Nanoporous Electrodes Research Articles

Operando Optoelectrochemical Analysis of Single Zinc Dendrites with a Reflective Nanopore Electrode.

Dendrites can severely impair zinc battery performance. An in-depth understanding of the dynamic morphology evolution of dendrites with operando approaches is pivotal when addressing these issues. However, in previous studies, the corresponding electrochemical signals are usually ensemble and averaged. It is very challenging to obtain detailed information about the key morphology-performance relationship. Herein, correlated high-resolution operando optical and electrochemical studies of single dendrites on Pt reflective nanopore electrodes are reported. The zinc deposition and dissolution can be directly imaged by a high NA optical microscope, while corresponding galvanic charging and discharging curves are obtained. The correlated information of morphology changes and dynamic overpotential fluctuations under different circumstances unveils the competition between active growth vs. passivation. The isolated zinc formation at the single dendrite level is also evaluated. The methodology can be further extended to elucidate the direct relationship between dendrite evolution and electrochemical responses in various battery systems.

Probing Nanoconfined Ion Transport in Electrified 2D Laminate Membranes with Electrochemical Impedance Spectroscopy.

The recent emergence of electrically conductive nanoporous membranes based on graphene and other 2D materials opens up new opportunities to revisit some longstanding nanoconfined ion transport problems under electrification. This work probes the ionic resistance in electrified multilayered graphene membranes with electrochemical impedance spectroscopy. This study demonstrates that the combination of additive-free feature and tunable slit pore sizes in the sub-10nm range in graphene-based membranes has made it possible to deconvolute the different ionic processes from the impedance obtained and examine the exclusive influence of pore size on the ionic resistance in a quantitative manner. The trends revealed for the ionic resistance at the pore entrance and inside the pores under severe nanoconfinement (<2nm) are found to be generally consistent with the microscale theoretical simulations previously reported. It also allows a quantitative analysis of the relative effects of the external polarization potential and ion identity under nanoconfinement. The results suggest that the classic electrochemical impedance spectroscopy technique, when applied to appropriate nanoporous electrode materials, can provide rich information about nanoconfined ion transport phenomena under electrification for fundamental understanding and application development.

Zinc detection in oil-polluted marine environment by stripping voltammetry with mercury-free nanoporous gold electrode

Detection of Zn(II) in oil-polluted seawater via square-wave anodic stripping voltammetry (SW-ASV) utilizing thin gold electrodes sputtered onto nanoporous poly(acrylic acid)-grafted-poly(vinylidene difluoride) (PAA-g-PVDF) membrane is herein reported. Prior to SW-ASV, PAA grafted nanopores demonstrated to efficiently trap Zn(II) ions at open circuit. This passive adsorption followed a Langmuir law. An affinity constant of 1.41 L upmu mol^{-1} and a maximum Zn(II) adsorbed mass q_{max} of 1.21 upmu mol g^{-1} were found. Applied SW-ASV protocol implied an accumulation step (− 1.2 V for 120 s) followed by a stripping step (− 1.2 to 1 V; 25 Hz; step: 4 mV; amplitude: 25 mV; acetate buffer (pH 5.5)). It revealed a Zn redox potential at − 0.8 V (Ag/AgCl pseudo-reference). Multiple measurements in synthetic waters close to the composition of production waters exhibited a decreasing precision with the number of readings R (1.65% (R = 2) and 6.56% (R = 3)). These membrane-electrodes should be used as disposable. The intra-batch mean precision was 14% (n = 3) while inter-batches precision was 20% (n = 15). Linear and linear-log calibrations allow exploitation of Zn(II) concentrations ranging from 10 to 500 upmu g L^{-1} and 100 to 1000 upmu g L^{-1} respectively. The LOD was 4.2 upmu g L^{-1} (3S/N). Thanks to obtained calibration, a detected Zn(II) content of 1 ppm in a raw production water from North Sea oil platform was determined.

