Nanoporous Electrodes Research Articles

Nanocrystalline tin oxide electrodeposited on carbon nanotube for high performance electrochemical capacitive energy storage

In this work, 3D nanoporous composite electrode with tin oxide nanoparticles of 3–5 nm dispersed uniformly on the surface of multiwalled carbon nanotube film was prepared by electrodeposition technique. This composite electrode presents high specific capacitance (588 Fg−1 at 15 Ag−1), excellent rate capability (450 Fg−1 at a high scan rate of 200 mVs−1) and good cycle stability (5% capacity loss after 5000 cycles at 15 Ag−1). This result indicates that the nanostructured composite electrode with hierarchical porous structure and good conductivity is a very promising structure and active composite material for electrochemical capacitor.

Nanoporous gold chemically de-alloyed from Au-based amorphous thin film for electrochemical nonenzymatic H2O2 sensing

Abstract Au-based amorphous thin films prepared by magnetron sputtering were used to fabricate nanoporous gold by chemical de-alloying obtaining three dimensional bicontinuous ligament-nanopore structure. The surface topography and microstructure of the nanoporous thin films were monitored after varying the de-alloying conditions such as de-alloying time and electrolyte concentration. The as-prepared nanoporous gold electrodes were investigated for H2O2 sensing by CV curves and chronoamperometry techniques. The results demonstrated the nanoporous gold thin film exhibited high sensitivity towards H2O2 sensing under the applied potential of −0.45 V versus SCE, suggesting their use as H2O2 sensor.

Single Pt-Pd Bimetallic Nanoparticle Electrode: Controllable Fabrication and Unique Electrocatalytic Performance for the Methanol Oxidation Reaction.

Understanding the electrocatalytic activity at single nanoparticles/nanoclusters level is extremely important. In this work, a method for the electro-deposition of single Pt-Pd nanoparticles (NPs) is described using a single nanopore electrode as a template. The electro-deposition process was investigated carefully and the results show that the process is controlled by diffusion and electro-crystallization process, simultaneously, and the glass sheath property around the nanopore has a large impact on the formation of single Pt-Pd NPs due to the "edge effect". The prepared single Pt-Pd NPs exhibit excellent electrocatalytic activity in the methanol oxidation reaction, which can be used to screen electrocatalysts with high efficiency for utility in the energy field.

Synthesis and Morphology Control of Nanoporous Cu₂O/Cu and Their Application as Electrode Materials for Capacitors.

In this paper, nanoporous copper (NPC) was prepared by dealloying ZrCuAl metallic glass ribbons with HF acid solutions. The effect of dealloying time on the porous structures and thickness of the obtained NPC films was investigated. It was found that the ligament sizes of the NPC could be tuned in a range from 20 to 300 nm, and the thicknesses of the NPC films from 3.1 to 14.4 μm, with properly selected dealloying times. Furthermore, nanoporous composites made of NPC and nanoporous Cu2O were prepared by oxidizing the NPC with ethanol. The nanoporous composite electrodes exhibited superior charge-discharge performance and would have broad potential applications in flexible high-performance energy storage devices.

Fructose 1,6-bisphosphate trisodium salt as a new organic phosphorus source for synthesis of nanoporous amorphous nickel phosphate microspheres electrode materials in supercapacitors

Nanoporous amorphous nickel phosphate (Ni3(PO4)2) with microsphere structures have been investigated for applications as electrode material owing to their excellent electrochemical performance. However, Ni3(PO4)2 are usually prepared traditionally from inorganic phosphorus. Herein, we report a new synthetic strategy by using fructose 1,6-bisphosphate trisodium salt (FBP) as an organic phosphorus source and a porogen. The formation of nanoporous amorphous Ni3(PO4)2 microspheres structures, as well as the effect of applied calcination temperatures on the morphology and crystallinity of the final phosphate materials, is systematically researched. According to data, our amorphous Ni3(PO4)2 material possess a superior specific capacitance of 1040 F g−1 at the current density of 0.5 A g−1 and a favourable rate performance, as compared to various phosphate nanomaterials reported previously. Furthermore, the Ni3(PO4)2 electrodes fabricated in this work are low-cost, efficient, and composed of naturally abundant materials, becoming a potential energy storage material.

