Nickel hydroxide has been a cornerstone cathode material in rechargeable alkaline batteries for over a century, yet its performance at high charge/discharge rates remains a challenge. While cobalt additives are commonly used to enhance conductivity and rate capability, the fundamental sources of polarization and capacity loss are not well quantified. This work systematically investigates the polarization losses during discharge in electrodeposited nickel hydroxide coatings, both pure and cobalt-doped, and compares them with a composite electrode made from commercial nickel hydroxide powders to identify the primary bottlenecks in high-rate performance. We found that, contrary to common assumptions, cobalt doping did not significantly affect ionic diffusivities, contact resistances or charge transfer rates for the Ni0.85Co0.15(OH)2 composition. For the thin electrodeposited films, concentration polarization due to proton diffusion was identified as the dominant factor limiting high-rate discharge performance, with ohmic losses playing a secondary role. In contrast, for the commercial powder-based electrode, both diffusional and ohmic polarization contribute nearly equally to the sharp energy density decline at high discharge current densities. We conclude that for high-rate nickel hydroxide materials, optimizing performance is more effectively achieved through morphological engineering to shorten diffusion pathways rather than through cobalt doping.

In this work we characterize mixed Mo-W acidic deposition solutions with Mo content ranging from 0 to 100 mol.% by Raman and UV-Vis spectroscopy. The obtained distribution diagram of mixed isopolyanions allows one to explain the observed change in film deposition rate with increase in Mo content. It was found that the initial decrease in deposition rate correlates with decrease in [W10O32](4)(-) concentration, while the further increase in deposition rates correlates with the increase in [H3Mo3W15O60](9-) complex concentration in deposition solutions. The EDX and UV-Vis analysis of film compositions confirms the preferential deposition of mixed oxotungstate film with Mo:W ratio similar to 1:4 in solutions with >20 mol.% Mo. XRD and Raman confirmed that films consist of solid solutions with composition MoxW1-xO32H(2)O, with Mo fraction x ranging from 0 to 0.22. For the first time, the possibility of forming such single-phase solutions over a wide composition range was demonstrated. Potential-dependent optical absorption, coloration-decoloration kinetics, and capacity of the films are studied. Mo doping shifts the onset of coloration to more positive potentials and increases the optical density around 600 nm compared with undoped films. Although the coloration time increases slightly with Mo addition (from 1 to 3 s), the self-bleaching rate decreases by nearly an order of magnitude, indicating improved stability of the colored state.

The electrochemical carbon dioxide reduction reaction (CO2RR) on copper offers a route to produce valuable multi-carbon fuels and chemicals. While studies on single-crystal Cu(hkl) electrodes have established a strong correlation between surface structure and selectivity, translating this knowledge to nanostructured catalytic surfaces remains highly desirable. Herein, we employ a potentiodynamic oxidation-reduction protocol in halidecontaining solutions to nanostructure polycrystalline copper foils, creating surfaces enriched in (n10) domains. During CO2RR, the nanostructured electrodes exhibit enhanced selectivity toward C2+products and hydrocarbon oxygenates, compared to basal Cu(hkl) planes and smooth polycrystalline Cu. In situ shell-isolated nanoparticleenhanced Raman spectroscopy provides direct spectroscopic evidence for stabilized *OCCO dimer intermediates on the nanostructured surfaces, linking the improved C-C coupling efficiency to the (n10) geometry.

The study explores cobalt sulfide electrocatalysts for alkaline water splitting, focusing on the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). We compare sulfur-rich and sulfur-poor amorphous cobalt-based materials, specifically examining how composition, morphology, and chemical speciation influence catalytic activity and stability under reaction conditions. A key finding is the different transformation behaviors of sulfur-poor and sulfur-rich materials in alkaline environments and their impact on HER and OER performance. The study highlights that the chosen electrodeposition method significantly impacts the composition, morphology, and most importantly, the dynamic surface transformation behavior of cobalt sulfide catalysts, which, in turn, dictates their performance and stability for either OER or HER in alkaline water splitting. The sulfur-rich materials deposited from nonaqueous solutions underwent a fast and complete transformation into oxyhydroxide species, which represent the OER-active centers. Sulfur-poor materials obtained from aqueous solutions, which exhibited relative stabilization of the sulfide functionality, are more effective for the HER. However, the active sulfide species present in these materials is unstable under prolonged polarization in alkaline HER conditions, and as the pristine sulfide transforms into a hydroxide, the catalytic activity declines significantly.

