With the growing emphasis on sustainable development, the demand for environmentally friendly solvents in green chemical processes and carbon dioxide capture is increasing. Ionic liquids (ILs), as promising green solvents, offer significant potential but face considerable challenges, particularly in solvent selection. To overcome the limitations of traditional screening methods, machine learning (ML) techniques have recently been applied, offering a more efficient and data-driven approach. This review provides an overview of key ML methods used in solvent screening and compares them with traditional experimental and theoretical techniques. It examines the role of descriptor selection in structure‒property-based methods, such as quantitative structure-activity relationships (QSAR) and quantitative structure‒property relationships (QSPR), which are critical for predicting IL properties. The review also explores the application of these methods to screen IL properties, including toxicity, viscosity, density, and CO₂ solubility. Additionally, it discusses challenges in selecting appropriate models based on data scale and task complexity, integrating physical information for model interpretability, and achieving multi-objective optimization to balance key properties in ionic liquid (IL) design. Finally, it summarizes the achievements, limitations, and prospects of ML applications in ILs research, offering insights into how these methods can advance the development of sustainable ILs.

Perovskite-based photovoltaic devices have garnered significant interest owing to their remarkable performance in converting light into electricity. Recently, the focus in the field of perovskite solar cells (PSCs) has shifted towards enhancing their durability over extended periods. One promising strategy is the incorporation of two-dimensional (2D) perovskites, known for their ability to enhance stability due to the large organic cations that act as a barrier against moisture. However, the broad optical bandgap and limited charge transport properties of 2D perovskites hinder their efficiency, making them less suitable as the sole light-absorbing material when compared to their three-dimensional (3D) counterparts. An innovative approach involves using 2D perovskite structures to modify the surface properties of 3D perovskite. This hybrid approach, known as 2D/3D perovskites, while enhancing their performance. Beyond solar energy applications, 2D perovskites offer a flexible platform for chemical engineering, allowing for significant adjustments to crystal and thin-film configurations, bandgaps, and charge transport properties through the different organic ligands and halide mixtures. Despite these advantages, challenges remain in integration of 2D perovskites into solar cells without compromising device stability. This review encapsulates the latest developments in 2D perovskite research, focusing on their structural, optoelectronic, and stability attributes, while delving into the challenges and future potential of these materials.

Rechargeable aqueous metal-ion batteries are promising alternative energy storage devices in the post-lithium-ion era due to their inherent safety and environmental compatibility. Among them, aqueous zinc ion batteries (AZIBs) stand out as next-generation energy storage systems, offering low cost, high safety, and eco-friendliness. Nevertheless, the instability of Zn metal anodes, manifested as Zn dendrite growth, interfacial side reactions, and hydrogen (H₂) evolution, remains a major obstacle to commercialization. To address these challenges, extensive research has been conducted to understand and mitigate these issues. This review comprehensively summarizes recent advances in Zn anode stabilization strategies, including artificial solid electrolyte interphase (SEI) layers, structural optimization, electrolyte modification, and bioinspired designs. These approaches collectively aim to achieve uniform Zn deposition, suppress parasitic reactions, and enhance cycling stability. Furthermore, it critically evaluates the advantages and feasibility of different strategies, discuss potential synergistic effects of multi-strategy integration, and provide perspectives for future research directions.

As intrinsically carbon-free molecules, ammonia and hydrogen are considered as fuels for internal combustion engines, mainly for long-distance or off-road applications. These alternative fuels have different combustion characteristics, reactivity, and exhaust gas compositions compared to conventional fuels, raising questions about the suitability of lubricants in engines operating with them. The impact of ammonia, hydrogen, and their blends on lubricants in internal combustion engines is a relatively new topic, with few reference studies available. However, degradation processes of lubricants have been studied in the context of hydrocarbon fuels, and in compressors using ammonia as a refrigerant, for example. This work presents a review of the literature on engine oil degradation phenomena in relation to ammonia and hydrogen combustion characteristics. In particular, it highlights the current state of knowledge regarding compatibility with unburnt gases, elevated nitrogen oxide levels, and water. Additionally, it summarizes the latest insights into the contribution of lubricants to pollutant emissions.

