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First-Principles Study of Adsorption of CHsub.4 on a Fluorinated Model NiFsub.2 Surface
Electrochemical fluorination on nickel anodes, also known as the Simons’ process, is an important fluorination method used on an industrial scale. Despite its success, the mechanism is still under debate. One of the proposed mechanisms involves higher valent nickel species formed on an anode acting as effective fluorinating agents. Here we report the first attempt to study fluorination by means of first principles investigation. We have identified a possible surface model from the simplest binary nickel fluoride (NiF[sub.2]). A twice oxidized NiF[sub.2](F[sub.2]) (001) surface exhibits higher valent nickel centers and a fluorination source that can be best characterized as an [F[sub.2]][sup.−] like unit, readily available to aid fluorination. We have studied the adsorption of CH[sub.4] and the co-adsorption of CH[sub.4] and HF on this surface by means of periodic density functional theory. By the adsorption of CH[sub.4], we found two main outcomes on the surface. Unreactive physisorption of CH[sub.4] and dissociative chemisorption resulting in the formation of CH[sub.3]F and HF. The co-adsorption with the HF gave rise to four main outcomes, namely the formation of CH[sub.3]F, CH[sub.2]F[sub.2], CH[sub.3] radical, and also physisorbed CH[sub.4].
Journal Article
Revitalizing interface in protonic ceramic cells by acid etch
Protonic ceramic electrochemical cells hold promise for operation below 600 °C (refs.
1
,
2
). Although the high proton conductivity of the bulk electrolyte has been demonstrated, it cannot be fully used in electrochemical full cells because of unknown causes
3
. Here we show that these problems arise from poor contacts between the low-temperature processed oxygen electrode–electrolyte interface. We demonstrate that a simple acid treatment can effectively rejuvenate the high-temperature annealed electrolyte surface, resulting in reactive bonding between the oxygen electrode and the electrolyte and improved electrochemical performance and stability. This enables exceptional protonic ceramic fuel-cell performance down to 350 °C, with peak power densities of 1.6 W cm
−2
at 600 °C, 650 mW cm
−2
at 450 °C and 300 mW cm
−2
at 350 °C, as well as stable electrolysis operations with current densities above 3.9 A cm
−2
at 1.4 V and 600 °C. Our work highlights the critical role of interfacial engineering in ceramic electrochemical devices and offers new understanding and practices for sustainable energy infrastructures.
A simple acid treatment can improve high-temperature annealed electrolyte surfaces, resulting in improved performance and stability at lower temperatures for protonic ceramic fuel/electrolysis cells, offering new understanding for sustainable energy infrastructures.
Journal Article
Sensitive and selective determination of upadacitinib using a custom-designed electrochemical sensor based on ZnO nanoparticle-assisted molecularly imprinted polymer
Upadacitinib (UPA) is a selective and reversible oral Janus kinase (JAK) 1 inhibitor and is of great importance in treating inflammatory bowel disease (Zheng et al., Int Immunopharmacol 126:111229, 2024; Foy et al., JAAD Case Rep 42:20–22, 2023). Although there are limitations to the effectiveness of UPA, it has received positive responses in clinical trials and is approved for the treatment of atopy dermatitis (AD) (Li et al., Int Immunopharmacol 125:111193, 2023). In this study, a nanoparticle-doped molecularly imprinted polymer (MIP)-based electrochemical sensor was developed for sensitive and selective detection of UPA. The developed sensor was designed as a thin film layer using the photopolymerization method on the surface of the prepared nanoparticle-doped polymerization solution glassy carbon electrode (GCE). Various nanoparticles, such as multi-walled carbon nanotube, titanium dioxide, oxide, and zinc oxide (ZnO) nanoparticles, were the most suitable for UPA. Surface characterization of the developed sensor was done by scanning electron microscopy (SEM), and electrochemical characterization was done by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The quantitative analysis of UPA was performed in 5.0 mM [Fe (CN)6]3−/4− solution using the differential pulse voltammetry (DPV) technique. Under optimum conditions, the calibration range was between 0.1 and 1 pM. The limit of detection (LOD) and limit of quantification (LOQ) were calculated as 0.005 pM and 0.017 pM, respectively. The sensor’s accuracy was proven by performing a recovery study in serum. The sensor’s selectivity was also evaluated using common interfering substances such as KNO3, CaCl2, Na2SO4, uric acid, ascorbic acid, dopamine, and paracetamol. According to the results obtained, the performance of the designed sensor was found to be quite sensitive and selective in determining UPA. The developed UPA-ZnO/3-APBA@MIP-GCE sensor showed high sensitivity and selectivity towards UPA. In addition, the selectivity, the most important feature of the MIP-based sensor, was confirmed by imprinting factor (IF) calculations using tofacitinib (TOF) and ruxolitinib (RUX). The sensor’s unique selectivity is demonstrated by its successful performance even in the presence of UPA impurities.
