioxide (CO2) into chemical fuels has raised a lot of interest due to its role in removing greenhouse gasses from the atmosphere to store them as a potential source of energy. CO2 removal techniques have been widely studied and are of great interest because they can be used synergistically as a low-cost source of carbon to supplement and support the existing chemical synthesis of feedstocks and hydrocarbon fuels. One of the most common approaches to the remediation of atmospheric CO2 is the electrochemical reduction of CO2. We have been studying the formation of copper (Cu) films and its alloys with gold (Au). Metal alloys have been shown to exhibit interesting properties to enhance chemical processes beyond those of their individual components, improving the applications in the plasmonic and catalysis fields.

Cu and Au are both excellent plasmonic and catalytic materials that show tunable optical properties, strong absorptions in the visible and near infrared, and catalytic activity. However, the applications of Cu materials alone are limited due to Cu’s chemical instability and tendency to oxidation, which inhibits their plasmonic properties and reduces their catalytic performance. By alloying Cu with Au, we have overcome copper’s chemical instability and improved the catalytic properties due to synergistic effects.

As a result of our studies, we have also developed a method to deposit Cu2O single crystal film, a material that exhibits semiconductor properties and opens a new line of opportunities for plasmonic applications. In this poster, we will show an overview of our results and discuss the potential applications to plasmonic electrocatalysis and sensors.