Elevated Current Density Research Articles

Electrodeposited Ni-Based Catalysts for the Oxygen Evolution Reaction

Alkaline water electrolysis is one of the most mature technologies for producing green hydrogen. However, there still are possibilities to enhance this process by using better electrocatalysts for the kinetically limited oxygen evolution reaction (OER). While there are several existing methods for catalyst synthesis, such as spray coating, coprecipitation and hydrothermal synthesis, they face challenges of either versatility or scalability.[1,2] In this regard, electrodeposition is a promising catalyst synthesis method, due to its excellent process control and ease of scalability.In this work, electrodeposition is used to prepare nickel-based catalysts as a benchmark system. These catalysts are deposited on expanded Ni-mesh supports. Initially, the deposition parameters are optimized to obtain uniform Ni deposits, which provide reproducible activity measurements. Herein, we observe that the deposited Ni catalysts exhibit better OER activities than the Ni mesh support, most likely due to the evolution of a pyramidal morphology with an increased surface area (Fig. 1). The optimized deposition parameters are further used to deposit different Ni-based alloys such as Ni-Fe and Ni-Co, by adding the respective ionized metal species to the Ni electrolyte. The microstructure and composition of these catalysts is analyzed using material characterization techniques like scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Finally, the OER activity and long-term stability of the deposited catalysts is evaluated in an in-house developed electrochemical beaker cell at elevated concentration, temperature, and current densities (30 wt.% KOH, 80 °C, up to 1 A/cm2). The results obtained for the different catalysts are compared to understand the correlation of the catalyst structure and composition with their electrochemical OER performance under industrial conditions. Bibliography [1] Lu Xunyu et al.; Nature Communications; DOI: 10.1038/ncomms7616[2] Zuraya Angeles-Olvera et al.; Energies; DOI: 10.3390/en15051609 Figure 1

Towards Sustainable Hydrogen Peroxide Electroproduction: Activated Carbon from Sewage Sludge As an Eco-Friendly Electrode Material

Hydrogen peroxide (H2O2) has emerged as a chemical of paramount importance, finding diverse applications as a bleaching agent, medical disinfectant, and environmentally benign oxidant [1]. The industrial production of H2O2 currently relies on the anthraquinone oxidation process, primarily executed within large-scale industrial plants [1]. Herein lies a challenge— H2O2, typically concentrated to an 80% level, introduces inherent hazards concerning storage and transportation, prompting a quest for a safer alternative. One way to overcome such problems is by the in-situ electrogeneration of H2O2, which would allow an adjustable production of the chemical on demand directly for its application, avoiding storing costs and safety issues. The in-situ electrogeneration can be done by using a gaseous-diffusion electrode (GDE), which typically enables the application of elevated current densities or substantial overpotentials, consequently facilitating the generation of high concentrations of H2O2, since there is less limitation due to O2 mass transport to the electrode surface [2]. Commonly, these electrodes are constructed from amorphous carbon materials, due to their highly active surface area with oxygenated functional groups, excellent conductivity, and innate selectivity for H2O2 electroproduction. However, a notable challenge emerges – bare carbon's selectivity for H2O2 presents its highest response at high overpotentials, entailing heightened energy consumption. The studies in this field are currently focused on using these types of carbon as support for other catalytic materials that are more active and selective towards H2O2 electroproduction [3, 4]. Numerous studies in the literature have explored the use of carbon materials, with the most commonly employed carbon supports for such applications being Printex 6L (Orion) and Vulcan XC 72R (Cabot). These materials are obtained from the incomplete combustion of heavy petroleum products at high temperatures, being non-sustainable and environmentally unfriendly. A potential solution lies in the use of environmentally conscious carbon sources. While amorphous carbon can be obtained from various carbon-rich wastes through an activation process, their utility in H2O2 electrogeneration remains underexplored. This study sought to obtain activated carbon from sewage sludge, focusing on its efficacy in H2O2 electrogeneration. Acid (H3PO4) and alkaline (KOH/NaOH mixture) carbon activators were analyzed in concentrations ranging from 0 – 30 %m/v, temperatures of 400 – 900 ºC, and activation time from 0 – 2 h at the selected temperature. The obtained materials were analyzed through linear sweep voltammetry using an RRDE setup in N2-saturated and O2-saturated, in a 0.05 M K2SO4 (pH 3) electrolyte solution. Results have shown that the most successful materials for H2O2 electrogeneration were those produced under 900 ºC for 2h impregnated with 5 % m/v H3PO4 and 597 ºC, zero of plateau time impregnated with 20 % m/V mixture of KOH/NaOH in the ratio of 50.5 KOH: NaOH. These optimized materials exhibited remarkable selectivities of ≈ 90% and ≈ 81% at -0.8 V vs. Ag/AgCl, respectively. This level of electrocatalytic performance is on par with that of the commercial reference material, Printex 6L. These findings highlight the promise of our material as a viable carbon support for in-situ H2O2 electrogeneration, offering a more sustainable alternative compared to commercial black carbons. Acknowledgments The authors are sincerely grateful to the Brazilian research funding agencies, including the Brazilian National Council for Scientific and Technological Development - CNPq (grants no. 465571/2014-0, 302874/2017-8, and 427452/2018-0), São Paulo Research Foundation (FAPESP – grants no. #2023/04230-2, #2023/07750-7, 2022/04058-2, #2021/12053-8, #2019/04421-7, #2017/10118-0, and #2013/02762-5).

