Andrey A. Nechitailov

Proton-exchange membranes are crucial for water electrolyzers and fuel cells, but their performance declines under low humidity due to dehydration. Existing reviews mainly list experimental results without analyzing the mechanisms of proton conductivity stabilization. This review systematically summarizes approaches to enhance moisture-independent proton conductivity and evaluates their prospects. Key factors governing conductivity include microstructure, sulfonic group concentration, and hydration level. Stability under dry conditions depends on water retention and thermal resistance. Main strategies involve hybrid composite membranes, ionomer structure control via pre-treatments, and novel proton-conducting polymers. Promising directions include oriented channel structures, MOFs, and graphene-based materials. The stabilization mechanism relies on retaining water through hydrophilic additives that form stable hydrates, enabling proton transport even under harsh conditions (up to 120 °C and 50% RH, per US DOE targets). Among Nafion alternatives, sulfonated aromatic polymers and phosphoric-acid-doped polybenzimidazole demonstrate good performance at elevated temperatures (100–200 °C), though durability remains a challenge for the latter. Despite ongoing research, Nafion-based composites still offer one of the best overall balances of conductivity, stability, and processability. A significant research gap persists: long-term membrane performance is poorly studied, and many additives degrade over time or block proton transport sites due to ion exchange with metal cations.

Graphene-reinforced proton exchange membranes (PEMs) offer a promising route to reduce fuel crossover while enhancing mechanical strength, chemical durability, and thermal stability in electrochemical energy systems such as fuel cells and water electrolyzers. Achieving these improvements requires graphene with controlled thickness, low defect density, and minimal oxygen content, yet the scalable production of such materials remains a challenge. Two scalable deposition techniques, electrophoretic coating (e-coating) and spray-coating, were systematically evaluated for coating formation. Comparative analysis using UV-Vis spectroscopy indicated that e-coating may induce slight membrane degradation, whereas spray-coating preserves the native polymer structure. Scanning electron microscopy confirmed the formation of uniform, submicron coatings. The graphene e-coating demonstrated the highest barrier efficacy, lowering the crossover current density to 0.9 mA/cm², a substantial improvement over the 6 mA/cm² observed for the uncoated membrane. The spray-coated sample exhibited a crossover current density of 1.3 mA/cm². Furthermore, the e-coated membrane showed superior barrier properties and lower proton resistance at elevated temperatures (>60 °C) compared to the spray-coated counterpart. The peak short-circuit current densities were attained at 40-50 °C. These findings establish e-coating as an effective method for fabricating high-performance graphene-based barrier layers on PEMs, enabling reduced crossover and extended operational lifetime.

Stability and durability of electrochemical energy conversion systems are significant issues. In this study, few-layer graphene and polytetrafluoroethylene were applied to both sides of the Nafion type membrane as barrier layers to increase the device's resistance to electrochemical exposure. Electrochemical performance was assessed in a two-electrode configuration: potentiostatic aging at 2.5 V and hydrogen crossover measurements. The characterization of materials functioning as barrier layers was conducted using scanning and transmission electron microscopy, laser correlation spectroscopy, and differential thermal analysis. It is shown that both components stabilize Nafion through interfacial interactions, resulting in a longer service life and reduced hydrogen crossover. While the reference sample showed increased crossover, the modified samples exhibited reductions of 50% and 33%. These findings underscore the potential of the studied materials in enhancing the stability of polymer electrolyte membrane water electrolyzers, contributing to the advancement of more durable and efficient systems for hydrogen energy applications.

This work presents a comparative study of graphene exfoliation technologies from various graphite precursors—spectral graphite and thermally expanded graphite (Graflex)—using ultrasonic treatment and electrochemical methods in the presence of the ionic surfactant Nafion. The influence of exfoliation parameters, the nature of the starting material, and the presence of surfactant additives on the morphology, dispersibility, stability, and structural characteristics of the resulting graphene-containing dispersions was investigated. Particular attention is paid to a two-step technology combining pulsed electrochemical exfoliation with subsequent mild ultrasonic treatment. Comprehensive characterization of the samples was carried out using UV–Vis spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), electron microscopy, electron diffraction (ED), dynamic light scattering (DLS), and X-ray photoelectron spectroscopy (XPS). It was found that the use of Nafion significantly enhances exfoliation efficiency and contributes to the stabilization of the dispersions. Graphene sheets obtained from Graflex exhibit significantly larger lateral dimensions (up to 1 μm or more) compared to those exfoliated from spectral graphite (100–300 nm). The approach combining the use of Graflex and pulsed electrochemical exfoliation in the presence of Nafion with subsequent low-power ultrasonic treatment enables the production of few-layer graphene (1–3 layers) with high stability.