Journal Article
An electrochemical sensor for voltammetric detection of ciprofloxacin using a glassy carbon electrode modified with activated carbon, gold nanoparticles and supramolecular solvent
A highly sensitive and novel electrochemical sensor for ciprofloxacin (CIP) has been developed using gold nanoparticles deposited with waste coffee ground activated carbon on glassy carbon electrode (AuNPs/AC/GCE) and combined with supramolecular solvent (SUPRAS). The fabricated AuNPs/AC/GCE displayed good electrocatalytic activity for AuNPs. The addition of SUPRAS, prepared from cationic surfactants namely didodecyldimethylammonium bromide (DDAB) and dodecyltrimethylammonium bromide (DTAB), increased the electrochemical response of AuNPs. The detection of CIP was based on the decrease of the cathodic current of AuNPs. The electrochemical behavior of the modified electrode was investigated using cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. Under optimum conditions, the calibration plot of CIP exhibited a linear response in the range 0.5–25 nM with a detection limit of 0.20 nM. The fabricated electrochemical sensor was successfully applied to determine CIP in milk samples with achieved recoveries of 78.6–110.2% and relative standard deviations of <8.4%. The developed method was also applied to the analysis of pharmaceutical formulation and the results were compared with high-performance liquid chromatography.
Graphical abstract
Journal Article
Electrochemical Deposition of Nanomaterials for Electrochemical Sensing
The most commonly used methods to electrodeposit nanomaterials on conductive supports or to obtain electrosynthesis nanomaterials are described. Au, layered double hydroxides (LDHs), metal oxides, and polymers are the classes of compounds taken into account. The electrochemical approach for the synthesis allows one to obtain nanostructures with well-defined morphologies, even without the use of a template, and of variable sizes simply by controlling the experimental synthesis conditions. In fact, parameters such as current density, applied potential (constant, pulsed or ramp) and duration of the synthesis play a key role in determining the shape and size of the resulting nanostructures. This review aims to describe the most recent applications in the field of electrochemical sensors of the considered nanomaterials and special attention is devoted to the analytical figures of merit of the devices.
Journal Article
Electrochemical Impedance Spectroscopy in the Characterisation and Application of Modified Electrodes for Electrochemical Sensors and Biosensors
Electrochemical impedance spectroscopy is finding increasing use in electrochemical sensors and biosensors, both in their characterisation, including during successive phases of sensor construction, and in application as a quantitative determination technique. Much of the published work continues to make little use of all the information that can be furnished by full physical modelling and analysis of the impedance spectra, and thus does not throw more than a superficial light on the processes occurring. Analysis is often restricted to estimating values of charge transfer resistances without interpretation and ignoring other electrical equivalent circuit components. In this article, the important basics of electrochemical impedance for electrochemical sensors and biosensors are presented, focussing on the necessary electrical circuit elements. This is followed by examples of its use in characterisation and in electroanalytical applications, at the same time demonstrating how fuller use can be made of the information obtained from complete modelling and analysis of the data in the spectra, the values of the circuit components and their physical meaning. The future outlook for electrochemical impedance in the sensing field is discussed.
