Search Results (59)

This study investigates Li-ion diffusion characteristics in Li-contained and Li-free bismuth oxide crystals, aiming to explore their potential as solid electrolytes for next-generation lithium-ion batteries. Although bismuth oxide has been widely applied as a solid electrolyte in fuel cells, its suitability for Li-ion battery applications remains unexplored. Using molecular dynamics simulations, we analyzed the Li-ion diffusion behavior in two distinct Li-contained bismuth oxide crystals with layered and non-layered structures, as well as four Li-free bismuth oxide phases. It is demonstrated that the layered structure exhibits a simpler and more organized diffusion pathway compared to the complex and bottlenecked pathways in the non-layered structure, resulting in superior Li-ion diffusivity. For Li-free bismuth oxide phases, diffusion coefficients vary significantly depending on structural characteristics, with the highest diffusion coefficient observed in the phase with minimal void fraction. A notable inverse relationship between void fraction and Li-ion diffusivity efficiency highlights the importance of structural design in enhancing ionic transport. This study provides valuable insights into the diffusion mechanisms of Li ions in bismuth oxide systems and offers strategic guidance for designing high-performance solid electrolytes, contributing to the advancement of all-solid-state battery technologies. Full article

Solid oxide fuel cells (SOFCs) have garnered significant attention as a promising technology for clean and efficient power generation due to their ability to utilise renewable fuels such as hydrogen and ammonia. As carbon-free energy carriers, hydrogen and ammonia are expected to play a pivotal role in achieving net-zero emissions. However, a critical research question remains: how does the electrochemical performance of SOFCs compare when fuelled by hydrogen vs. ammonia, and what are the implications for their practical application in power generation? This mini-review paper is premised on the hypothesis that while hydrogen-fuelled SOFCs currently demonstrate superior stability and performance at low and high temperatures, ammonia-fuelled SOFCs offer unique advantages, such as higher electrical efficiencies and improved fuel utilisation. These benefits make ammonia a viable alternative fuel source for SOFCs, particularly at elevated temperatures. To address this, the mini-review paper provides a comprehensive comparative analysis of the electrochemical performance of SOFCs under direct hydrogen and ammonia fuels, focusing on key parameters such as open-circuit voltage (OCV), power density, electrochemical impedance spectroscopy, fuel utilisation, stability, and electrical efficiency. Recent advances in electrode materials, electrolytes, fabrication techniques, and cell structures are also highlighted. Through an extensive literature survey, it is found that hydrogen-fuelled SOFCs exhibit higher stability and are less affected by temperature cycling. In contrast, ammonia-fuelled SOFCs achieve higher OCVs (by 7%) and power densities (1880 mW/cm² vs. 1330 mW/cm² for hydrogen) at 650 °C, along with 6% higher electrical efficiency. Despite these advantages, ammonia-fuelled SOFCs face challenges such as NO_x emissions, nitride formation, environmental impact, and OCV stabilisation, which are discussed alongside potential solutions. This mini review aims to provide insights into the future direction of SOFC research, emphasising the need for further exploration of ammonia as a sustainable fuel alternative. Full article

Epitaxial layers of water-soluble Sr₃Al₂O₆ were fabricated as sacrificial layers on SrTiO₃ (100) single-crystal substrates using the Pulsed Laser Deposition technique. This approach envisages the possibility of developing a new generation of micro-Solid Oxide Fuel Cells and micro-Solid Oxide Electrochemical Cells for portable energy conversion and storage devices. The sacrificial layer technique offers a pathway to engineering free-standing membranes of electrolytes, cathodes, and anodes with total thicknesses on the order of a few nanometers. Furthermore, the ability to etch the SAO sacrificial layer and transfer ultra-thin oxide films from single-crystal substrates to silicon-based circuits opens possibilities for creating a novel class of mixed electronic and ionic devices with unexplored potential. In this work, we report the growth mechanism and structural characterization of the SAO sacrificial layer. Epitaxial samarium-doped ceria films, grown on SrTiO3 substrates using Sr₃Al₂O₆ as a buffer layer, were successfully transferred onto silicon wafers. This demonstration highlights the potential of the sacrificial layer method for integrating high-quality oxide thin films into advanced device architectures, bridging the gap between oxide materials and silicon-based technologies. Full article

