Working Electrode Material Research Articles

Formation of MnO2-coated ITO electrodes with high catalytic activity for enzymatic glucose detection.

We present the formation of a cheap and environmentally friendly working electrode material for glucose biosensors with good catalytic properties. The classic electrode in such devices consists of a conductive material modified with the enzyme glucose oxidase. The working principle is the electrochemical detection of hydrogen peroxide as a product of the enzymatic transformation of glucose. As a base material, we offer manganese dioxide; it is a natural highly selective catalyst for the decomposition of H2O2 and is electrochemically deposited onto the surface of ITO. We approached the formation of MnO2 films systematically. By changing parameters such as the deposition method, pH of the electrolyte, and the drying temperature of the precipitate, a series of electrodes were formed. These electrodes were characterized by SEM, electrochemical impedance spectroscopy, and XPS and their electrocatalytic activity was studied. Significant differences in the sensitivity of the electrodes were detected. The manganese dioxide film with the best catalytic characteristics is formed in the electrolyte with pH 1 by cyclic voltammetry and then drying at 60 °C. The surface of the electrode was then modified with a solution of GOx enzyme with a concentration of 2 mg ml-1 (100-250 units per mg solid). The sensitivity of such an electrode is 117.8 μA mmol-1 cm-2. The range of determined concentrations of glucose is from 0.1 mM to 3 mM. The sensitivity is comparable to that of electrodes based on expensive materials such as graphene and noble metals.

Enhancing electrocarboxylation reactions efficiency by cathode material selection

Electrocarboxylation reactions hold significant promise as a sustainable and efficient method for carbon-carbon bond formation driven by electricity enabling the direct conversion of carbon dioxide (CO2) into valuable organic compounds. Despite the potential and advantages of electrocarboxylation reactions over traditional methods, there are still challenges to address for their widespread implementation. In this contribution, our objective is to shed light on the role of these reactions in recycling and converting CO2 into valuable chemicals. Specifically, we focus on exploring potential correlations between the performance of CO2-based carboxylation and the choice of working electrode material in combination with the functional groups present in the substrates.

Research Progress of Working Electrode in Electrochemical Extraction of Lithium from Brine

Efficient extraction of Li from brine at a low cost is becoming a key technology to solve energy and environmental problems. Electrochemical extraction of Li has become a research hotspot due to its low energy consumption, high selectivity, and environmental friendliness. LiMn2O4, LiFePO4, and LiNi1/3Co1/3Mn1/3O2 are widely used as cathode materials for the electrochemical extraction of Li but they also have some drawbacks, such as a small adsorption capacity. In this paper, the principle of electrochemical Li extraction from brine is reviewed and the research progress and analysis of the above three working electrode materials is summarized. In addition, analysis of the extraction of other rare ions from the working electrode material and the effect of micro-organisms on the working electrode material is also presented. Next, the shortcomings of working electrode materials are expounded upon and the research direction of working electrode materials in electrochemical Li extraction technology are prospected. It is hoped that this paper can provide insights and guidance for the research and application of electrochemical Li extraction from brine.

Size-tunable bismuth quantum dots for self-powered photodetectors under ambient conditions

Although black phosphorus analogue, bismuthene, has been extensively investigated in recent years, yet the investigation into the photoelectronic devices is still in its infancy. In this contribution, uniform zero-dimensional (0D) bismuth (Bi) quantum dots (QDs) with different sizes were successfully synthesized by a simple solvothermal method. The as-synthesized 0D Bi QDs serve as working electrode materials by a direct deposition for photoelectrochemical (PEC)-type photodetection. The PEC results demonstrate that the as-fabricated 0D Bi QD-based electrode not only possess suitable self-powered broadband photoresponse, but also displays excellent photodetection performance. Under simulated light, the photocurrent density and photoresponsivity of the as-fabricated 0D Bi QD-based electrode can reach 2690 nA cm−2, and 22.0 μA W−1, respectively. In addition, the as-prepared Bi QDs with the average diameter of 17 nm exhibit the best PEC photoresponse behavior in the studied size range of Bi QDs, mainly ascribed to the synergistic effect of suitable band gap and accessible active sites. It is anticipated that the uniform Bi QDs can be served as building blocks for a variety of photoelectronic devices, further expanding the application prospects of bismuthene, and can provide in-depth acknowledge on the performance optimization of monoelement Bi-based optical devices.