SDS‐modified Nanoporous Silver as an Efficient Electrocatalyst for Selectively Converting CO2 to CO in Aqueous Solution

Summary of main observation and conclusionSelectively electrochemical conversion of CO2 into organic fuel using renewable electricity is one of the most sought‐after processes. In this paper, we report the electrochemical reduction of CO2 (CO2RR) on the nanoporous Ag electrodes made of compacted Ag nanoparticles (AgNPs), which were prepared by one‐step reduction in the water phase with or without the surfactant sodium dodecyl sulfate (SDS). The scanning electron microscope (SEM) characterizations show that the compacted Ag electrodes have the nanoporous morphology formed by stacking AgNPs. Compared with the nanoporous Ag electrode without SDS modification (C‐AgNPs), the SDS‐modified AgNPs electrode (C‐AgNPs‐SDS) is highly effective in improving selective CO production in a wide range of potentials (–0.69 V — –1.19 V, vs. RHE), with a Faradaic efficiency of 92.2% and a current density of –8.23 mA·cm–2 for CO production at –0.79 V (vs. RHE). C‐AgNPs‐SDS is also catalytically stable with only less than 7% deactivation after 8 h of continuous electrolysis.

A positive-negative alternate adsorption effect for capacitive deionization in nano-porous carbon aerogel electrodes to enhance desalination capacity

Carbon aerogels (CAs) with different microstructure were prepared via ambient pressure drying for capacitive deionization (CDI) of NaCl solution. The activated CAs exhibit a hierarchical porous structure, whose micro-, meso- and macropore size distribution can be varied with the molar ratio of resorcinol to catalyst (R/C). Desalination experiments illustrate that CA electrode with R/C of 200 shows the maximum salt adsorption capacity (SAC) of 10.34 mg/g at a working voltage of 1.5 V. It is found that electrosorption capacity of CA electrodes dose not only depend on the micro-porosity for large surface area but also the mesopores who provide transport channels. A positive-negative alternate adsorption (PNAA) method by alternating the polarity of voltage applied on the electrodes was developed to enhance the desalination capacity. The ultimate SAC of CA electrode with R/C of 200 is 25.45 mg/g, which is more than twice of the adsorption amount for the single adsorption. This method makes full use of the pores of the CAs and provides a further enhancing capacity for CA CDI.

Atomistic Perspectives on Mechanical Properties of Nanoporous Li-Mn-O Cathode upon Li-Intercalation

Atomistic modeling plays a vital role in advancement and understanding of microstructural evolution and mechanical properties of electrode materials. We present progress in the simulated synthesis of Li-Mn-O nanoporous electrode materials, from an atomic perspective during which the amorphization and recrystallization technique has been employed. The effect of lithiation on structural integrity and intercalation host capability of the LMO electrode are investigated under the NST ensemble. Evolution of a composite structured material is captured on the microstructures snapshots and XRD graphs, particularly co-existing formation of spinel and layered components. The nanoporous materials crystallize successfully although multiple grains are observed for Li1.75Mn2O4 (nanoporous structure corresponding to cubic lattice boxes of side lengths 67 Å and 75 Å) and subsequently yield a single crystals for Li2Mn2O4. However, this is not inherent on nanoporous 69 Å with the same concentration. Intercalation induced volume changes are observed during simulation of the discharge process, specifically when the lithium content in the system is increased above 75% (Li1.5Mn2O4). The nanoporous material contracts inwardly and such accommodative nature may be attributed to flexing/relaxation into its pore/channel, unlike in the bulk structure, which suffers from drastic volume expansion. It is imperative to exclusively note the single crystallinity of the nanoporous (69 Å), that potentially contributes to the retention of yield strength unlike in the case of nanoporous (67 and 75 Å), where the simulations reveal that Li intercalation weakens the systems as the yield stresses (particularly for Li1.75Mn2O4), are reduced with gradual lithium intercalation into the lattice.