Composite chitosan (Cht) scaffolds containing stabilized hydroxyapatite (HA) and copper (Cu) particles were synthesized using a two-phase CO2/H2O system under high pressure. The study systematically investigated the influence of key factors—such as the method of HA incorporation (in situ vs. ex situ), chitosan concentration, and temperature conditions—on the structural properties of the Cht/HA_Cu composite materials. Characterization techniques including SEM, XRD, and IR-ATR were employed to analyze the resulting structures. It was found that composites produced from a more concentrated polymer solution (2

In this study, we present a unified and comprehensive investigation into the asymmetry of deintercalation and intercalation kinetics in LiFePO4 materials, focusing on the previously unexplored asymmetry in nucleation kinetics. Through experimental studies of de/intercalation kinetics in LiFePO4 using an aqueous electrolyte, we identified three key factors contributing to the faster rate of deintercalation compared to intercalation. To elucidate the origins of the asymmetry in nucleation kinetics, we estimated the parameters of Classical Nucleation Theory using Density Functional Theory and Finite Element Method. The theory revealed that differences in strain energy are the primary driver of slower lithiation compared to delithiation. While other factors, such as differences in diffusion coefficients and molar volumes, also favor faster delithiation, their influence is less significant. Our findings provide valuable insights into the experimentally observed de/intercalation kinetics asymmetry and contribute to a deeper understanding of the processes in phase-transforming materials.

In this work we characterize mixed Mo-W acidic deposition solutions with Mo content ranging from 0 to 100 mol.% by Raman and UV-Vis spectroscopy. The obtained distribution diagram of mixed isopolyanions allows one to explain the observed change in film deposition rate with increase in Mo content. It was found that the initial decrease in deposition rate correlates with decrease in [W10O32]4- concentration, while the further increase in deposition rates correlates with the increase in [H3Mo3W15O60]9− complex concentration in deposition solutions. The EDX and UV-Vis analysis of film compositions confirms the preferential deposition of mixed oxotungstate film with Mo:W ratio ∼ 1:4 in solutions with >20 mol.% Mo. XRD and Raman confirmed that films consist of solid solutions with composition MoxW1-xO3·2H2O, with Mo fraction x ranging from 0 to 0.22. For the first time, the possibility of forming such single-phase solutions over a wide composition range was demonstrated. Potential-dependent optical absorption, coloration-decoloration kinetics, and capacity of the films are studied. Mo doping shifts the onset of coloration to more positive potentials and increases the optical density around 600 nm compared with undoped films. Although the coloration time increases slightly with Mo addition (from 1 to 3 s), the self-bleaching rate decreases by nearly an order of magnitude, indicating improved stability of the colored state.

The quest for active, selective, and stable electrocatalysts to convert CO2 into valuable products like carbon monoxide and formate has garnered significant attention in recent years, driven by both fundamental research and practical applications. Recent findings on copper-tin electrocatalysts reveal an intriguing shift in selectivity of CO2 reduction - from producing CO at low Sn concentrations to generating formate with nearly unity selectivity when the Sn content is increased. This shift raises important questions about the factors influencing the dramatic changes in CO2 reduction product distribution as the Cu-Sn material composition varies. However, existing experimental data primarily derive from multiphase Cu-Sn materials, which typically undergo phase changes under CO2 reduction conditions, which introduces interpretation uncertainties. In this study, we developed stable single-phase Cu-Sn materials, specifically a tin solid solution in Cu with the composition of Cu97Sn3 and the intermetallic Cu6Sn5, which were fabricated as dispersed foams to facilitate kinetic measurements. Our findings indicate that the high activity and selectivity of the Cu-Sn solid solution in the CO2-to-CO conversion process are likely due to more favorable kinetics for the formation of the *COOH intermediate, and not due to easier carbon monoxide desorption, as was previously suggested. In contrast, the formate production kinetics for the HCOO-selective Cu6Sn5 phase are significantly inhibited compared to pure copper. We hope our results will motivate further investigation into the nature of the active sites in Cu-Sn electrocatalysts, providing a deeper mechanistic understanding of the observed selectivity/activity trends.

