Large Electrode Research Articles

Effects of micro-alloying Ag on microstructure, mechanical properties and corrosion behavior of extruded Mg-2Zn-0.2Ca-xAg alloys

The present work investigates effects of micro-alloying Ag on the microstructure, mechanical properties and corrosion behavior of as-extruded Mg-2Zn-0.2Ca alloys. The addition of Ag, up to 0.5 wt%, induce limited difference on microstructural characteristics such as slightly coarser microstructures due to the enhanced dynamic recrystallization process and the presence of refined precipitates. The tensile properties of the alloy were not significantly changed by Ag addition, i.e., all the alloys exhibited exceptional elongation of ∼30%, moderate tensile yield strength and ultimate strength of ∼140 MPa and ∼240 MPa, respectively. The corrosion performance of the alloys was progressively deteriorated with increasing Ag content i.e., the corrosion rate increased from 0.40 ± 0.23 mm/y for Mg-2Zn-0.2Ca alloy to 3.27 ± 0.24 mm/y for the Mg-2Zn-0.2Ca-0.5Ag alloy. The compromised corrosion performance was attributed to a large electrode potential difference between the nobler Ca2Mg6Zn3 phase and the α-Mg matrix as well as a less protective corrosion film, by increasing Ag addition.

Preparation and soldering performance of SAC305@Sn-bi Core-shell solder balls based on eutectic co-deposition

SnBi eutectic thin film alloys are widely used in microelectronic devices, sensors, biomedical devices due to their high resistance, low temperature coefficient, chemical stability, and biocompatibility. However, the large standard electrode potential difference (454 mV) between Sn (−0.136 V) and Bi (+0.3118 V) makes them difficult to be co-deposited, especially with eutectic composition. In this study, cathodic polarization curves were used to analyze the negative shift of the cathodic reduction potentials of Sn and Bi induced by gelatin and EDTA-2Na, respectively, which reduced the potential difference between the two to 184 mv (Sn:-0.958 v; Bi:-0.774 v) and enabled the co-deposition of Sn and Bi; cathodic overpotentials were analysed to show that catechol not only improves the degree of cathodic polarization, but also raises the overpotentials, resulting in flatter surface coatings; By adjusting the temperature, current density, and pulse current, a SnBi eutectic thin film coating with good weldability, controllable thickness, flat surface, density, and uniformity was obtained on copper foil using a platinum as the anode in a methanesulfonic acid solution. The results indicate that it is feasible to deposit SnBi solder alloy at eutectic points (Sn41.53Bi58.47, At.%). Under the synergistic effect of gelatin and unidirectional square wave pulse, a typical eutectic network morphology can be obtained, which is the same as the microstructure of industrial SnBi eutectic solder. Based on these, a core-shell composite soldering material for low-temperature soldering was obtained by using SAC305 solder balls as cores and a SnBi low-temperature soldering material coating was roll-plated on their surfaces. This study provides a reliable technical way and theoretical guidance for low-temperature soldering, preparation of low-temperature solderable core-shell composite soldering material, and application of sensors and optoelectronic devices.

A 97-Channel Read-Out ASIC for an Electrophysiological Mapping Catheter With an Optical Link.

Electrophysiological (EP) mapping catheters are medical equipment, which are widely used to diagnose and treat atrial fibrillation. The electrophysiology signals are sensed by the catheter's electrodes, for which a large electrode count becomes more and more essential because of the demand for a higher local resolution. A drawback of the large electrode count is the effort to pass through and to integrate the wires inside the catheter shaft. To overcome with this issue, this article describes the realization of an EP ASIC, which is placed close to the 97 electrodes and to perform an in-tip digitization. Thanks to an integrated optical link, only a single fiber is required to connect the catheter tip to an externally located electro-optical unit and thus shrinking the shaft volume to a minimum. The fiber is used to guide light from the electro-optical unit to the catheter tip and illuminate a blue LED, which is located close to the EP ASIC and acts as a photovoltaic cell. The EP ASIC is designed to use the LED as power source and a data transceiver while performing signal conditioning and digitization of the EP signals at the same time. The EP signals are captured with the ASIC's multi-channel read-out circuit consisting of 97 fully differential preamplifiers and additional filter stages. A switch network sequentially selects one single channel for further amplification and digitization of the EP signal. The read-out circuit is designed to process signals in the range of 500 μVpp to 20 mVpp with a bandwidth of 5 Hz to 100 Hz.

