Energy storage and conversion is a very important link between the steps of energy production and energy consumption. Traditional fossil fuels are a natural and unsustainable energy storage medium with limited reserves and notorious pollution problems, therefore demanding a better choice to store and utilize the green and renewable energies in the future. Energy and environmental problems require a clean and efficient way of using the fuels. Fuel cell functions to efficiently convert oxidant and chemical energy accumulated in the fuel directly into DC electric, with the by-products of heat and water. Fuel cells, which are known as effective electrochemical converters, and electricity generation technology has gained attention due to the need for clean energy, the limitation of fossil fuel resources and the capability of a fuel cell to generate electricity without involving any moving mechanical part. The fuel cell technologies that received high interest for commercialization are polymer electrolyte membrane fuel cells (PEMFCs), solid oxide fuel cells (SOFCs), and direct methanol fuel cells (DMFCs). The optimum efficiency for the fuel cell is not bound by the principle of Carnot cycle compared to other traditional power machines that are generally based on thermal cycles such as gas turbines, steam turbines and internal combustion engines. However, the fuel cell applications have been restrained by the high cost needed to commercialize them. Researchers currently focus on the discovery of different materials and manufacturing methods to enhance fuel cell performance and simplify components of fuel cells. Fuel cell systems’ designs are utilized to reduce the costs of the membrane and improve cell efficiency, durability and reliability, allowing them to compete with the traditional combustion engine. In this review, we primarily analyze recent developments in fuel cells technologies and up-to-date modeling for PEMFCs, SOFCs and DMFCs.

https://www.mdpi.com/2077-0375/10/5/99/pdf

New Perspectives on Fuel Cell Technology: A Brief Review

Lithium metal is a promising anode to provide high energy density for next-generation batteries. However, it has not been implemented due to its low cycling efficiency, which results from the formation of an unstable solid electrolyte interphase (SEI). The SEIs formed with traditional liquid electrolytes are heterogeneous and easy to crack during cycling, thus resulting in the formation of dendritic and dead Li, and further devastating the electrode performance. To solve these issues, efforts have been made to replace natural SEIs with artificial SEIs (ASEIs). Here, we discuss critical design principles of ASEIs based on the understanding of SEI failure mechanisms. Three key principles for a successful ASEI are identified: (1) mechanical stability, which can be either high strength or adaptivity, (2) spatially uniform Li+ transport with moderate conductivity and even single-ion conduction, and (3) chemical passivation to mitigate Li-electrolyte parasitic reactions. Selected examples of recently developed ASEIs are categorized and elaborated. Finally, future directions are given for ASEI designs.

Design Principles of Artificial Solid Electrolyte Interphases for Lithium-Metal Anodes

Progress in hybrid composite Nafion®-based membranes for proton exchange fuel cell application

Membrane is one of the most important components in proton exchange membrane fuel cells (PEMFCs), which determines the transport phenomena, performance, and durability. With the rapid development of novel membranes, many transport coefficients in membranes applied in numerical studies are outdated due to the lack of experimental data for new membranes. In this review, the fundamentals of commercially available membranes are scrutinized, followed by the fundamental working mechanisms. A detailed examination of the transport phenomena within the membranes, including transport mechanisms, mathematical description, and experimental methods, is conducted for protonic conduction, electro-osmosis drag, diffusion, hydraulic permeation, and gas crossover, which are urgently needed for theoretical and numerical studies. It is found that various empirical or analytical correlations have been established to predict the transport coefficients of the membranes. However, empirical models may not be accurate for all types of membranes since there is no sufficient experimental data for a solid correlation and validation. The experimental methods reviewed in the present study can be applied for new membranes, which is essential to quantify the transport phenomena and its further impact on cell performance and durability. The key transport-phenomena-related factors that affect the performance and failure modes of membranes are also reviewed in this study, which helps to develop strategies in improving membranes’ performance and durability during operation. This review deepens the understanding of the short-term and long-term performance of the membrane in PEMFCs and provides important insights into the further design of novel membranes.

A review of membranes in proton exchange membrane fuel cells: Transport phenomena, performance and durability

Nowadays, ion-exchange membranes have numerous applications in water desalination, electrolysis, chemistry, food, health, energy, environment and other fields. All of these applications require high selectivity of ion transfer, i.e., high membrane permselectivity. The transport properties of ion-exchange membranes are determined by their structure, composition and preparation method. For various applications, the selectivity of transfer processes can be characterized by different parameters, for example, by the transport number of counterions (permselectivity in electrodialysis) or by the ratio of ionic conductivity to the permeability of some gases (crossover in fuel cells). However, in most cases there is a correlation: the higher the flux density of the target component through the membrane, the lower the selectivity of the process. This correlation has two aspects: first, it follows from the membrane material properties, often expressed as the trade-off between membrane permeability and permselectivity; and, second, it is due to the concentration polarization phenomenon, which increases with an increase in the applied driving force. In this review, both aspects are considered. Recent research and progress in the membrane selectivity improvement, mainly including a number of approaches as crosslinking, nanoparticle doping, surface modification, and the use of special synthetic methods (e.g., synthesis of grafted membranes or membranes with a fairly rigid three-dimensional matrix) are summarized. These approaches are promising for the ion-exchange membranes synthesis for electrodialysis, alternative energy, and the valuable component extraction from natural or waste-water. Perspectives on future development in this research field are also discussed.

https://www.mdpi.com/1422-0067/21/15/5517/pdf

Selectivity of Transport Processes in Ion-Exchange Membranes: Relationship with the Structure and Methods for Its Improvement

Recent approaches to improve Nafion performance for fuel cell applications: A review

Potential use of deep eutectic solvents (DESs) to enhance anhydrous proton conductivity of Nafion 115® membrane for fuel cell applications

A comprehensive review on the proton conductivity of proton exchange membranes (PEMs) under anhydrous conditions: Proton conductivity upper bound

Effect of deep eutectic solvents hydrogen bond acceptor on the anhydrous proton conductivity of Nafion membrane for fuel cell applications

In this research, deep eutectic solvents (DESs) were prepared and employed as the electrolyte in Nafion membranes. Different factors, such as the water content and Nafion counterions (H+, Li+, Na+ and K+), which could influence the PEM performance, were evaluated. The obtained results showed that the presence of water may have a constructive or destructive effect on the DES and Nafion/DES properties, which should be considered for their final applications. Also, the electronegativity of the counterion can significantly influence the Nafion/DES proton conductivity. The prepared Nafion/DES composite membranes showed superconducting properties as a result of a Grotthuss-like mechanism for proton conduction. The conductivities of the prepared membranes were compared to those of other membranes based on an upper bound concept, which showed the potential use of DESs as a promising alternative to conventional ionic liquids. Finally, the fuel cell performances of the prepared membranes at different temperatures were evaluated.

Non-humidified fuel cells using a deep eutectic solvent (DES) as the electrolyte within a polymer electrolyte membrane (PEM): the effect of water and counterions.

Fereidoon Mohammadi

Papers

Recent approaches to improve Nafion performance for fuel cell applications: A review

Potential use of deep eutectic solvents (DESs) to enhance anhydrous proton conductivity of Nafion 115® membrane for fuel cell applications

A comprehensive review on the proton conductivity of proton exchange membranes (PEMs) under anhydrous conditions: Proton conductivity upper bound

Effect of deep eutectic solvents hydrogen bond acceptor on the anhydrous proton conductivity of Nafion membrane for fuel cell applications

Non-humidified fuel cells using a deep eutectic solvent (DES) as the electrolyte within a polymer electrolyte membrane (PEM): the effect of water and counterions.