ChemElectroChem最新文献

The front cover picture represents a meta–air battery composed of a metal anode and a graphite cathode modified with pyridine penta-coordinated Fe phthalocyanine, which is an extremely active catalyst for the oxygen reduction reaction when the NaOH supporting electrolyte is used. When in the presence of other electrolytes, the activity of the catalyst decreases as the Fe active sites are poisoned by the interaction with the anions. Therefore, batteries with lower power density are obtained if in the presence of Cl⁻>Br⁻>HSO₄⁻> ClO₄⁻>NO₃⁻>OH⁻. More information can be found in the Research Article by Federico Tasca and co-workers (DOI: 10.1002/celc.202400186).

Polymer electrolyte membrane fuel cells (PEMFCs) are an important enabler of the nascent hydrogen economy. However, due to the reliance on precious metal catalysts like platinum, reducing the cost and broad penetration of PEMFCs beyond vehicle application remains a challenge. In this respect, alternative non-precious metal catalysts and other carbon-based catalysts remain the holy grail toward advanced low-cost PEMFC. This review summarizes recent progress along the development of non-precious catalysts and their performance under PEMFC operation. Critical factors such as the activity, stability, and durability of non-precious metal catalysts and their associated mechanisms including the paths leading to degradation are discussed. Ultimately, the review concludes by highlighting the impressive activity and potential of NPM catalysts and the areas of focus to enable the translation of non-precious catalysts to commercially viable PEMFC systems.

Electrochemistry became a unique and powerful tool for the preparation of a plethora of valuable chemical species including functional materials, drug candidates and clinically approved pharmaceuticals. Organic electrosynthesis well satisfies main goals of green chemistry development and is considered as one of the useful approaches toward the creation of sustainable future. Since nitrogen heterocyclic scaffolds still retain their importance for the construction of novel materials and medications, one of the emerging trends in organic electrochemistry is the discovery of novel green and sustainable synthetic methods toward the assembly of heterocyclic subunits. In this regard, organic electrochemistry provides an efficient platform for environmentally benign generation of various nitrogen-centered radicals which are prominent intermediates in the synthesis of nitrogen heterocycles. In this Review, recent developments in the creation of green synthetic methods for the construction of nitrogen heterocycles via electrochemical generation of nitrogen-centered radicals are summarized. The special emphasis is devoted to the influence of solvent, electrodes and electrolytes on the electrochemical step, since these crucial parameters regulate the process efficiency.

The electrochemical applications of gold span the entire pH spectrum. Recently, gold dissolution in acidic and alkaline media has been studied, but less attention has been given to electrolytes at intermediate pH values. To address this gap, this work uses on-line electrochemical dissolution inductively coupled plasma mass spectrometry (ICP-MS) to examine gold dissolution across a pH range of 1 to 12.7 using phosphate buffer solutions. All experimental parameters, except pH, are kept constant, enabling a clear investigation of pH effects on anodic (gold oxidation) and cathodic (gold oxide reduction) dissolution processes. Results show that dissolution amounts are lowest at neutral pH values between 3 and 7, varying with the applied potential and exposure time. Anodic and cathodic dissolution dominate in acidic and alkaline electrolytes, respectively. Depending on the highest applied potentials and time exposure, the main dissolution mechanism shifts at pH=5, 7, and 9. The pH dependence of Au dissolution is proposed to be linked to the nature of gold oxides formed, the kinetics of oxide formation/reduction, gold ion redeposition, and the influence of the oxygen evolution reaction (OER) on dissolution. These results provide fundamental insights into gold dissolution under neutral pH conditions.

Cobalt is considered an essential element for layered cathode active materials supporting enhanced lithium-ion conductivity and structural stability. Herein, we investigated the influence of Co concentration on the physicochemical properties and electrochemical performance of lithium-rich layered oxides (LRLOs) with different Co content (Li_1.2Ni_0.2-x/2Mn_0.6-x/2Co_xO₂, x=0, 0.04, and 0.08). Though the presence of Co grants structural stability to LRLOs, superior long-term cycling stability is achieved with the Co-free LRLO retaining 88.1 % of the initial specific capacity (vs. 75.9 % of Li_1.2Ni_0.16Mn_0.56Co_0.08O₂) after 300 galvanostatic cycles at 250 mA g⁻¹ (1 C). The chemical stability on the surface of LRLOs containing Co declines faster, indicating a higher bulk structural stability not being the primary determinant of the LRLOs’ cycling performance. Ex-situ investigations indicate that the superior cycling stability of Co-free LRLO is obtained by reducing the Mn-related redox at discharge, which contributes to the large degree of polarization and low energy efficiency. Finally, the full-cell configured with the optimized LRLO as cathode and graphite anode delivers an energy density of 464 Wh kg⁻¹ at C/10, and 74.4 % and 94.3 % of retention in discharge specific capacity and average voltage at the 1000^th cycle, demonstrating the applicability of Co-free LRLO for sustainable LIBs.