Cassava peel derived self-doped and hierarchical porous carbon as an optimized electrode for the ultra-high energy density of supercapacitor

The development of advanced electrode materials with optimized properties, including structural morphology, high porosity, and functional group doping, is very important to enhance the energy density of solid-state supercapacitors. Here, a hierarchical 3D porous carbon self-doping obtained from cassava peel through an environmentally benign approach to optimize the supercapacitor working electrode material. The unique sponge-like interconnected pore structure and self-doping features are controlled through chemical impregnation (CIP) of ZnCl2 (CIP/Z), KOH (CIP/K), and H3PO4 (CIP/H) and high-temperature pyrolysis in an N2&CO2 gaseous environment. Furthermore, the optimized CIP/Z carbon material exhibits high content of 94.606 % and a self-doping oxygen heteroatom of about 2.672 %. The unique sponge-like morphology possessed enriches micropores of 94 %, indicating high performance as an electrode material. The electrochemical properties were assessed through a symmetric supercapacitor system assembled in a solid free-binding coin yielding an excellent specific capacitance of 257 F g−1 at 1 A g−1. Meanwhile, the optimized electrode has a high rate capability of 92.43 % and maintained a coulombic efficiency of up to 91.10 % at 10 A g−1. The best working efficiency supercapacitor cell can show a jump in energy density of 35.69 Wh kg−1 at a specific power of 167.68 W kg−1 in an aqueous electrolyte of 1 M H2SO4. These excellent results provide important insights for optimizing electrode materials derived from cassava peel-based porous carbon for symmetrically designed supercapacitors of binder-free solid coins in aqueous electrolytes with high energy density.

Investigation of electrochemical behaviour and annealing effect on zinc cobaltite nanoparticles as working electrode material for energy storage device

Investigation of electrochemical behaviour and annealing effect on zinc cobaltite nanoparticles as working electrode material for energy storage device

Electrochemically Assaying Dopamine with p-Doped Silicon Nanowires

Neuroblastoma, a pediatric cancer, is characterized by high urinary excretion of dopamine (DA). Silicon nanowires (SiNWs), which are nontoxic and known to resist surface fouling in biological samples, were investigated for practical use as working electrode materials to assay dopamine. Undoped, p-doped, and n-doped SiNWs were deposited onto glassy carbon electrodes (GCEs) and used to measure dopamine in aqueous solution. Within this series, p-doped SiNWs had the highest sensitivity in the series and are the focus of this study. Optimum measurements were obtained at pH 5.0. Cyclic voltammetry (CV) determination of dopamine showed that oxidation at +0.4801 V versus Ag/AgCl provided the highest sensitivity and also for chronoamperometric (CA) analysis. A calibration curve using chronoamperometry showed a linear (R2 = 0.9896) range from 50 to 900 µM. Randles-Sevçik analysis showed that the interaction of dopamine with the electrode surface was diffusion controlled reversibly with coefficients (D) equal to 2.77 × 10−5 and 2.01 × 10−5 cm2·s−1 for the oxidation and reduction potentials, respectively. The sensor was demonstrated to be selective in the presence of uric acid, acetaminophen, H2O2, folic acid, and glucose.

The function of porous working electrodes for hydrogen production from water splitting in non-thermal plasma reactor