Evaluation of a Combined Approach for Sulfate and Ammonia Recovery from Treated Brine Using a Simultaneous Chemical Precipitation and Electrocoagulation Processes

Soda ash (Na2CO3) is produced using the traditional Solvay process. It entails the reaction of CO2 with high-salinity water in the presence of ammonia (NH3), which produces insoluble sodium bicarbonate (NaHCO3) and soluble ammonium chloride (NH4Cl). In the current work, a newly combined approach has been developed to effectively manage the removal of ammonia and sulfate from the effluent of the Solvay process. The devised technique centers on an electrochemical coagulation process, complemented with the utilization of calcium oxide (CaO) as a buffering reagent. This innovative approach excels at achieving high recovery rates for both ammonia and sulfate. The recovered ammonia holds the potential for recycling, thereby contributing to the sustainability of the Solvay process by reusing ammonia in its initial stages. Furthermore, sulfate ions are recuperated in the form of calcium sulfate, a value-added product boasting various industrial applications. The results gleaned from this study underscore the efficacy of the ammonia recovery process, particularly when operating at elevated current densities and with higher calcium oxide concentrations. On the other hand, sulfate recovery demonstrates superior performance when exposed to moderate current densities and limited calcium oxide concentrations. Consequently, the integration of both stages within a single, cohesive process necessitates the development of an optimization methodology to cater to varying operational conditions. To address this need, second-order polynomial equations were formulated and employed to anticipate ammonia and sulfate removal rates in the integrated approach. Four independent variables come into play: calcium oxide concentration, current density, temperature, and mixing rate. The findings reveal that most of these variables exert substantial influences on both ammonia and sulfate removal rates, underscoring the need for careful consideration and fine-tuning to optimize the overall process. The maximum ammonia and sulfate removal were found to reach 99.50% and 96.03%, respectively, at a calcium oxide concentration of 3.5 g/100 mL, a current density of 19.95 mA/cm2, a temperature of 35 °C, and a mixing rate of 0.76 R/s. The results are promising, and the developed process is also suitable for recovering high concentrations of sulfate and ammonia from various wastewater sources.

A Noncontact Method for Estimating Thin Metal Film Adhesion Strength Through Current-Induced Void Growth

Abstract Studies have reported that the electromigration-induced void growth velocity in metal thin films is inversely related to the adhesion strength of the metal thin film with the base and passivation layers. It was also observed that the contribution of interface adhesion strength to electromigration resistance decreases with an increase in temperature. In this study, an expression is derived for the diffusive void growth velocity induced by electromigration from a generalized thermodynamically consistent continuum-based theory for reaction–diffusion driven solid-state interface evolution. This relation captures the effect of adhesion with the base and passivation layers on electromigration resistance of thin metal films. Electromigration experiments were carried out at elevated temperatures and high current density to induce voiding in thin Cu metal film deposited on a base layer of TiN and passivated with TiN or SiNx. The degradation of interface adhesion strength with temperature is modeled using an Andrade-type of relationship. The void growth rates characterized in these experiments are combined with the expression for void growth rate to estimate the interface adhesion strength for the Cu–TiN and Cu–SiNx interfaces. The methodology for estimating the adhesion strength of the metal-passivation layer interface is validated through comparison with interface adhesion strengths from mechanical de-adhesion tests reported in the literature.