Wireless Nanopore Electrode for Electron Transfer Imaging in Live Cells

Wireless Nanopore Electrode for Electron Transfer Imaging in Live Cells

Antifouling (Bio)materials for Electrochemical (Bio)sensing.

(Bio)fouling processes arising from nonspecific adsorption of biological materials (mainly proteins but also cells and oligonucleotides), reaction products of neurotransmitters oxidation, and precipitation/polymerization of phenolic compounds, have detrimental effects on reliable electrochemical (bio)sensing of relevant analytes and markers either directly or after prolonged incubation in rich-proteins samples or at extreme pH values. Therefore, the design of antifouling (bio)sensing interfaces capable to minimize these undesired processes is a substantial outstanding challenge in electrochemical biosensing. For this purpose, efficient antifouling strategies involving the use of carbon materials, metallic nanoparticles, catalytic redox couples, nanoporous electrodes, electrochemical activation, and (bio)materials have been proposed so far. In this article, biomaterial-based strategies involving polymers, hydrogels, peptides, and thiolated self-assembled monolayers are reviewed and critically discussed. The reported strategies have been shown to be successful to overcome (bio)fouling in a diverse range of relevant practical applications. We highlight recent examples for the reliable sensing of particularly fouling analytes and direct/continuous operation in complex biofluids or harsh environments. Opportunities, unmet challenges, and future prospects in this field are also pointed out.

Nanoporous water oxidation electrodes with a low loading of laser-deposited Ru/C exhibit enhanced corrosion stability.

For the oxidation of water to dioxygen, oxide-covered ruthenium metal is known as the most efficient catalyst, however, with limited stability. Herein, we present a strategy for incorporating a Ru/C composite onto a novel nanoporous electrode surface with low noble metal loading and improved stability. The Ru/C is coated on the pore walls of anodic alumina templates in a one-step laser-induced deposition method from Ru3(CO)12 solutions. Scanning electron microscopy proves the presence of a continuous Ru/C layer along the inner pore walls. The amorphous material consists of metallic Ru incorporated in a carbonaceous C matrix as shown by X-ray diffraction combined with Raman and X-ray photoelectron spectroscopies. These porous electrodes reveal enhanced stability during water oxidation as compared to planar samples at pH 4. Finally, their electrocatalytic performance depends on the geometric parameters and is optimized with 13 μm pore length, which yields 2.6 mA cm−2, or 49 A g−1, at η = 0.20 V.

H2O2 biosensor consisted of hemoglobin-DNA conjugate on nanoporous gold thin film electrode with electrochemical signal enhancement

In this research, we developed electrochemical biosensor which was composed of hemoglobin (Hb)-DNA conjugate on nanoporous gold thin film (NPGF) for hydrogen peroxide (H2O2) detection. For the first time, Hb and DNA was conjugated as a sensing platform for uniform orientation of Hb on electrode. The newly developed Hb-DNA conjugate was designed to prevent Hb from aggregation on electrode. DNA hybridization of Hb-DNA conjugate and complementary DNA (cDNA) on NPGF electrode induced uniformly assembled biosensor. Furthermore, NPGF electrode fabrication method was introduced to the increment of the surface area. To confirm the conjugation of Hb-DNA conjugate, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and ultraviolet–visible spectroscopy (UV–VIS) were used. Formation of the NPGF electrode was verified by scanning electron microscope (SEM). Atomic force microscopy (AFM) was operated for the confirmation of Hb-DNA immobilization on electrode. The electrochemical property of fabricated electrode was investigated by cyclic voltammetry (CV). Also, H2O2 sensing performance of fabricated electrode was investigated by amperometric i-t curve technique. This sensor showed a wide linear range from 0.00025 to 5.00 mM and a correlation coefficient of R2 = 0.9986. The detection limit was 250 nM. Proposed biosensor can be utilized as a sensing platform for development of biosensor.