Construction of a uniform zeolitic imidazole framework (ZIF-8) nanocrystal through a wet chemical route towards supercapacitor application.

Exploring larger surface area electrode materials is crucial for the development of an efficient supercapacitors (SCs) with superior electrochemical performance. Herein, a cost-effective strategy was adopted to synthesize a series of ZIF8 nanocrystals, and their size effect as a function of surface area was also examined. The resultant ZIF8-4 nanocrystal exhibits a uniform hexagonal structure with a large surface area (2800 m2 g-1) and nanometre size while maintaining a yield as high as 78%. The SCs performance was explored by employing different aqueous electrolytes (0.5 M H2SO4 and 1 M KOH) in a three-electrode set-up. The SC performance using a basic electrolyte (1 M KOH) was superior owing to the high ionic mobility of K+. The optimized ZIF8-4 nanocrystal electrode showed a faradaic reaction with a highest capacitance of 1420 F g-1 at 1 A g-1 of current density compared to other as-prepared electrodes in the three-electrode assembly. In addition, the resultant ZIF8-4 was embedded into a symmetric supercapacitor (SSC), and the device offered 350 F g-1 of capacitance with a maximum energy and power density of 43.7 W h kg-1 and 900 W kg-1 at 1 A g-1 of current density, respectively. To determine the practical viewpoint and real-world applications of the ZIF8-4 SSC device, 7000 GCD cycles were performed at 10 A g-1 of current density. Significantly, the device exhibited a cycling stability around 90% compared to the initial capacitance. Therefore, these findings provide a pathway for constructing large surface area ZIF8-based electrodes for high-value-added energy storage applications, particularly supercapacitors.

Mechanical modulation effects of gold electrodes on geometries and electronic transport properties of azobenzene molecular junctions

The azobenzene molecular junction has aroused much interest of scientists due to its switching property arising from its photoinduced isomerism. Owing to the existence of the cis and trans isomers, the electronic transport properties of the azobenzene molecules are promised to show significant differences. The experimental investigations indicate that the cis azobenzene molecule commonly shows high conductance, while the trans azobenzene molecule shows low conductance. However, the computations give the opposite results. To reveal this significant difference, the effects of electrode mechanical modulation on the geometries and electronic transports of the azobenzene molecules are studied. The effects of the electrode geometries on the electronic transports of the azobenzene molecular junctions are also investigated. The electrode compressing process and the electrode stretching process of the azobenzene molecular junctions are simulated based on the first principles calculations. The electronic transport properties are further calculated by using non-equilibrium Green’s function (NEGF) method. The numerical results show that the structures of the cis and trans azobenzenes with sulfur anchors are stable in the stretching process and compressing process of electrode. For the cis azobenzene molecular junction, the cis geometry remains unchanged until the electrode distance is stretched to about 0.1 nm longer than the stable electrode distance of the trans azobenzene molecular junction. Though the trans azobenzene molecule is bent when squeezed by the electrodes, the C—N—N—C dihedral still maintains its trans structure even when the electrode distance is compressed to about 0.2 nm shorter than the stable electrode distance of the cis azobenzene molecular junctions. It is intriguing that the conductance values of cis and trans azobenzene molecular junctions vary inversely with the electrode distance. The conductance value of the cis azobenzene molecular junction increases with the elongating of the electrode distance, while the conductance value of the trans azobenzene molecular junction increases with the compression of the electrode. The conductance is very sensitive to the electrode distance for both the cis azobenzene molecular junction and the trans azobenzene molecular junctions, which can change more than 10 times with the change of the electrode distance. In the lower bias regime, the conductance of the trans azobenzene is higher than that of the cis one if the two electrodes are planar. However, when the molecule is sandwiched between two pyramid-shaped electrodes, the condutance of the cis azobenzene is higher. Thus, the higher conductance of cis azobenzene may be caused either by the pyramid-shaped electrodes or by the large electrode distance.

