AbstractIron phthalocyanine (FePc) was penta‐coordinated with pyridine ligand (Py) grafted on carbon nanotube (CNT), to form (FePc‐Py‐CNT). The complex was studied as a catalyst for the oxygen reduction reaction ORR in seven different supporting electrolytes: OH− (0.1 M), OH− (1 M), NO3− (1 M), HSO4− (1 M), ClO4− (1 M), Br− (1 M), Cl− (1 M), to unveil anion‐poisoning effects and mechanism. Through cyclic voltammetry and polarization curves in N2 and O2 saturated atmospheres, thermodynamic and kinetic data were acquired. In acid media, the formal potential Fe(III)/(II) (E0’Fe(III)/(II)) of the complex is biased to more negative potentials by the anion presence. Similar effects were observed for the onset potential (Eonset) during polarization curves for the ORR. When the ORR was performed in the presence of either ClO4−, or HSO4−, anions, Tafel analysis showed different values depending if were derived from the low or from the high overpotential regions, revealing an inner‐sphere electron transfer mechanism (ISET). The Tafel values derived from measurements in the presence of Cl− and Br− anions do not change when extracted at low or at high overpotentials evidencing an outer‐sphere reaction mechanism (OSET). Gibbs free energies were derived from poisoning tests confirming the ISET and OSET mechanisms. The poisoning effect is responsible for the immediate loss of performance for these catalysts during the ORR in acidic media.

AbstractAqueous zinc ion batteries (ZIBs) are currently gaining a significant amount of attention as a low‐cost and high safety energy storage option. While mostly inorganic structures are used as cathode materials in aqueous zinc batteries, these materials undergo structural degradation, therefore, alternative organic cathodes are expected to be developed to replace inorganic materials in aqueous zinc ion batteries (AZIBs). In this work, pillar[5]quinone (P5Q) is used as a cathode in AZIBs for the first time. Besides investigating the charge storage mechanism and interfacial property evolution of P5Q by various ex situ analyses, electrochemical quartz crystal microbalance (EQCM) and density functional theory (DFT) demonstrates both Zn2+ and H+ incorporation. The P5Q exhibits >99 % Coulombic efficiency through 10000 cycles at ultra‐fast (500 °C) current density, yielding a capacity value of approximately 120 mAh g−1 at the end of the cycle. When the current density is changed from 500 °C to 120 °C, an initial discharge capacity of approximately 182 mAh g−1 is achieved, demonstrating outstanding performance with over 80 % capacity retention for the subsequent 7000 cycles.

AbstractThe utilization of Si anode in sulfide‐based all‐solid‐state batteries (ASSBs) has gained more research attention in recent years to overcome the interface challenges associated with ASSB‐containing Li metal anode. However, the volume expansion feature of the Si, stress/strain evolution inside the electrode, and the parasitic side reaction at the Si/sulfide SE interface are the most predominant limiting factors for practical device applications. It is necessary to investigate and understand the interface challenges through in‐depth analysis in real‐time battery operation to design highly efficient ASSBs for commercial device applications. Hence, this perspective paper provides a summary of the characterization tools and the analysis results related to the Si/sulfide SE interface. Moreover, in this perspective, we emphasize the importance of further investigation of the interface through more advanced in‐depth/operando analysis tools to gain insightful information about the anodic interface, which could be useful for the researchers to design efficient research strategies for solving the challenging issues associated with the anodic interface.

AbstractHydrogen transport in the anode of a proton‐exchange membrane fuel cell (PEMFC) has been studied with a modulation technique relating the hydrogen flow‐rate ( ) and the faradaic current ( ), called Current‐modulated Hydrogen flow‐rate Spectroscopy (CH2S). A simple analytical expression for the transfer function, H(jω)=n F / , is provided, showing a skewed semicircle in Nyquist representation (−H'' vs. H'), extending from H’=0 to H’=1, and with the maximum frequency at ωmax=2.33(DH2 /Li2), where DH2 is the effective hydrogen diffusivity and Li the thickness of the anode gas diffusion layer (GDL). The expression for CH2S is also calculated with an existing reversible chemical reaction in the GDL. Experimental results under different operation conditions show two transport processes limiting the anode reaction, one attributed to molecular diffusion through the partially saturated GDL, and the other to the microporous layer (MPL), or its interfaces with GDL or with the catalyst layer (CL). CH2S provides the hydrogen diffusivities (DH2,i) associated to each process under the different conditions. Current density decreases slightly the diffusivity of the GDL, while it becomes activated in the MPL; using two GDLs in the anode improves both GDL and MPL diffusivities; humidification decreases the diffusivity in both, GDL and MPL; finally, a superhydrophobic anodic CL prepared by electrospray improves hydrogen diffusivity in GDL and MPL.

