ChemElectroChem最新文献

Electroanalytical techniques are powerful tools in biological sensing because of their sensitivity and versatility. In recent decades, great attention has been given to the fabrication of electroactive nanomaterial-based biosensors. In this context, carbon quantum dots (CQDs) have received special attention and have been used to develop many sensors because of their remarkable advantages such as high photostability, high solubility and stability in water, biocompatibility, high photoluminescence emission intensities, and simple methods of synthesis. Since they are very small in size, they have high surface area to volume ratios which in turn can allow good catalytic activities of the working electrodes in electrochemical reactions. Being motivated by these advantages, in this work we prepared two types of carbon quantum dots (CQD-COOH and CQD-NH₂) and used them to modify screen printed carbon electrodes (SPCEs) for detection of Troponin I (cTnI). These carbon quantum dot – modified SPCE immunosensors have offered promising results for the determination of cTnI with a limit of detection 62 pg/mL and 171 pg/mL, respectively. This simple approach to sensor design further offers valuable insights into the construction of paper based printed electrodes modified with new carbon-based nanomaterials as immunosensors for detection of other biomarkers of various diseases.

Since the excessive exploitation of fossil fuels will cause wars for oil, developing sustainable and eco-friendly energy resources to solve the energy crisis and realize the carbon-neutrality goal has been a hot issue. Water electrolysis has been acknowledged as a promising technology for hydrogen (H₂)/oxygen (O₂) evolution reaction (HER/OER) since the overall water splitting reaction rates can be well controlled by applying appropriate electrode voltage. Whereas the sluggish electrochemical reactions kinetics on both the cathode and anode have greatly restricted the energy conversion efficiency. Thus, developing highly active electrocatalysts to reduce the overpotentials required for electrolytic HER/OER is of great significance in increasing the utilization rates of electrical power and lowering production costs. ABO₃-structured perovskite-oxides based electrocatalysts possess the merits of low cost, high structural stability, and lattice compatibility, and thus they have attracted intense research attention in recent decays. To inspire both theoretical and experimental researchers to design novel perovskite-oxide electrocatalysts for efficient HER/OER, the fundamental electrode reaction mechanisms, the effects of synthetic methods on material morphologies, recently reported perovskite-oxide electrocatalysts and effective tuning strategies on enhancing the electrocatalytic activities of existing perovskite-oxides have been fully discussed in this review.

An analytical approach is presented for the voltammetric and chronoamperometric study of a second-order cyclic-type mechanism where two species are ‘activated’ electrochemically and subsequently react in solution, as observed in co-reactant electrochemiluminescence mechanisms. Closed-form expressions are derived for the current-potential-time response and for the surface species concentrations as a function of the chemical rate constant, the concentration ratio of the initial species, and their formal potentials. Their effects on the voltammetric signal are analyzed, pointing out a wave-splitting behaviour for fast kinetics, which is tied to the rates of formation and consumption of the ‘activated’ co-reactant.

High-manganese content sodium-ion positive electrodes have received heightened interest as an alternative to contemporary Li-ion chemistries due to their high abundance, low toxicity, and even geographical distribution. However, these materials typically suffer from poor capacity, unstable cycling performance, and sluggish Na⁺ kinetics. Herein, we explore a manganese-based layered transition metal oxide (Na_xN_0.25Mn_0.75O₂) and show by X-ray diffraction (XRD) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) that careful variation of the sodium content can instigate the formation of a biphasic intergrowth. This intergrown P2/P3 material offered a higher capacity than its monophasic P2 counterpart due to the P3 structure having greater low-voltage Mn^3+/4+ redox. Further, the intergrowth material offers greatly enhanced kinetics and cycling stability when compared to single-phase P3 material, due to the stabilizing nature of the P2 structure, elucidated by galvanostatic intermittent titration technique (GITT) and operando synchrotron X-ray diffraction. These results highlight the beneficial effect that the intergrowth structure has on the electrochemical performance of high-manganese content positive electrode for future sodium-ion batteries.

The Front Cover illustrates crystal structures of inorganic solid electrolytes (ISEs) featuring exceptional Na⁺ ion conductivities at room temperature in solid-state sodium batteries (SSSB). Rational structural design and doping strategies can enhance the Na⁺ ion conductivity and electrochemical stability of ISEs. However, significant interfacial challenges remain for the practical implementation of SSSBs. More information can be found in the Review Article by Patrick Joohyun Kim, Junghyun Choi, and co-workers (10.1002/celc.202400612).

3Dtransition metal coordination clusters, as structurally diverse and designable metal-organic hybrid systems, enable deliberate modulation of active sites and bridging motifs within their structural kernels, making them ideal precursors for tailored nanostructures via pyrolysis. Through precise control over metal/organic ratios, the composition, spatial configuration, and electronic structure of derived nanomaterials can be effectively regulated, holding great promise for establishing structure-property relations and achieving optimized functional materials. In this review, nanostructures of Schiff base coordination clusters to control and optimize electrochemical energy storage/conversion performances. Specifically, coordination framework engineered clusters have been pyrolyzed into electrode materials for supercapacitors and electrocatalysts for oxygen/hydrogen evolution reactions, exhibiting significantly enhanced capacitance and catalytic activity. Furthermore, perspectives are provided on employing molecular-level design principles of clusters in combination with pyrolysis optimization to develop next-generation customized energy systems. Additional investigation into structure-performance interdependencies will shed light on targeted optimization of cluster-derived nanostructures.

