ChemElectroChem最新文献

Hard carbon is commonly used as negative electrode in sodium-ion-batteries (SIBs). Another type of disordered carbon, soft carbon (SC, also known as graphitizable carbon), is considered as unsuitable for SIB applications, due to sodium storage at higher potentials and with lower capacities. However, SCs exhibit structural flexibility, enabling graphene rearrangements at higher temperatures. This property was utilized in the current study to introduce closed porosity in carbon black (CB) and to alter the nanostructure to achieve a beneficial sodium storage mechanism for higher energy densities. For that, CB is CO₂ activated at 900 °C and different holding times to generate different porosities. High-temperature treatment (HTT) at 1500 °C induces the graphitization process and closure of pore entrances. N₂ and CO₂ physisorption confirm the pore generation after activation and reduced porosity after HTT. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy show no other structural alteration compared to nontreated CB. Galvanostatic charge-discharge experiments reveal an extension of the low-voltage plateau, showing a “hard carbon like” storage in correlation with the micropore volume introduced. These findings add to the knowledge of the sodium storage mechanism and showcase the possible need for revising the common carbon classification in the context of SIB research.

The Front Cover article presents a wearable paper-based biofuel cell that enables self-powered monitoring of sweat lactate levels via a low-power wireless transmission device. More information can be found in the Research Article by Isao Shitanda, Noya Loew, and co-workers (DOI: 10.1002/celc.202500222).

With the rising prevalence of metabolic diseases, infections, and mental health disorders, there is a growing demand for noninvasive diagnostic tools that enable early detection and continuous health monitoring. In this context, exhaled breath biomarkers provide insight into physiological and pathological processes. Electrochemical breath sensors (EBSs) have emerged as a promising platform for rapid, real-time, and cost-effective disease tracking via the detection of volatile breath biomarkers, such as NH₃, NO, and CO₂. Recent advancements in electrode materials, biological recognition elements, and sensor architectures—spanning nanomaterials, enzymes, aptamers, and molecularly imprinted polymers—have enhanced the analytical performance of EBSs. Nonetheless, challenges remain in achieving biologically relevant detection ranges, selectivity in complex breath matrices, and long-term environmental stability. This perspective article provides a critical overview of recent innovations and enduring limitations in EBS development. Beyond their role in monitoring physiological diseases, we highlight the emerging potential of EBSs for mental health assessment through the detection of gut-derived metabolites in exhaled breath, such as short-chain fatty acids, H₂S, and ammonia, as indicators of gut–brain axis activity. The EBS-based, noninvasive, real-time measurement of these metabolites represents a transformative and underexplored approach for the diagnosis and treatment of psychiatric disorders.

While all lanthanides have a stable trivalent oxidation state, three lanthanides are known to form divalent states: europium, ytterbium, and samarium. While the divalent states of europium and samarium have been extensively studied under various experimental conditions, little research has been done on divalent ytterbium. Herein, the electrochemical behavior and kinetics of the Yb(III)/Yb(II) redox couple are investigated in three oxygenated solvents (dimethyl sulfoxide, N,N-dimethylformamide, and ethylene glycol). Passivation effects and the effect of low water concentrations on the redox behavior are investigated by cyclic and linear-sweep voltammetry. The presence of water is found to have a diminishing effect on the observed passivation. A kinetic study of Yb(III) is conducted using cyclic voltammetry and linear sweep voltammetry with a rotating disc electrode, an approach not previously applied to the Yb(III) reduction in organic systems. Koutecký–Levich analysis is applied to accurately determine electrochemical rate constants. The electrochemical behavior of Yb(III) varies significantly as the solvent distinctly influences the stabilization of the different oxidation states. The Yb(III)/Yb(II) redox couple is found to be quasi-reversible in each solvent system, and the calculated parameters align with previously reported values for Eu and Sm systems as well as with those obtained from simulations.

The continuous monitoring of sweat lactate is a critical task in sports and medical applications. This paper introduces a self-powered biosensor for the continuous monitoring of sweat lactate. A biofuel cell (BFC)is prepared using thionine as a bioanode mediator, with poly(ethylene glycol) diglycidyl ether and a chitosan–genipin membrane incorporated in the bioanode. This system achieves an open-circuit voltage of 0.75 V and output power density of 0.163 mW cm^–2 in the presence of 100 mM lactate. The self-powered biosensor is constructed by integrating the BFC with a voltage booster and Bluetooth transmitter. An on-body test is conducted on an exercising individual. The output signal of the self-powered biosensor is converted into lactate concentrations through manual pH adjustment. A correlation between the lactate concentrations in sweat and blood is observed. Overall, the proposed self-powered lactate biosensor can continuously monitor sweat lactate, with potential applications in the sports and medical domains.

GaAs is an excellent candidate for high-performance photoelectrochemical water splitting due to its appropriate band-edge and bandgap energies, as well as its excellent transport properties. The most significant limitations of GaAs for photoelectrochemical applications are its instability against corrosion, the high substrate cost, and the huge overpotentials required for triggering water electrolysis. The monolithic epitaxial integration of GaAs thin films directly on the Earth-abundant Si fundamentally limits the costs associated with the substrate fabrication. Herein, photocathodes made of 1 µm thick GaAs layers epitaxially grown on p-doped Si substrates are developed and their performances are compared to those of bare p-doped GaAs electrodes. Sulfur passivation and standard interfacing with Pt catalyst are applied and analyzed for both series of photocathodes. A massive onset potential shift of 0.63 V is demonstrated for GaAs/Si photocathodes after electroless Pt deposition and sulfur passivation, reaching an onset potential of 0.4 V versus the reversible hydrogen electrode. The stability of the Pt/GaAs/Si photocathode is finally assessed over more than 112 h. These findings are essential for further development toward the fabrication of cost-efficient and stable unassisted photoelectrochemical cells for green hydrogen production.