Insights into the hydrogen evolution reaction in vanadium redox flow batteries: A synchrotron radiation based X-ray imaging study

The parasitic hydrogen evolution reaction (HER) in the negative half-cell of vanadium redox flow batteries (VRFBs) causes severe efficiency losses. Thus, a deeper understanding of this process and the accompanying bubble formation is crucial. This benchmarking study locally analyzes the bubble distribution in thick, porous electrodes for the first time using deep learning-based image segmentation of synchrotron X-ray micro-tomograms. Each large three-dimensional data set was processed precisely in less than one minute while minimizing human errors and pointing out areas of increased HER activity in VRFBs. The study systematically varies the electrode potential and material, concluding that more negative electrode potentials of −200 mV vs. reversible hydrogen electrode (RHE) and lower cause more substantial bubble formation, resulting in bubble fractions of around 15%–20% in carbon felt electrodes. Contrarily, the bubble fractions stay only around 2% in an electrode combining carbon felt and carbon paper. The detected areas with high HER activity, such as the border subregion with more than 30% bubble fraction in carbon felt electrodes, the cutting edges, and preferential spots in the electrode bulk, are potential-independent and suggest that larger electrodes with a higher bulk-to-border ratio might reduce HER-related performance losses. The described combination of electrochemical measurements, local X-ray micro-tomography, AI-based segmentation, and 3D morphometric analysis is a powerful and novel approach for local bubble analysis in three-dimensional porous electrodes, providing an essential toolkit for a broad community working on bubble-generating electrochemical systems.

Conformal Electrodeposition of Mesoporous Silica over High Aspect Ratio (AR>100) Nanomesh Electrodes

The high surface area provided by the nanopores of ordered mesoporous silica thin films enables a wide range of electrochemical applications such as sensors, catalysis, energy storage and ion-selective membranes. Further improvements are possible by coating such thin films on large surface area electrodes with high aspect ratios (> 100) to increase the active surface area. Atomic layer deposition (ALD) is often preferred to deposit conformal thin film oxides on high aspect ratio structures. Such vapor-phase depositions are limited by the available surface reactive sites to deposit thin films of thickness ranging from sub-nanometer to few tens of nanometer. However, there is a tradeoff in terms of deposition time/cycles to achieve quality films especially when high aspect ratios (>100) substrates are introduced. Electrochemistry offers an alternative, versatile method to conformally coat layers on 3D electrode surfaces. The electrochemically assisted self-assembly (EASA) of mesoporous silica, utilizes electrochemical reactions to locally increase the pH near the electrode surface, which in turn catalyzes the silica gelation and surfactant self-assembly, thus causing the controlled growth of mesoporous silica thin films [1]. Recently, our group has shown that good quality mesoporous silica films with thickness between 20-2000 nm could be achieved by controlling the hydrodynamic layer in a rotating disc electrode setup [2]. Moreover, EASA of mesoporous silica offers meso-channels that are aligned perpendicular to the underlaying conductive substrate which is optimal for mass-transport.In this follow-up work, we demonstrate a reliable, electrochemically controlled, conformal deposition of mesoporous silica onto large surface area nanomesh electrodes with an aspect ratio close to 100. Nanomesh electrodes developed in our group at imec, is built up of a regularly spaced (50 nm), inter-connected network of vertical and horizontal nanowires of diameter ~40 nm. These electrodes offer an 80x area enhancement (80 cm2 per geometric cm2) while maintaining a porosity close to 75%. We show that, the extent of silica deposition over these nanomesh electrodes can be electrochemically controlled from conformal coatings (~10 nm thick) uniformly coating the whole nanomesh architecture to complete fill and overfill of the nanomesh electrodes (~4 µm thick). Furthermore, excellent mass-transport properties of various silica coated nanomesh electrodes has been demonstrated using a ruthenium hexaammine redox probe. Finally, the area enhancement offered by the silica coated Ni nanomesh is demonstrated using the characteristic accumulation of a positively charged [Ru(NH3)6]3+ probe within the negatively charged silica nanochannels, which shows 55x increase for the amount of charge from the probe stored in the coated nanomesh, compared to a planar silica layer, consistent with the expected surface area enhancement of the 4 µm thick nanomesh electrodes.

(Invited) Development of Sustainable Electrocatalysts for Anion Exchange Membrane Fuel Cells and Electrolyzers