The hydrogen production via water splitting in non-thermal plasma (NTP) reactors seems a promising pathway for renewable energy conversion and storage. Herein, based on an NTP-assisted water-splitting reactor system, the effects of air cooling and quenching, water content, total gas flow rate, working electrode material and porous working electrode were investigated systematically. The application of air cooling and quenching apparently improves the hydrogen yield by lowering the temperatures of the plasma zone and products. After optimization, the best feeding condition is 300 sccm 3 vol% H2O/Ar and the best water-splitting performance is achieved at 6.93 kVp-p. Compared with the stainless-steel working electrode, the application of a porous working electrode composed of stainless-steel rod and Cu mesh enhances the water-splitting performance especially the energy efficiency, due to the large surface area of the Cu mesh and the narrowing of the discharge gas. The Cu electrode performs better than the stainless-steel electrode for water splitting. The poor contacts between the Cu rod and the Cu foam as well as the two layers of Cu foam lead to the not outstanding performance of the Cu rod + Cu foam working electrode. The best all-around performance, i.e., 7.09% hydrogen yield and 0.68% energy efficiency, was achieved with the porous working electrode composed of a stainless-steel rod and Cu mesh. The application of porous working electrodes in NTP-assisted water splitting reveals a new route for performance improvement.

Solid-state potentiometric sensors with platinized SnO2(Sb) and calixarene/phosphotungstic acid composite electrolyte selective to CO in hydrogen-air atmosphere

All-solid-state electrochemical systems with a composite electrolytes based on calixarene sulfonic acid and phosphotungstic acid used as a proton-conducting membrane and platinised oxide SnO2(Sb) used as a working electrode material were studied. Variation in the composition of the electrolyte made it possible to improve the characteristics of potentiometric gas sensors for CO at ambient temperature with a short response time (12 s for 1 vol% of CO) and recovery time of 30–35 min. The system with optimal composition is selective to carbon monoxide in air-hydrogen mixture with H2 concentration comparable to that of CO (up to 1 vol%).

Composition and structure of Ti–Al alloy powders formed by electrochemical co-deposition in KCl–LiCl–MgCl2–TiCl3–AlCl3 molten salt

Direct electrochemical deposition from titanium and aluminum chlorides is a green and short process for preparing Ti–Al alloy powders, thereby relevant for replacing the conventional smelting process characterized by intermittent and high production costs. However, the morphologies and compositions of resulting Ti–Al alloy powders have not yet been systematically studied. Here, Ti–Al alloy powders with different compositions and morphologies were successfully prepared from a molten KCl–LiCl–MgCl2 salt containing AlCl3 and TiCl3 under different electrodeposition parameters. The electrochemical behaviors of Ti and Al ions were examined on Mo and Al working electrodes by cyclic voltammetry at different temperatures. The results revealed variable numbers of redox peaks with temperature and working electrode material. The influences of the cathodic parameters on compositions and morphologies of Ti–Al alloy products studied through potentiostatic and galvanostatic electrolysis revealed that factors like cathodic potentials, initial current densities, and mole ratios of TiCl3/AlCl3 greatly influenced the chemical compositions of Ti–Al alloy products except for temperatures. Also, phase compositions of Ti–Al alloy products were mainly controlled by the electrodeposition potentials and mole ratios of TiCl3/AlCl3. Meanwhile, the morphologies and particle sizes of Ti–Al alloy powders varied with temperature, current density, and electrolyte composition. In sum, these findings look promising for future formation of Ti–Al alloy powders for various uses.

Post‐Transition Metal Electrodes for Sensing Heavy Metal Ions by Stripping Voltammetry

AbstractHeavy metal ions contamination is an ever‐growing threat to human health and ecosystems. Analytic sensing of heavy metal ions is a prerequisite step toward addressing this challenge. Electroanalytical technique is an effective and convenient way to detect heavy metal ions. Especially, stripping voltammetry techniques have been utilized for sensing metal ions at trace levels in different sample matrices. The choice of the working electrode materials plays a decisive role in the precision and sensitivity of stripping voltammetry. Post‐transition metals (including elements in group 12) are elements with low melting points, demonstrating unique properties including amalgamation with heavy metal ions that enhance the performance of stripping voltammetry during the pre‐concentration step, which make them particularly suitable for heavy metal ion sensing. Here, for better understanding the features and advantages of post‐transition metals in stripping voltammetry, eight classes of working electrodes based on zinc (Zn), mercury (Hg), gallium (Ga), indium (In), tin (Sn), lead (Pb), antimony (Sb), and bismuth (Bi), are reviewed, with their efficiency and effectiveness compared and recent progresses discussed. Additionally, liquid metal electrodes based on post‐transition metals and alloys are also presented. This review provides viable directions for future development of heavy metal ion sensors based on post‐transition metals.

