ChemElectroChem最新文献

The electrochemical reduction of CO₂ (ERCO₂) to valuable chemicals such as acetic acid/acetate offers a promising route to revolutionize chemical production and enhance sustainability. Here, we report the hydrothermal preparation of an electrocatalyst consisting of copper/titanium dioxide/reduced graphene oxide (Cu-TiO₂/rGO) for ERCO₂ in aqueous medium. The metal-support (TiO₂/rGO) was pre-synthesized by combining an aqueous solution of TiO₂ and GO in an autoclave at 150 °C for 20 h. Then TiO₂/rGO was added to synthesized Cu colloid formed through the reduction of copper (II) nitrate trihydrate resulting in the formation of Cu-TiO₂/rGO. The Cu-TiO₂/rGO hybrid nanocomposite was fully characterized using spectroscopic and microscopic techniques. This study explored the versatility of the rotating ring-disc electrode (RRDE) as an in situ electroanalytical tool for the selective detection of products formed during ERCO₂. The well-designed hybrid electrocatalyst, containing Cu⁰/Cu⁺ active sites, facilitated the eight-electron transfer for acetic acid (AA) formation at low potentials. AA formation was detected on the RRDE and validated by conventional NMR and HPLC techniques. This work highlights and expands the scope of selective hydrogenation of CO₂ towards value-added products.

Soluble lead redox flow battery (SLRFB) is an emergent energy storage technology appropriate for integrating solar and wind energy into the primary grid. It is an allied technology of conventional lead-acid batteries. This appraisal compares lead-acid batteries and SLRFB apropos their general characteristics. SLRFBs can overcome the inadequate cycle-life of Lead-Acid batteries as the electrodes of SLRFB do not participate in the reaction, which helps extending its durability. However, SLRFB has challenges of dendrite formation, oxygen evolution reaction, passivation of PbO₂ and shunt current. These problems need to be resolved before SLRFBs can be projected for large-scale energy storage applications. In this technical update, we have reviewed the recent studies pertinent to dendrite formation, mechanism of the lead electrode, and reversibility of the PbO₂ electrode in the state-of-art of SLRFB along with progress in advances while developing a 12 V – 250 Wh 8-cell SLRFB stack.

Herein, we report on (a) the application of cobalt(II) tellurium oxide (Co₃TeO₆) as a photo-electrocatalyst, to enhance the photo-electrocatalytic (PEC) oxygen evolution reaction (OER) in alkaline media, compared to the electrocatalytic (EC) OER (in the absence of light), and (b) to store charge upon illumination and release charge upon the termination of illumination under OER potential bias conditions. These nanomaterials were synthesized employing the sol-gel method and calcined at temperatures ranging from 400 to 1100 °C. They were physically characterized and tested for their capacity to (i) act as a catalyst towards the OER, under EC and PEC conditions, and (ii) to convert and store light-energy as chemical-energy. Under PEC conditions CTO-900, which predominantly consisted of Co₃TeO₆, exhibited a five-fold increase in activity compared to EC conditions as current density increased from 0.58 mA cm⁻² (EC) to 3.10 mA cm⁻² (PEC) at 1.8 V (vs. RHE). Additionally, CTO-900 displayed the ability to not only store charge (upon illumination), but to also release this stored charge (after the termination of illumination), realising a current density of 2.07 mA cm⁻² in the dark (under OER potential bias conditions). Photo-induced charge storage is due to the intercalation of potassium ions into Co₃TeO₆.

Mediated processes using a solid material, often called “solid booster”, have been proposed to increase the energy density in redox flow batteries (RFB). The strategy alters the energy storage in the dissolved redox species to a solid active material placed in a compartment of the device. Understanding the reaction kinetics of the dissolved redox mediator and the solid booster is crucial for proposing feasible pairs of solid boosters and dissolved redox mediators. We demonstrate a nanoelectrochemical methodology to monitor the reaction between the dissolved species in solution and the solid active material electrodeposited in recessed carbon nanoelectrodes. Our strategy overcomes issues inherent to standard methodologies, such as mass transport limitation, and evaluation of the intrinsic reactivity of the solid material. As a proof of concept, Prussian blue was electrodeposited in a recessed carbon nanoelectrode and used as a confined-solid material platform to evaluate the reaction between the reduced form of Prussian blue and triiodide, $$. A high conversion rate of the solid booster was observed in the presence of μM concentrations of the dissolved redox species. The proposed nanoelectrode was successfully employed as a potentiometric sensor to monitor the evolution of the reaction with the dissolved active species.