Ruthenium dioxide (RuO₂) is a benchmark catalyst for the oxygen evolution reaction (OER) in acidic media but suffers from slow dissolution under operating conditions, limiting its long-term durability. Here, density functional theory combined with the computational hydrogen electrode model is employed to elucidate the atomistic mechanisms governing RuO₂ surface corrosion across a relevant potential window from 0 to 1.5 V_{standard hydrogen electrode (SHE)}. The study reveals a potential-dependent switch in dissolution pathways: at anodic potentials above 1.21 V_SHE, direct oxidative dissolution leads to soluble RuO₄, whereas at lower potentials, coupled proton–electron transfer reactions drive the formation of soluble hydroxylated species, specifically Ru(OH)₄ and RuO₂(OH)₂. Key surface intermediates act as energetic basins, regulating transient dissolution during potential cycling and shutdown. Furthermore, it is shown that doping RuO₂ with W, Ti, or Ir shifts the onset potentials for these corrosion pathways, enhancing surface stability by widening the potential window where the materials are stable. These insights advance the mechanistic understanding of RuO₂ degradation and support rational strategies for designing durable OER catalysts in acidic water-splitting technologies.

Nano hexagon NiCeO₂ is synthesized via a simple one-pot hydrothermal method and evaluated as a highly efficient electrocatalyst for the oxygen reduction reaction (ORR) in an Al-air battery (AAB). Structural analysis using X-ray diffraction reveals peak shifts and lattice contraction, confirming the successful incorporation of Ni into the CeO₂ host matrix. Raman spectroscopy identified a characteristic peak associated with oxygen vacancies, indicating defect formation. Thermogravimetric analysis showed a 4.97% weight gain, likely due to the filling of oxygen vacancies at elevated temperatures. Transmission electron microscope revealed a nano hexagon morphology with an average particle size of 20 nm. X-ray Photoelectron Spectroscopy analysis confirmed the presence of both cerium and nickel elements. Electronic structure calculations, performed using density functional theory via Quantum ESPRESSO, indicated that Ni doping introduces new 3d states into the CeO₂ band structure, resulting in bandgap narrowing and a lowered Fermi level. Electrochemical testing demonstrated that NiCeO₂ exhibits superior ORR performance compared to commercial Pt/C catalysts. Kinetic analysis suggested a near four-electron transfer pathway. Durability is assessed using chronoamperometry, showing that NiCeO₂ retained 90% of its initial current after 20 h of operation, outperforming Pt/C. Furthermore, an AAB is constructed using NiCeO₂ as the cathode, which achieved an open circuit voltage of 1.65 V with a discharge capacity of 1070 mAh·g⁻¹, delivering a notable power density of 77.64 mW·cm⁻². The enhanced ORR activity is attributed to the synergistic interaction between CeO₂ and Ni, which significantly improves the overall performance of the AAB These findings suggest that NiCeO₂ is a promising cathode material for high-performance AABs.

With sunlight as the most abundant energy source on earth, solar water splitting has the potential to produce renewable hydrogen at a commercially competitive cost. Monoclinic BiVO₄ is a promising n-type semiconductor for photocatalytic and photoelectrochemical (PEC) water oxidation. One of the simplest and most energy-efficient approaches for producing BiVO₄ is hydrothermal synthesis. This method is carried out at moderate temperatures, while particle size, shape, and crystallinity are controlled by a wide range of synthesis parameters, which can be further expanded by using additives. In this work, these parameters systematically vary to study their influence on the hydrothermal synthesis of BiVO₄, with a focus on KCl as an additive are systematically vary. By X-ray diffraction, scanning electron microscopy, and transmission electron microscopy is shown that KCl acts as structure-directing agent, leading to significant changes in morphology and crystallinity. Since the color and the optical spectra of BiVO₄ powders indicate a redshift with increasing KCl concentration, an additional anionic substitution by Cl⁻ takes place is proposed, a hypothesis supported by X-ray photoelectron spectroscopy measurements and density functional theory calculations. The highest photocatalytic performance (1328 µmol g⁻¹h⁻¹) is reached for 25 mmol L⁻¹ KCl, while particle-based photoelectrodes decorated with CoPi cocatalysts showed an improved photocurrent density (393 µA cm⁻²) at 1.23 V vs. reversible hydrogen electrode (RHE).

Hydrogen peroxide is decomposed by tungsten oxide within the water domains of a proton exchange membrane in a fuel cell, while cerium ions quench aggressive hydroxyl radicals that arise from the reaction between hydrogen peroxide and ferrous ions. The illustration contrasts the roles of the two additives: cerium protects but slows proton transport, whereas tungsten oxide prevents degradation without hindrance. Together they represent a balanced strategy that prevents membrane degradation while maintaining high fuel cell performance. More information can be found in the Research Article by Kazuma Shinozaki and co-workers (DOI: 10.1002/celc.202500214).