Preparation and Electrochemical Analysis of Ni-Based Metal Organic Frameworks Containing Binary Ligands for Capacitor Electrodes.

As one of the energy storage systems, supercapacitors have quite long charge-discharge cycle life. Among many kinds of electrode materials, metal organic frameworks (MOFs) have unique properties such as high specific surface areas and large pore volume as supercapacitor electrode materials. Nickel-MOFs consist of binary ligand such as 1,3,5-Trimesic acid (H₃BTC) and terephthalic acid (TPA) were used as working electrode materials in three electrode cell for capacitor system. When synthesizing MOFs, it is possible to prepare uniform crystals using hydrothermal synthesis. The morphology of composites was analyzed by field emission scanning electron microscopy (FE-SEM). Electrochemical properties were measured by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) in 6M KOH electrolyte.

On-Chip Cyclic Voltammetry Measurements Using a Compact 1024-Electrode CMOS IC.

Complementary metal–oxide–semiconductor (CMOS) microelectrode arrays integrate amplifier arrays with on-chip electrodes, offering high-throughput platforms for electrochemical sensing with high spatial and temporal resolution. Such devices have been developed for highly parallel constant voltage amperometric detection of transmitter release from multiple cells with single-vesicle resolution. Cyclic voltammetry (CV) is an electrochemical method that applies voltage waveforms, which provides additional information about electrode properties and about the nature of analytes. A 16-channel, 64-electrode-per-channel CMOS integrated circuit (IC) fabricated in a 0.5 μm CMOS process for CV is demonstrated. Each detector consists of only 11 transistors and an integration capacitor with a unit dimension of 0.0015 mm2. The device was postfabricated using Pt as the working electrode material with a shifted electrode design, which makes it possible to redefine the size and the location of working electrodes. The system incorporating cell-sized (8 μm radius) microelectrodes was validated with dopamine injection tests and CV measurements of potassium ferricyanide at a 1 V/s scanning rate. The cyclic voltammograms were in excellent agreement with theoretical predictions. The technology enables rigorous characterization of electrode performance for the application of CMOS microelectrode arrays in low-noise amperometric measurements of quantal transmitter release as well as other biosensing applications.

Enhanced photovoltaic performance of dye-sensitized solar cells based Ag2O doped BiFeO3 hetrostructures

In the present study, hierarchical bismuth ferrite (BFO) and Ag2O-doped bismuth ferrite (Ag2O/BFO) nanostructures are successfully fabricated using hydrothermal methods. The fabricated nanostructures were characterized via several analytical techniques. BiFeO3 (BFO) nanoparticles were found to be 30–50 nm in diameter with pure perovskite phase. The nanocomposites were used for the preparation of photoanode to fabricate the dye-sensitized solar cells (DSSCs). The results revealed that the doping of Ag2O nanoparticles with BFO improves the transportation of electrons and decreased the recombination of photogenerated charges. Because of these advantages, the DSSC based on the Ag2O/BFO photoanode has been fabricated and shows the efficiency of energy conversion about to 4.25%, which indicates>100% development equated to the DSSCs fabricated using pure BFO nanoparticle based photoanode and prepared under the similar conditions. These results indicate that the BFO based nanocomposites doped with silver oxide can potentially be used as working electrode materials in DSSCs.