A national energy crisis has emerged in South Africa due to the country’s increasing energy needs in recent years. The reliance on fossil fuels, especially oil and gas, is unsustainable due to scarcity, emissions, and environmental repercussions. Researchers from all over the world have recently concentrated their efforts on finding carbon-free, renewable, and alternative energy sources and have investigated microbiology and biotechnology as a potential remedy. The usage of microbial electrolytic cells (MECs) and microbial fuel cells (MFCs) is one method for resolving the problem. These technologies are evolving as viable options for hydrogen and bioenergy production. The renewable energy technologies initiative in South Africa, which is regarded as a model for other African countries, has developed in the allocation of over 6000 MW of generation capacity to bidders across several technologies, primarily wind and solar. With a total investment value of R33.7 billion, the Eastern Cape’s renewable energy initiatives have created 18,132 jobs, with the province awarded 16 wind farms and one solar energy farm. Utilizing wastewater as a source of energy in MFCs has been recommended as most treatments, such as activated sludge processes and trickling filter plants, require roughly 1322 kWh per million gallons, whereas MFCs only require a small amount of external power to operate. The cost of wastewater treatment using MFCs for an influent flow of 318 m³ h⁻¹ has been estimated to be only 9% (USD 6.4 million) of the total cost of treatment by a conventional wastewater treatment plant (USD 68.2 million). Currently, approximately 500 billion cubic meters of hydrogen (H₂) are generated worldwide each year, exhibiting a growth rate of 10%. This production primarily comes from natural gas (40%), heavy oils and naphtha (30%), coal (18%), electrolysis (4%), and biomass (1%). The hydrogen produced is utilized in the manufacturing of ammonia (49%), the refining of petroleum (37%), the production of methanol (8%), and in a variety of smaller applications (6%). Considering South Africa’s energy issue, this review article examines the production of wastewater and its impacts on society as a critical issue in the global scenario and as a source of green energy. Full article

Thin films of gadolinium-doped ceria (GDC) nanoparticles were fabricated as electrolytes for low-temperature solid oxide fuel cells (SOFCs) by combining electrophoretic deposition (EPD) and the successive ionic layer adsorption and reaction-air spray plus (SILAR-A+) method. The Ce_1−xGd_xO_2−x/2 solid solution was synthesized using hydrothermal (HY) and solid-state (SS) procedures to produce high-quality GDC nanoparticles suitable for EPD fabrication. The crystalline structure, cell parameters, and phases of the GDC products were analyzed using X-ray diffraction. Variations in oxygen vacancy concentrations in the GDC samples were achieved through the two synthetic methods. The ionic conductivities of pressed pellets from the HY, SS, and commercial G_0.2DC samples, measured at 150 °C, were 0.6 × 10⁻⁶, 2.6 × 10⁻⁶, and 2.9 × 10⁻⁶ S/cm, respectively. These values were determined using electrochemical impedance spectroscopy (EIS) with a simplified equivalent circuit method. The morphologies of G_0.2DC thin films prepared via EPD and SILAR-A+ processes were characterized, with particular attention to surface cracking. Crack-free GDC thin films, approximately 730–1200 nm thick, were successfully fabricated on conductive substrates through the hybridization of EPD and SILAR-A+, followed by hydrothermal annealing. EIS and ionic conductivity (1.39 × 10⁻⁹ S/cm) measurements of the G_0.2DC thin films with thicknesses of 733 nm were performed at 300 °C. Full article

The necessity for high operational temperatures presents a considerable obstacle to the commercial viability of solid oxide fuel cells (SOFCs). The introduction of active co-dopant ions to polycrystalline solid structures can directly impact the physiochemical and electrical properties of the resulting composites including crystallite size, lattice parameters, ionic and electronic conductivity, sinterability, and mechanical strength. This study proposes cobalt–iron-substituted gadolinium-doped ceria (Co_xFe_1-xGDC) as an innovative, nickel-free anode composite for developing ceramic fuel cells. A new co-precipitation technique using ammonium tartrate as the precipitant in a multi-cationic solution with Co²⁺, Gd³⁺, Fe³⁺, and Ce³⁺ ions was utilized. The physicochemical and morphological characteristics of the synthesized samples were systematically analysed using a comprehensive set of techniques, including DSC/TGA for a thermal analysis, XRD for a crystallographic analysis, SEM/EDX for a morphological and elemental analysis, FT-IR for a chemical bonding analysis, and Raman spectroscopy for a vibrational analysis. The morphological analysis, SEM, showed the formation of nanoparticles (≤15 nm), which corresponded well with the crystal size determined by the XRD analysis, which was within the range of ≤10 nm. The fabrication of single SOFC bilayers occurred within an electrolyte-supported structure, with the use of the GDC as the electrolyte layer and the CoO–Fe₂O₃/GDC composite as the anode. SEM imaging and the EIS analysis were utilized to examine the fabricated symmetrical cells. Full article

