ChemElectroChem最新文献

Cryogels made of colloidal nanoparticles (NPs) are a unique material class with a high specific surface area and tunable microstructure. Flash freezing of the nanoparticle building blocks and subsequent freeze-drying of the gels, the so-called cryoaerogelation, allows significant control over morphology, stability and improved electrocatalytic performance. In the present work, the first bimetallic Pt/Pd cryogel films of mixed Pt and Pd NPs are prepared in different molar ratios. High-resolution microscopic and spectroscopic characterization techniques are applied to confirm the final Pt : Pd ratio besides the distribution of nanoparticles throughout the cryogel structure. Scanning electron microscopy (SEM) images of the different prepared cryogel films show a cellular to dendritic superstructure regardless of the Pt and/or Pd composition in a highly reproducible manner. Elemental analysis shows homogenous distribution of Pt and Pd NPs at the microscale for all samples. Since the prepared materials are of utmost importance for catalytic applications, their electrocatalytic activity toward ethanol oxidation reaction (EOR) is investigated. Fine-tuning the concentration of the building blocks, the structure, thickness, and composition of the porous coatings enables high electrocatalytic activity to be achieved. Cryogel thin films with an atomic ratio of 1 : 4 Pt : Pd have the highest electrocatalytic activity for EOR.

This study presents the correlation between electrolyte pH, surface morphology, chemical speciation and electro-catalytic oxygen evolution activity of additive-free electrodeposited NiFe catalysts for application in anion exchange membrane water electrolysis. Spherical morphologies were identified at pH 0, shifting towards honey-combed structures at pH 4 with increasing surface area, especially at pH 3. Further, the electrolyte pH was found to influence the NiFe composition and electro-catalytic activity. Enhanced OER activity was noted at pH 2 with overpotentials of 214 mV at 10 mA cm⁻² and 267 mV at 100 mA cm⁻². The results reveal that the electrolyte pH is a parameter not only influencing the morphology but also tailoring the surface area, Fe oxide and Fe hydroxide composition and consequently the catalytic activity. Further, the outcomes highlight the electrolyte pH as a key process parameter that should be adjusted according to the application, and may substitute the addition of electrolyte-additives, proposing a simpler method for improving catalyst electrodeposition.

Investigating the ORR under practical conditions is vital for optimizing metal–air batteries and alkaline fuel cells. Herein, we characterized Pt and Ag gas diffusion electrodes (GDE) in a GDE half-cell in high alkaline concentrations at elevated temperatures by polarization curves and electrochemical impedance spectroscopy (EIS) combined with the distribution of relaxation times (DRT) analysis. The Pt catalyst's polarization curve displays substantial losses below 0.82 V vs. RHE. The DRT analysis reveals significantly increased charge transfer resistance and a decelerated ORR at that potential. RRDE measurements attributed the polarization loss observed for Pt catalysts to increased peroxide formation in this potential region triggered by the desorption of oxygenated species. Therefore, the ORR activity of Ag exceeds some of the here-used Pt catalysts at high current densities. This work combines the benefits of the RRDE and the GDE half-cell to study catalysts and identify the reaction mechanisms under conditions relevant to practical fuel cells and batteries. Moreover, the DRT analysis is introduced as an analytical tool to determine the charge transfer resistance contribution and the corresponding frequency of the ORR.

Electrocatalytic CO reduction (COR) is a promising approach for converting C₁ feedstock into valuable multi-carbon fuels using renewable electricity. At ambient temperature, COR, particularly on Cu-based catalysts, typically produces C₂ chemicals as the dominant products, with long-chain hydrocarbons containing more than five carbon atoms rarely forming. In contrast, Fischer-Tropsch synthesis (FTS), a thermocatalytic process converting CO and H₂, selectively generates long-chain hydrocarbons. In this study, we utilized Ru nanoparticles for electrochemical COR under elevated conditions (423 K and 2.8 MPa). Long-chain products with up to 21 carbon atoms were detected, achieving a Faradaic efficiency of 32 % and a weight selectivity of 65 % for C₅₊ products. We propose an FTS-like pathway for this electrocatalytic process. Unlike thermocatalytic FTS, where adsorbed H atoms form via H₂ dissociation, in this electrocatalytic version, the H atoms are generated through the Volmer reaction from water. Subsequently, the chemisorbed and activated CO species are hydrogenated, forming CH_x intermediates that propagate into long-chain products.

