Electrochem, Volume 1, Issue 1 (March 2020) – 7 articles

High entropy oxides (HEOs) constitute a promising class of materials with possibly new and largely unexplored properties. The virtually infinite variety of compositions (multi-element approach) for a single-phase structure allows the tailoring of their physical properties and enables unprecedented materials design. Nevertheless, this level of versatility renders their characterization as well as the study of specific processes or reaction mechanisms challenging. In the present work, we report the structural and electrochemical behavior of different multi-cationic HEOs. Phase transformation from spinel to rock-salt was observed upon incorporation of monovalent Li⁺ ions, accompanied by partial oxidation of certain elements in the lattice. This transition was studied by X-ray diffraction, inductively coupled plasma-optical emission spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and attenuated total reflection infrared spectroscopy. In addition, the redox behavior was probed using cyclic voltammetry. Especially, the lithiated rock-salt structure HEOs were found to exhibit potential for usage as negative and positive electrode materials in rechargeable lithium-ion batteries. Full article

Electroreduction allows for the transformation of a chemically inert molecule such as CO₂ into a wide variety of useful carbon products. Unlike other approaches operating at higher temperatures, electrochemical reduction holds great promise since it achieves reduction under ambient conditions, thereby providing more control over the reaction selectivity. By controlling basic parameters such as the potential and the composition of the electrode, CO₂ can be transformed into a variety of products including carbon monoxide, syngas (CO/H₂), methane, and methanol. This reduction process takes place without external hydrogen, since water can be used as a source of both electrons and protons. Furthermore, this technology, when combined with renewable wind- or solar-derived electricity, has the potential to serve as a storage system for excess electricity. Despite these advantages, a number of challenges need to be overcome before reaching commercialization. New (and cheaper) electrocatalyst formulations with high faradaic selectivities are required. Impressive progress has been made on carbon-doped materials, which, in certain cases, have outperformed expensive noble metal-based materials. Research is also needed on new electrochemical reactor configurations able to overcome kinetic/mass transport limitations, which are crucial to reduce overpotentials. Fine control over the nature of the active sites and the reaction conditions is important to avoid parasitic reactions such as the hydrogen evolution reaction (HER), and therefore increases the faradaic efficiency towards the desired products. Full article

Controlled potential electrolyses of caffeine (CAF) were carried out at a Pt electrode in undried acetonitrile (ACN) and ACN-H₂O and the products of the anodic oxidation were analyzed by HPLC-PDA-ESI-MS/MS. A higher current efficiency occurred in ACN-H₂O, but an analogous chromatographic outline was found in both media, evidencing a reactive pathway of the electrogenerated radical cation CAF^•+ with water, added or in trace, as nucleophile. No dimeric forms were evidenced, excluding any coupling reactions. Neither was 1,3,7-trimethyluric acid found, reported in the literature as the main oxidative route for CAF in water. Four main chromatographic peaks were evidenced, assigned to four proposed structures on the base of chromatographic and spectral data: a 4,5-diol derivative and an oxazolidin-2-one derivative were assigned as principal oxidation products, supporting a mechanism proposed in a previous work for the primary anodic oxidation of the methylxanthines olefinic C⁴ = C⁵ bond. Two highly polar degradation products were also tentatively assigned, that seemed generating along two different pathways, one opening the imidazolic moiety and another one opening the purinic one. Full article

This perspective gives the reader a broad overview of the progress that has been made in understanding the physics of the exsolution process and its exploitation in electrochemical devices in the last five years. On the basis of this progress, the community is encouraged to pursue unreported and under-reported opportunities for the advancement of exsolution in electrochemical applications through new materials discovery. Full article

The control of the interface and the adhesion process are key issues for the development of new application based on electrochromic materials. In this work the functionalization of an electrode’s surface through electroreduction of diazonium generated in situ from 4-(2,5-di-thiophen-2-yl-pyrrol-1-yl)-phenylamine (SNS-An) has been proposed. The synthesis of the aniline derivative SNS-An was performed and the electrografting was investigated by cyclic voltammetry on various electrodes. Then the organic thin film was fully characterized by several techniques and XPS analysis confirms the presence of an organic film based on the chemical composition of the starting monomer and allows an estimation of its thickness confirmed by AFM scratching measurements. Depending on the number of electrodeposition cycles, the thickness varies from 2 nm to 10 nm, which corresponds to a few grafted oligomers. In addition, the grafted film showed a good electrochemical stability depending on the scan rates up to 400 V/s and the electrochemical response of the modified electrode towards several redox probes showed that the attached layer acts as a conductive switch. Therefore, the electrode behaves as a barrier to electron transfer when the standard redox potential of the probe is below the layer switching potential, whereas the layer can be considered as transparent towards the electron transfer for redox probes with a redox potential above it. Full article

This work emphasizes the development of a green synthetic approach for growing ultrathin film Pt_xPd_(1-x) alloy catalysts for formic acid oxidation (FAO) by surface limited redox replacement of underpotentially deposited H sacrificial layer. Up to three-monolayers-thick Pt_xPd_(1-x) films with different composition are generated on Au electrodes and characterized for composition and surface roughness using XPS and electrochemical methods, respectively. XPS results show close correlation between solution molar ratio and atomic composition, with slightly higher Pt fraction in the deposited films. The accordingly deposited Pt₄₂Pd₅₈ films demonstrated remarkable specific and mass activities of up to 35 mAcm⁻² and 45 Amg⁻¹ respectively, lasting for more than 1500 cycles in FAO tests. This performance, found to be better twice or more than that of pure Pt counterparts, renders the Pt₄₂Pd₅₈ films comparable with the frontrunner FAO catalysts. In addition, the best alloy catalyst establishes a nearly hysteresis-free FAO CV curve a lot earlier than its Pt counterpart and thus supports the direct FAO pathway for longer. Overall, the combination of high Pd activity and CO tolerance with the remarkable Pt stability results in highly active and durable FAO catalysts. Finally, this facile and cost-effective synthetic approach allows for scaling the catalyst production and is thus appropriate for foreseeable commercialization. Full article

Our aim of journal Electrochem is to provide reviews, regular research papers, and communications in all areas of electrochemistry including methodologies, techniques, and instrumentation in both fundamental and applied fields. In this Editorial, the various technological demands for electrochemistry from academic and industrial fields are discussed and some problems to be solved in electrochemistry are proposed for next-generation science and technology. Under these technological demands, open access journals such as Electrochem will provide the solutions and new technology in electrochemistry to the world. Full article