Proton Exchange Membrane Fuel Cells (PEMFCs) represent a promising green solution for energy production, traditionally relying on platinum-group-metal (PGM) electrocatalysts. However, the increasing cost and limited global availability of PGMs have motivated extensive research into alternative catalyst materials. PGM-free oxygen reduction reaction (ORR) catalysts typically consist of first-row transition metal ions (Fe, Co) embedded in a nitrogen-doped carbon framework. Key factors affecting their efficacy include intrinsic activity and catalyst degradation. Thus, alternative materials with improved characteristics and the elucidation of reaction and degradation mechanisms have been the main concerns and most frequently explored research paths. High intrinsic activity and active site density can ensure efficient reaction rates, while durability towards corrosion, carbon oxidation, demetallation, and deactivation affects cell longevity. However, when moving to the actual application in PEMFCs, electrode engineering, which involves designing the catalyst layer, and other critical operational factors affecting fuel cell performance play a critical role. Electrode fabrication parameters such as ink formulation and deposition techniques are thoroughly discussed herein, explicating their impact on the electrode microstructure and formed electrochemical interface and subsequent performance. Adjusting catalyst loading, ionomer content, and porosity are part of the optimization. More specifically, porosity and hydrophobicity determine reactant transport and water removal. High catalyst loadings can enhance performance but result in thicker layers that hinder mass transport and water management. Moreover, the interaction between ionomer and catalyst affects proton conductivity and catalyst utilization. Strategies to improve the three-phase boundary through the proper ionomer amount and distribution influence catalyst utilization and water management. It is critical to find the right balance, which is influenced by the catalyst–ionomer ratio and affinity, the catalyst properties, and the layer fabrication. Overall, understanding how composition and fabrication parameters impact electrode properties and behaviour such as proton conductivity, mass transport, water management, and electrode–electrolyte interfaces is essential to maximize electrochemical performance. This review highlights the necessity for integrated approaches to unlock the full potential of PGM-free materials in PEMFC technology. Clear prospects for integrating PGM-free catalysts will drive cleaner and more cost-effective, sustainable, and commercially viable energy solutions. Full article

Due to high greenhouse gas emissions, countries worldwide are stepping up their emission reduction efforts, and the global demand for new, carbon-free fuels is growing. Ammonia (NH₃) fuels are popular due to their high production volume, high energy efficiency, ease of storage and transportation, and increased application in power equipment. However, their physical characteristics (e.g., unstable combustion, slow flame speed, and difficult ignition) limit their use in power equipment. Based on the structural properties of the power equipment, NH₃ fuel application and emissions characteristics were analyzed in detail. Combustion of NH₃ fuels and reduction measures for NO_x emissions (spark plug ignition, compression ignition, and gas turbines) were analyzed from various aspects of operating conditions (e.g., mixed fuel, fuel-to-exhaust ratio, and equivalence ratio), structure and strategy (e.g., number of spark plugs, compression ratio (CR), fuel injection, and ignition mode), and auxiliary combustion techniques (e.g., preheating, humidification, exhaust gas recirculation, and secondary air supply). The performance of various NH₃ fuel cell (FC) types was analyzed, with a focus on the maximum power achievable for different electrolyte systems. Additionally, the application and NO_x emissions of indirect NH₃ FCs were evaluated under flame and catalytic combustion conditions. The system efficiency of providing heat sources by burning pure NH₃, anode tail gas, and NH₃ decomposition gas was also compared. Based on a comprehensive literature review, the key factors influencing the performance and emissions of NH₃-powered equipment were identified. The challenges and limitations of NH₃-powered equipment were summarized, and potential strategies for improving efficiency and reducing emissions were proposed. These findings provide valuable insights for the future development and application of NH₃ FCs. Full article