Wood-Based Self-Supporting Nanoporous Three-Dimensional Electrode for High-Efficiency Battery Deionization.

Developing highly efficient advanced battery deionization (BDI) electrode materials at a low cost is vital for seawater desalination. Herein, a high-efficiency wood-based BDI electrode has been fabricated for seawater desalination, benefiting from the self-supporting three-dimensional (3D) nanoporous structure and rich redox-active sites. The finely tuned rich electrochemical redox active C═O groups on the surface of the wood electrode derived from the facile thermochemical conversion of lignin play a crucial role in the Faradaic cation removal dynamics of BDI. Coupling the 3D wood electrode and a polyaniline-modified wood electrode as the cathode and anode, an all-wood-electrode-based deionization battery has been successfully assembled with a state-of-the-art ion removal capacity of up to 164 mg g-1 in seawater. Our work reported an example of utilizing wood as the BDI electrode via fine-tuning the redox-active sites, demonstrating a novel resource utilization pathway of converting cheap biomass into BDI electrodes for highly efficient seawater desalination.

Effects of Ionic Size and Hydrophobicity on Charging Dynamics at Microporous Pt

Nanoporous electrodes with extremely small pores have been developed for improved supercapacitors and electroanalysis. Ion transport into nanoconfined spaces has been studied using nanoporous carbon. Herein, we explore the size effect and hydrophobicity of ions on the charging dynamics using microporous Pt by cyclic voltammetry and electrochemical impedance spectroscopy. As the size of the effective hydrated ions decreased, the capacitance increased, and the movement of ions into and within the nanopores was less restricted. The effect of ionic size was more pronounced for hydrophobic organic cations than for hydrophilic alkali cations in microporous Pt. In addition, the microporous Pt electrode exhibited better performance in terms of capacitance and charging dynamics than the mesoporous carbon electrode when the hydrophilic electrolyte is dissolved in an aqueous solution. These findings provide insight into the formation of an electrical double layer at microporous metal electrodes and their applications in supercapacitors, electrocatalysts, and electroanalysis.

An electrochemical NADH biosensor based on a nanoporous gold electrode modified with diaphorase and an osmium polymer

NADH is a cofactor used by a wide range of dehydrogenases. Measurement of the concentration of NADH is widely used to measure the activity of enzymes. Extensive efforts have been made to develop electrochemical sensors for NADH determination at low overpotentials to avoid interferences. The development of an enzymatic electrochemical biosensor for the detection of NADH is described. Nanoporous gold electrodes were utilised for the immobilization of diaphorase and osmium-based polymer Os(bpy)2(PVI). Nanoporous gold electrodes of different pore sizes were manufactured by varying the dealloying temperature. To optimise the enzymatic response, the concentrations of polymer and enzyme, average pore size and the operating temperature were examined with the optimal performance observed using 10 µL of Os(bpy)2(PVI) and 5 µL of diaphorase at concentrations of 6 and 10 mg/mL, respectively, on nanoporous gold electrodes with an average pore size of 5.9 nm. The biosensor showed a high sensitivity of 89.6 µA/cm2 mM, a low LOD of 0.8 µM and a linear range from 5 to 100 µM at a potential of 0.35 V vs Ag/AgCl at a temperature of 40 °C.

Scalable fabrication of MXene-based flexible micro-supercapacitor with outstanding volumetric capacitance