Copper-based electrocatalytic materials with high surface area are essential for various processes, such as water splitting and the electroreduction of carbon dioxide and nitrates. Three-dimensional nanostructured electrodes offer distinct advantages in these applications due to their expansive surface area, which enhances charge transfer and mass transport. For bimetallic systems, however, the phase state, whether a solid solution or a mechanical mixture of metals, is critically important for catalytic performance. This study explores the formation of Cu-Ni solid solutions via electrodeposition using the dynamic hydrogen bubble template method. Two types of electrolyte were employed: sulfate-based and citrate-based. Through characterization by X-ray diffraction, scanning electron microscopy, elemental mapping, and X-ray fluorescence spectroscopy, we demonstrate that metallic foams deposited from sulfate solutions are heterogeneous, with poor control over nickel content. In contrast, the use of citrate-based solutions allows the nickel content in the deposits to be effectively controlled by varying the solution composition, thereby enabling the formation of a solid solution.

Composite chitosan films containing stabilized silver nanoparticles were synthesized using aqueous solutions of carbonic acid (i.e., water saturated with carbon dioxide) under varying pressure (6–50 MPa) and temperature conditions (25–90 °C). Carbonic acid is a biocompatible and antimicrobial medium. The influence of various factors, such as the molar ratio of chitosan to silver, pressure variations, and temperature, on the structural properties of the composite chitosan/silver composites was studied systematically using transmission electron microscopy (TEM) and X-ray diffractometry (XRD). A correlation was identified between the characteristics of the water saturation with carbon dioxide (pressure and temperature of the carbonic acid solution) and the structural features of the composite films. All films exhibited small silver nanoparticles measuring 1–2 nm in diameter. At specific pressure and temperature values, a phase of larger nanoparticles with sizes in the tens of nanometers was also present within the chitosan matrix. The relationship between the structure of the produced films and their antimicrobial properties has been established.

The reduction of permanganate on a rotating disk electrode is accompanied by an inhibition of depositing birnessite. The addition of potassium ferrate(VI) leads to an increase of inhibition. The obtaining of electrode material based on Fe-doped birnessite under alkaline conditions is demonstrated in experiment with deposition at inhibition potentials. This birnessite is single phase and highly disordered. The Fe content varies from 0 to 10 mol

Hematite photoanodes have shown potential for use in practical applications of photoelectrochemical (PEC) water splitting cells due to their abundance and stability, yet their efficiency needs to be improved. To optimize photoanode performance, co-catalysts such as amorphous nickel/iron oxyhydroxide layers are often deposited on the surface of hematite to enhance activity by catalyzing oxygen evolution. Recent studies have shown that the role of oxyhydroxide layers in changing PEC activity can vary depending on factors such as film morphology, co-catalyst layer thickness, and electrolyte composition. In this study, we investigate the effect of NiOOH and (Ni,Fe)OOH layers on the PEC activity of electrodeposited nanostructured hematite films. Our analysis of charge transfer and recombination rate constants determined from chronoamperometry and electrochemical impedance data suggests that the coatings' role is purely passivating, which is crucial for discontinuous electrodeposited films. Importantly, we show that the passivating properties of these coatings are enhanced by the presence of ppm concentrations of Fe in the electrolyte. We believe that our findings will be useful for further development of hematite photoanodes.