Research has been conducted on solid oxide fuel cells (SOFCs) for their fuel flexibility, modularity, high efficiency, and power density. However, the high working temperature leads to the deterioration of materials and increased operating costs. Considering the high protonic conductivity and low activation energy, the proton conducting SOFC, i.e., the protonic ceramic fuel cell (PCFC), working at a low temperature, has been wildly investigated. The PCFC is a promising state-of-the-art electrochemical energy conversion system for ecological energy; it is characterized by near zero carbon emissions and high efficiency, and it is environment-friendly. The PCFC can be applied for the direct conversion of various renewable fuels into electricity at intermediate temperatures (400–650 °C). The construction of the PCFC directly affect its properties; therefore, manufacturing technology is the crucial factor that determines the performance. As a thinner electrolyte layer will lead to a lower polarization resistance, a uniformly constructed and crack-free layer which can perfectly bond to electrodes with a large effective area is challenging to achieve. In this work, different fabrication methods are investigated, and their effect on the overall performance of PCFCs is evaluated. This article reviews the recent preparation methods of PCFCs, including common methods, 3D printing methods, and other advanced methods, with summarized respective features, and their testing and characterization results. Full article

The management of drainage water (DW), which is produced during the soilless cultivation of plants, requires a high energy input. At the same time, DW is characterized by a high electrolytic conductivity, a high redox potential, and is also stable and putrefaction-free. In the present study, the natural properties of drainage water and a biotreatment method employing an external organic substrate in the form of citric acid (C/N 1.0, 1.5, 2.0) were utilized for energy recovery by a microbial fuel cell (MFC). The cathode chamber served as a retention tank for DW with a carbon felt electrode fixed inside. In turn, a biological reactor with biomass attached to the filling in the form of carbon felt served as the anode chamber. The filling also played the role of an electrode. The chambers were combined by an ion exchange membrane, forming an H letter-shaped system. They were then connected in an external electrical circuit with a resistance of 1k Ω. The use of a flow-through system eliminated steps involving aeration and mixing of the chambers’ contents. Citric acid was found to be an efficient organic substrate. The voltage of the electric current increased from 44.34 ± 60.92 mV to 566.06 ± 2.47 mV for the organic substrate dose expressed by the C/N ratio ranging from 1.0 to 2.0. At the same time, the denitrification efficiency ranged from 51.47 ± 9.84 to 95.60 ± 1.99% and that of dephosphatation from 88.97 ± 2.41 to 90.48 ± 1.99% at C/N from 1.0 to 2.0. The conducted studies confirmed the possibility of recovering energy during the biological purification of drainage water in a biofilm reactor. The adopted solution only required the connection of electrodes and tanks with an ion-selective membrane. Further research should aim to biologically treat DW followed by identification of the feasibility of energy recovery by means of MFC. Full article

The application of protonic ceramic electrolysis cells (PCECs) for ammonia (NH₃) synthesis has been evaluated over the past 14 years. While nitrogen (N₂) is the conventional fuel on the cathode side, various fuels such as methane (CH₄), hydrogen (H₂), and steam (H₂O) have been investigated for the oxygen evolution reaction (OER) on the anode side. Because H₂ is predominantly produced through CO₂-emitting methane reforming, H₂O has been the conventional carbon-free option thus far. Although the potential of utilizing H₂O and N₂ as fuels is considerable, studies exploring this specific combination remain limited. PCEC fabrication technologies are being developed extensively, thus necessitating a comprehensive review. Several strategies for electrode fabrication, deposition, and electrolyte design are discussed herein. The progress in electrode development for PCECs has also been delineated. Finally, the existing challenges and prospective outlook of PCEC for NH₃ synthesis are analyzed and discussed. The most significant finding is the lack of past research involving PCEC with H₂O and N₂ as fuel configurations and the diversity of nitrogen reduction reaction catalysts. This review indicates that the maximum NH₃ synthesis rate is 14 × 10⁻⁹ mol cm⁻² s^−1, and the maximum current density for the OER catalyst is 1.241 A cm⁻². Moreover, the pellet electrolyte thickness must be maintained at approximately 0.8–1.5 mm, and the stability of thin-film electrolytes must be improved. Full article

The development of energy storage systems (ESS) has become an important area of research due to the need to replace the use of fossil fuels with clean energy. Redox flow batteries (RFBs) provide interesting features, such as the ability to separate the power and battery capacity. This is because the electrolyte tank is located outside the electrochemical cell. Consequently, it is possible to design each battery according to different needs. In this context, zinc–bromine flow batteries (ZBFBs) have shown suitable properties such as raw material availability and low battery cost. To avoid the corrosion and toxicity caused by the free bromine (Br₂) generated during the charging process, it is necessary to use bromine complexing agents (BCAs) capable of creating complexes. As an overview, the different BCAs used have been listed to compare their behavior when used in electrolytes in ZBFBs. In addition, the coulombic and energy efficiencies obtained have been compared. Full article