This work demonstrates a facile and reliable process for scalable and sustainable manufacturing of on-chip and flexible microsupercapacitor (MSC) devices for future applications in wearable/portable and miniaturized microelectronics. MSCs, which can provide high power density and a virtually unlimited lifetime, can be used as power supplies integrated into electronic systems. However, lower volumetric capacitance and energy density of conventional double-layer carbon supercapacitors limits their practical applications. In this study, a microfabrication process based on photolithography and a solution process were used to fabricate interdigitated micro-patterns of pristine MXene and 3D interconnected nanoporous MXene electrodes, which were then transferred onto flexible substrates. These flexible MSCs have properties that meet expectations for scalable manufacturing (107 chips in an 8 in.-wafer). They have an outstanding volumetric capacitance of 1,727F cm−3 (the highest ever reported for MXenes), desirable customization (essential at the 8-inch level of integrated microelectronics), and a remarkable energy density of 41.9 mWh cm−3, which is maintained at a high-power density of 26.8 W cm−3. Furthermore, the volumetric capacitance increased by approximately 140 % after 10,000 bending cycles, which was only observed in the planar interdigitated electrode micropatterns made of 2D MXene sheets and subjected to tensile stress on flexible polymer substrates.

Effect of partial oxidation and repolarization of TiC-derived nanoporous carbon electrodes on supercapacitor performance using a pH-neutral aqueous electrolyte

Effect of partial oxidation and repolarization of TiC-derived nanoporous carbon electrodes on supercapacitor performance using a pH-neutral aqueous electrolyte

Use of a nano-porous gold film electrode modified with chitosan / polypyrrole for electrochemical determination of metronidazole in the Presence of Acetaminophen

This study, it was aimed to provide a sensitive, easy and selective method for designing Nano-porous gold film electrode (NPGF) electrode for simultaneous measurement of metronidazole (MT) and acetaminophen (AC). For this purpose, the NPGF electrode surface was modified with chitosan (CS) and poly pyrrole (PPY) by electrochemical method, and then CS and PPY modified NPGF (PPY-CS-NPGF) electrode were used to measure these drugs. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) are employed for the characterization of the attained PPY-CS-NPGF electrode. Using cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and chronoamperometry, the electrochemical behavior of MT was investigated with the modified electrode. By differential pulse voltammetry, linear ranges of concentration 0.005–100 μM with linear coefficients of 0.9898 and a detection limit of 0.0009 μM were obtained for MT. Finally, an electrochemical sensor was used to measure MT in a real sample, which yielded acceptable results. PPY-CS-NPGF electrodes have a wide linear range, high selectivity, sensitivity and stability and can be used successfully to determine these drugs.

Phosphorus-doping promotes the electrochemical etching of metals to nanoporous electrodes for efficient and durable overall water splitting

Electrocatalysts play a central role in electrochemical water splitting to store renewable energy in the chemical fuel of hydrogen. Nanoporous metal electrodes are promising to boost hydrogen production efficiency while challenging in synthesis. Here, a phosphorus-doping assisted electrochemical etching strategy is developed to construct highly nanoporous surfaces on metal electrodes, leading to a remarkable catalytic performance for overall water splitting under lab-level or industrial electrolysis conditions. Specifically, the nanoporous FeCoNiCu foil shows 46 times higher electrochemical surface area, lowering the overpotentials by 102 mV for oxygen evolution reaction and 157 mV for hydrogen evolution reaction. The viability of the strategy is further demonstrated in the prevailing industrial electrodes of nickel meshes, enabling a cell voltage of only 1.931 V under the harsh industrial electrolytic condition (80 °C, 30 wt% KOH, and a current density of 500 mA cm−2). It is 126 mV lower than that of a bare nickel mesh-based electrolyzer and corresponds to a ∼4% improvement in energy-conversion efficiency. This work offers a facile and ease-to-scale-up approach for the upgrading of widespread metal electrodes, possessing great prospects in energy conversion and storage devices including electrolyzers, fuel cells, batteries, and supercapacitors.