Accurate measurements of real surface area (RSA) are essential in fundamental electrocatalysis for evaluating the intrinsic activity of various materials. However, existing electrochemical methods for determining RSA values in metallic alloys, particularly those containing active metals, remain underexplored. This study critically assesses the efficacy of capacitance measurement techniques for calculating RSA values in copper-zinc alloys, which are commonly employed as electrocatalysts for CO2 reduction. We investigate optimal conditions for estimating RSA through cyclic voltammetry, focusing on electrolyte selection and appropriate potential ranges to ensure reliable RSA assessments. Additionally, we emphasize the necessity of using suitable reference samples for accurate specific capacitance calculations. Our findings reveal that potential uncertainties arising from the use of inappropriate reference samples across different Cu-Zn compositions can reach an order of magnitude, rendering them unsuitable for electrocatalytic studies. This research highlights the need for robust surface area quantification techniques to reduce uncertainties in reporting the activities of alloy-based materials in various electrochemical applications.

Copper-based electrocatalytic materials play a critical role in various electrocatalytic processes, including the electroreduction of carbon dioxide and nitrate. Three-dimensional nanostructured electrodes are particularly advantageous for electrocatalytic applications due to their large surface area, which facilitates charge transfer and mass transport. However, the real surface area (RSA) of electrocatalysts is a crucial parameter that is often overlooked in experimental studies of high-surface-area copper electrodes. In this study, we investigate the roughness factors of electrodeposited copper foams with varying thicknesses and morphologies, obtained using the hydrogen bubble dynamic template technique. Underpotential deposition (UPD) of metal adatoms is one of the most reliable methods for estimating the RSA of highly dispersed catalysts. We aim to illustrate the applicability of UPD of lead for the determination of the RSA of copper deposits with hierarchical porosity. To find the appropriate experimental conditions that allow for efficient minimization of the limitations related to the slow diffusion of lead ions in the pores of the material and background currents of the reduction of traces of oxygen, we explore the effect of lead ion concentration, stirring rate, scan rate, monolayer deposition time and solution pH on the accuracy of RSA estimates. Under the optimized measurement conditions, Pb UPD allowed to estimate roughness factors as high as 400 for 100 µm thick foams, which translates into a specific surface area of ~6 m2·g−1. The proposed measurement protocol may be further applied to estimate the RSA of copper deposits with similar or higher roughness.

The pursuit of novel techniques for obtaining dispersed copper-based catalysts is crucial in addressing environmental issues like decarbonization. One method for producing nanostructured metals involves the reduction of their oxides, a technique that has found widespread use in CO2 electroreduction. Currently, the intrinsic activities of oxide-derived copper electrocatalysts produced via different routes cannot be compared effectively due to the lack of information on electrochemically active surface area values, despite the availability of electrochemical methods that enable estimation of surface roughness for highly dispersed copper coatings. In this study, we aim to explore the potential of oxide-derived copper to achieve a high electrochemically active surface area by examining samples obtained from acetic and lactic acid deposition solutions. Our results revealed that Cu2O oxides had distinct morphologies depending on the electrodeposition solution used; acetate series samples were dense films with a columnar structure, while electrodeposition from lactic acid yielded a fine-grained, porous coating. The roughness factors of the electroreduced films followed linear relationships with the deposition charge, with significantly different slopes between the two solutions. Notably, a high roughness factor of 650 was achieved for samples deposited from lactic acid solution, which represents one of the highest estimates of electrochemically active surface area for oxide-derived copper catalysts. Our results highlight the importance of controlling the microstructure of the electrodeposited oxide electrocatalysts to maximize surface roughness.

