ChemElectroChem最新文献

Sweat glucose serves as a significant biomarker of health, necessitating accurate determination at the micromolar level for noninvasive monitoring. To address this need, we design an organic field-effect transistor (OFET)-based enzymatic sensor to quantify glucose levels in human sweat. The extended-gate structure of the OFET device ensures stable analyte detection in human sweat owing to its isolated configuration. The extended-gate-type OFET has been functionalized with glucose oxidase and an N-ethylphenazonium-based mediator-attached monolayer. This configuration facilitates electron relay, enabling accurate and reproducible glucose detection. Leveraging the amplification ability of the OFET, the enzymatic sensor exhibited highly sensitive glucose detection, achieving a low limit of detection (2.9 μM) suitable for sweat analysis requirements. In addition, the sensor exhibited high discriminability in detecting glucose amidst interferents commonly found in sweat, indicating its practical feasibility for sweat analysis. Validation of glucose recovery rates (95–105 %) in human sweat, without pretreatment, was performed using established instrumental analysis methods.

Sulfonated poly(oxy-1,4-phenylene-oxy-1,4-phenylenecarbonyl-1,4-phenylene) also known as SPEEK is a chemically robust cation conductor with good solution processability. A thin film (approx. 0.7 μm) coated asymmetrically over a 10 μm diameter microhole in a Teflon substrate film (5 μm thickness) produces ionic diode effects in aqueous electrolyte media even at high ionic strengths up to 2 M NaCl. The enhancement in the ionic diode performance under high salt conditions is tentatively attributed to a (partial) switch from a concentration polarisation effect (dominant for high diode currents) to interfacial polarisation (dominant at low current; proposed for molecularly rigid ionomers). Ionic strength effects on the diode performance seem relatively low further indicative of a mechanism for the diode effect caused by interfacial polarisation without significant concentration polarisation. Preliminary comparison of diode phenomena in aqueous HCl, LiCl, NaCl, and MgCl₂ reveals cation specific effects due to interaction with the polymer.

Photocatalyst-assisted charge transfer at the interface between two immiscible electrolyte solutions (ITIES) has been previously proven. However, its practical application requires information on its performance under solar irradiation. We investigated photocatalyst-assisted oxidation of water at ITIES under solar irradiation using TCNQ 7,7,8,8-Tetracyanoquinodimethane (TCNQ) as electron scavenger and bis(triphenylphosphoranylidene) ammonium tetrakis(4-chlorophenyl)borate (BTPPA-TPBCl) as organic phase electrolyte. No enhancement of water oxidation after assembling photocatalyst nanoparticles at the ITIES was observed. Photocurrents with photocatalyst were similar to those without but in the presence of TCNQ. Photocurrents observed both with and without photocatalyst are shown to be due to photogeneration of TCNQ⋅⁻, either by reaction with the organic electrolyte or by interfacial oxidation of water. The former dominates at positive potentials and results in a positive photocurrent due to transfer of TCNQ⋅⁻ across the ITIES. The latter dominates at negative potentials and results in a negative photocurrent. Electron paramagnetic resonance (EPR) detected TCNQ⋅⁻ and revealed its stabilisation by formation of an adduct with BTPPA⁺, which must contribute to making the photoactivity of TCNQ the dominant process even with photocatalyst. These findings highlight the necessity of research on alternative suitable electron scavenger-supporting electrolyte combinations for implementing ITIES in the photoelectrocatalytic conversion of solar energy.

Electrochemical sensors based on self-assembled monolayer (SAM) were synthesized using metal-organic frameworks (MOFs), quantum dots (QDs) and their composite (QDs@MOFs) to modify gold electrode (AuE) that was used as electrochemical sensors for bisphenol A detection. The molecular layer was assembled on the surface of the gold electrode by adsorption and provide a highly flexible method to tailor the interfaces between analyte and the electrode. Single crystal X-ray of the MOF revealed a six-coordinate copper(II) ion that bidentately coordinate two molecules of p-anisic acid and two molecules of 1H-benzimidazole to form a distorted octahedral geometry around the copper(II) ion. Electrochemical studies revealed that under optimal conditions, the modified gold electrode sensors show excellent sensing of bisphenol A, however, QDs@MOFs modified electrode is the best sensor with the highest oxidation peak current of 8.43E-05 μA and the lowest charge transfer resistance of 19.4 Ω within a wide concentration range of 0.1–1 μM and a limit of detection (LOD) of 0.252 μM. This could be attributed to the electrocatalytic activity of the composite (QDs@MOFs) modified sensor, and the synergistic effect of the MOFs and QDs in the composite. The LOD is comparable to other electrochemical methods of sensing BPA which indicates that QDs@MOFs modified gold electrode could be develop as sensor for BPA.

