Anodic Layer Research Articles

Ultrathin ALD Coatings of Zr and V Oxides on Anodic TiO2 Nanotube Layers: Comparison of the Osteoblast Cell Growth.

The current study investigates and compares the biological effects of ultrathin conformal coatings of zirconium dioxide (ZrO2) and vanadium pentoxide (V2O5) on osteoblastic MG-63 cells grown on TiO2 nanotube layers (TNTs). Coatings were achieved by the atomic layer deposition (ALD) technique. TNTs with average tube diameters of 15, 30, and 100 nm were fabricated on Ti substrates (via electrochemical anodization) and were used as primary substrates for the study. The MG-63 cell growth and proliferation after 48 h of incubation on hybrid TNTs/ZrO2 and TNTs/V2O5 surfaces was evaluated in comparison to the uncoated TNTs of each diameter. The density of viable MG-63 cells was assessed for all the TNT surfaces, along with the cell morphology and the spreading behavior (i.e., the cell length). The ultrathin coatings retained the original morphology of the TNTs but changed the surface chemical composition, wettability, and cell behavior, whose interplay is the subject of the present investigation. These findings offer interesting views on the influence of the composition of biomedical implant surfaces, triggered by ALD ultrathin coatings on them. The outcomes of this work shed light on the assessment of the biocompatibility of the two different ALD coatings.

Surface-Treated Composite Polymer as a Stable Artificial Solid Electrolyte Interphase Layer for Lithium Metal Anodes

Surface-Treated Composite Polymer as a Stable Artificial Solid Electrolyte Interphase Layer for Lithium Metal Anodes

Al2O3-Induced Phase Conversion Regulation of WS2 Anode Enhances the Lithium Storage Reversibility.

WS2 is an attractive anode in alkali metal ion batteries (AMIBs) due to its 2D-layered structure and high theoretical capacity. However, the shuttle effect of sulfur and the spontaneous growth of W nanoparticles are key issues that limit the alkali-ion accommodation ability. Now, it is still a great challenge to achieve in situ control of the microstructure evolution paths in enclosed batteries for extending the cycling reversibility/lifespan. Herein, the phase conversion paths of both film- and powder-type WS2 anodes are investigated in lithium-ion batteries. It is found that the reversible conversion mechanism is beneficial for alleviating the shuttle effect through strong W-LixSy bonding. Also, once the size of the phase-converted W/WS2 redox pair exceeds ∼10 nm inside the anode layer, the Li+ storage ability will severely decay due to uncontrollable W precipitation. To maintain high reversibility, amorphous Al2O3 is introduced upon pristine WS2. After initializing the battery test, the particle size of the W/WS2 redox pair is in situ modulated within the range of ∼3-5 nm because of the refinement effect of gradually pulverized Al2O3. Thus, the decay suppression effect lasting over 750-1400 cycles is obtained with enhanced W ↔ WS2 conversion efficiency and good capacity retention. This is expected to promote the optimization of Mo-group sulfides/selenides/tellurides toward AMIBs.

TWO STAGE HALL TYPE SOURCE: DISCHARGE CHARACTERISTICS AND ELECTRON ENERGY DISTRIBUTION FUNCTION

The influence of working gas pressure and potentials of the cathodes of the two-stage plasma source with an anode layer on the dynamic current-voltage and power-voltage characteristics of separate stages of the discharge has been established. The effect of the source operating modes on the EEDF was determined by the method of emission optical diagnostics. In particular, the existence of a group of electrons with energy of ≈ 35…50 eV was found in the axial zone of the plasma source.

INFLUENCE OF DISTANCE BETWEEN ANODE - METAL HYDRIDE CATHODES ON YIELD OF H־ IONS FROM PENNING DISCHARGE

The behavior of extracted axial current of H־ ions formed in plasma volume of Penning discharge with different distances between metal hydride cathodes and an anode is discussed. The discharge operation is ensured on hydrogen locally injected from metal hydride cathodes due to ion current impact from plasma. Efficient formation of H־ ion is achieved due to high vibrational excitation of hydrogen molecules because of nonequilibrium desorption process. It has been shown that at high magnetic field an increase of the H־ ion current is registered at the negative electric bias supply on a cathode. At low magnetic field H־ ions are pushed out by the negative space charge of anode layer which expands towards the axis. The optimal anode-cathode distance for effective yield of H־ ions was found.