The electrocatalytic hydrogen oxidation (HOR) and evolution (HER) reactions under alkaline conditions are kinetically slow processes even when Pt group metals are employed. This presentation discusses our strategies to improve the activity of non platinum catalysts. For example, to improve the alkaline HOR activity of transition metal nanoparticles we look at engineering strong interactions with metal oxides incorporated with carbon-based catalyst supports.(1,2) Another strategy involves utilizing novel carbon materials such as onion like carbon (OLC). We have shown that the combination of CeO2 and OLC in Pd–CeO2/OLC induces surface defects and modifies the electronic structure of the Pd-OLC interface, significantly improving electrical conductivity due to enhanced charge redistribution. Such results were corroborated by density functional theory (DFT) calculations.(3) Using this strategy, peak power densities of up to 2 W cm-2 have been achieved when Pd-CeO2 is incorporated in AEMFCs.(4) Regarding the alkaline HER, mixed phase Ni-Mo and MoO3-x materials are known to have enhanced alkaline hydrogen evolution reaction (HER) activity. Here we describe the optimization of the preparation of an active HER catalyst composed of MoO2 surface nanorod arrays on nickel foam (see Figure). Large circular cathode electrodes (Area 80 cm2) were prepared and tested in a three cell stack AEM electrolyser.(5) M. V. Pagliaro, C. L. Wen, B. Sa, B. Y. Liu, M. Bellini, F. Bartoli, S. Sahoo, R. K. Singh, S. P. Alpay, H. A. Miller and D. R. Dekel, ACS Catal., 10894 (2022).M. V. Pagliaro, M. Bellini, F. Bartoli, J. Filippi, A. Marchionni, C. Castello, W. Oberhauser, L. Poggini, B. Cortigiani, L. Capozzoli, A. Lavacchi, H. A. Miller and F. Vizza, Inorg. Chim. Acta, 543 (2022).J. Ogada, A. K. Ipadeola, P. V. Mwonga, A. B. Haruna, F. Nichols, S. W. Chen, H. A. Miller, M. V. Pagliaro, F. Vizza, J. R. Varcoe, D. M. Meira, D. M. Wamwangi and K. I. Ozoemena, ACS Catal., 12, 10938 (2022).H. A. Miller, M. Bellini, D. R. Dekel, and F. Vizza, Electrochemistry Communications, 135, 107219 (2022).F. Bartoli, L. Capozzoli, T. Peruzzolo, M. Marelli, C. Evangelisti, k. Bouzek, J. Hnat, G. Serrano, L. Poggini, K. Stojanovski, V. Briega-Martos, S. Cherevko, H. A. Miller and F. Vizza, J. Mater. Chem. A, 11, 5789 (2023). Figure 1

How to Make a Single-Layer Pouch Cell That Matches the Performance of a Commercial Li-Ion Cell

As lithium-ion batteries (LIBs) have exploded in popularity due to the consumer electronics and electric vehicle industries, many resources are poured into research. While the simplest cell format requiring the least amount of active material to make in a research laboratory to study various aspects of the cell is usually the coin cell, it is far from the most representative of commercial LIBs. Oftentimes, coin cells are made with a large negative electrode overhang to reduce the risk from positive/negative electrode misalignment, but the overhang region can cause Li+ to become effectively trapped at higher C-rates1. While this is a necessary trade-off in today’s commercial LIB manufacturing, the overhang area is normally a much smaller fraction of the total negative electrode area in a commercial cell than in a laboratory coin cell, which can lead to discrepancies in cycle testing. Moreover, during assembly of commercial stacked or wound cells, there is always a region in which one side of a double-sided coating, typically the negative, is not needed and thus a single-sided electrode should be used. However, not all manufacturers eliminate the outward-facing second side and elect to simply use double-sided coatings throughout. Therefore, studying the effects of excess electrode in single-layer pouch cells will be explored in this presentation. In this presentation, cells made in various formats (coin and stacked pouch) will be compared to single-layer pouch cells made with and without negative electrode overhang. Single-layer pouch cells are the easiest format for assembling full cells without overhang because they are neither too small nor too big for positive/negative electrode alignment to be difficult. Moreover, single-layer pouch cells made with double-sided coatings (without overhang) and cycled using Ultra-High Precision Coulometry (UHPC) will be shown to have poor cycling. This is for two reasons: 1) for a double-sided negative, the outward-facing coating of the electrode can trap Li+ just like the overhang on the inward-facing coating; and 2) the outward-facing positive can be deintercalated and provide more capacity than desired2, possibly even surpassing the negative/positive areal capacity ratio. Single-layer pouch cells with no overhang are shown in Figure 1a to outperform all other cell formats tested, retaining 90% of their original capacity after 500 cycles at C/3 and 40 °C, and have the lowest difference in capacity between typical C/3 and C/20 checkup cycles as shown in Figure 1b. The stacked pouch cells in Figure 1 are composed of 3 positive and 4 negative electrodes that are all double-sided, meaning there are two outward-facing negative electrode coatings that can trap Li+, possibly resulting in the much poorer capacity fade to 80% after 500 cycles illustrated in Figure 1a. Thus, single-layer pouch cells without overhang give the most realistic cycling results for the tested electrode materials. Figure 1. C/3 cycling of full cells of various formats denoted in the legend. Plotted in (a) is the normalized discharge capacity and (b) is the difference in areal discharge capacity between the C/20 checkup cycle and preceding C/3 cycle. REFERENCES Gyenes, B., Stevens, D.A., Chevrier, V.L., and Dahn, J.R. (2015). Understanding Anomalous Behavior in Coulombic Efficiency Measurements on Li-Ion Batteries. J Electrochem Soc 162, A278–A283. 10.1149/2.0191503jes.Smith, A., Stüble, P., Leuthner, L., Hofmann, A., Jeschull, F., and Mereacre, L. (2023). Potential and Limitations of Research Battery Cell Types for Electrochemical Data Acquisition. Batter Supercaps e202300080. doi.org/10.1002/batt.202300080. Figure 1