Ammonia, as a zero-carbon fuel, has great potential for meeting decarbonization targets in the internal combustion engine sector. This paper summarizes recent studies in which ammonia is used as a fuel for compression-ignition engines. Due to its low combustion reactivity, ammonia must be used in conjunction with a high reactivity fuel, such as diesel, to ensure stable engine operation. Currently, two main approaches are used to supply ammonia to the engine combustion chamber: ammonia port injection and in-cylinder direct injection. In the two routes, ammonia-diesel engines commonly face challenges such as low ammonia energy rate (AER), limited thermal efficiency, and high emissions of nitrogen-containing pollutants, especially under high ammonia substitution conditions. To address these challenges, this study reviews combustion technologies capable of achieving relatively high AER, such as premixed charge compression ignition (PCCI) and reaction-controlled compression ignition (RCCI), and analyzes their impact on combustion and emissions characteristics. This paper also examines combustion technologies under ultra-high AER conditions and finds that technologies such as diesel pilot injection and ammonia-diesel stratified injection can support stable engine operation. This review provides insights into current progress, remaining challenges, and future directions in ammonia-diesel engine combustion technologies.

Hydrogen, with its carbon-free composition and the availability of abundant renewable energy sources for its production, holds significant promise as a fuel for internal combustion engines (ICEs). Its wide flammability limits and high flame speeds enable ultra-lean combustion, which is a promising strategy for reducing NO_x emissions and improving thermal efficiency. However, lean hydrogen-air flames, characterized by low Lewis numbers, experience thermo-diffusive instabilities that can significantly influence flame propagation and emissions. To address this challenge, it is crucial to gain a deep understanding of the fundamental flame dynamics of hydrogen-fueled engines. This study uses high-speed planar SO₂-LIF to investigate the evolutions of the early flame kernels in hydrogen and methane flames, and analyze the intricate interplay between flame characteristics, such as flame curvature, the gradients of SO₂-LIF intensity, tortuosity of flame boundary, the equivalent flame speed, and the turbulent flow field. Differential diffusion effects are particularly pronounced in H₂ flames, resulting in more significant flame wrinkling. In contrast, CH₄ flames, while exhibiting smoother flame boundaries, are more sensitive to turbulence, resulting in increased wrinkling, especially under stronger turbulence conditions. The higher correlation between curvature and gradient of H₂ flames indicates enhanced reactivity at the flame troughs, leading to faster flame propagation. However, increased turbulence can mitigate these effects. Hydrogen flames consistently exhibit higher equivalent flame speeds due to their higher thermo-diffusivity, and both hydrogen and methane flames accelerate under high turbulence conditions. These findings provide valuable insights into the distinct flame behaviors of hydrogen and methane, highlighting the importance of understanding the interactions between thermo-diffusive effects and turbulence in hydrogen-fueled engine combustion.

The widespread commercial adoption of fuel cells requires continued improvements in cost-effectiveness, performance, and durability. A tree-like nitrogen-doped carbon (T-NC) support structure was developed for low-platinum (Pt) loaded fuel cells. Carbon nanotubes serve as the conductive backbone, while ZIF-8-derived carbon, synthesized from 2-methylimidazole zinc salt, forms the branches that provide attachment sites for platinum group metals (PGMs). In cathodes with a Pt loading of 0.1 mg_Pt/cm², this novel Pt/T-NC electrode exhibited a remarkable 30% reduction in concentration loss at 2.0 A/cm² and a 12.7% increase in peak power density, compared to conventional Pt/C electrodes. Additionally, the corrosion resistance of the electrode was improved. Following 5000 cycles of accelerated durability testing (ADT) for carbon corrosion, the fuel cell retained 50.8% of its original performance, while conventional electrodes retained only 38%. The T-NC structure is broadly applicable for supporting various advanced PGM catalysts. This advancement offers a promising approach to bridge the gap between theoretical catalytic activity and practical output, leading to substantial improvements in both performance and durability of fuel cells.