Triple‐Functional Amorphous In2O3 Anode Protection Layer Design for High‐Performance Aqueous Zinc Ion Batteries

AbstractProtective coatings for Zn anode are developed to suppress Zn dendrite growth, inhibit hydrogen evolution reaction (HER), and provide good anti‐corrosion properties. However, preparing protective coatings with all three of these characteristics remains a challenge. In this study, a triple‐functional amorphous In2O3 protective layer for Zn anodes is designed. The high redox potential of In/In3+ ensures the stability of the coating in aqueous electrolytes and effectively suppresses HER. Theoretical calculations indicate that the amorphous In₂O₃ protective layer has high Zn2⁺ affinity, which lowers the nucleation barrier for Zn2⁺ and suppresses dendrite growth. Furthermore, the anisotropy of this amorphous material provides homogeneous Zn2+ adsorption sites and enhances corrosion resistance. Consequently, amorphous In2O3@Zn symmetric batteries have excellent stability and a cycle life far exceeding that of bare Zn, showing the ability to undergo continuous stripping/plating at 1 mA cm−2 for >5400 h. At a current density of 10 A g−1, an amorphous In2O3@Zn//Ca‐V2O5 full cell retains a specific capacity of 307.3 mA h g−1 after 5000 cycles (cycle retention: 76%). The successful preparation of In2O3@Zn provides a new approach for obtaining highly stable and long‐life Zn anodes.

Etidronic Anodizing of Aluminum Alloys: Growth and Properties of Anodic Layers

Anodizing is a well-known electrochemical process used to increase the thickness of the natural oxide present on the surface of aluminum alloys. This process is commonly employed to enhance properties such as anticorrosion and hardness. Sulfuric acid is the most frequent used electrolyte for aluminum alloy anodizing, offering significant corrosion resistance. For applications requiring a hard anodic layer, a specialized sulfuric anodizing can be implemented, where the bath temperature is around 0°C. However, when anodizing is necessary at room temperature, Huang et al. [1] have suggested the use a new electrolyte: etidronic acid (HEDP). The present work focuses on the study of this new hard anodizing process, with etidronic acid. Electrochemical analyses as well as anodic layer characterizations have been performed for various aluminum alloys including 1050, 2024 and 7075 alloys. The growth of the anodic layer varies depending on the alloy type. Two modes of anodization have been identified: a conventional anodization mode (for 1050 alloy) and a second mode which can be considered as micro-arc anodization (for 2024 et 7075 alloys). These anodization regimes will induce modifications in the thickness, morphology, crystallinity, and hardness of the anodic layers.[1] H. Huang, J. Qiu, X. Wei, E. Sakai, G. Jiang, H. Wu, T. Komiyama, Ultra-fast fabrication of porous alumina film with excellent wear and corrosion resistance via hard anodizing in etidronic acid, Surface & Coatings Technology 393 (2020) Figure 1

Understanding the Mechanism of Evaporation-Induced Islands during the Formation of Catalyst Layers and Their Influence on the Alkaline Oxidation Evolution Reaction

Advancements in anode development substantially reduce the cost and enhance the performance of water electrolysis. The strategic configuration of nano-sized catalyst materials on anode supports is a pivotal factor in the expansion of the production of catalyst layers and has a significant influence on their electrochemical performance [1–3]. Therefore, it is essential to understand the structure formation mechanisms during electrode fabrication. This contribution aims to explore the inherent drying mechanisms in the coating process and their subsequent influence on the morphological evolution of anodes, ultimately establishing a linkage between these morphological changes and electrochemical performance and stability metrics. The initial phase of the study involved a detailed characterization of commercial nickel cobalt oxide nanoparticles via advanced analytical techniques, including transmission electron microscopy and energy-dispersive X-ray spectroscopy [4]. Subsequently, a stable ink was formulated by dispersing the catalyst alongside a binder in a solvent, which was then uniformly applied to a conductive nickel plate utilizing an ultrasonic spray coater. Prior to application, the catalyst inks underwent optimization based on the Hansen solubility parameters of catalyst materials [5, 6] and subsequent visualization of their stability and dispersibility characteristics through transmittogram analysis [7]. The drying process of the coating was conducted at two distinct temperatures, 50 °C and 150 °C, to investigate the effect of temperature on solvent evaporation. Morphological and structural analyses of the anodes were subsequently performed using scanning electron microscopy (SEM), laser scanning microscopy (LSM), and atomic force microscopy (AFM), providing insight into the alterations induced by the drying process. The analyses conducted in this study elucidate significant modifications in the morphology of the layer structures attributable to variations in drying temperatures as illustrated in Figure 1. Specifically, lower temperature resulted in reduced evaporation rates that facilitated the formation of larger, isolated regions/islands on the anode support. These are indicative of a non-uniform coating distribution. In contrast, a higher temperature promoted rapid evaporation, resulting in a quite homogeneous distribution of smaller islands accompanied by the emergence of voids within the anode layer. Electrochemical analysis revealed that these morphological changes are of vital importance: they govern the wetting behaviour and the dynamics of bubble formation which are important for the electrochemical performance and durability of the catalyst layers. Moreover, the insights gleaned from this study are instrumental in identifying optimal configurations of catalyst layer structures, i.e., features that should be maintained during scale-up. In conclusion, this study significantly advances the field by revealing novel principles governing the design and optimization of electrode structures for the oxygen evolution reaction. In particular, the complicated relationship between drying temperatures and morphological evolution, which significantly influences electrochemical performance is explained.