The review addresses the problem of durability of operation of low-temperature proton exchange membrane fuel cells. Fuel cells are of considerable interest for the transition to renewable energy sources; however, the durability of these devices is still not sufficiently long (10 to 40 thousand hours). The increase in the durability is a relevant task. The review presents a systematic account and evaluation of the methods used for stabilization of electrochemical energy conversion systems with a proton exchange membrane and defines promising approaches to increase their lifetime. The bibliography includes 197 references.

The subject of the study was the optical properties of aqueous glycerol solutions of the neutral-red organic dye and polyvinyl alcohol (PVA) films into which this dye is introduced from these solutions. The purpose of the work was to examine the spectral characteristics of the neutral-red organic dye in aqueous glycerol solutions and PVA films in the ultraviolet, visible, and near-infrared ranges and to investigate the features influenced by the polymer matrix. Method. The method involved preparation of solutions by mixing glycerol, water, and dye in appropriate proportions and producing films by drying dye-containing water–glycerol mixtures on glass substrates. Absorption spectra, in the wavelength range of 190–1100 nm, were obtained using a spectrophotometer. Main results. Results showed that the characteristic absorption bands of the dye were significantly affected by the polymer matrix, whereas the addition of glycerol resulted in only minor changes. A noticeable shift in the infrared absorption peak of water, due to glycerol, was observed in the solution spectra. Practical significance. The investigated PVA-based film materials with color additives, including those plasticized with glycerol, have potential applications in the fabrication of optical filters, flexible polarizers, and other components used in applied optics.

Ensuring the stable operation of proton exchange membrane fuel cells is conducive to their real-world application. A promising direction for stabilizing electrodes is the stabilization of the ionomer via the formation of surface compounds with graphene. A comprehensive study of the (electrochemical, chemical, and thermal) stability of composites for fuel cell electrodes containing a modifying additive of few-layer graphene was carried out. Electrochemical stability was studied by cycling the potential on a disk electrode for 5000 cycles. Chemical stability was assessed via the resistance of the composites to H₂O₂ treatment using ion-selective potentiometry. Thermal stability was studied using differential thermal analysis. Composites were characterized by UV-Vis spectroscopy, Raman spectroscopy, EDX, and SEM. It was shown that graphene inhibits Nafion degradation when exposed to heat. Contrariwise, Nafion is corrosive to graphene. During electrochemical and chemical exposure, the determining change for carbon-rich composites is the carbon loss (oxidation) of the carbon material. In the case of carbon-poor composites, the removal of fluorine and sulfur from the Nafion polymer with their partial replacement by oxygen prevails. In all cases, the F/S ratio is stable. The dispersity of Nafion in a sample affects its chemical stability more than the G/Nafion ratio does.

A technology for obtaining graphene by means of ultrasonic dispersion of thermally expanded graphite in the presence of a surface-active polymer Nation is presented. The technology makes it possible to obtain large amounts of low-layer (1–3 layers) graphene in a relatively short time. An approach to control the dispersion process based on UV spectroscopy of dispersions is described. A mechanism is proposed for the effect of a surface-active polymer on the production of low-layer graphene by ultrasonic dispersion.

This paper presents a study of the platinum activity in the ORR in a hydrogen polymer electrolyte membrane fuel cell with electrodes containing multi-walled CNTs in a wide range of compositions and conditions. The data of the comparative analysis of the platinum activity on a fraction of Nafion in the electrode, the composition of the oxidizing agent (oxygen, air), pressure, and temperature are provided. The reasons for the dependence of the platinum surface activity on the component composition of the electrode are considered. Specific mass activity and surface activity of platinum in the ORR in MEA with the electrodes with CNTs depend on the ionomer/platinum ratio. Both dependences have a maximum at the level of the 25% Nafion fraction. The maximum appears as a result of an optimal structure formation, which ensures the fullest use of the platinum surface and minimal concentration overvoltages. Specific mass activity and surface activity of platinum for the sample with 34% CNTs at T = 60 °C and excessive pressure of p = 2 atm amount to 0.46 A/mg and 0.72 mA/cm², respectively.