Scalable Production of Nickel-Cobalt Based Anode Materials for Alkaline Electrolysis: A Multi-Technique Approach from Micro Powder Analysis to Electrochemical Performance

The growing concern about environmental degradation caused by the use of conventional fossil fuels has triggered a significant paradigm shift in the research and development of sustainable energy sources such as hydrogen. Water electrolysis is a promising approach for achieving efficient energy conversion and storage [1]. While this process has made significant advancements recently, an in-depth understanding of the entire process chain from commercial powder materials to electrodes and their electrocatalytic activity with useful correlations between involved steps are still underexplored.Here our research aims toward a thorough and continuous evaluation of Ni-Co-O-based electrocatalysts to parameterize the process chain to unravel interdependencies and understand the correlation between the material, manufacturing process, electrode structure and final cell performance. The applied methodology incorporates various complementary techniques to analyze the physical and chemical properties of the materials involved consistently throughout the entire process chain. After preliminary characterization of commercial Ni-Co-O micropowder using transmission electron microscopy and energy-dispersive X-ray spectroscopy, ink formulations, obtained from the powder, were optimized using analytical centrifugation [2] and Hansen parameter calculations [3]. Then selected inks were transferred to electrodes by coating these inks on Ni plates via ultrasonic spray deposition. Effect of post-treatments such as vacuum annealing and surface plasma treatment on the electrode stability against delamination was also investigated. To quantify micro features of large electrode areas and analyze their surface characteristics, we developed a framework by employing atomic force microscopy. So evaluated electrodes were finally tested for their functionality as anodes for alkaline water electrolysis where useful correlations were established between the properties of the catalyst ink/ coated electrodes and their electrochemical activity/ stability. In agreement to the identified structural features, our preliminary results indicate that plasma treated Ni-Co-O electrodes show lower overpotentials and higher stabilities in comparison with the pristine and vacuum annealed electrodes due to increased adhesion and surface properties (roughness etc.) induced by plasma.This study highlights the need for careful evaluation of the entire process chain at various stages with knowledge feedback from previous steps for continuous electrode improvisation. Optimization of each individual step is crucial to enhance the final performance of the catalyst. In our future attempts, we plan to scale-up our approach to larger electrode areas (up to 100x100 cm2) where a systematical analysis and optimization of all involved steps can be easily adapted closer to industrial settings. Wang, S., A. Lu, and C.-J. Zhong, Hydrogen production from water electrolysis: role of catalysts. Nano Convergence, 2021. 8: p. 1-23.Bapat, S., et al., On the state and stability of fuel cell catalyst inks. Advanced Powder Technology, 2021. 32(10): p. 3845-3859.Anwar, O., et al., Hansen parameter evaluation for the characterization of titania photocatalysts using particle size distributions and combinatorics. Nanoscale, 2022. 14(37): p. 13593-13607. Figure 1

Enhancing Material Analysis with Statistical and Computer Vision Techniques: A Comprehensive Approach for Evaluating Electrode Quality