Numerical analysis of carbon-based perovskite tandem solar cells: Pathways towards high efficiency and stability

Multi-junction solar cells exhibit superior power conversion efficiency (PCE) in comparison with their single-junction counterparts. The tunable bandgap, low-cost, elevated short circuit current density (Jsc), and open-circuit voltage (Voc) of perovskite solar cells (PSCs) have led to their widespread adoption as top sub-cells in tandem devices. Stability remains a significant challenge for these cells. To address this issue, carbon perovskite solar cells (CPSCs) have emerged as a potential solution, offering enhanced stability without hole transport layers (HTLs). This study focuses on the simulation of HTL-free CPSCs using an improved electron transport material (ETM) instead of TiO2. The implementation of this enhancement leads to a notable increase in the PCE of the CPSCs, rising from 7.97 % to 14.38 %. Through optimizing the defect concentration and doping density of the perovskite absorber layer, a significant improvement in the PCE is achieved, reaching 16.87 %. A novel configuration incorporating a gradient doping profile in the perovskite layer is introduced, leading to a remarkable enhancement in the PCE, which reaches 22.22 %. Two absorber materials are suggested, CIGS and GeTe, as bottom sub-cells. Three tandem cell configurations, PSC/CIGS, CPSC/CIGS, and CPSC/GeTe, are rigorously explored based on the optimized sub-cells. The PCEs of the proposed configurations are found to be 30.52 %, 22.7 %, and 36.59 %, respectively. Computational analysis reveals that the PSC/CIGS tandem cell exhibits lower stability against temperature variations compared to CPSC/CIGS and CPSC/GeTe. Additionally, the proposed CPSC/GeTe tandem is highly praised as a favorable contender, offering both high efficiency and stability among the various configurations considered in this study.

Lithium-compatible and air-stable vacancy-rich Li9N2Cl3 for high-areal capacity, long-cycling all-solid-state lithium metal batteries.

Attaining substantial areal capacity (>3 mAh/cm2) and extended cycle longevity in all-solid-state lithium metal batteries necessitates the implementation of solid-state electrolytes (SSEs) capable of withstanding elevated critical current densities and capacities. In this study, we report a high-performing vacancy-rich Li9N2Cl3 SSE demonstrating excellent lithium compatibility and atmospheric stability and enabling high-areal capacity, long-lasting all-solid-state lithium metal batteries. The Li9N2Cl3 facilitates efficient lithium-ion transport due to its disordered lattice structure and presence of vacancies. Notably, it resists dendrite formation at 10 mA/cm2 and 10 mAh/cm2 due to its intrinsic lithium metal stability. Furthermore, it exhibits robust dry-air stability. Incorporating this SSE in Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode-based all-solid-state batteries, we achieve substantial cycling stability (90.35% capacity retention over 1500 cycles at 0.5 C) and high areal capacity (4.8 mAh/cm2 in pouch cells). These findings pave the way for lithium metal batteries to meet electric vehicle performance demands.

Controllable Electron Distribution Reconstruction of Spinel NiCo2O4 Boosting Glycerol Oxidation at Elevated Current Density