Influence of anionic precursors on electrochemical properties of tin oxide nanoparticles: a comparative analysis

A cost-effective chemical precipitation method has been adopted to synthesis tin oxide (SnO2) nanomaterials with the help of two different anionic sources (NH3OH and NaOH). Initially, the X-ray diffraction (XRD) studies confirm the formation of regular rutile tetragonal crystal structure of SnO2. The functional group analysis by Fourier transform infra-red (FTIR) spectroscopy identifies the presence of Sn-OH stretching mode of vibration. The morphological with elemental confirmation by HRSEM with EDAX analysis observes the formation of SnO2 agglomeration in appropriate ratio (Sn and O) without showing any other impurities. The particle size analysis (PSA) reveals that the synthesized SnO2 nanomaterials are in a nano-sized range of 10 nm to 33 nm. The optical analysis using UV–Visible (UV) and photoluminescence (PL) spectroscopy reveals that the bandgap energy of synthesized materials is found to be 4.12 eV and 4.14 eV, blue-shifted from bulk materials. The electrochemical behavior of synthesized tin oxide nanomaterials as working electrodes are examined by a conventional three-electrode system with analyzed parameters such as cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). This study exposes the highest specific capacitance Csp value of 405.15 F g−1 at a scan rate of 1 mV s−1 and 403.72 F g−1 at a current density of 0.5 Ag−1. The highest energy density and power density value of 27.48 Wh kg−1 at 0.5 Ag−1 and 145.83 W kg−1 at 1 Ag−1, respectively, presents a promising positive working electrode material for supercapacitor applications.

Simples fabrication of hierarchical NiCoSe4 nanorods grown on carbon nanofibers as excellent electrocatalysts for tryptophan oxidation

In this study, a simple approach is established to fabricate NiCoSe4 nanorods grown onto carbon nanofiber (CNF) skeletons by combining electrospinning and a hydrothermal process. We achieved the rapid and ultrasensitive electrocatalytic sensing of tryptophan (Trp) in 0.1 M KOH by using intrinsically metallic NiCoSe4 anchored on CNFs as an alternative working electrode material. Benefiting from the large surface area due to rich defect active sites and the high electrocatalytic behavior of NiCoSe4 with CNF, the fabricated sensor exhibits a lower electron-transfer resistance of Rct 92 Ω with respect to the CNF–NiCo and CNFs electrodes. The results of voltammetric technique confirmed that the CNF–NiCoSe4-GCE showed higher anodic peak intensity and a lower anodic potential for Trp detection than CNFs-GCE and CNF–NiCo-GCE electrodes since the integration of sp2 carbon on the surface of the CNFs and bimetallic selenides improves the sensing performance. The amperometric I-t curve showed a linear response in the Trp concentration range of 5–95 nM and a detection limit of 0.68 nM at low potential of 0.4 V vs. Hg/HgO. The CNF–NiCoSe4-GCE was successfully utilized for the electrocatalytic monitoring of Trp from human serum, milk, and tomato juice samples with a recovery of 95.4–105.5%.

Electrochemical simulation of metabolic reduction and conjugation reactions of unsymmetrical bisacridine antitumor agents, C-2028 and C-2053

Electrochemistry (EC) coupled with analysis techniques such as liquid chromatography (LC) and mass spectrometry (MS) has been developed as a powerful tool for drug metabolism simulation. The application of EC in metabolic studies is particularly favourable due to the low matrix contribution compared to in vitro or in vivo biological models. In this paper, the EC(/LC)/MS system was applied to simulate phase I metabolism of the representative two unsymmetrical bisacridines (UAs), named C-2028 and C-2053, which contain nitroaromatic group susceptible to reductive transformations. UAs are a novel potent class of antitumor agents of extraordinary structures that may be useful in the treatment of difficult for therapy human solid tumors such as breast, colon, prostate, and pancreatic tumors. It is considered that the biological action of these compounds may be due to the redox properties of the nitroaromatic group. At first, the relevant conditions for the electrochemical conversion and product identification process, including the electrode potential range, electrolyte composition, and working electrode material, were optimized with the application of 1-nitroacridine as a model compound. Electrochemical simulation of C-2028 and C-2053 reductive metabolism resulted in the generation of six and five products, respectively. The formation of hydroxylamine m/z [M+H-14]+, amine m/z [M+H-30]+, and novel N-oxide m/z [M+H-18]+ species from UAs was demonstrated. Furthermore, both studied compounds were shown to be stable, retaining their dimeric forms, during electrochemical experiments. The electrochemical method also indicated the susceptibility of C-2028 to phase II metabolic reactions. The respective glutathione and dithiothreitol adducts of C-2028 were identified as ions at m/z 873 and m/z 720. In conclusion, the electrochemical reductive transformations of antitumor UAs allowed for the synthesis of new reactive intermediate forms permitting the study of their interactions with biologically crucial molecules.