The optimization of electrodes for electrocatalysis is critical to the efficient operation of energy conversion applications, i.e., performance and efficiency can be improved by optimizing their fabrication process [1]. In the surface microstructure of anodes has been recognized as a fundamental aspect influencing their functionality [2]. Consequently, it is vital to precisely characterize the microstructure of electrodes. Atomic force microscopy (AFM) has demonstrated to be a potent technique for scrutinizing the nanoscale microstructure of anodes. Nevertheless, AFM has limitations in investigating vast areas, thereby posing a challenge when evaluating the surface microstructure of large-scale electrodes.In this study, we developed a multi-stage data quantification method to overcome the limitations of AFM to measure large electrode areas. The efficacy of the developed approach that combines statistical analysis and computer vision techniques was validated by scrutinizing anodes made under various spray coating process conditions. The results demonstrated that the proposed method facilitated the in-depth evaluation of the degree of homogeneity, surface smoothness, and the presence of cracks or defects, thereby enabling a comprehensive assessment of electrode quality. It was possible to establish structure-performance relationships and delineate the interdependence between surface morphology and anode performance, activity, and cycling stability by combining surface analysis measurements with electrochemical analysis.In conclusion, this link between surface and electrochemical analysis will provide critical insights into anode performance and, in turn, drive the development of advanced materials for energy conversion technologies. Therefore, we believe our method has a high potential to expand the material scientist's toolkit and extend its application to analyze the micro/nanostructure of diverse materials in a wide range of applications, providing novel insights for their optimization. References Siegmund, D., et al., Crossing the valley of death: from fundamental to applied research in electrolysis. Jacs Au, 2021. 1(5): p. 527-535.Chatenet, Marian, et al. "Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments." Chemical Society Reviews (2022).

Highly sensitive analysis of trace germanium derived from the efficient electrosynthesis and spectral introduction of GeH4 on foam electrode

BackgroundThe electrochemical hydride generation technology, which uses electrolysis instead of chemical reagents to generate reducing species to achieve gaseous transformation and sample introduction of the tested elements, has received widespread attention in the field of atomic spectroscopy due to its simple, economical, and green characteristics. However, limited by the effective area of the electrode, the introduction efficiency and spectral signal of most elements (e.g., germanium) in practical applications are lower than traditional chemical hydride generation. ResultsIn this paper, an efficient electrochemical hydride generation (EHG) method based on metal foam electrode for μg L−1 level germanium was constructed. Systematic electrochemical and spectral tests showed that the low charge transfer resistance and the high electrochemical activity of nickel-based foam electrodes jointly promoted the efficient electroreduction of Ge(IV). Besides, the porous network structure of the metal foam material improves the contact probability of reactants while reducing the gas-evolution effect caused by bubble accumulation. Interestingly, adequate reaction sites are crucial for the conversion of germanium, but large foam electrodes are not always compatible with analytical performance. After coupling atomic fluorescence spectroscopy, this new electrolysis method has been proven to be suitable for efficient conversion and quantitative detection of Ge over a wide concentration range (5–150 μg L−1). SignificanceOur proposal to improve the electrosynthesis efficiency of germanane (GeH4) by using metal foam electrode is extremely effective for the detection of trace or ultra-trace germanium. The exploration of electrode material, structure, and especially effective area will also provide ideas for the establishment of highly sensitive analysis methods in the future.

Tuning the selectivity of CO2 electroreduction on Cu/In2O3 heterogeneous interface

The electrochemical reduction of CO2 is an effective approach to reduce and utilize CO2 for carbon neutral under mild conditions, meanwhile, the development of efficient and stable catalysts with large area and low cost is more conducive to the industrialization of CO2 electroreduction. The metal-oxide heterogeneous interface can promote the activation and conversion of CO2 due to the synergy effect between the metal and the oxide. Therefore, Cu/In2O3 electrodes are fabricated by magnetron sputtering in one step to achieve high selectivity of CO or CH3OH at different potentials. The highest Faradaic efficiency of CO is 78% at − 0.75 V, and unexpectedly, the Faradaic efficiency of CH3OH at − 0.55 V can reach 56%. The abundance of heterogeneous interfaces in Cu/In2O3 provides more active sites, reduces the work function and shifts the d‐band center upward. The catalytic performance was improved by electron transfer promotion and enhanced CO adsorption. Such advantages are responsible for the unique catalytic properties of the metal-oxide electrodes and provide a novel insight to develop large area metal-oxide electrodes for CH3OH preparation.

Distally-referred surface electrical nerve stimulation (DR-SENS) for haptic feedback