Bimetallic nickel-iron based oxides are regarded as one of the most promising catalysts for the oxygen evolution reaction (OER). In this study, we show that the precursor metal salts can affect the OER activity of the resulting Ni/Fe oxide under the same hydrothermal synthesis conditions. Pure sulfate, pure nitrate and mixed sulfate/nitrate metal salts were used to fabricate NiFe based oxide materials and to study the importance of the precursor choice for the OER. The results show that the nature of the precursor used in the synthesis of the bimetallic nickel-iron materials can influence different multi-phase catalysts to form which effects the OER.

Lithium metal, with its high theoretical capacity and low redox potential, is the most promising next-generation high-energy-density battery anode material. However, the formation of uneven surface layers and dead lithium, significant volume changes in the electrode, and dendrite growth lead to rapid capacity degradation, low cycling stability, and safety issues, limiting the commercialization of lithium metal batteries (LMBs). As a strategy to improve the stability of LMBs, introducinga three-dimensional (3D) structure with a large surface area can accommodate lithium (Li) inside the structure and homogenize local current density. Also, as a current collector and host material, free-standing carbon materials, with the advantages of lightness, low cost, electrochemical and mechanical stability, and excellent electronic conductivity, can effectively enhance energy density and cycle performance. In this review, we first discuss the chemical properties of carbon, and then summarize recent research progress related to the 3D structuring and chemical modification of carbon materials as a Li metal host. Finally, we present perspectives on future research for the practical application of free-standing carbon materials for LMBs.

Electrochemical water oxidation with single atom catalysts (SACs) has garnered immense interest because of their high atom utilization, extraordinary activity, and elucidation of the reaction mechanism. In SACs, while the atomic sites offer active centers for substrate binding and reaction intermediates, their interaction with the solid support is crucial for the stabilization and enhancement of catalytic activity. Coordinated elements surrounding the atomic site create a ligand-like environment that influences electrochemical properties. As a result, tuning the coordination environment of SACs allows for modulation of their oxygen evolution reaction (OER) activity. In light of this, the question arises: What is the role of the support in stabilizing single atoms (SAs) and controlling their electrochemical activity during water oxidation? This review addresses this question using recent examples. Spectroscopic characterizations and density functional theory (DFT) calculations provide a direct answer: In SACs, the atomic centers exhibit strong interactions with the support via neighboring atoms, influencing OER activity.

The stability of Fe−N−C oxygen reduction reaction (ORR) electrocatalysts has been considered a primary challenge for their practical application in proton exchange membrane fuel cells (PEMFCs). While several studies have attempted to reveal the possible degradation mechanism of Fe−N−C ORR catalysts, there are few research results reporting on their stability as well as the possible Fe species formed under different voltages in real PEMFC operation. In this work, we employ in-situ X-ray absorption near-edge structure (XANES) to monitor the active-site degradation byproducts of an atomically dispersed Fe−N−C ORR catalyst under a H₂/O₂-operating PEMFC at 90 % relative humidity and 80 °C. For this, stability tests were carried out at two constant cell voltages, namely 0.4 and at 0.8 V. Even though the ORR activity of the Fe−N−C catalyst decreased significantly and was almost identical at the end of the tests for the two voltages employed, the analysis of the XANES recorded under H₂/N₂ configuration at 0.6 and 0.9 V within the stability test suggests that two different degradation mechanisms occur. They are demetalation of iron cations followed by their precipitation into Fe oxides upon operation at 0.8 V, versus a chemical carbon oxidation close to the active sites, likely triggered by reactive oxygen species (ROS) originated from the H₂O₂ formation, during the operation at 0.4 V.

Aging processes occurring in electrical double layer capacitors greatly influence the lifetime of these energy storage devices and an increasing attention has been directed toward their understanding. While most studies approach this topic based on the overall electrochemical performance of the cell (such as enhanced resistance) or the materials degradation, addressing its failure causes at the electrolyte level is of great importance. Doing so, more precise strategies to improve the lifetime and performance can be developed for a wide range of applications. This article provides an overview of the current state of separation tools regarding gas chromatography and detection tools in various combinations with mass spectrometry. The aim of this work is to present the present state of the current knowledge on aging processes, with a focus on gas chromatography and mass spectrometry. Then, an outlook onto the challenges as well as ideas of combining methods is given. Here, the work offers a judgement into future challenges.

The necessary separation of anodic and cathodic compartments in the electrochemical multicomponent synthesis of alkyl arenesulfonates in batch was overcome by the transfer of this reaction in an undivided electrochemical flow cell. The yield was increased from an initial 23 % to 67 % by optimization using Design of Experiments (DoE). The experiments were carried out using an automated experimental flow electrolysis setup controlled by the automation software LABS (Laboratory Automation and Batch Scheduling), an open-source software that allows to plan and conduct experiments with an arbitrary, freely selectable experimental setup. The automated experimental setup turned out to be stable and provides reproducible results. In total, 6 examples are demonstrated with isolated yields up to 81 %. In addition, the robust scalability of the electrochemical reaction was demonstrated in a 10-fold scale-up.