Investigation of the Effect of Initial Anode Structures on the Durability of Water Electrolysis Cells

Introduction: Water electrolysis is an essential technology for efficiently combining renewable energy with hydrogen energy. Long-term durability against voltage fluctuations is necessary to produce hydrogen by water electrolysis directly using renewable energy. In our previous study, potential fluctuation protocols have been developed based on actual wind power voltage fluctuations (1). In our recent work, the durability of water electrolysis cells has been evaluated for 320 days (2). Reversible and irreversible performance losses were present. As an irreversible performance loss, delamination of IrO2 anode layer was found, which was most likely due to increase in the internal pressure derived by stagnation of generated gases, as similarly seen in the durability test up to 160 days (1). However, regarding to changes in pore structures, the trend was different from our previous study. That was assumed that the change in initial pore structures of anode layers derived by different ionomer/catalyst ratio, rather than the change in the length of the durability test, made different trends.Therefore, in the first part of this study, the durability test condition was aligned with that of the previous study (1), equivalent to 160 days, and the effect of the initial pore structure on durability was examined. In the second part, for the purpose of developing more durable anode pore structure, addition of a hydrophobic material was considered since partially hydrophobic surface probably promotes releasing of gas bubbles to eliminate gas stagnation. Experimental: A water electrolysis cell was made by spray printing 0.3 mg Pt/cm2 using 46.3% Pt/KB for the cathode and 0.5 mg IrO2/cm2 using commercial IrO2 (Tokuriki Honten) for the anode on Nafion117 membrane. The amount of Nafion ionomer in the anode was kept to 15% in this study. The resulting membrane electrode assembly (MEA) was placed in a holder which can flow water in the both anode and cathode with porous transport layers of titanium mesh and carbon paper for the anode and cathode, respectively. After initial electrochemical measurements of AC impedance and I-V performance were taken, a durability test of 80 sets corresponding to 160 days was performed using a potential fluctuation protocol developed in our laboratory (1). The potential was applied to the anode while the cathode was maintained at 0 V. Electrochemical measurements were similarly taken at the end of each set. In addition to electrochemical properties, anode structural properties were evaluated from 3D reconstructed images made by hundreds of FIB-SEM images. For the second part of this study, MEAs with an increased hydrophobic property were prepared by adding 10-30 wt% of polypyrrole against the mass of IrO2 to the anode. Results and discussion: The current density at 2.0 V was monitored during the durability test equivalent to 160 days. Both MEAs with 33% (1) and the 15% Nafion ionomer in the anode showed a similar trend of the current decrease and recovery even though initial performance was higher for MEA with 15% Nafion ionomer. However, the irreversible current loss was larger for MEA in this study. This irreversible current loss is most likely caused by the stagnation of the generated gases based on our previous studies (1), (2). Since gas stagnation is deeply related to the pore structure of the anode layer, 3D reconstruction of the anode was performed using several hundred FIB-SEM images, and comparison to our previous study (1) was done. As a result, when pore size distributions based on 3D reconstructed images were analyzed as shown in Figure 1, a denser anode structure was found with 15% Nafion ionomer. In other words, MEA with 15% Nafion ionomer has high initial IV performance but low durability, while 33% Nafion has low initial IV performance but high durability, indicating that there is a trade-off between the two.Optimizing the amount of Nafion ionomer and the mixing method is one way to achieve both high performance and high durability. However, in the second part of this study, addition of a hydrophobic material was rather considered since partially hydrophobic surface promotes releasing of gas bubbles to eliminate gas stagnation. Polypyrrole was chosen because of its conductivity as well as it hydrophobicity. Unlike the addition of an insulator, PTFE, there was almost no change in initial IV performance up to 30% addition, but a significant improvement in hydrophobicity was observed. The durability of MEA with the anode containing 30% polypyrrole has been evaluated.