Conventional flat-plate photovoltaic-thermal (PV-T) collectors generate electricity and heat simultaneously; however, the outlet temperature of the latter is typically below 60 °C, limiting their widespread application. The use of optical concentration can enable higher-temperature heat to be generated, but this can also lead to a rise in the operating temperature of the PV cells in the collector and, in turn, to a deterioration in their electrical performance. To overcome this challenge, an optical spectral-splitting filter that absorbs the infrared and transmits the visible portion of the solar spectrum can be used, such that wavelengths below the bandgap are sent to the cells for electricity generation, while those above it are sent to a thermally decoupled absorber for the generation of heat at a temperature that is considerably higher than that of the cells. In this study, a triangular primary PV-T channel, wherein the primary heat transfer fluid (water) flows, is integrated into a parabolic trough concentrator of geometrical concentration ratio ~10, while a secondary liquid filter (water, AgSiO₂-eg or Therminol-66) is introduced for spectral splitting. Optical, electrical and thermal-fluid (sub-)models are developed and coupled to study the performance of this collector. Each sub-model is individually checked against results taken from the literature with maximum deviations under 10%. Subsequently, the optical and electrical models are coupled with a 3-D thermal-fluid CFD model (using COMSOL Multiphysics 6.1) to predict the electrical and thermal performance of the collector. Results show that when water is used as the optical filter, the maximum overall thermal (filter channel plus primary channel) and electrical efficiencies of the collector reach ~45% and 15%, respectively. A comparison between water, AgSiO₂-eg and Therminol-66 reveals that AgSiO₂-eg improves the thermal efficiency of the filter channel by ~25% (absolute) compared to Therminol-66 and water, however, this improvement – which arises from the thermal performance of the filter – comes at an expense of a ~5% electrical efficiency loss.

The presence of alkaline earth metal ions in biodiesel can exacerbate engine wear, impair fuel oxidation stability, and substantially reduce combustion efficiency. Improving the quality of biodiesel is therefore crucial for promoting its adoption as a viable alternative to conventional fossil fuels. This study investigates the removal of alkaline earth metal calcium (Ca²⁺) and magnesium (Mg²⁺) from Jatropha biodiesel using four amino polycarboxylate chelating agents: ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), 1,2-cyclohexanediaminetetraacetic acid (CDTA), and N-(2-hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA). The results showed that CDTA demonstrated the highest removal efficiency and selectivity for Ca²⁺ and Mg²⁺ among the four chelating agents, resulting in removal rates of 98.6% and 94.3%, respectively. Furthermore, the oxidative stability of biodiesel, measured as induction period, increased from 3.38 to 8.31 h after treatment with EDTA solution and reached a maximum of 8.68 h after treatment with CDTA. Density functional theory (DFT) calculations were performed to analyze Mulliken charges, electrostatic potential, frontier molecular orbitals, and interaction energies. The results indicate that the four chelating agents form cyclic structure complexes by simultaneously coordinating with a metal ion through multiple coordination atoms (N atom in amino group and O atom in carboxyl group). CDTA has the strongest interaction energies with Ca²⁺ and Mg²⁺, calculated at –826 and –915 kcal/mol, respectively, corroborating its superior chelation performance.

The non-uniform pore size distribution and high flammability of commercial separators pose significant challenges to the safe application of high-energy-density lithium-ion batteries. In this study, a flame-retardant composite separator (P@HLi) with high thermal stability was successfully developed, which not only suppressed lithium dendrite growth but also improved high-temperature cycling performance of batteries and significantly enhanced their thermal safety. Li//Li symmetric batteries equipped with P@HLi-20 separators demonstrated stable cycling for over 600 h at a low polarization potential (approximately 50 mV), effectively reducing the formation of “dead lithium” and lithium dendrites. The LFP//Li and NCM811//Li cells with P@HLi-20 separators delivered initial discharge specific capacities of 142.0 and 167.9 mAh/g, respectively. Notably, the LFP//Li battery with P@HLi-20 separator showed excellent high-temperature cycling performance, maintaining 98.0% capacity retention and a discharge capacity of 131.1 mAh/g after 100 cycles at 1 C at 90 °C. Furthermore, pouch cells assembled with P@HLi-20 separators exhibited reductions of 52.67% in peak heat release rate (PHRR) and 68.42% in total heat release (THR) compared to those using Celgard separators, demonstrating superior thermal safety. These results confirm that the P@HLi separator offers comprehensive improvements in both electrochemical performance and safety characteristics.