We report oscillations of current which accompany anodic deposition from Mn(II) solutions in a neutral acetic buffer and also cathodic birnessite deposition from alkaline permanganate solutions. We demonstrate that for both processes, oscillations appear at high enough overpotentials. The current oscillations are affected by solution convection. The results of rotating disc electrode experiments favor mixed control, with higher diffusion contribution in case of cathodic deposition. Electron microscopy combined with electron and X-ray diffraction and coulometric analysis is applied to assign oscillations to certain morphological features of the deposits. A pronounced difference in microstructure is found for anodic and cathodic deposits formed under oscillating growth conditions: “anodic” birnessite consists of parallel layers of small crystals, whereas “cathodic” birnessite is globular. This difference is interpreted with account for specific crystallographic features. Namely, the more ordered birnessite lattice formed by reduction of permanganate favors a preferentially lateral growth of thin lamellas, in contrast to birnessite having a pronounced interplane distortion, formed in the course of anodic deposition. We assign the periodic current decrease to diffusion limitations in growing porous layers and assume that the subsequent current increase in each period corresponds to dendrite-like growth of a low number of crystals located in the outer diffusion layer.

Firmly bonded antimicrobial protective coating of biomatrix significantly enhances functionality of medical devices, in particular bioprostheses, for example, bioprosthetic heart valves in cardiac surgery. In our work, we have obtained a special coating based on chitosan nanoparticles (including those doped with Ag nanoparticles) that were obtained and single-step applied using a biocompatible and self-neutralizing carbonic acid as a polymer solvent. This approach makes it possible to obtain a biomatrix with a covalently bonded polymer screen of nanoparticles, which, in turn, can be doped with antimicrobial agents. For the first time ever, it has been demonstrated that one can form chitosan nanoparticles in solutions in carbonic acid, which are even more stable than in a classical solvent with a higher zeta potential (|zeta|-35 mV). Moreover, a highly-accurate analysis using a tritium labelling technique shows a fourfold increase in the deposition of nanoparticles compared to the depo-sition from conventional solvent. Using a high-resolution microscopy, it was possible to identify an ultra-thin coating of polymer spherical nanoparticles (-50 nm) clinging to collagen fibrils. Analysis of antimicrobial ac-tivity shows a possibility of induced antimicrobial response due to changes in conformation of polymer nano -particles and release of antimicrobial agents in case of pathogen growing on the bioprosthesis. A threefold increase in strength of the bioprosthesis due to coating has been identified.

We report cathodic deposition of birnessite oxide from permanganate alkaline solutions into porous flexible cloth consisting from carbon nanotubes. Oxide distribution in the pores is studied by means of electron microscopy, including transmission microscopy of microtom cross-sections and local elemental analysis. Oxide distribution depends on applied deposition mode. The intermittent potentiostatic mode favors the penetration of permanganate reagent into the pores of CNT cloth and allows us to fabricate more homogeneous hybrid material. We demonstrate a number of advantages of hybrid materials with oxide located mostly inside the cloth pores as compared to oxide located at external surface of the cloth.

Arrays of superconducting nanowires may be useful as elements of novel nanoelectronic devices. The superconducting properties of nanowires differ significantly from the properties of bulk structures. For instance, different vortex configurations of the magnetic field have previously been predicted for nanowires with different diameters. In the present study, arrays of parallel superconducting In nanowires with the diameters of 45 nm, 200 nm, and 550 nm-the same order of magnitude as coherence length ξ-were fabricated by templated electrodeposition. Values of magnetic moment M of the samples were measured as a function of magnetic field H and temperature T in axial and transverse fields. M(H) curves for the arrays of nanowires with 45 nm and 200 nm diameters are reversible, whereas magnetization curves for the array of nanowires with 550 nm diameter have several feature points and show a significant difference between increasing and decreasing field branches. Critical fields increase with a decrease in diameter, and the thinnest nanowires exceed bulk critical fields by 20 times. The qualitative change indicates that magnetic field configurations are different in the nanowires with different diameters. Variation of M(H) slope in small fields, heat capacity, and the magnetic field penetration depth with the temperature were measured. Superconductivity in In nanowires is proven to exist above the bulk critical temperature.