Direct Use of Ammonia in Solid Oxide Fuel Cells

With the global movement to suppress carbon use, hydrogen is emerging as an effective alternative to fossil fuels. However, there are difficulties in entering the energy market due to the lack of infrastructure and difficulties in storage/transportation when using hydrogen. Ammonia attracts attention as a promising solution to the hydrogen problem through well-established infrastructure around the world.Direct use of ammonia in solid oxide fuel cells (SOFCs) offers more attractive aspects such as high efficiency and compact system size. However, instability in long-term operation has been reported in many literatures, which is mostly attributed to Ni nitridation. To overcome Ni nitridation, the current study proposes an alloy-based fuel electrode and its facile fabrication process. In this study, we intend to improve ammonia cracking in anode layer in SOFCs, contributing to improvement both fuel cell performance and long-term stability. The details on the current work will be presented.

Robust Lif–Rich SEI Inducing Protective Layer for High Energy Density Si Anodes in Li–Ion Batteries

As the electric vehicle (EV) market has rapidly grown, the need for Li ion batteries (LIBs) with high energy density is increasing to achieve a longer driving range. However, since the graphite anodes in conventional LIBs have almost reached their theoretical capacity, it is urgently needed to develop a new battery chemistry to meet the demands for long-range EVs. In this regard, Si is considered as the most promising anode materials for high-energy-density LIBs owing to its high theoretical capacity (3579 mAh g-1), low operating potential (~ 0.4 V vs. Li/Li+), and earth abundance. Unfortunately, the employment of Si anodes is hindered by the large volume change (~ 300 %) during the lithiation/delithiation process, which accompanies with electrode pulverization, unstable solid electrolyte interphase (SEI), and continuous electrolyte decomposition.The SEI layer is the interface layer between the electrolyte and anode, which is formed via the reduction of the electrolyte components during the first lithiation process. Typically, the SEI layer is depicted as a mosaic structure that is mainly consisted of organic and inorganic constituents. The organic SEI constituents, which are the byproducts of the decomposition of the electrolytes, show poor Li ion conductivity with an unstable structure. In contrast, the inorganic SEI constituents are ideal SEI components owing to their excellent electrochemical stability. The ideal SEI layer should not only passivate the anode surface and prevent the direct contact of anode surface with the electrolyte, which causes continuous electrolyte decomposition, but also provide exhibit excellent Li ion transfer kinetics. In this respect, LiF is considered as the most ideal SEI component with its stability against the electrolyte and the high Li ion conductivity.To achieve a LiF-rich SEI layer on the Si anode, various strategies have been devised, such as electrolyte additive and LiF coating on the anode surface. The electrolyte additives such as FEC, has been widely used to construct a LiF-rich SEI layer. Unfortunately, the additives are continually consumed over repetitive cycling, which eventually results in a rapid capacity decay of the Si anodes, when they are exhausted. In case of the LiF coating, the coating layer indeed induces LiF-rich SEI layer during the first cycle. However, if the coating layer has insufficient mechanical strength, the severe volume change during the lithiation/delithiation process leads to the breakage of the SEI layer, resulting in uncontrollable electrolyte decomposition and following (re-)formation of the SEI layer. This causes a depletion of electrochemically available Li ions in the electrolyte and a thick-insulating SEI layer with poor Li ion kinetics. Therefore, not only forming an inorganic-rich SEI layer, but also constructing a robust interfacial layer with sufficient physicochemical stability is highly important to achieve stable cycle performances of the Si anodes.In this study, we propose a new strategy to construct a robust LiF-rich SEI layer on the Si anode by employing a LiF-rich SEI inducing protective layer (LPL) comprising of aluminum fluoride (AlF3) and poly(acrylic acid) (PAA) (LPL@Si). In the LPL@Si, the AlF3 induces a LiF-rich SEI layer with high Li ion conductivity, while the polymeric PAA provides a sufficient mechanical strength to alleviate the large volume change of the Si anode. In addition, the PAA in the LPL also acts a role of SEI stabilizer, which promotes the faster formation of the LiF-rich SEI layer owing to the abundant carboxyl groups, resulting in a rapid reduction of Li salts in the electrolyte. Due to these synergistic effects, the LPL@Si anode delivered significantly enhanced electrochemical performances in Li metal cell tests compared to that of the bare Si anode. Moreover, the LPL@Si anode exhibited an enhanced cycle performance than the bare Si anode in a full cell test with a NCM811 cathode. These results prove that our strategy for constructing a mechanically stable LiF-rich SEI layer would initiate further studies for achieving a highly stable Si anode in next-generation high energy density LIBs.