Heteroatom doping of graphene is a powerful approach to develop high-performance Li and Na ion battery anodes. In this study, silicon-nitrogen co-doped graphene (Si−N−GN) nanostructures were successfully synthesized via a rational and scalable solvothermal process. The performances of Si−N−GN in Na⁺ and Li⁺ half-cells were investigated in detail by advanced electrochemical techniques and the obtained results were analyzed in terms of Si−N−GN surface properties, reaction kinetics, and electrode/interface interactions. Si−N−GN exhibited a superior capacity of 540 mAh g⁻¹ at a current density of 0.5 A g⁻¹ for Li⁺ and improved rate capability for both Li⁺ and Na⁺ which are linked with the increased interlayer spacing and enlarged graphene sheets upon Si-doping. Importantly, the capacity increased with the number of cycles owing to surface electron density redistribution and Si−N−GN/SEI interactions, supported by DFT.

Screen-printed electrochemical sensing platforms are ubiquitous within the field of electrochemistry where they provide benefits of being disposable, cost-effective, reproducible, easily customisable, portable and allow one to transfer the laboratory approach into the field. In this review, we introduce the concept of screen-printed electrodes, we summarise positive and negative aspects before moving into the current highlights of using traditional screen-printed carbon electrodes within the field of electroanalysis. We then look to cover metallic and bulk modified varieties, geometric changes (micro, microband and associated arrays), electrode activation and finally the physical length of screen-printed electrodes, providing insights for future research.

An electrical double-layer capacitor (EDLC) comprises two porous electrodes sandwiching an electrolyte-permeable separator, which prevents the electrodes from short-circuiting. While previous studies have mainly focused on electrolyte and electrode properties of EDLCs, the device configuration in terms of electrode and separator sizes received less attention, with separators often simplistically modelled as infinitely large reservoirs of ions. Herein, we investigate how the relationship between electrode and separator thicknesses impacts EDLC charging. We find that the assumption of bulk reservoir holds only under specific conditions. Moreover, we identify a tradeoff between stored energy density and pressure variations within the separator, potentially jeopardizing the EDLC durability. We also explore the influence of ionic liquid additives on EDLC charging. While prior research has shown that trace amounts of uncharged additives with strong electrode affinity can significantly enhance energy storage, we observe this effect as negligible for electrodes and separators of comparable sizes. Instead, we show how to optimize EDLC performance by fine-tuning the concentration of additives and separator-to-electrode size ratio to maximize stored energy density.

The front cover illustrates a comparison between the wet and dry electrode coating processes for Li-ion batteries. On the left side, the wet electrode coating process is depicted, requiring a lengthy drying process and generating toxic solvents. This is represented by a background of a heavily polluted city with smog and emissions. On the right side, the dry electrode coating process, which does not require drying or the use of solvents, is shown as eco-friendly. This is depicted by an electric vehicle equipped with batteries made using the dry process, maintaining a clean and green city environment. More information can be found in the Review Article by Tae-Hee Kim, Jinsoo Kim, and co-workers (DOI: 10.1002/celc.202400288). Cover design by Cube3D Graphic.

Nickel-iron layered double hydroxide (NiFe LDH) are high performance catalysts for the oxygen evolution reaction (OER) which become unstable under potential in alkaline media. According to the preparation method, they can present different type of impurities at their surface. The cover picture depicts how the oxidizing potential during OER operation leads to the secondary phase dissolution and a faster degradation of the catalyst, hindering the evolution of oxygen. More details can be found in the Research Article by Axel Zuber, Michelle P. Browne, and co-workers (DOI: 10.1002/celc.202400151).

To meet the rising demand for green hydrogen, efficient alkaline water electrolysis demands highly active and low-cost electrocatalysts for the oxygen evolution reaction (OER). We address this issue by focusing our work on optimizing the conditioning of promising Ni-(Fe)-based electrodes to improve their electrocatalytic performances. Systematic parameter variation for cyclic voltammetry conditioning revealed that a large potential window, low scan rate, and a high number of cycles result in improved activation. If the conditioning time is fixed, a high scan rate was found beneficial. A remarkable 47±6 mV potential drop at 10 mA cm⁻² was achieved for Ni₇₀Fe₃₀ when conditioning between −0.35–1.6 V at 100 mV s⁻¹ for just 30 min. We could demonstrate that this activation persisted over 100 h at 100 mA cm⁻², underscoring its enduring efficacy. We suggest that this activation effect results from the growth of a hydrous hydroxide layer, which is supported by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Fe incorporation or dissolution played only a minor role in the differences in electrode activation, as demonstrated by variation of the Fe content in the electrolyte. Our work stresses the importance of conditioning in enhancing OER performance and explores how to improve the catalysts′ effectiveness by tailoring oxides.