Objective. This study’s objective is to understand distally-referred surface electrical nerve stimulation (DR-SENS) and evaluates the effects of electrode placement, polarity, and stimulation intensity on the location of elicited sensations in non-disabled individuals. Approach. A two-phased human experiment was used to characterize DR-SENS. In Experiment One, we explored 182 electrode combinations to identify a subset of electrode position combinations that would be most likely to elicit distally-referred sensations isolated to the index finger without discomfort. In Experiment Two, we further examined this subset of electrode combinations to determine the effect of stimulation intensity and electrode position on perceived sensation location. Stimulation thresholds were evaluated using parameter estimation by sequential testing and sensation locations were characterized using psychometric intensity tests. Main Results. We found that electrode positions distal to the wrist can consistently evoke distally referred sensations with no significant polarity dependency. The finger-palm combination had the most occurrences of distal sensations, and the different variations of this combination did not have a significant effect on sensation location. Increasing stimulation intensity significantly expanded the area of the sensation, moved the most distal sensation distally, and moved the vertical centroid proximally. Also, a large anodic-leading electrode at the elbow mitigated all sensation at the anodic-leading electrode site while using symmetric stimulation waveforms. Furthermore, this study showed that the most intense sensation for a given percept can be distally referred. Lastly, for each participant, at least one of the finger-palm combinations evaluated in this study worked at both perception threshold and maximum comfortable stimulation intensities. Significance. These findings show that a non-invasive surface electrical stimulation charge modulated haptic interface can be used to elicit distally-referred sensations on non-disabled users. Furthermore, these results inform the design of novel haptic interfaces and other applications of surface electrical stimulation based haptic feedback on electrodes positioned distally from the wrist.

Hydrous ruthenium oxide quantum dots anchored on carbon nanocages for Zn-ion hybrid capacitors

Zn-ion hybrid capacitors (ZICs) are a novel and promising electrochemical energy storage system, while exploring high-performance cathode materials is essential for the development of ZICs. Herein, we propose hydrous ruthenium oxide quantum dots (RuO2 QDs) anchored on porous carbon nanocages (PCNCs) as a new cathode material for ZICs. For the RuO2 QDs@PCNCs material, hydrous RuO2 QDs with a small size of 2–3 nm uniformly disperse on the PCNC support, providing large electrode–electrolyte interface for electrochemical reactions and abundant active sites for ion storage. Consequently, the RuO2 QDs@PCNCs cathode material displays desirable electrochemical performance in ZICs, including a large capacity of 224 mAh g−1 at 0.4–1.8 V, superior rate capability (showing 156 mAh g−1 capacity even at a large current of 20 A g−1) and good stability during a long-term cycling test over 20,000 cycles, significantly superior to currently-reported cathode materials for ZICs. An ultrahigh energy density of 180 Wh/kg is achieved for the RuO2 QDs@PCNCs cathode-based ZICs. Mechanism investigations point out the capacitive behavior-dominated and Zn2+/H+ co-participated charge storage process with fast electrochemical kinetics for the RuO2 QDs@PCNCs cathode in ZICs. This work not only provides a new choice for high-performance cathodes but also enriches the electrochemical theory of ZICs.

Disposable Electrochemical Sensor Based on MXene/Graphene Nanoplatelets/Ionic Liquid for the Determination of Anticancer Drug Imiquimod

This study describes the development of a novel, ultrasensitive, and selective electrochemical sensor to determine imiquimod (IMQ) using a screen-printed carbon electrode (SPCE) modified with MXene (Ti3C2Tx), graphene nanoplatelets, and ionic liquid (Ti3C2Tx/GNPs/IL). This work reveals the synergistic effect of Ti3C2Tx, GNPs, and IL, where Ti3C2Tx and GNPs provide a large active electrode area and excellent electron transport, and IL exhibits remarkable electrocatalytic behavior. Benefiting from the excellent electrochemical properties of the composite, the developed sensing platform enabled superior electrochemical performance for IMQ in the broad linear range of 0.071–92.0 μM (R2 = 0.999) with a limit of detection (LOD) of 0.487 nM and a detection sensitivity of 7.558 μA μM−1 cm−2. Meanwhile, the sensor has shown good repeatability, reproducibility, stability, and anti-interference ability and has been subsequently used to detect IMQ in cream formulations with satisfactory recoveries (98.33%–99.34%) and lower relative standard deviations (<3%). The findings indicate that the newly developed sensor can contribute to the development of a portable, robust, and high-performance sensing strategy for multidisciplinary targets.