Aqueous zinc-ion batteries (AZIBs) have emerged as promising candidates for next-generation energy storage systems due to their inherent safety, cost-effectiveness, and high theoretical capacity. However, their practical application remains constrained by limited cycling stability and sluggish ion diffusion kinetics, particularly under high mass loading conditions. These limitations are primarily attributed to the restricted ion transport pathways within the electrode structure and structural degradation caused by repeated zinc-ion insertion and extraction in highly loaded electrodes. To address these challenges, formamide (FA)-inserted VOPO₄ (FA-VOPO₄) nanosheet cathodes were designed with expanded interlayer spacing (9.3 Å), where FA molecules partially replace interlayer water, thereby enhancing both structural stability and ion transport pathways. This unique structural modification, supported by synergistic hydrogen bonding between FA and residual water, significantly improves Zn²⁺ diffusion kinetics and charge transfer properties, as confirmed by electrochemical tests and theoretical analysis. Consequently, FA-VOPO₄ electrodes delivered a remarkable volumetric capacity of 733 mAh/cm³ at 40 mA/g, approximately 8 times higher than that of the VOPO₄·2H₂O electrode, and retained 82.1% of their capacity after 1000 cycles at 1 A/g with a mass loading of 10 mg/cm². Even at a high mass loading of 20 mg/cm² (4.4 mAh/cm²), the FA-VOPO₄ cathode maintained a volumetric capacity of 535 mAh/cm³. These findings provide valuable insights into electrode design strategies for high-performance AZIBs, contributing to the development of safer, more efficient energy storage technologies with potential applications in grid storage and portable electronics.

Thermal runaway presents a significant challenge for large-scale application of lithium-ion batteries (LIBs), often leading to the release of flammable, explosive, and toxic gases. In this study, porous flowerlike cerium dioxide microspheres (FL-CeO₂) were investigated to eliminate hydrogen fluoride (HF) gas generated during thermal runaway. A dedicated test device and method were developed for this purpose. The FL-CeO₂ was synthesized via a hydrothermal method and coated onto nickel foam to fabricate a gas filter. During thermal runaway of a 5 Ah lithium iron phosphate (LiFePO₄) battery, the filter—loaded with 1.2 g CeO₂—achieved an instantaneous HF removal rate of up to 82.24% within approximately 40–50 s. X-ray photoelectron spectroscopy (XPS) results indicate that F⁻ ions replace O²⁻ ions in the CeO₂ lattice. Additionally, the potential for reusability of the CeO₂ microspheres was evaluated through multiple HF adsorption and desorption cycles. After 10 cycles, the regenerated CeO₂ microspheres retained a HF adsorption rate of 76.11%, demonstrating promising reusability.

Polyanionic silicate-based cathode materials have attracted considerable attention due to their intrinsic structural stability, strong thermal and chemical resistance, and ability to achieve high operating voltages through the inductive effects of polyanion groups. In this study, atomistic simulations were conducted to explore the energetics of intrinsic point defect formation, Na-ion migration pathways, and dopant incorporation in Na₂FeSiO₄, providing key insights into its viability as a cathode material for sodium-ion batteries (SIBs). Among the native defects, the Na Frenkel pair exhibited the lowest formation energy, suggesting a natural preference for vacancy-mediated Na-ion migration. The calculated migration energy barriers of 0.38 and 0.41 eV further support the material’s capability for efficient sodium-ion transport. Doping analysis identified K, Zn, and Ge as the most favorable isovalent dopants at the Na, Fe, and Si sites, respectively, while Ga showed a strong tendency to substitute at Fe sites and facilitate Na-vacancy formation. Furthermore, Al substitution at the Si site was found to increase the overall sodium content in the lattice. The electronic structure of these promising dopants was further investigated using density functional theory (DFT), offering deeper insights into their influence on the electrochemical behavior of Na₂FeSiO₄.

Both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for advancing the industrial application of fuel cells and metal-air batteries. This paper reports a bifunctional oxygen catalyst (CoNC@FePc) synthesized by anchoring FePc molecules onto cobalt nanoparticles embedded within a Co-ZIF-derived nitrogen-doped carbon matrix (CoNC). By leveraging the significant electron transfer between Co nanoparticles and FePc molecules, the synthesized catalyst demonstrated outstanding performance for both ORR and OER, further validated by density functional theory (DFT) calculations. The catalyst achieved a half-wave potential of 0.87 V for ORR and a low overpotential of 314 mV at 10 mA/cm² for OER, surpassing the performance of commercial Pt/C and RuO₂, respectively. Additionally, the rechargeable zinc-air batteries incorporating CoNC@FePc exhibited a remarkable peak power density of 150.2 mW/cm² and maintained outstanding cyclic stability for over 100 h. This study offers a straightforward approach to improving the bifunctional oxygen electrocatalytic performance of metal phthalocyanine-based catalysts.