Journal Article
Rhenium Electrodeposition and Its Electrochemical Behavior in Molten KF-KBFsub.4-Bsub.2Osub.3-KReOsub.4
The electrochemical behavior of rhenium ions in the molten KF-KBF[sub.4]-B[sub.2]O[sub.3] salt was systematically studied, and pure metallic rhenium was obtained at the cathode. The processes of rhenium ions reduction and diffusion in molten KF-KBF[sub.4]-B[sub.2]O[sub.3] were determined using cyclic voltammetry, stationary galvanostatic and polarization curves analyses. The values of diffusion coefficients were 3.15 × 10[sup.−5] cm[sup.2]/s and 4.61 × 10[sup.−5] cm[sup.2]/s for R[sub.1] and R[sub.2,] respectively. Rhenium electrodeposition was carried out at a constant potential. The process of rhenium cathode reduction in KF-KBF[sub.4]-B[sub.2]O[sub.3] at 773 K was found to be a one-step reaction Re(VII) → Re, and rhenium electrodeposition presumably occurred from two types of complex rhenium ions (KReO[sub.4] and K[sub.3]ReO[sub.5]). Both processes are quasi-reversible and controlled by diffusion. The obtained cathode deposit was analyzed by SEM, EDX, ICP-OES and XRD methods. The obtained deposit had a thread structure and rhenium was the main component.
Journal Article
Self-sustainable protonic ceramic electrochemical cells using a triple conducting electrode for hydrogen and power production
The protonic ceramic electrochemical cell (PCEC) is an emerging and attractive technology that converts energy between power and hydrogen using solid oxide proton conductors at intermediate temperatures. To achieve efficient electrochemical hydrogen and power production with stable operation, highly robust and durable electrodes are urgently desired to facilitate water oxidation and oxygen reduction reactions, which are the critical steps for both electrolysis and fuel cell operation, especially at reduced temperatures. In this study, a triple conducting oxide of PrNi
0.5
Co
0.5
O
3-δ
perovskite is developed as an oxygen electrode, presenting superior electrochemical performance at 400~600 °C. More importantly, the self-sustainable and reversible operation is successfully demonstrated by converting the generated hydrogen in electrolysis mode to electricity without any hydrogen addition. The excellent electrocatalytic activity is attributed to the considerable proton conduction, as confirmed by hydrogen permeation experiment, remarkable hydration behavior and computations.
While producing renewable fuel is crucial for a sustainable energy economy, there is still a need for active and durable materials capable of efficient fuel generation and utilization. Here, authors demonstrate a triple-conductive oxide as an oxygen electrode for H
2
or electricity production.
Journal Article
Impedimetric determination of cortisol using screen-printed electrode with aptamer-modified magnetic beads
A non-invasive aptamer-based electrochemical biosensor using disposable screen-printed graphene electrodes (SPGEs) was developed for simple, rapid, and sensitive determination of cortisol levels. Selective detection of cortisol based on a label-free electrochemical assay was achieved by specific recognition of the cortisol DNA aptamer (CApt). The CApt was modified with streptavidin magnetic beads (MBs) before simple immobilization onto the electrode surface using a neodymium magnet. The electrochemical behavior of the aptamer-based biosensor was assessed by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) (vs Ag/AgCl). The specific binding between cortisol and CApt resulted in a decrease in charge transfer resistance (R
ct
) from EIS using [Fe(CN)
6
]
3−/4−
with increasing cortisol concentration. Under optimal conditions, a linear range from 0.10 to 100 ng/mL with a low detection limit (3SD/slope) of 2.1 pg/mL was obtained. Furthermore, the proposed biosensing system exhibited a satisfactory recovery in the range 97.4–109.2% with 5.7–6.6% RSD in spiked artificial human sweat. Regarding the applications of this tool, the aptamer-based biosensor has potential to be a versatile and point-of-care (POC) device for simple, sensitive, selective, disposable, and low-cost cortisol detection.
Graphical abstract
Journal Article