Room-temperature liquid metal synthesis of nanoporous copper-indium heterostructures for efficient carbon dioxide reduction to syngas

Nanoporous metals show promising performances in electrochemical catalysis. In this paper, we report a self-supporting bimetallic porous heterogeneous indium/copper structure synthesized with a eutectic gallium-indium (EGaIn) material on a copper substrate. This nanoporous copper-indium heterostructure catalyst exhibits excellent performance in the reduction of carbon dioxide to syngas. The ratio of H2/CO is tunable from 0.47 to 2.0 by changing working potentials. The catalyst is highly stable, showing 96% maintenance of the current density after a 70-h continuous test. Density functional theory calculations reveal that the indium/copper interface induces charge redistribution within the copper surface, leading to the formation of two distinct active sites, namely, Cuδ and Cu0, and enabling a high-performance generation of CO and H2. This work provides a new strategy for obtaining self-supporting nanoporous metal electrode catalysts.

Self-repairing nanoporous MCNT/Ag/AgCl composite electrode as a low-cost and long-term stable marine potentiometric sensor

Maintenance-free, cost-effective, and long-lasting potentiometric sensors are highly anticipated for marine detection. Solid-state silver/silver chloride (Ag/AgCl) is considered the most suitable non-polarizable electrode for that purpose. However, the conventional fabrication of thin-film or porous Ag/AgCl electrodes has limitations in the case of simultaneous cost-effectiveness and stability endurance. In the present study, the multi-walled carbon nanotube (MCNT)/Ag/AgCl composite electrode with a 70 mg/cm2 Ag load was prepared, having nanoporous MCNT/Ag conductive skeleton, and a three-dimensionally spreading Ag/AgCl thin layer. The prepared MCNT/Ag/AgCl composite electrode showed an excellent electrode performance, including low resistance, high exchange current density, and stable potential with long-term stability and low cost. The process kinetics and self-repairing mechanism between Ag and AgCl with the help of MCNT were elucidated. The usage of MCNT/Ag/AgCl composite electrode as a solid-state reference electrode and ocean electric field sensor was successfully evaluated, which provides a promising marine potentiometric sensor application for this nanoporous metal composite electrode via a novel preparation method.

SEEDING to Enable Sensitive Electrochemical Detection of Biomarkers in Undiluted Biological Samples (Adv. Mater. 24/2022)

Electrochemical Pollination In article number 2200981, Yoon-Kyoung Cho and co-workers discuss electrochemical roughening, a method based on the etching and redeposition of material from a flat surface, to create homogeneous, nanostructured, and nanoporous gold electrodes. The process is not efficient, as most of the etched material typically diffuses away. However, the addition of surfactant generates micelles that can electrostatically capture the freshly etched material and, in a process that evokes pollination from bumblebees, increase redeposition efficiency.

Noble metal-free La0.80Sr0.20CoO3 thin film electrode for sodium formate electrooxidation

A noble metal-free catalyst is prepared for formate electrooxidation. A nanoporous thin film electrode of strontium doped lanthanum cobalt oxide (LSCO), coated on fluorine-doped tin oxide (FTO) substrate is employed to study the electrocatalytic oxidation of sodium formate. A series of studies using cyclic voltammetry, chronoamperometry and gas-chromatography were performed to investigate the reactions. The formation of both CO and CO2 is observed in thegasanalysis.At1.8 V vs RHE, the current density of 4.0 mA.cm−2 is achieved in a solution of 0.5 M sodium formate and phosphate buffer (PBS, pH = 7). Thin-film electrode remains active for a long period showing a slow process of CO poisoning on the surface.

Redox Potential Correlates with Changes in Metabolite Concentrations Attributable to Pathways Active in Oxidative Stress Response in Swine Traumatic Shock.