The conventional Ni–YSZ (yttria-stabilized zirconia) fuel electrode experiences severe degradation due to Ni- agglomeration and migration away from the electrolyte. Therefore, herein, we have considered Ni free electrodes, i.e., La_0.6Sr_0.4MnO_3-δ (LSM)-based perovskite oxides as fuel electrodes. The LSM perovskite phase transforms into a Ruddlesden–Popper LSM (RP-LSM) phase with exsolved MnO_x under reducing atmospheres. The RP-LSM is mainly interesting due to its good electrical conductivity, redox stability, and acceptable electrochemical behaviour. In this work, we synthesized the LSM powder and characterized it using several methods including X-ray diffraction (XRD), thermogravimetry analyses (TGA), four-probe conductivity, and scanning electron microscope with energy-dispersive X-ray spectroscopy (SEM-EDX). Finally, the electrolyte-supported single cells were fabricated and electrochemically characterized using AC and DC techniques under electrolysis conditions. In addition to pure LSM fuel electrodes, we have also investigated the electrochemical behaviour of LSM + YSZ (50:50) and LSM + GDC (50:50) composite fuel electrodes. The single cells containing LSM and LSM + GDC fuel electrodes show higher cell performance than LSM + YSZ. For instance, current densities of 1, 1.03, and 0.51 A·cm⁻² at 1.5 V are obtained for LSM, LSM + GDC, and LSM + YSZ fuel electrodes containing single cells, respectively, with a 50% N₂ and 50% H₂O feed gas mixture. Moreover, the performance of the cell was also investigated under co-electrolysis with 50% CO₂ and 50% H₂O and under direct CO₂ electrolysis conditions with 100% CO₂ fuel gas. Full article

Solid oxide fuel cells with protonic ion conducting electrolytes (H-SOFCs) are recognized and anticipated as eco-friendly electrochemical devices fueled with several kinds of fuels. One distinct feature of SOFCs that makes them different from others is fuel flexibility. Ammonia is a colorless gas with a compound of nitrogen and hydrogen with a distinct strong smell at room temperature. It is easily dissolved in water and is a great absorbent. Ammonia plays a vital role as a caustic for its alkaline characteristics. Nowadays, ammonia is being used as a hydrogen carrier because it has carbon-free molecules and prosperous physical properties with transportation characteristics, distribution options, and storage capacity. Using ammonia as a fuel in H-SOFCs has the advantage of its ammonia cracking attributes and quality of being easily separated from generated steam. Moreover, toxic NO_x gases are not formed in the anode while using ammonia as fuel in H-SOFCs. Recently, various numerical studies have been performed to comprehend the electrochemical and physical phenomena of H-SOFCs in order to develop a feasible and optimized design under different operating conditions rather than doing costlier experimentation. The aim of this concisely reviewed article is to present the current status of ammonia-fueled H-SOFC numerical modeling and the application of numerical modeling in ammonia-fueled H-SOFC geometrical shape optimization, which is still more desirable than traditional SOFCs. Full article

Hydrogen is a prospective energy carrier because there are practically no gaseous emissions of greenhouse gases in the atmosphere during its use as a fuel. The great benefit of hydrogen being a practically inexhaustible carbon-free fuel makes it an attractive alternative to fossil fuels. I.e., there is a circular process of energy recovery and use. Another big advantage of hydrogen as a fuel is its high energy content per unit mass compared to fossil fuels. Nowadays, hydrogen is broadly used as fuel in transport, including fuel cell applications, as a raw material in industry, and as an energy carrier for energy storage. The mass exploitation of hydrogen in energy production and industry poses some important challenges. First, there is a high price for its production compared to the price of most fossil fuels. Next, the adopted traditional methods for hydrogen production, like water splitting by electrolysis and methane reforming, lead to the additional charging of the atmosphere with carbon dioxide, which is a greenhouse gas. This fact prompts the use of renewable energy sources for electrolytic hydrogen production, like solar and wind energy, hydropower, etc. An important step in reducing the price of hydrogen as a fuel is the optimal design of supply chains for its production, distribution, and use. Another group of challenges hindering broad hydrogen utilization are storage and safety. We discuss some of the obstacles to broad hydrogen application and argue that they should be overcome by new production and storage technologies. The present review summarizes the new achievements in hydrogen application, production, and storage. The approach of optimization of supply chains for hydrogen production and distribution is considered, too. Full article