AbstractThe demand for innovative batteries with high specific energy densities has increased. Li‐metal batteries employing Li‐metal anodes, regarded as the ultimate anodes with a high theoretical capacity, have been extensively studied over the past few decades. However, the poor reversibility and safety concerns regarding Li‐metal anodes remain unresolved. The importance of the electrode/electrolyte interface, especially the solid electrolyte interphase (SEI), for achieving reversibility of Li metal anodes has been extensively studied. Herein, we focused on the impact of the Li ion transport properties in oligoether (glyme)‐based electrolytes on the deposition/dissolution efficiency of Li metal anodes. Analysis of the low‐frequency impedance spectra of Li‐plated Cu/Li cells revealed that the diffusion resistance of Li ions (Rdiffusion) may be a dominant contributor to the internal resistance of the cells employing glyme‐based electrolytes. A higher Rdiffusion in poor‐mass‐transport electrolytes with a lower Li ion transference number resulted in larger polarization during Li deposition/dissolution, leading to more pronounced unfavorable side reactions and lower Coulombic efficiency. Rdiffusion rather than interfacial resistance affected the reversibility of the Li metal anode. Enhancing the Li ion mass transport ability of electrolytes is important for achieving highly reversible charge‐discharge performance of Li metal anodes at high current densities.

AbstractPhytoremediation and constructed wetlands are widely employed processes for the decontamination of soils and waters. These sustainable, effective, and cost‐efficient technologies rely solely on the use of plants. However, the application of these processes results in the accumulation of lignocellulosic residues, like it occurs with natural wetlands, which present a significant challenge due to the potential entry into the food chain of the adsorbed pollutants or the risk of initiating uncontrolled fires due to the accumulation of dead biomass. Nevertheless, rather than being perceived as a drawback, this can be seen as a potential source of materials. Carbonaceous materials are gaining increasing significance in the field of electrochemistry, normally improving their features through some type of thermal treatment. In this study, different types of thermal treatments applied to lignocellulosic wastes are reviewed pointing out pyrolysis and hydrothermal carbonization (HTC). Additionally, four environmental and energy electrochemical applications where this type of waste has been used as precursors of electrode materials are briefly examined: energy storage (supercapacitors, Li−Na‐ion batteries), hydrogen production (H2), microbial fuel cells (MFCs) and hydrogen peroxide (H2O2) production. Recent research findings, as discussed throughout this review, suggest a promising future for the utilization of lignocellulosic waste in electrochemical applications.

AbstractThis research focused on harnessing amino‐functionalized montmorillonite (Mt) clay, achieved through the grafting of [3(2‐aminoethyl)amino]propyltrimethoxysilane (AEP‐TMS), as carbon paste electrode (CPE) modifier for the electroanalysis of ciprofloxacin (CF). The characterization of both Mt and the amino‐functionalized (Mt‐NH2) materials was carried out using various techniques including Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X‐ray diffraction (XRD). Afterwards, various CPEs modified using Mt and Mt‐NH2 were prepared and characterized employing SEM‐energy dispersive X‐ray (EDX), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). By EIS, Mt‐NH2‐CPE exhibited significantly faster electron transfer with lower charge‐transfer resistance (438.5 Ω) compared to Mt‐CPE (3572.1 Ω) and to the bare CPE (2066.1 Ω). Additionally, CV experiments performed by using redox probes demonstrated the excellent accumulation capability of [Fe(CN)6]3− ions on Mt‐NH2‐CPE surface. The Mt‐NH2‐CPE was subsequently applied using square wave voltammetry to determine CF in the presence of cetyltrimethylammonium bromide (CTAB), yielding an impressive linear range from 30 to 240 μM (R=0.999) and a low detection limit of 0.07 μM (23.2 μg L−1). The method exhibited stable and reproducible responses (RSD=3.25 %; n= 6) under optimized conditions. Following interference studies, the optimized method was effectively applied to quantify CF concentrations in pharmaceutical and water samples.

AbstractMethane, the simplest hydrocarbon, has a high energy density and is widely used as chemical feedstocks or fuels. Converting CO2 to methane through electrochemical reduction offers a promising strategy for managing the global carbon balance, but is a challenge due to the lack of effective electrocatalysts. Herein, the Co single atom catalyst supported by MoS2 antisite defect (Co‐MoS2) is designed from both the activity and selectivity aspects. By virtue of i) moderately electron‐deficient state (Coδ+) ensuring efficient CO2 activation and HER suppression; ii) the strong adsorption capability for intermediate enhancing selectivity; iii) the single atomic active site avoiding the formation of C2 products, Co‐MoS2 could selectively convert CO2 to CH4 with a limiting potential of −0.45 V vs. RHE, which outperforms most of the present catalysts, and is expected to be a promising substitution for Cu‐based catalysts.

AbstractElectrochemical energy storage and conversion systems (EESCSs), including batteries, supercapacitors, fuel cells, and water electrolysis technologies, enabling the direct conversion between chemical and electrical energies. They are key to the flexible storage and utilization of renewable energy and play an important role in future energy technologies. The physical and chemical properties of electrode materials significantly influence the performance of EESCSs, necessitating the development of materials with both high cost‐effectiveness and superior electrochemical storage and catalytic capabilities. Layered double hydroxides (LDHs), due to their unique properties as high surface area, evenly distributed active sites, and tunable compositions, makes themselves and the derivatives have become focal points in the EESCSs. This review summarizes recent advances of LDH and their derivates for diverse EESCSs applications, aims to elucidate the modification strategies of LDH materials and provide valuable insights for exploring LDH‐derived materials in various electrochemical devices, offering interdisciplinary perspectives for the rational design of LDH‐based materials.