Voltammetry measurements in lithium chloride-lithium oxide (LiCl–Li2O) salt: An evaluation of working electrode materials

Instrumentation to provide process monitoring (PM) and safeguards for the oxide reduction (OR) step in the electrochemical processing of used oxide nuclear fuel is necessary to ensure equipment is operated as declared. Cyclic voltammetry (CV) has been proposed for real-time monitoring of the operation of an OR process for safeguards purposes. In this study, 316L stainless steel (SS), tantalum (Ta), molybdenum (Mo), tungsten (W), platinum (Pt), and iridium (Ir) were evaluated as potential working electrode (WE) materials based on their chemical inertness, corrosion resistance, and sensitivity in detecting lithium oxide (Li2O) and other chloride salts in the OR electrolyte. Of the electrodes evaluated, 316L SS, Ir, and Pt all performed reasonably well in the lithium chloride-lithium oxide (LiCl-Li2O) electrolyte. SS was operated in the cathodic potential, had reasonable corrosion resistance, and is relatively inexpensive. Ir could be operated in both the cathodic and anodic potentials and was the most corrosion-resistant of the materials evaluated. Pt is limited to the anodic potential range, had reasonable corrosion resistance, and was the most sensitive to Li2O concentrations in the salt. In the development of a stand-alone safeguards instrumentation, our recommendation is a CV probe fitted with both Ir and Pt WEs. The results of this study may also be helpful for anode material selection in other electrometallurgy industries, such as molten salt electrolysis.

Enhancing hydrogen production from steam electrolysis in molten hydroxides via selection of non-precious metal electrodes

There are still gaps in the field of reference electrode that is needed to assist electrolysis in high temperature electrolytes (e.g. molten hydroxides) for H2 gas production. This research aims to fill the gaps by preparing Ni/Ni(OH)2 reference electrode and more importantly testing its effectiveness against important performance factors including; ion conducting membrane (e.g. mullite tubes), internal electrolyte composition, working temperature and electrochemical control (e.g. potential scan rate). Then, this reference electrode was used to study the electrocatalytic activity various cheaper working electrode materials including; stainless steel (St.st), Ni, Mo and Ag in comparison with Pt by the means of chronoamperometry and voltammetry. The effect of introducing steam into electrolyte (eutectic mixture of NaOH and KOH) on the electrocatalytic activity of these working electrodes was also studied. It was observed that the potential of hydrogen evolution with different working electrodes followed an order as; Pt > Ni > St. st > Ag > Mo (positive to negative). The performance of each working electrode was confirmed through chronoamperometry for hydrogen evolution at a constant potential of −0.7 V. It was also found in cyclic voltammetry and confirmed by chronoamperometry that the introduction of steam was apparent as increasing the current density at cathodic limit for hydrogen evolution. This study could help to develop non-precious metal electrodes for the production of hydrogen fuel. In future, there will be a potential in the threshold concentration of steam for H2 gas production.

Zero-consumption Clark-type microsensor for oxygen monitoring in cell culture and organ-on-chip systems

Clark-type oxygen microsensors promise zero analyte consumption if the feedback mode (Ross principle) is successfully implemented. Our approach was a microsensor with platinum as working and counter electrode material, a pHEMA hydrogel layer containing buffer solution as electrolyte and PDMS as gas-permeable membrane. We were able to demonstrate successful implementation of the Ross principle by measurement of the counter electrode potential. The microsensors could be stored dry and activated by immersion into aqueous analyte. Chronoamperometric protocols were applied to enable long-term stability for more than one week without recalibration. The microsensors were integrated in conventional tissue culture flasks for cell measurements. Respiration monitoring was done in T-47D breast cancer monolayer culture. The unique feature combination of zero analyte consumption, 1-point calibration and sufficient long-term stability make these sensors an ideal candidate to monitor oxygenation and respiration in different cell culture and organ-on-chip systems.