A deeper understanding of electrified solid/liquid interfaces of polycrystalline materials is crucial for optimizing energy conversion and storage devices, such as fuel cells, electrolyzers, and supercapacitors. After more than a century of research, the double-layer capacitance (C_DL) has proven to be one of the few relatively easily experimentally accessible quantitative measures for characterizing such interfaces. However, despite their great importance, systematic C_DL measurements are still not frequently associated with other interfacial properties. This work investigates the effect of the electrolyte pH on the C_DL for polycrystalline platinum (Pt(pc)) and gold (Au(pc)) electrodes using cyclic voltammetry and impedance spectroscopy in acidic solutions with a pH ranging from 0 to 2 without adding any supporting electrolyte. Interestingly, under these conditions, the C_DL for the Pt(pc) electrode increases with increasing electrolyte pH, while the C_DL for the Au(pc) electrode shows the opposite trend. The increasing trend for Pt(pc) cannot be quantitatively described by the classical Stern model due to the stronger adsorption phenomenon on Pt surfaces. Moreover, positive linear trends with pH were found for the potentials of minimum C_DL values and the potentials of maximum entropy for both electrodes, which closely correlate with reaction activities. However, the transition potentials of the constant phase element exponent (an element commonly used to approximate the behavior of the double layer in experiments) are only observed for the Pt electrode due to the phase transitions within the hydrogen adsorption/desorption and double-layer regions. These findings pose an important step toward revealing the interplay between essential interfacial parameters, which is crucial for a complete understanding of the electrical double layer.

The discovery of high-performance electrocatalysts for water electrolysis is highly important. We use a strategy for catalyst discovery based on high-throughput screening of a broad range of materials compositions on a thin-film materials library to identify noble-metal-lean multi-metal compositions with high activity towards the hydrogen evolution reaction in alkaline electrolyte. We demonstrate this strategy using a quaternary materials library containing Mo, Ag, Ti, and Ru fabricated by combinatorial magnetron sputtering on a 10 cm diameter wafer providing 342 measurement areas. Surprisingly, binary Mo−Ru-containing catalyst compositions with comparatively low Ru content exhibited the highest activity. Using the polymer/metal precursor-based spray technique, Ni foam electrodes were modified with the Mo−Ru hit compositions and evaluated in a model electrolyzer in membrane electrode assembly (MEA) configuration. The electrodes showed a very low overpotential of only 132 mV at a comparatively high current density of −2 A cm⁻² and a 24 h electrolysis stability at −1 A cm⁻² with no observable degradation after the initial electrode conditioning.

Electrochemical nitrate reduction reaction (NO₃⁻RR) represents a promising ammonia (NH₃) production approach and has garnered significant attention in recent years. Owing to the highly tunable electronic structures and physicochemical properties, alloy materials have emerged as highly efficient catalysts for electrochemical NO₃⁻RR. This review systematically examines the recent advancements in alloy catalysts including binary alloys and multi-metal alloys for electrochemical NO₃⁻RR, comprehensively analyzing their structure, catalytic activity, and the mechanisms for NO₃⁻RR. In addition, the relationship between alloy catalysts′ composition, active sites, and catalytic activity are described, aiming to elucidate the underlying principles for high catalytic activity and guide the rational design of future alloy catalysts. Finally, this review addresses the challenges of alloy catalysts and proposes directions for future research and development.

Iron(II) complexes with 1,10-phenanthroline (phen) and 2,2′;6′,2“-terpyridine (terpy) ligands bearing different functional groups (methyl, 4-pyridyl, chloro, carboxylic acid) were evaluated for aqueous flow battery applications, detecting oxidation processes followed by coupled chemical reactions. Redox potentials of these compounds were sufficiently high for suitable positive electrolytes (0.88–1.29 V vs. SHE). Randles-Ševčík equation and finite element modelling with COMSOL Multiphysics were utilized in evaluating the diffusion coefficient and the apparent rates of the electron transfer and coupled chemical reactions for the compounds studied by cyclic voltammetry. The systems experience weak adsorption of reactants at glassy carbon, leading to difficulties in determining the latter kinetic parameters. Flow battery tests indicate sufficient flow battery performance with dimethyl functionalized phenanthroline complex [Fe(II)(DMe-phen)₃]²⁺ with 0.06 % per cycle (2.78 % per day) capacity decay. However, [Fe(II)(DMe-phen)₃]²⁺, as well as [Fe(II)(phen)₃]²⁺, experience the discharge at two different thermodynamic conditions, suggesting dimer discharge as the source of the lower voltage plateau. The energy efficiency of [Fe(II)(DMe-phen)₃]²⁺ battery was improved by cycling at higher cut-off voltage for 10 cycles, after which the lost capacity was recovered with lower cut-off voltage in one cycle. [Fe(II)(terpy)₂]²⁺ had too many side reactions at lower potentials to be suitable for flow battery applications.