Supercapacitors (SCs) have emerged as promising candidates for efficient and sustainable energy storage devices due to their unique merits, including high power density and long lifespan. However, despite these advantages, SCs face significant challenges related to their relatively low energy density. Current collectors are critical components of SCs, which significantly impacts the efficiency and overall performance by connecting active materials and external devices. However, the reviews on SCs are predominantly focused on electrode active materials or electrolyte materials, with insufficient comprehensive summaries regarding current collectors. This review focuses on the research progress related to current collectors in SCs. Firstly, the article outlines the modification objectives mechanism and inherent nature of SC current collectors. Building on this foundation, the authors further classify the current collector materials towards metallic, carbon-based, polymers and other ones and highlights their modification strategies. Finally, the future development trends and challenges of SCs current collectors are comprehensively discussed.

The Glycerol Electrooxidation Reaction (GEOR) is a promising alternative to oxygen evolution in electrochemical processes like hydrogen production and CO₂ reduction. Although GEOR has attracted increasing attention, its oxidation kinetics in alkaline media are not well understood. In this study, electrochemical characterization and kinetic analysis were conducted using nickel foil as the electrocatalyst. Four galvanostatic conditions (1, 3, 5, and 10 mA cm⁻²) were evaluated to study product distribution. Increasing the current density from 3 to 5 mA cm⁻² led to a fivefold decrease in formate production, indicating a shift in GEOR selectivity within the Oxygen Evolution Reaction (OER) region. At 10 mA cm⁻², formate remained as major product, followed by glycolate and glycerate, while tartronate and oxalate production were significantly inhibited, reducing the total Faradaic Efficiency (FE) by half relative to 5 mA cm⁻². Rate constants showed increased kinetics for glycerate, glycolate, oxalate, and tartronate as current increased, surpassing formate production at 5 mA cm⁻². Spectroelectrochemical measurements revealed the reaction order for GEOR (α_GEOR ~1) and OER (α_OER ~3), showing that GEOR proceeds via a more efficient oxidative pathway, requiring interaction with just one NiOOH species, while OER involves three highly oxidized Ni-species.

Sustainable ammonia synthesis, a key focus in electrochemistry, has seen significant advancements with the emergence of Metal-Organic Frameworks (MOFs). This review provides a comprehensive analysis of the recent strides in MOF-based materials for green ammonia production, reflecting the urgency to develop eco-friendly and energy-efficient chemical commodities. It explores the reaction mechanisms, emphasizing the importance of structure-performance relationships in MOF optimization and the design of MOF-based electrocatalysts, including metal node engineering and hybrid materials. The review also highlights in-situ characterization techniques that are crucial for understanding MOF catalytic activity. It establishes a correlation between MOF features, synthesis methods, and material performance, showcasing their potential in catalysis. Finally, it identifies challenges and future directions for MOFs in green ammonia production, aiming to inspire innovation towards sustainable and economically viable processes.

[The Acknowledgements should be changed from “The authors are grateful for the financial support from the NCN, Poland, UMO-2020/39/B/ST8/02937.” To “The authors are grateful for the financial supports from Project Number 101092189 (Acronim: HEDAsupercap) under the framework of HORIZON-CL4-2022-RESILIENCE-01, funded by European Commission“]

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Active particle materials with high capacity, safety, and abundance, such as Sn and Si-based materials, and nickel-rich layered materials like LiNi_xCo_yMn_1−x−yO₂ (with x≥0.8) are viewed as promising candidates for the evolution of next-generation batteries. However, structural degradation during cycling often limits the application of these active particle materials. Currently, research efforts are focused on developing new characterization techniques to understand the structural degradation mechanisms of active particle materials during the cycle, to improve their performance. This paper reviews advanced single-particle electrochemical and structural characterization techniques and their main findings. These findings included lattice displacement and rotation, microstructure evolution, and reaction kinetics of single-particle during cycling. In addition, we also discuss the potential future applications and developments of single-particle measurement technologies.

The Front Cover shows how the most typical elements present in electrochemistry work together to power and light up the 10th anniversary sign celebrating the last decade of excellent research published in ChemElectroChem. Cover art by Tomáš Belloň (IOCB Prague).