Effects of the Dynamic Loading Frequency on Performance of the Proton Exchange Membrane Water Electrolysis.

Green hydrogen production via PEM water electrolysis is challenged by fluctuating input power when coupled with renewable energy sources. This study investigates the effects of dynamic loading frequencies on membrane electrode assembly (MEA) performance and durability. We found that higher loading frequencies facilitate the growth of the oxide layer of Ti porous transport layer (Ti-PTL) due to increased duration in the voltage spike region. These thicker and coarser oxide layers directly induce cracks and delamination in the anodic catalyst layers by spontaneously adsorbing an ionomer. These changes negatively impact the interface contact quality and anodic electrochemical active area, ultimately reducing the performance of the MEA, with higher frequencies accelerating this degradation. Additionally, applying a Pt coating to PTL effectively mitigates these adverse effects. This work highlights the importance of dynamic loading studies and reveals that effective management of the Ti-PTL and catalyst/PTL interface is necessary to achieve long-term operational durability of PEM water electrolysis.

Growth of Anodic Oxide Layers on Titanium Alloys Including Noble Metal and Transition Metal

Anodic TiO2 nanotubes have attracted attention, especially in the field of photocatalysis, enabling the generation of hydrogen from water. It has been reported that the hydrogen production can be enhanced by decorating co-catalysts onto nanotubes, and that, nanoparticles consisting of noble metal alloys can be deposited onto TiO2 nanotubes by anodization of Ti alloys containing noble metals at reducing reliance on noble metals. In this study, we studied the anodization behavior and oxide layer formation on titanium alloys containing both noble and transition metals to reduce the amount of noble metals used. Titanium alloys containing noble metals (Au, Pt) and transition metals (Cu, Fe, Co) were fabricated via the arc melting method. Anodization was conducted in ethylene glycol solutions containing fluorides and water using a two-electrode cell with a Pt plate serving as the counter electrode. Current generated during anodization oxidation was monitored, and the surface and cross-section of the oxide layers formed were observed with FE-SEM. In the present work, ammonium fluoride and hydrofluoric acid were used as fluoride source. In the case of the electrolyte containing ammonium fluoride, SEM observations confirmed the formation of TiO2 nanotubes, along with the decoration of co-added metal nanoparticles on their surfaces and cross-sections. In contrast, in the electrolyte containing hydrofluoric acid, the formation of nanograss was confirmed. A significant number of co-added metal nanoparticles were observed on the surface and cross-sections of the formed nanograss. In this presentation, the effect of water content in the organic electrolytes on the formation of TiO2 nanotubes decorated with nanoparticles will be discussed.

Multilayer Porous Transport Layers for Polymer Electrolyte Water Electrolysis to Replace Thin Protective Pt Coating at Low IrO2 Loading

The use of expensive PGM catalysts for the OER and HER leads to high production costs of Polymer electrolyte water electrolysis (PEWE). Moving towards lower iridium oxide (IrOx) catalyst loadings for the anode side can severely affect performance and stability [1]. Recent studies revealed that the structure of the interface between the anodic porous transport layer (PTL) and the catalyst layer (CL) is a crucial factor limiting cell efficiency and contributes significantly to the performance and use of the CL. The coarse structure PTL can develop inactive zones of the catalyst layer, which happens when the catalyst layer is not “close” to the connecting titanium structure [2]. The situation becomes worse when the IrO2 catalyst loading is reduced, and the catalyst layers become thinner. Recent evidence has shown that having additional Microporous layers (MPL) can overcome some of these issues by maximizing catalyst utilization and increasing cell efficiency. However, at low Ir loadings, a thin protective Pt coating on MPL is needed to avoid formation of TiOx passivation layer on the MPL surface and increase surface conductivity [3].In this work, we attempt to replace the thin protective Pt coating by adding an additional layer of Ti or TiN on the existing MPL aiming when using low loadings of IrO2 (0.5 – 0.1 mgIr cm-2). Vacuum plasma spraying (VPS) technology was used to apply TiN on the surface of MPL, while Ti was spray-coated, and vacuum sintered to create a hierarchically structured 3-layer PTL. Electrochemical performances of both Ti and TiN coated MPLs were evaluated by polarization curves and Electrochemical Impedance Spectroscopy measurements. The results are compared with a Pt coated MPL reference.