CoCr2O4/Graphene modified glass carbon electrode for highly dual-sensing detection of hydrogen peroxide and glucose

The development of a non-enzymatic electrochemical sensor possessing well dual-sensing to H2O2 and glucose remains challenging due to less report. Herein, spinel CoCr2O4 nanoparticles with small size were synthesized by sol–gel reaction, which were then simply mixed with commercial graphene under ultrasonic to obtain uniformly dispersed CoCr2O4/Graphene composite. They were deposited onto the surface of bare glassy carbon electrode (GCE) through a common drop-coating method. The CoCr2O4/Graphene/GCE sensor firstly achieves highly dual-sensing to H2O2 and glucose in 0.1 M NaOH solution. At 0.4 and 0.55 V, its sensitivities to H2O2 and glucose can separately reach up to 1168.6 and 1722.5 μA mM−1 cm−2, and the corresponding detection limits are as low as 18 nM and 12 nM. These key indexes are the best among reported dual-functional spinel oxide-based electrodes. This excellent electrochemical sensing ability stems from its large electrode active area, good conductivity, and the synergism between graphene and CoCr2O4 nanoparticles with mixed redox couplings, which provides an efficient platform for dual-sensing detection. In addition, the modified electrode can accurately determine glucose in human tears, rat serum and orange juice, as well as H2O2 in milk whey, mouthwash and disinfectant, thus predicting its good application prospects.

2D Amorphous Iron Selenide Sulfide Nanosheets for Stable and Rapid Sodium-Ion Storage.

Sodium ion batteries (SIBs) suffer from large electrode volume change and sluggish redox kinetics for the relatively large ionic radius of sodium ions, raising a significant challenge to improve their long-term cyclability and rate capacity. Here, it is proposed to apply 2D amorphous iron selenide sulfide nanosheets (a-FeSeS NSs) as an anode material for SIBs and demonstrate that they exhibit remarkable rate capability of 528.7 mAh g-1 at 1 A g-1 and long-life cycle (10000 cycles) performance (300.4 mAh g-1 ). This performance is much more superior to that of the previously reported Fe-based anode materials, which is attributed to their amorphous structure that alleviates volume expansion of electrode, 2D nature that facilitates electrons/ions transfer, and the S/Se double anions that offer more reaction sites and stabilize the amorphous structure. Such a 2D amorphous strategy provides a fertile platform for structural engineering of other electrode materials, making a more secure energy prospect closer to a reality.

Multi-metal interaction boosts reconstructed FeCoCrCuOx@CF toward efficient alkaline water electrolysis under large current density

Electrolysis of water is one of most promising technologies for green hydrogen production. However, the green hydrogen has a market of 4 % only, as the key-component for the technology, electrocatalyst, is expensive, inefficient or unstable. Herein, we design a series of multi-metal oxides (FeCoOx@CF, FeCoCrOx@CF, FeCoCuOx@CF, and FeCoCrCuOx@CF) on cobalt foams to achieve the high efficiency, low cost, and long-term stability by a simple thermal decomposition and electrochemical activation. Among them, FeCoCrCuOx@CF shows remarkable catalytic activity with an ultra-low overpotential (40 mV at 10 mA cm−2) and Tafel slope (27.3 mV dec−1) for hydrogen evolution reaction (HER), which is superior to most reported transition-metal catalysts and comparable to commercial Pt/C, because of the synergistic effect of multiple metals and strong Cr-OH interaction on the reconstructed surface as induced by the dynamic dissolution and redeposition process in the reaction. In addition, the catalyst shows excellent long-term stabilities for HER and overall water splitting at 500 mA cm−2. Importantly, FeCoCrCuOx@CF has the excellent activity and high stability (100 h with only 2 % increment in applied voltage) in the industrial working environment (6 M KOH, ∼ 60 °C). Most importantly, only 3.18 V is needed to obtain > 30 A on a large size electrode for AWE (16.5 cm2, ∼ 1.84 A cm−2) in the industrial conditions. Our findings should provide novel strategies for the design of efficient and stable catalysts toward industrial water electrolysis.

Direct In Situ Determination of the Surface Area and Structure of Deposited Metallic Lithium within Lithium Metal Batteries Using Ultra Small and Small Angle Neutron Scattering

AbstractDespite being the major cause of safety and performance issues in lithium metal batteries, experimental difficulties in quantifying directly the morphology of lithium deposited at electrode surfaces have meant that the mechanism of metallic lithium growth within batteries remains elusive. This study demonstrates that quantitative detail about the morphology of metallic lithium within batteries can be derived non‐destructively and directly using in situ ultra‐small and small‐angle neutron scattering. This information is obtained over a large electrode area in cells where lithium deposition processes are typical of real‐world applications. Complex variations of surface area and interfacial distances 1–10 µm and 100–300 nm are revealed in size that are influenced by current density and cell cycling history, providing valuable insight into the growth of metallic lithium features detrimental to battery performance. Such quantitative insight into the process of lithium growth is required for the development of safer high‐performance lithium metal batteries.