AbstractElectrocatalytic glycerol oxidation reaction (GOR) is an effective way to convert biomass byproduct to high value‐added chemicals, which; however, suffers from the low oxidation activity and conversion ratio of the presently available catalysts. Herein, the NiCo2O4/NF bimetallic oxide nanoarray is controllably fabricated by Ni substituting for octahedral Co3+ in Co3O4, which exhibits excellent GOR catalytic activity at elevated current densities (E300 = 1.42 V, E600 = 1.62 V) and overall Faradaic efficiency of 97.5% at 1.42 V (FEformic acid = 89.9% and FEglycolic acid = 7.62%). The high performance is attributed to the structure evolution including the rapid generation of NiIII‐OOH and CoIII‐OOH active species, the optimized intermediates adsorption, and the accelerated electron transfer owing to the Ni introduction, which are evidenced by the operando spectroscopy measurements and density functional theory calculations, respectively. The GOR/hydrogen evolution coupled two‐electrode electrolytic cell voltage is ≈299 mV lower than that of the water splitting at 50 mA cm−2. More importantly, compared to conventional water splitting, this electrolyzer is stable for over 200 h at 1.75 V, reducing energy consumption by 16.9% and obtaining high value‐added products at the anode concurrently.

A π‐Conjugated Porphyrin Complex as Cathode Material Allows Fast and Stable Energy Storage in Calcium Batteries

AbstractRechargeable calcium batteries (RCB) are prospective candidates for sustainable energy storage, as they hold the promise of the high energy density of lithium‐ion batteries (LIBs) while simultaneously combining it with highly abundant raw materials. However, for long time, calcium batteries have faced severe issues with regard to cycling stability, until recently developments demonstrated improved battery cycle life when employing CaSn alloy anodes with fluorinated alkoxyborate electrolytes. These findings opened up the possibility to study cathode materials for RCBs not only in a more comparable manner, but also in a practical full cell design. As representative of emerging organic electrode materials (OEMs), we investigated tetrakis(4‐pyridyl) porphyrin as both free ligand (H2TPyP) and in the form of its copper MOF complex (CuTPyP−MOF) as active cathode species in RCBs. The cells demonstrated high capacities and excellent cycling stability at the same time. Even at elevated current densities of e. g., 2000 mA/g the full cells delivered stable capacities of ~90 mAh/g proving its excellent rate capability. This study explores the electrochemical performance of porphyrin active materials in calcium batteries and represents a significant step forward in the progress toward organic electrodes for multivalent energy storage systems.

Polycrystalline phases grown in-situ engendering unique mechanism of charge storage in polyaniline-graphite composite

We report on a simple surfactant/template free chemical route for the synthesis of semi-polycrystalline polyaniline-graphite (SPani-graphite) composite and its application as an electroactive material in electrochemical charge storage. The synthesized material exhibits well-defined poly-crystallographic lattices in high resolution transmission electron micrographs and sharp peaks in x-ray diffraction spectra suggesting crystalline nature of the material. The specific capacitance computed from the galvanostatic charge-discharge (GCD) data obtained from 3-electrode cell configuration using 1 M aq. Na2SO4 as an electrolyte was 111.4 F g−1 at a current density of 0.1 A g−1 which rises to 269 F g−1 at an elevated current density of 1.0 A g−1. A similar pattern of increase in the specific capacitance values with an increase in the current density was observed in the results obtained from 2-electrode symmetric device configuration using polymer gel electrolyte (xanthan gum in 1 M aq. Na2SO4). The specific capacitance computed from the GCD data obtained from the device configuration was 20 F g−1 at the current density of 1.0 A g−1. The device delivers an energy density of 1.7 Wh kg−1 and a power density of 2.48 kWh kg−1 at an applied current density of 0.5 A g−1 suggesting an excellent rate capability and power management. In addition, the device exhibits ⁓92 % specific capacitance retention up to 8000 continuous GCD cycles and ⁓80 % coulombic efficiency up to 10,000 continuous GCD cycles indicating excellent cycling stability. The unique feature of increasing specific capacitance with respect to applied current density is attributed to the presence of semi-polycrystalline phases in the SPani-graphite matrix. The material behaves as a surface redox supercapacitor and its unique mechanism of charge storage is discussed in detail in the article.