Effect of Li on the Uniformity of Zn Recharge Reaction in the Anodic ZnO Passivation Layer

Alkaline rechargeable Zn batteries are regarded as next-generation energy storage systems owing to their cost-effectiveness, safety, and high theoretical capacity. Nevertheless, their application is limited because of the degradation of Zn anodes during charge-discharge cycles. The most notable example of the degradation phenomena is dendrite formation during charge. Under conditions with high current density, current is concentrated at the protruding points of the electrode surface due to significant growth of the diffusion layer. This induces dendritic structures to grow perpendicular to the substrate, which causes short circuits in the worst case. Several methods, such as adding additives to the electrolyte and modifying the surface of electrodes via alloying or coating, have been proposed to suppress dendrites. In particular, additives have been widely investigated to achieve a cost-effective and simple battery manufacturing process. Their effects are often explained in terms of adsorption behavior on pristine Zn surfaces. In practical cases, however, surface states of Zn are more complicated due to the ZnO formation during discharge. Previous studies have suggested that the passivation layer on metal anodes (e.g. Al and Li) has a significant influence on dendritic growth behavior.[1, 2] Therefore, in this study, we investigate the additive effect on the dendritic growth of Zn in the presence of the ZnO passivation layer formed after discharge. In particular, we focus on the additive effect of Li+. Li+ induces crystalline defects in ZnO by inhibiting the crystallization process.[3] Since the electrical properties of ZnO are greatly affected by crystalline defects, Li+ is a qualified additive to focus on in this study, which investigates the influence of the ZnO passivation layer. In addition, Li+ is an interesting target to investigate its additive effects during recharge since it has been identified by our group as an effective additive to inhibit undesirable property changes such as mossy growth and passivation.[3, 4] Fig. 1 shows the surface morphology of the Zn recharged in the presence of varying concentrations of Li+. Without Li+, the Zn electrodeposits contain leaf-like dendrites. In contrast, 0.1 M Li+ addition leads to finer morphology with fewer dendrites. Conversely, with 2 M Li+ addition, the rough deposits containing more and larger dendrites are observed. Notably, the Zn deposition morphology at the initial charge was independent of the concentration of Li+. Therefore, Zn deposition morphology during recharge was most likely affected by the property difference of the ZnO passivation layer formed during discharge. Moreover, the potential profile of Zn during recharge suggested that the conductivity of the ZnO passivation layer was dependent on the concentration of Li+: it increased with 0.1 M Li+ addition and decreased with 2 M Li+ addition. The conductivity changes were attributed to the carrier density change due to crystalline defect formation. These results suggest that the ZnO passivation layer with high conductivity is ideal for suppressing the dendritic growth of Zn during recharge. Furthermore, controlling crystalline defects with additives is an effective strategy for forming a conductive ZnO passivation layer.

Advanced Dual-Layer Protection for Lithium Metal Anodes in Lithium-Sulfur Batteries with Reduced Electrolyte Volume

To surpass the energy capacity of current lithium-ion technology, it's vital to develop lithium-sulfur (Li-S) batteries using a minimal amount of electrolyte. However, the quick depletion of electrolyte, driven by reactions at the lithium metal anodes (LMAs), leads to decreased sulfur reaction efficiency and shortened battery lifespan. Addressing this challenge requires a robust protective strategy for LMAs that can withstand the changing dynamics at the interface between the anode and protective layers (PLs). This research highlights the importance of two factors—surface free energy (SFE) and Young’s modulus—in maintaining an adaptable interface between PLs and LMAs, determined through solid mechanics simulations and experiments across three PL configurations. Introducing a dual-layer adaptive protective layer (APL) aims to counter early PL detachment, triggered by lithium pitting. This APL, tailored to adjust to the evolving PL|LMA interface, features a high-SFE polymer inner layer to minimize interfacial energy with the LMA surface, coupled with an elastic outer polymer layer acting as a barrier against electrolyte and lithium polysulfides intrusion. Implementing APL on LMA significantly enhanced the cycling stability of Li-S batteries, effectively doubling their cycle life compared to unprotected LMA configurations, and outperforming single-layer PL setups.