Transition metal dichalcogenides (TMDs) have garnered attention as potential catalysts for water splitting owing to their unique structures, diverse electronic properties, and composition from earth-abundant elements. While certain TMD catalysts, notably MoS₂, have shown promising activity for hydrogen evolution reactions (HER), achieving performance comparable to traditional platinum catalysts remains a challenge. While significant effort has been invested into understanding the effect of TMD's structural properties, such as defectiveness and crystalline phases, recent work has emphasized the role of extrinsic factors on HER. This review summarizes the current understanding of the impact of commonly overlooked electrocatalytic effects that exhibit an enhanced importance in TMD-based HER. By combining recent advances in theoretical modeling and experimental work, we review the dominating effects of extrinsic factors including electronic resistance, interfacial barriers, surface roughness, oxidation, and valence impurities. Our work aims to provide insights into optimizing TMDs as highly efficient catalysts for HER, facilitating future advancements in hydrogen generation technology.

In scanning electrochemical microscopy (SECM), the addition of a redox active species plays an essential role. Those deliberately added mediators may alter results in SECM studies. In investigations of lithium-ion battery (LIB) materials, especially of the positive electrode, the oxidation potentials of commonly used mediator substances such as ferrocene are located within the operation potential of the electrode. Thus, they possibly interfere with the regular charge/discharge processes. In situ studies are therefore in need of approaches reducing or eliminating the use of mediators. Within this publication, a novel mediator dosing (MD) concept is introduced. A capillary was closely positioned at the tip of the scanning probe. By gravity flow, stable flow rates of mediator solution of up to 32.4±0.6 μL h⁻¹ were achieved. These low amounts were found to be sufficient to form a ferrocene zone at the probe tip enabling feedback mode SECM measurements with comparable quality to measurements directly in ferrocene solution. Proof of concept experiments were conducted by investigation of a thin-film electrode with a micro-structured surface. Furthermore, the MD concept was applied in imaging experiments of a commercially available LIB graphite electrode.

In this work, we developed a direct strategy to fabricate Palladene (i. e. Palladium metallene) aerogels and propose a temperature-dependent growth mechanism. Besides the typical three-dimensional networks and wrinkled surface morphologies, the as-prepared $$ aerogel is endowed with abundant Pd²⁺. The as-prepared $$ aerogel exhibits an excellent mass activity in the formic acid oxidation reaction and a good half-wave potential in the oxygen reduction reaction in comparison with Pd/C and a Pd aerogel. This work expands the range of metal aerogels from the perspective of the building block units and demonstrates a direct approach to fabricate highly promising bifunctional electrocatalysts for fuel cells.

The aim of this investigation was to explore the possibility to perform an asymmetric reduction, utilising a CBS-type catalyst, of prochiral aryl methyl ketones under electrochemical conditions to generate the needed BH₃ upon oxidation of NaBH₄ with in situ generated I₂ in the anode compartment. Therefore, various electrochemical parameters were optimised to conduct the desired formation of the chiral secondary alcohols in high to quantitative yields with a high stereochemical induction, although the catalyst loading had to be chosen relatively high to concur with the racemic reduction of the ketones by the electrogenerated BH₃.

The front cover illustrates the recycling of spent Li-ion batteries by the acid leaching method and the utilization of the residue solid carbon-based materials as electrocatalysts for oxygen reduction to hydrogen peroxide generation. The relationship between the structure and composition of the battery waste and its ORR electrocatalytic activity is explored. More information can be found in the Research Article by Magdalena Warczak and co-workers (DOI: 10.1002/celc.202400248). Cover design by Dr. Magdalena Osial.