Oxidation-reduction (redox) reactions, and the redox potential (RP) that must be maintained for proper cell function, lie at the heart of physiologic processes in critical illness. Imbalance in RP reflects systemic oxidative stress, and whole blood RP measures have been shown to correlate with oxygen debt level over time in swine traumatic shock. We hypothesize that RP measures reflect changing concentrations of metabolites involved in oxidative stress. To test this hypothesis, we compared blood and urine RP with concentrations of multiple metabolites in a swine traumatic shock model to identify meaningful RP-metabolite relationships. Seven swine were subjected to traumatic shock. Mixed venous (MV) RP, urine RP, and concurrent MV and urine metabolite concentrations were assessed at baseline, max O 2 Debt (80 mL/kg), end resuscitation, and 2 h post-resuscitation. RP was measured at collection via open circuit potential using nanoporous gold electrodes with Ag/AgCl reference and a ParstatMC potentiostat. Metabolite concentrations were measured by quantitative 1 H-NMR spectroscopy. MV and urine RP were compared with time-matched metabolites across all swine. LASSO regression with leave-one-out cross validation was used to determine meaningful RP/metabolite relationships. Metabolites had to maintain magnitude and direction of coefficients across 6 or more swine to be considered as having a meaningful relationship. KEGG IDs of these metabolites were uploaded into Metscape for pathway identification and evaluation for physiologic function. Meaningful metabolite relationships (and mean coefficients across cross-validation folds) with MV RP included: choline (-6.27), ATP (-4.39), glycine (5.93), ADP (1.84), glucose (15.96), formate (-13.09), pyruvate (6.18), and taurine (-7.18). Relationships with urine RP were: betaine (4.81), urea (4.14), glycine (-2.97), taurine (10.32), 3-hydroxyisobutyrate (-7.67), N-phenylacetylglycine, PAG (-14.52), hippurate (12.89), and formate (-5.89). These meaningful metabolites were found to scavenge extracellular peroxide (pyruvate), inhibit ROS and activate cellular antioxidant defense (taurine), act as indicators of antioxidant mobilization against oxidative stress (glycine + PAG), and reflect renal hydroxyl radical trapping (hippurate), among other activities. Real-time RP measures demonstrate significant relationships with metabolites attributable to metabolic pathways involved in systemic responses to oxidative stress, as well as those involved in these processes. These data support RP measures as a feasible, biologically relevant marker of oxidative stress. As a direct measure of redox state, RP may be a useful biomarker and clinical tool in guiding diagnosis and therapy in states of increased oxidative stress and may offer value as a marker for organ injury in these states as well.

Phase-transition tailored nanoporous zinc metal electrodes for rechargeable alkaline zinc-nickel oxide hydroxide and zinc-air batteries

Secondary alkaline Zn batteries are cost-effective, safe, and energy-dense devices, but they are limited in rechargeability. Their short cycle life is caused by the transition between metallic Zn and ZnO, whose differences in electronic conductivity, chemical reactivity, and morphology undermine uniform electrochemical reactions and electrode structural stability. To circumvent these issues, here we propose an electrode design with bi-continuous metallic zinc nanoporous structures capable of stabilizing the electrochemical transition between metallic Zn and ZnO. In particular, via in situ optical microscopy and electrochemical impedance measurements, we demonstrate the kinetics-controlled structural evolution of Zn and ZnO. We also tested the electrochemical energy storage performance of the nanoporous zinc electrodes in alkaline zinc-nickel oxide hydroxide (NiOOH) and zinc-air (using Pt/C/IrO2-based air-electrodes) coin cell configurations. The Zn | |NiOOH cell delivers an areal capacity of 30 mAh/cm2 at 60% depth of discharging for 160 cycles, and the Zn | |Pt/C/IrO2 air cell demonstrates 80-hour stable operation in lean electrolyte condition.