Japan aims to establish an international hydrogen supply chain by utilizing low-cost and abundantly available hydrogen sources and liquid hydrogen carriers to realize a future hydrogen economy that will enhance energy security and help achieve carbon neutrality. While hydrogen does not emit CO₂ when used as a fuel to generate energy, CO₂ emissions can be attributed to hydrogen due to the energy and other resources required at each stage of the hydrogen supply chain. Therefore, from a life cycle perspective, if hydrogen is to contribute to the world’s carbon neutrality goal, the entire hydrogen supply chain must be low-carbon. This paper explores the life cycle CO₂ emissions of international hydrogen supply chains envisaged by Japan. The target supply chains involve hydrogen produced from renewable electricity via electrolysis, as well as from fossil fuels with carbon capture and storage, sourced from resource-rich countries and imported to Japan using liquid hydrogen carriers such as liquid hydrogen, methylcyclohexane (MCH), and ammonia (NH₃). In addition, this paper addresses potential options for reducing life cycle CO₂ emissions to effectively establish a low-carbon hydrogen supply chain.

The environmental impacts of hydrogen production can vary widely depending on the production energy source and process. This implies that the collection and management of sustainability data for hydrogen production globally is desired to ensure accountable development of the sector. Life cycle assessment (LCA) is an internationally recognized tool for environmental impact assessment. Integrating LCA in the holistic evaluation of the hydrogen value chain is desirable to ensure the cleanness and sustainability of the various available hydrogen production pathways. The objective of this review is to evaluate the methodology used in assessing the life cycle impact of hydrogen production including proposed documentation such as the guarantee of origin (GO) and certification schemes, and review case studies from Australia. An analysis of the sustainability strategies and schemes designed by the Australian government, aimed at mitigating climate change and promoting the hydrogen economy, was conducted. The case studies that were discussed identified the preferred available scaled routes of clean hydrogen production to be water electrolysis, which is based on technologies using renewable energy. Other dominant technologies which incorporate carbon capture and storage (CCS) were envisaged to continue playing a role in the transition to a low carbon economy. Additionally, it is critical to assess the greenhouse gas (GHG) emissions using appropriate system boundaries, in order to classify clean hydrogen production pathways. Harmonizing regulatory stringency with appropriate tracking of renewable electricity can promote clean hydrogen production through certification and GO schemes. This approach is deemed critical for the sustainable development of the hydrogen economy at the international level.

A just energy transition (JET) to low-carbon fuels, such as green hydrogen, is critical for mitigating climate change. Countries with abundant renewable energy resources are well-positioned to meet the growing global demand for green hydrogen. However, to improve the volumetric energy density and facilitate transport and distribution over long distances, green hydrogen needs to be converted into an energy carrier such as green ammonia. This study conducted a comparative life cycle assessment (LCA) to evaluate the environmental impacts of green ammonia production, with a particular focus on greenhouse gas (GHG) emissions. The boundary of the study was from cradle-to-production gate, and the design was based on a coastal production facility in South Africa, which uses renewable energy to desalinate seawater, produce hydrogen, and synthesise ammonia. The carbon intensity of production was 0.79 kg CO₂-eq per kg of ammonia. However, if co-products of oxygen, argon and excess electricity are sold to market and allocated a portion of GHG emissions, the carbon intensity was 0.28 kg CO₂-eq per kg of ammonia. Further, without the sale of co-products but excluding the embodied emissions of the energy supply system, as defined in the recent international standard (ISO/TS 19870), the carbon intensity was 0.11 kg CO₂-eq per kg of ammonia. Based on the hydrogen content of ammonia, this is equivalent to 0.60 kg CO₂-eq per kg of hydrogen, which is well below the current threshold for certification as a low-carbon fuel. The process contributing most to the overall environmental impacts was electrolysis (68%), with particulate matter (55%) and global warming potential (33%) as the dominant impact categories. This reflects the energy intensity of electrolysis and the carbon intensity of the energy used to manufacture the infrastructure and capital goods required for green ammonia production. These findings support the adoption of green ammonia as a low-carbon fuel to mitigate climate change and help achieve net-zero carbon emissions by 2050. However, achieving this goal requires the rapid decarbonisation of energy supply systems to reduce embodied emissions from manufacturing infrastructure.