Fabrication and Characterization of Nanoporous Gold Electrodes for Sensor Applications

Nanoporous gold electrodes are fabricated by etching white gold leaf in nitric acid. Samples of various thickness and alloy composition are used and etch time is varied. Electrode pore structure is characterized by scanning electron microscopy. Significant coarsening of ligament and pore structure is observed as etching time is varied from 5 to 90 min. Nanoporous gold electrode impedance is determined via electrochemical impedance spectroscopy. Test cells are constructed for this purpose consisting of two electrodes and an electrolyte. Both water and dichloroethane are examined as electrolyte solvents. A constant phase element with exponent greater than 0.9 is shown to provide an excellent description of interface impedance behavior for these test cells. Optimization is used to determine pseudo‐capacitance and exponent in each case. A comparison of nanoporous gold electrode impedance to planar gold electrode impedance is made to derive the effective area of the nanoporous gold electrode. It is found in all cases that interfacial impedances are much lower (>40 ×) than those of conventional electrodes. Test results show that significant variations in effective area can occur depending on the electrolyte employed.

Electric field assisted ion adsorption with nanoporous SWCNT electrodes

The permeable single wall carbon nanotube (SWCNT) film electrodes of high electrical conductivity for filtration of ions are promising for future water treatment technology. The permeable SWCNT film electrodes were obtained by the use of the Zn/Al-based dispersant-aided SWCNT ink. The G band peak position and ID/IG value of Raman spectra do not change before and after the polarization of the SWCNT electrodes, showing the robustness of permeable SWCNT film electrodes. The analysis of N2 adsorption isotherms showed that microporosity and specific surface area of the SWCNT electrodes were larger than those of the pristine SWCNT, due to the debundling of SWCNTs and removal of the caps of SWCNT on the dispersion treatment. Application of the electric voltage above − 3 V to the SWCNT electrodes enhanced markedly the adsorption-mediated permeability of K+ ions, reaching the removability of 90%. The removability dependence of Na+ ions on the initial ion concentration showed that the SWCNT permeation electrodes filter was efficient for diluted Na+ ionic solution. The ions of smaller Stokes radius were adsorbed for the mixed ionic solution of Li+, Na+, K+, Rb+, and Cs+, suggesting that the inner tube space of SWCNT electrodes is important for adsorption of ions.

Long-battery-life flexible zinc–air battery with near-neutral polymer electrolyte and nanoporous integrated air electrode

A flexible zinc–air battery based on near-neutral gel polymer electrolyte and integrated nanoporous Co3O4nanosheets exhibits long battery life.

Chemically monodisperse tin nanoparticles on monolithic 3D nanoporous copper for lithium ion battery anodes with ultralong cycle life and stable lithium storage properties.

In this report, a simple and effective low-temperature synthesis route has been proposed to smoothly achieve monodisperse tin nanoparticles upon monolithic 3D nanoporous copper (3D-NPC@MTNPs) from chemical dealloying of as-cast Al-45 at% Cu alloy sheets in HCl solution; they exhibit superior Li storage properties and ultralong cycle life as the anode for lithium ion batteries (LIBs). The results show that the 3D-NPC@MTNPs composite can be fabricated on a large scale by electroless plating of Sn on a uniform NPC matrix with a pore size of ca. 200 nm in an acidic plating bath below room temperature. Compared to two dimensional copper foil supported tin thin films (2D-CF@TTFs), the 3D-NPC@MTNPs electrode displays a markedly higher first reversible capacity of 0.485 mA h cm-2 as well as superior cycling stability with 52.4% capacity retention and over 96.7% coulombic efficiency after 500 cycles. This can be largely ascribed to the synergistic effect between the favorable monodispersity of Sn nanoparticles with ultrafine particle size and single crystal nature and the unique 3D nanoporous electrode architecture with a large specific surface area and a good mass transfer channel, which facilitates the accommodation of mechanical strain, improvement of structural stability, enhancement of bonding force, and acceleration of mass transfer, which are indicative of a quite promising candidate as a high-performance anode for LIBs.