SEEDING to Enable Sensitive Electrochemical Detection of Biomarkers in Undiluted Biological Samples

Electrochemical biosensors have shown great potential for simple, fast, and cost-effective point-of-care diagnostic tools. However, direct analysis of complex biological fluids such as plasma has been limited by the loss of sensitivity caused by biofouling. By increasing the surface area, the nanostructured electrode can improve detection sensitivity. However, like a double-edged sword, a large surface area increases the nonspecific adsorption of contaminating proteins. The use of nanoporous structures may prevent fouling proteins. However, there is no straightforward approach for creating nanostructured and nanoporous surfaces compatible with microfabricated thin-film electrodes. Herein, the preferential etching of chloride and surfactant-assisted anisotropic gold reduction to create homogeneous, nanostructured, and nanoporous gold electrodes is demonstrated, yielding a 190±20times larger surface area within a minute without using templates. This process, "surfactant-based electrochemical etch-deposit interplay for nanostructure/nanopore growth" (SEEDING), on electrodes enhances the sensitivity and antibiofouling capabilities of amperometric biosensors, enabling direct analysis of tumor-derived extracellular vesicles (tEVs) in complex biofluids with a limit of detection of 300tEVsµL-1 from undiluted plasma and good discrimination between patients with prostate cancer from healthy ones with an area under the curve of 0.91in urine and 0.90in plasma samples.

Nano-Porous Self-Supporting Ta2O5 Thin Film Electrode for Highly Reversible Li Ion Storage

Nano-porous Ta2O5 thin film electrodes are prepared by magnetron sputtering at low pressure in the presence of an oxygen atmosphere with an inert gas. The sputtered Ta2O5 thin film is subsequently annealed at 350∘C for 2[Formula: see text]h in high pure N2 (Ta2O5-350) to introduce oxygen deficiency. The Ta2O5-350 electrode possesses highly reversible lithium ion storage and good rate capability, which has high specific capacities of about 480[Formula: see text]mAh g[Formula: see text] at a rate of 0.1[Formula: see text]C. Furthermore, after 2000 cycles at a rate of 5[Formula: see text]C the Ta2O5-350 electrode shows no obvious capacity decay and retains specific capacity of about 160[Formula: see text]mAh[Formula: see text]g[Formula: see text]. The excellent lithium storage properties of Ta2O5-350 electrode can be correlated to the nano-porous electrode architecture and oxygen deficiency.

Improved Sensitivity and Selectivity for the Redox Potentiometric Measurement of Biological Redox Molecules Using Nafion-Coated Platinum Decorated Nanoporous Gold Electrodes

Sensitivity and selectivity are two important figures of merit in analytical measurements, but in redox potentiometry, they are often limited. In this study, we describe how the potentiometric sensitivity and selectivity can be improved using nanoporous gold (NPG) electrodes with hydrogen peroxide, dopamine, ascorbic acid, and a mixture of dopamine and ascorbic acid as the test analytes. The results show that the addition of platinum (Pt) to the nanoporous framework significantly improves electrode sensitivity for the analytes studied. Furthermore, it was only possible to potentiometrically detect hydrogen peroxide at the NPG-Pt electrodes. To further improve sensitivity and also impart some selectivity, the electrodes were spin-coated with Nafion. The addition of Nafion shifts the open-circuit potential to more positive values, increases sensitivity by almost a factor of 2, and imparts selectivity to the surface for the analysis of mixtures. Collectively, this works shows the promise of Pt-decorated nanoporous electrodes coupled with a Nafion film to improve the overall performance of redox potentiometry in analytical science.

Microscopic Simulations of Electrochemical Double-Layer Capacitors.

Electrochemical double-layer capacitors (EDLCs) are devices allowing the storage or production of electricity. They function through the adsorption of ions from an electrolyte on high-surface-area electrodes and are characterized by short charging/discharging times and long cycle-life compared to batteries. Microscopic simulations are now widely used to characterize the structural, dynamical, and adsorption properties of these devices, complementing electrochemical experiments and in situ spectroscopic analyses. In this review, we discuss the main families of simulation methods that have been developed and their application to the main family of EDLCs, which include nanoporous carbon electrodes. We focus on the adsorption of organic ions for electricity storage applications as well as aqueous systems in the context of blue energy harvesting and desalination. We finally provide perspectives for further improvement of the predictive power of simulations, in particular for future devices with complex electrode compositions.