Concurrent oxygen reduction and water oxidation at high ionic strength for scalable electrosynthesis of hydrogen peroxide

Electrosynthesis of hydrogen peroxide via selective two-electron transfer oxygen reduction or water oxidation reactions offers a cleaner, cost-effective alternative to anthraquinone processes. However, it remains a challenge to achieve high Faradaic efficiencies at elevated current densities. Herein, we report that oxygen-deficient Pr1.0Sr1.0Fe0.75Zn0.25O4-δ perovskite oxides rich of oxygen vacancies can favorably bind the reaction intermediates to facilitate selective and efficient two-electron transfer pathways. These oxides exhibited superior Faradic efficiencies (~99%) for oxygen reduction over a wide potential range (0.05 to 0.45 V versus reversible hydrogen electrode) and current densities surpassing 50 mA cm−2 under high ionic strengths. We further found that the oxides perform a high selectivity (~80%) for two-electron transfer water oxidation reaction at a low overpotential (0.39 V). Lastly, we devised a membrane-free electrolyser employing bifunctional electrocatalysts, achieving a record-high Faradaic efficiency of 163.0% at 2.10 V and 50 mA cm−2. This marks the first report of the concurrent oxygen reduction and water oxidation catalysed by efficient bifunctional oxides in a novel membrane-free electrolyser for scalable hydrogen peroxide electrosynthesis.

Adsorption Site Regulations of [W–O]-Doped CoP Boosting the Hydrazine Oxidation-Coupled Hydrogen Evolution at Elevated Current Density

HighlightsThe [W–O] group with strong adsorption capacity is introduced into CoP to fabricate a bi-functional catalyst towards HER and HzOR.The cell voltage of HzOR coupled electrolyzer with 6W–O–CoP/NF as both anode and cathode catalysts is 1.634 V lower than that of the water splitting system at 100 mA cm−2.A proof-of-concept self-powered H2 production system is assembled to realize the H2 evolution rate of 3.53 mmol cm−2 h−1.

Silver-Based Supportless Membrane Electrode Assemblies for Electrochemical CO2 Reduction

CO2 is one of the major contributors to the emission of greenhouse gases boosting climate change. Meanwhile, renewable energy production is fluctuating due to weather conditions, demanding for appropriate storage, e. g. by Power-to-X technology. The first step of these processes, the production of hydrogen via water electrolysis, is typically linked to a second step to obtain hydrocarbons [1]. Meanwhile, electrochemical CO2 reduction (eCO2R) is capable of generating chemical feedstocks by converting excess CO2, simultaneously using renewable energy sources during peak times. A promising pathway of eCO2R focuses on CO, as it can be produced with high selectivity at silver catalysts, concurrently generating hydrogen as the only byproduct [2]. To partly overcome the mass transport limitations resulting from the very limited solubility of CO2 in aqueous electrolytes, gas diffusion electrodes (GDEs) are typically used for eCO2R in a three-chamber setup with anolyte, catholyte and separate gas compartment [3].However, there are still considerable overpotentials in this setup, among others caused by ohmic losses such as the electrolyte resistance. Employing membrane electrode assemblies (MEAs), either both electrodes or one of them can be combined with the membrane to form a full- or half-MEA, respectively, resulting in a significant decrease in cell voltage. Although there have already been studies on the fabrication of MEAs employing silver catalysts for eCO2R [4, 5], they are still very limited in options and mostly based on carbon gas diffusion layers (GDLs).The manufacturing approach applied in this work is based on a catalyst ink recipe for sintered silver GDEs originally developed for chlor-alkali electrolysis by Moussallem et al. [6]. Instead of using Nickel mesh as a substrate, the suspension is spray-coated on a stainless steel plate to enable the required treatment at temperatures above 300 °C. Afterwards, the catalyst layer is hot-pressed on the prepared anion exchange membrane at more moderate temperatures, forming a supportless cathodic half-MEA.Resulting from variations in the manufacturing procedure, different MEAs are electrochemically characterized, examining Faradaic efficiencies as well as cell voltages, also in comparison to measurements performed in three-chamber setup. Addressing challenges in product efficiency and membrane degradation, it is shown that this type of MEA is capable of eCO2R to CO, already reducing the cell potential at elevated current densities by nearly 50 %, see fig. 1.[1] Tom Kober et al. Report: perspectives of power-to-X technologies in Switzerland: supplementary report to the white paper. en. Technical report. 2019. doi: 10.3929/ETHZ-B-000525806.[2] Yoshio Hori et al. “Electrocatalytic process of CO selectivity in electrochemical reduction of CO2 at metal electrodes in aqueous media”. Electrochimica Acta, 39 (11-12), (1994), 1833–1839.[3] Thomas Burdyny and Wilson A. Smith. “CO2 reduction on gas-diffusion electrodes and why catalytic performance must be assessed at commercially-relevant conditions”. Energy & Environmental Science, 12 (5), (2019), 1442–1453. doi: 10.1039/C8EE03134G.[4] Zengcai Liu et al. “CO2 electrolysis to CO and O2 at high selectivity, stability and efficiency using Sustainion membranes”. Journal of The Electrochemical Society, 165 (15), (2018), J3371–J3377. doi: 10.1149/2.0501815jes.[5] Jonghyeok Lee et al. “Electrochemical CO2 reduction using alkaline membrane electrode assembly on various metal electrodes”. Journal of CO2 Utilization, 31 (2019), 244–250. doi: 10.1016/j.jcou.2019.03.022.[6] Imad Moussallem et al. “Development of high-performance silver-based gas-diffusion electrodes for chlor-alkali electrolysis with oxygen depolarized cathodes”. Chemical Engineering and Processing: Process Intensification, 52 (2012), 125–131. doi: 10.1016/j.cep.2011.11.003. Figure 1