Highly compact, free-standing porous electrodes from polymer-derived nanoporous carbons for efficient electrochemical capacitive deionization

Highly compact, nanoporous electrodes fabricated by slip-roll compressing of polypyrrole-derived activated microporous carbon particles enable efficient electrochemical capacitive deionization.

A novel nanoporous bismuth electrode sensor for in situ heavy metal detection

A novel modified nanoporous bismuth electrode (modified-NPBiE) sensor was prepared by consecutive procedures which consist of bismuth (Bi) and tin (Sn) electroplating, thermal treatment for alloying Bi-Sn film, and selective chemical dealloying of Sn. The newly prepared modified-NPBiE sensor exhibited improved lifetime (2.7 times longer than a conventional nanoporous Bi-filmed electrode with over 40 repeated measurements) sensor with lower relative standard deviation (RSD), indicating enhanced stability and reproducibility for heavy metal detection. Using square wave anodic stripping voltammetry (SWASV), two noticeable peaks were observed at −0.65 V and −0.45 V associated with stripping currents of Cd2+ and Pb2+ in 0.1 M acetate buffer solution at pH 4.6, respectively. The calibration curves showed strong correlations with respect to various concentrations of Cd2+ and Pb2+ with the limit of detection (LOD) of 1.3 ppb for Cd2+ and 1.5 ppb for Pb2+. The newly modified-NPBiE sensor was then successfully applied for detecting Cd2+ and Pb2+ in a tap water environment and exhibited an acceptable performance for measuring heavy metals with a good reliability.

Heterogeneous Photocatalysis: Relationships with Heterogeneous Catalysis and Perspectives

In this paper, the performance of nano-porous electrodes made of a composite material of SrTiO3 and SnO2 are compared with those made of bare SnO2. When these particular devices are analyzed in a comparative mode the results confirmed the enhancement of photovoltaic parameters in the former device. The performance of respective cells were examined by several methods including I−V characteristic measurements, photocurrent action spectra, dark I−V measurements, Mott−Schottky measurements and X-ray diffraction measurements. Even though such improvements in this particular cell could be explicated by the formation of a potential energy barrier of SrTiO3 particles of comparably large width at the SrTiO3/SnO2 interface, the passivation of voids in the SnO2 film by SrTiO3 particles to a certain extent could not be totally ruled out. Besides, high energetic electrons injected by dye molecules move more credibly through mini-bands formed in the chain of nano-crystalline SnO2 particles to the back contact. The blocking of the recombination path and the shifting up of the uppermost electron occupied level of SnO2 accompanying the conduction band edge in the SrTiO3/SnO2 composite film, may have lead to the observed enhancement of the fill factor and photovoltage, respectively.

Redox Cycling in Individually Encapsulated Attoliter-Volume Nanopores.

Redox cycling electrochemistry in arrays of individually encapsulated attoliter-volume ( V ∼ 10 aL) nanopores is investigated and reported here. These nanopore electrode array (NEA) structures exhibit distinctive electrochemical behaviors not observed in open NEAs, which allow free diffusion of redox couples between the nanopore interior and bulk solution. Confined nanopore environments, generated by sealing NEAs with a layer of poly(dimethylsiloxane), are characterized by enhanced currents-up to 250-fold compared with open NEAs-owing to effective trapping of the redox couple inside the nanopores and to enhanced mass transport effects. In addition, electrochemical rectification ( ca. 1.5-6.3) was observed and is attributed to ion migration. Finite-element simulations were performed to characterize the concentration and electric potential gradients associated with the disk electrode, aqueous medium, and ring electrode inside the nanopores, and the results are consistent with experimental observations. The additional signal enhancement and redox-cycling-based rectification behaviors produced in these self-confined attoliter-volume nanopores are potentially useful in devising ultrasensitive sensors and molecular-based iontronic devices.