How to Assess the Degradation of the PEM Water Electrolysis Anode Catalyst on a Lab Scale?

Proton exchange membrane water electrolysis (PEMWE) is an established technology to produce green hydrogen. Further improvements in terms of material (cost) reduction, performance, and durability are required to meet the ramp-up targets of a large-scale production of PEMWE stacks and to reduce the levelized costs of hydrogen production. It is key to maintain or even increase the durability of the iridium-based anodic catalyst layer while further reducing its raw metal demand.Usually, the development of novel materials used as anode catalysts is progressing faster than the evaluation under PEMWE conditions in cell and stack tests. Therefore, accelerated stress tests (ASTs) have to be developed.1, 2 ASTs are degradation mechanism-specific protocols that have a targeted and accelerated effect, and significantly reduce the required test time.In this work, several voltage-controlled AST protocols and their application in PEMWE cell tests with various anode catalyst types and iridium loadings are analyzed. The AST protocols consist of rapid changes in the voltage between 1.9 V and either 1.25 V, open circuit voltage or 0 V. For reference the voltage is kept constant at 1.9 V. The effects of these protocols on the kinetic parameters of the oxygen evolution reaction (OER), e.g. the apparent exchange current density and the Tafel slope, are evaluated using three different methods. As state of the art, the voltage breakdown analysis (VBA) method is used and directly compared to two other methods, i.e. the constant Tafel slope (CT-VBA)3 method and the OER mass activity method. Furthermore, the influence of dynamic potential profiles on the kinetic overpotential is analyzed with an overpotential difference approach. Depending on the method used, the resulting trends for the OER kinetic parameters diverge. In doing so, we want to raise awareness about the strengths, weaknesses and limitations of each method and their impact of the respective interpretation.4 References S. M. Alia, S. Stariha and R. L. Borup, J. Electrochem. Soc., 166(15), F1164-F1172 (2019).A. Weiß, A. Siebel, M. Bernt, T.-H. Shen, V. Tileli and H. A. Gasteiger, J. Electrochem. Soc., 166(8), F487-F497 (2019). M. Rogler, M. Suermann, R. Wagner, S. Thiele and J. Straub, J. Electrochem. Soc., 170(11), 114521 (2023). M. Rogler, et al., to be submitted.

(Invited) One Dimensional Anodic TiO2 Nanotubes for Energy and Catalytic Applications

Self-organized TiO2 nanotube (TNT) layers, prepared by anodization of Ti have in suitable electrolytes, attracted considerable scientific and technological interest, especially due to their wide range of applications including (photo-) catalysis, hydrogen generation and biomedical uses [1,2].The advantages of anodic TNT layers compared to TiO2 nanotubes prepared by other methods (e.g. hydrothermal) are the tunability of dimensions, their directionality, the ability to absorb significant amount of incident light, and the possibility to utilize nanotube interiors and exteriors for decoration or coating with secondary materials [2].The presentation will review the recent advancements in TNT layer synthesis for their use for the photocatalytic degradation of pollutants in the liquid and in the gas phase. This will include the upscaling of TNT layers from the laboratory scale to several dozens of cm2 [3-6], with a strong focus on the anodization of 3D Ti substrates by bipolar electrochemistry, which cannot be directly connected to the potentiostat (such as Ti meshes) [5-6]. The application of these large scale TiO2 nanotube layers in flow-through photocatalytic reactors will be discussed [3-6]. Additionally, the selective etching of double wall TiO2 nanotube layers towards single wall TiO2 nanotube layers [7] and single nanotube powders [8, 9] will be presented, showing the possibility of preparing magnetically guidable single nanotube photocatalysts by a decoration with Fe3O4.The presentation will also summarize recent advancements in the utilization of TNT layers in energy conversion and energy storage applications [10], in particular Li-ion microbatteries. Experimental details and photocatalytic and battery results will be presented and discussed.