Hydrogen is a promising energy carrier that is expected to play a crucial role in helping Canada achieve its net-zero target by 2050. However, reducing the ambiguity in regulatory frameworks is essential to incentivize and facilitate international trade in hydrogen. To this end, regulators must agree on quantification methodologies that consider life cycle boundaries, process descriptions, co-product allocation, conversion constants, and certification units. Several studies have highlighted the importance of life cycle assessment (LCA) as a standardized, relevant method for estimating the carbon footprint associated with hydrogen production and evaluating its environmental sustainability. As such, LCA-based certification schemes could help create a transparent hydrogen market. The aim of this study is to validate the proposed harmonized LCA-based methodology for quantifying hydrogen production’s carbon intensity. This methodology follows a consistent scope and life cycle inventory (LCI) development criteria, alongside a rigorous data quality assessment. The well-to-gate carbon intensities of six hydrogen production pathways are compared, which range from 0.26 to 10.07 kg CO_2e per kg of hydrogen (kg CO_2e/kg H₂), against the hydrogen carbon intensity thresholds established by the Canadian Clean Hydrogen Investment Tax Credit (CHITC). For example, the biomass gasification with carbon capture (CC) pathway demonstrates the lowest carbon intensity, while thermochemical pathways, such as steam methane reforming of natural gas without CC, poses challenges to meeting the maximum CHTIC threshold of 4 kg CO_2e/kg H₂.

Hydrogen, recognized as a critical energy source, requires green production methods, such as proton exchange membrane water electrolysis (PEMWE) powered by renewable energy. This is a key step toward sustainable development, with economic analysis playing an essential role. Life cycle costing (LCC) is commonly used to evaluate economic feasibility, but traditional LCC analyses often provide a single cost outcome, which limits their applicability across diverse regional contexts. To address these challenges, a Python-based tool is developed in this paper, integrating a bottom-up approach with net present value (NPV) calculations and Monte Carlo simulations. The tool allows users to manage uncertainty by intervening in the input data, producing a range of outcomes rather than a single deterministic result, thus offering greater flexibility in decision-making. Applying the tool to a 5 MW PEMWE plant in Germany, the total cost of ownership (TCO) is estimated to range between €52 million and €82.5 million, with hydrogen production costs between 5.5 and 11.4 €/kg H₂. There is a 95% probability that actual costs fall within this range. Sensitivity analysis reveals that energy prices are the key contributors to LCC, accounting for 95% of the variance in LCC, while iridium, membrane materials, and power electronics contribute to 75% of the variation in construction-phase costs. These findings underscore the importance of renewable energy integration and circular economy strategies in reducing LCC.

This paper presents a techno-economic assessment (TEA) combined with an environmental life cycle assessment (LCA) of various hydrogen delivery options within Europe, aiming to identify the most sustainable and cost-effective methods for transporting renewable hydrogen. Five hydrogen carriers—compressed hydrogen, liquid hydrogen, ammonia, methanol, and a liquid organic hydrogen carrier—are compared, assuming that hydrogen is produced via renewable electrolysis in Portugal and transported to the Netherlands by either ship or pipeline. The findings align with much of the existing literature, indicating that the most economically and environmentally sustainable options for long-distance hydrogen delivery are shipping liquid hydrogen and transporting compressed hydrogen via pipeline. Chemical carriers tend to involve higher costs and environmental impacts, largely due to the additional energy and materials (e.g., extra solar panels) required in hydrogen conversion steps (i.e., packing and unpacking). While the findings offer valuable insights for policymakers, further research is needed to address the limitations of multi-criteria assessments for emerging hydrogen technologies, particularly the uncertainties associated with the early development stages of processes along the hydrogen value chain. Future research should also focus on extending the scope of sustainability assessments and enhancing model reliability, especially for underrepresented environmental and social impact categories.