Modeling Chemical Microenvironments in Porous Copper Electrodes for CO2 Reduction at Elevated Current Densities

Electrochemical CO2 reduction (CO2R) presents a promising pathway toward the reuse of CO2 emitted during the production of industrial commodities (e.g., cement, steel, and plastics) to form value-added commodities and fuels at ambient temperatures and pressures with renewably generated electrons. Copper (Cu) catalysts demonstrate the ability to convert CO2 to multicarbon (C2+) products. Additionally, 3-D structured porous Cu electrodes can facilitate the operation of CO2R to C2+ at significantly elevated current densities by enhancing the delivery of CO2 to catalytic active sites on Cu, offering the potential to translate lab-scale understanding to industrial operation. Nonetheless, there still exist selectivity limitations in porous electrode systems due to poor control of the chemical microenvironment, (i.e., the local pH, CO2 activity, and CO intermediate management), in these complex electrodes. Therefore, resolving microenvironment in porous Cu electrodes will be critical to advancing these systems towards industrialization.In this talk, we explore the use of continuum modeling to resolve and understand the effects of mass transfer and chemical environment in electrochemical CO2 reduction in porous Cu electrodes. We explore two scenarios of porous Cu electrodes performing electrochemical CO2 reduction. The first is the operation of a device employing a bipolar membrane (BPM) in reverse bias, wherein modeling reveals that the proton flux generated by the BPM substantially lowers the pH of the porous electrode and promotes selective CH4 and HCOOH generation. The second is the use of a micro-structured porous electrode that employs an anion-exchange membrane and more selectively generates C2+ products. 2-D modeling reveals heterogeneities in the porous electrode enable hotspots of increased pH that locally enhance C2+ selectivity. Ultimately, this talk underscores the powerful ability of continuum modeling to resolve microenvironments at spatial resolutions beyond what is achievable experimentally, as well as to link changes in microenvironment to changes in local selectivity. These simulations will rationalize and guide the engineering of microenvironment in next-generation porous electrodes for CO2 reduction to C2+ products at industrial scales.

How the Choice of Electrolyte Affects the Carbon Efficiency in Electrochemical CO2 Reduction at Silver Gas Diffusion Electrodes