The Contributions of Catalyst Layer Resistance on Overall Overpotentials in Anion Exchange Membrane Water Electrolyzers

Anion exchange membrane water electrolyzers (AEMWE) combine the benefits of traditional liquid alkaline (LAWE) and proton exchange membrane water electrolyzers (PEMWE), producing H2 at high current densities while allowing the use of low-cost, low-criticality PGM-free materials for catalysts and hardware. Advances in AEMWE performance have risen rapidly in recent decades, and research on AEMWEs has increased dramatically.1 However, despite significant component-level advances in catalysts and membranes,2,3 gaps remain to achieve performance parity with PEMWEs and the relative overpotentials of AEMWE remain high. Strategies are thus needed to understand, diagnose, and quantify the origins of overpotentials in AEMWEs and help bridge the gap between AEMWE and PEMWE performance.By utilizing Tafel analysis and electrochemical impedance spectroscopy, voltage breakdown analyses can be performed to decouple the origins of high overpotentials in electrolyzers. While such methods are used frequently in the literature to determine kinetic and Ohmic losses, voltage breakdown analyses are rarely performed beyond these contributions, even though other losses can often account for 100s of mVs (20-30% of non-thermodynamic losses). Recent works have demonstrated that catalyst layer resistances can be quantified in electrolyzers using transmission line theory for porous electrodes.4 To the best of our knowledge, however, this method has not yet been adapted to AEMWEs. Furthermore, differences in cell operation and performance (e.g., use of supporting electrolyte, high hydrogen evolution reaction overpotentials) leads to differences in the expected nature of catalyst layer resistances for these two technologies. There is therefore a need for AEMWE-specific methods to diagnose and quantify catalyst layer resistance.In this work, a method for determining catalyst layer resistance from transmission line theory for porous electrodes4 is adapted to AEMWE and applied to four anode catalyst materials tested in single-cell MEAs. Changes to the catalyst layer thickness, ionomer content, and electrolyte concentration reveal trends about the origins of catalyst layer resistances in AEMWE cells. Investigations of the anode transport layer show that this component introduces significant impedance, which thus must be considered for AEM diagnostics and performance optimization. Furthermore, the results suggest that discontinuities in electronic and ionic transport networks in the catalyst layer may explain discrepancies between idealized kinetic results from rotating disc electrode testing and those observed for MEAs. These results then inform the development of a model to understand and differentiate contributions from anode and cathode catalyst layers in AEMWEs. These results will ultimately allow for the design of more efficient catalyst layers, reducing overpotentials and facilitating AEM deployment commercially.[1] Volk, E. K. et al., EES Catalysis 2024, [2] Chen, N. et al., Trends Chem. 2022, [3] Plevová, M. et al., J. Power Sources 2021, [4] Padgett, E. et al., J. Electrochem. Soc. 2023

Stress-Induced Modification for Interlayers in Lithium Metal Batteries

As solid-state electrolytes (SSE) gain attention in the academic and industrial space, thin film interlayers are increasingly used to enhance wettability and lower interfacial resistance. Gold films, or interlayers, are frequently sputtered on ceramic electrolytes to improve their contact bonding with both anodic and cathodic layers. To-date, adherence between the SSE and current collector without cracks or delamination has been considered sufficient to qualify a “good” interlayer deposition. It is well known in the surface science community, however, that thin films can sustain high levels of residual stress, depending on dose-momentum of the depositing species.For the first time, this work demonstrates the effects of interlayer residual stress on first and subsequent charge-discharge cycles and formulates a theory identifying the governing physical mechanism. We fabricate Au-Cu electrodes imbued with residual stress (-50 to 160 MPa) and cycle electrodeposited lithium on and off the surface to demonstrate unique morphological, electrochemical, and performance characteristics. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) measurements show that tensile interlayers result in larger, more irregularly shaped lithium structures that have high irreversibility, while compressive interlayers result in small, densely packed lithium structures with minimal solid electrolyte interface (SEI) formation (Figure 1a-d).We characterize the Au-Cu surface using SEM, nanoindentation, optical spectroscopy (UV-Vis-NIR), and ultraviolet photoelectron spectroscopy (UPS) to relate the physical properties of the interlayer to the electrochemical behavior. The test results show that film stress causes the equilibrium electron energy levels to shift. As the surface becomes more tensile, the contact energy decreases, the color reddens, and the work function increases (Figure 1e-g). This evidences a change in the electronic configuration, leading to distinct thermodynamic behavior in lithium structures. This work demonstrates the high sensitivity of the electrochemical environment to even minor changes in the initial condition of interlayer state and presents a guide for consistent fabrication parameters that maximize the potential interlayer benefits offered by residual stress control. Figure 1