Reducing CO2 emissions by replacing fossil fuels with renewable energy sources is an important step in the context of climate change. Electrochemical CO2 reduction is a promising technology for supporting this shift, since it provides the possibility to store electrical energy in form of high value chemicals while consuming CO2. It is now generally accepted that the use of gas diffusion electrodes (GDEs) is beneficial due to the limited solubility of CO2 in water [1].To achieve a better understanding of the complex processes taking place in the electrode, the description by a mathematical model is desirable. We present a TFFA (thin-film flooded agglomerate) model for silver GDEs based on the approach presented by Franzen et al. [2] for the oxygen reduction reaction. The model describes the processes in the GDE, including reaction, diffusion, and migration. Therefore, the model provides an in-depth view on the local reaction environment in the electrode, which becomes highly alkaline at elevated current densities due to the formation of hydroxide ions by the electrochemical reactions [3]. This causes the rate of bicarbonate/carbonate formation to exceed the rate of electrochemical CO2 reduction, resulting in a limited carbon efficiency [4]. Using acidic electrolytes might significantly reduce this limitation by decreasing the local alkalinity. This has already been experimentally demonstrated for gold electrodes using electrolytes with pH values in the range of 2-4 [5]. In this study, we present experimental results for silver GDEs using acidic electrolytes. These results show that the carbon efficiency can be increased while maintaining a similar Faradaic efficiency as obtained for KHCO3 electrolytes at industrially relevant current densities. Our model calculations support these findings and give insights about the development of the local pH in dependence of the applied current density for different pH values of the bulk electrolyte.[1] T. Burdyny, W. A. Smith, CO2 reduction on gas-diffusion electrodes and why catalytic performance must be assessed at commercially-relevant conditions, Energy & Environmental Science 12 (5) (2019), 1442-1453.[2] D. Franzen, M. C. Paulisch, B. Ellendorff, I. Manke, T. Turek, Spatially resolved model of oxygen reduction reaction in silver-based porous gas-diffusion electrodes based on operando measurements, Electrochimica Acta 375 (2021), 137976.[3] M. Löffelholz, J. Osiewacz, A. Lüken, K. Perrey, A. Bulan, T. Turek, Modeling electrochemical CO2 reduction at silver gas diffusion electrodes using a TFFA approach. Chemical Engineering Journal 435(2) (2022), 134920.[4] J. A. Rabinowitz, M.W. Kanan, The future of low-temperature carbon dioxide electrolysis depends on solving one basic problem. Nature Communications 11 (2020), 5231.[5] M.C.O. Monteiro, M.F. Philips, K.J.P. Schouten et al., Efficiency and selectivity of CO2 reduction to CO on gold gas diffusion electrodes in acidic media. Nature Communication 12 (2021), 4943. Figure 1

Polypyrrole-Doped NH4 V3 O8 with Oxygen Vacancies as High-Performance Cathode Material for Aqueous Zinc-Ion Batteries.

The inherent slow diffusion dynamics of aqueous zinc-ion batteries (AZIBs) act as a significant hindrance to their universal utilization as energy storage systems, largely attributed to the scarcity of superior cathode materials. In this study, a novel method that amalgamates oxygen defect engineering and polymer intercalation, guided by theoretical computations, to confront this challenge, is introduced. Thisapproach begins with density functional theory calculations, demonstrating that the shielding effect rendered by polypyrrole (PPy) between NH4 V3 O8 (NVO) layers, along with the cooperative influence of oxygen defects (Od ), optimizes the kinetic transport of Zn2+ . Leveraging these theoretical outcomes, a two-step hydrothermal synthesis procedure is devised to fabricate PPy-intercalated NVO embedded with Od (NVO-Od @PPy). Theempirical findings corroborate the theoretical predictions, showcasing that the NVO-Od @PPy//Zn system manifests exceptional cycling stability. Specifically, the NVO-Od @PPy electrode delivers an optimal reversible capacity, yielding 421 mAh g-1 at a current density of 0.1 A g-1 . Remarkably, even at an elevated current density of 10 A g-1 , it sustains a capacity of 175.7 mAh g-1 , while maintaining a capacity retention of 99% over 1000 cycles. This research provides pivotal insights for the engineering of high-performing cathode materials for AZIBs, paving the way for their future advancements.

Mechanical stress state consideration for enhanced electromigration life prediction in aluminum wire bonds

In this study, 5 [mil] aluminum wire bonds are subjected to elevated ambient temperatures, current densities, and mechanical stresses using a novel accelerated testing mechanism. Failure of a wire bond in this study was a 10 % increase in electrical resistance. Temperature coefficient of resistance experiments in this study identified the wire temperatures resulting from joule heating and thermomechanical stress evaluations were completed using ANSYS to extract relevant stresses occurring at each experimental condition. Collection of the failure data and analysis of the results indicate that mechanical stress interacts with current density and that the introduction of externally applied mechanical stress reduces the lifetime of a wire bond. Comparisons have been drawn between time to failure estimates for Black's equation for electromigration and three model forms developed from the results of this study. The comparison indicates that Black's equation is insufficient when mechanical stresses interact with current density and that mechanical stress ought to be considered in the future when completing reliability evaluations for wired interconnects in high-temperature systems.

Synergistically enhanced sodium ion storage from encapsulating highly dispersed cobalt nanodots into N, P, S tri-doped hexapod carbon framework

Development of multitudinous heteroatoms co-doped carbon nanomaterials with pleasurable electrochemical behavior for sodium ion batteries is still an enormous challenge. Herein, high dispersion cobalt nanodots encapsulating into N, P, S tri-doped hexapod carbon (H-Co@NPSC) have been victoriously synthesized via H-ZIF67@polymer template strategy with using poly (hexachlorocyclophos-phazene and 4,4′-sulfonyldiphenol) as both carbon source and N, P, S multiple heteroatom doping sources. The uniform distribution of cobalt nanodots and the Co-N bonds are conducive to form a high conductive network, which synergistically increase a lot adsorption sites and lessens the diffusion energy barrier, thereby improving the fast Na+ ions diffusion kinetics. Consequently, H-Co@NPSC delivers the reversible capacity of 311.1 mAh g−1 at 1 A g−1 after 450 cycles with 70% capacity storage rate, while obtains the capacity of 237.1 mAh g- 1 after 200 cycles at the elevated current densities of 5 A g−1 as an excellent anode material for SIBs. These interesting results pave a generous avenue for the exploitation of promising carbon anode materials for Na+ storage.

P‐120: Accelerated Lifetime Testing and Degradation Mechanisms of a Blue TADF OLED

Organic light‐emitting diodes (OLEDs) are a widespread commercial display technology but they are still subject of ongoing research with the aim to expand their application ranges through stack and material design. Operational stability is one of the most important key properties that are steadily being improved. The long lifetimes of several thousands of hours of state‐of‐the‐art OLED structures at standard operating conditions demand for accelerated lifetime tests (ALTs) and the use of appropriate scaling laws for elevated temperatures and current densities. Here we present ALTs for a blue thermally activated delayed fluorescent (TADF) OLED and demonstrate the successful determination of the scaling parameters. Moreover, we study the microscopic degradation mechanisms using in‐situ electrical characterization methods.

Critical Role of Pressure for Chemo-Mechanical-Induced Stability of Sodium Metal Battery Anodes

In this work we demonstrate that cell pressure controls the morphology and stability of electroplated sodium metal deposits on carbon black nucleation layers in ether-based electrolytes. At pressures below 500 kPa we observe the presence of three-dimensional Na nuclei accompanied by low Coulombic efficiencies (CEs less than 98%). Conversely, at pressures between 500 and 1272 kPa we observe smooth, planar Na deposits, high CEs up to 99.9%, and stable electrochemical cycling. Through a series of tests conducted at elevated current densities and with or without rest stages, our findings elucidate the balance of important competing time scales for creep and morphology evolution under pressure and the rate of charge transfer that determines Na morphology and stability. This highlights how chemo-mechanical effects at pressure ranges relevant for battery packaging in coin and pouch cells are key factors in the design and operation of Na metal batteries.

Spatially resolved degradation effects in UVB LEDs stressed by constant current operation

InAlGaN-based UVB light-emitting diodes with an emission wavelength of 310 nm were operated at an elevated nominal current density of 200 A/cm2 and a heatsink temperature of 29 °C. The spatial intensity distributions of the electroluminescence and photoluminescence were measured before, during, and after dc stress. A decreasing homogeneity of the spatial intensity distributions with operation time was observed. It is concluded that the current density distribution changes during operation. Furthermore, the active region degrades more rapidly in the areas of higher current density. By quantitatively evaluating the current density distribution, it is proposed that a decreasing radiative recombination efficiency of the active region is causing the decrease in the total optical power of the LEDs during operation.