Hydrogen

Hydrogen Fuel Cell Electric Buses (FCEBs) are a promising solution for decarbonizing public transport. Their operational feasibility in developing countries depends on hydrogen-supply costs and infrastructure readiness. The Ministry of Energy has reported a 400% increase in imported natural-gas costs due to current geopolitical tensions between the United States and Iran, exposing the strategic vulnerability of relying on imported diesel for public transport. This study assesses the operational hydrogen demand, fuel-cost implications, and avoided diesel tailpipe carbon dioxide (CO₂) emissions associated with gradually integrating FCEBs into Jordan’s Bus Rapid Transit (BRT) project. The baseline system consists of 64 diesel buses covering about 11 million kilometers annually, consuming around 3 million liters of diesel and emitting roughly 8108.3 tons of CO₂. Fleet transition scenarios are assessed for 2030, 2035, and 2040, with FCEB-integration ratios of 10%, 15%, and 25%. Under the reference assumption of equivalent-duty replacement, avoided diesel tailpipe CO₂ emissions increase with the diesel service displaced by FCEBs, reaching 25.7% at the highest penetration level. At the $6/kg reference hydrogen-price input, FCEB integration results in higher operational fuel costs than diesel-only operation. Under the constant diesel-price reference, mixed-fleet operation becomes cost-competitive at hydrogen prices of $1/kg and $2/kg, with operational fuel-cost savings of up to 16.97%. Within the operational fuel-cost boundary of this study, mixed-fleet competitiveness is influenced by both the assumed hydrogen fuel price and diesel-price trajectory. The results support gradual deployment, subject to the greenhouse-gas intensity of the hydrogen-production and delivery pathway and the readiness of hydrogen supply and depot infrastructure. Full article

Hydrogen has attracted growing interest across the Association of Southeast Asian Nations (ASEAN) region in recent years, driven by net-zero commitments and national decarbonisation strategies. This study explores the evolving role of hydrogen in the ASEAN energy landscape and its potential to support a just and inclusive transition towards sustainable energy systems. Employing an exploratory research approach, this study integrates two complementary transition management frameworks—Multi-Level Perspective (MLP) and Strategic Niche Management (SNM)—to analyse the dynamics of energy transitions across niche, regime, and landscape levels. The integration of these frameworks supports our understanding of how transitions unfold within complex socio-technical systems. The analysis draws on government documents, the academic literature, and the grey literature on evolving hydrogen development projects across ASEAN. The findings indicate that climate commitments and global hydrogen narratives are placing increasing pressure on fossil-fuel-dominated energy regimes across ASEAN. While hydrogen development remains uneven across the region, several countries have made measurable progress through policy development, pilot projects, and international partnerships. This research contributes to the literature by combining MLP and SNM to provide a multi-level understanding of hydrogen transitions in ASEAN and highlights the importance of nurturing niche innovations to enable long-term systemic transformation. Full article

Hydrogen sampling is an essential part of ensuring reliable and accurate hydrogen fuel quality for expanding heavy-duty vehicle applications. Hydrogen sampling at refuelling stations is highly sensitive to operational conditions, especially temperature, pressure, storage homogeneity, and nozzle-purging procedures. The direct sampling method operates with a hydrogen fuelling station in maintenance mode and requires that parameters be set properly. This study investigated the impact of temperature, pressure, storage bank selection, and venting on hydrogen sample quality. This study shows that hydrogen sampling at refuelling stations is strongly influenced by operational parameters, with temperature and pressure mainly affecting the water content while other contaminants remain largely stable; storage bank composition and insufficient nozzle purging can also significantly bias results through contamination or non-representative sampling. To ensure reliable measurements, this study recommends conducting sampling under representative operational conditions, including matching the delivery temperature and nominal delivery pressure, verifying storage homogeneity, and applying adequate nozzle-purging procedures. However, further validation across different systems is still needed. Full article

Against the background of the “dual carbon” goals and the integration of a high proportion of renewable energy, hydrogen energy storage, with its advantages of long duration and large scale storage as well as clean energy conversion, has become an important approach to improving the flexibility and security of energy systems. To address the accident risks associated with leakage from high pressure hydrogen storage in stationary hydrogen energy storage facilities, this study takes an integrated hydrogen energy storage station involving hydrogen production, storage, compression, and utilization as the research object. A numerical model for hydrogen leakage and dispersion from high-pressure storage cylinders in an open environment is established to investigate the effects of leakage aperture, natural ventilation, mechanical ventilation, and emergency shutdown on hydrogen cloud evolution and deflagration risk. The results show that an increase in leakage diameter significantly increases the flammable hydrogen volume and Q9 peak value. Large-scale leakage is prone to local accumulation under the influence of blast walls and obstacles, resulting in a 780 m³ combustible volume and 14.7 m³ Q9; medium-scale leakage has a longer duration, whereas small-scale leakage presents the lowest risk. Under natural wind conditions, crosswind provides better dilution, reducing Q9 by 53%. Mechanical ventilation can effectively reduce the value of Q9 by 36%, with ventilation layout exerting a more significant influence than wind speed. The combined use of mechanical ventilation and emergency shutdown can further reduce the 42% flammable volume and shorten the duration of high concentration hydrogen clouds. The findings can provide guidance for the safety layout, ventilation design, and emergency protection of hydrogen energy storage stations. Unlike conventional CFD-based leakage consequence analyses, this study couples hydrogen dispersion simulation with Q9-based deflagration risk assessment and a hierarchical safety strategy involving natural, mechanical ventilation, and emergency shutdown. Full article

Associated gas in the Permian Basin is a methane-rich but spatially fragmented and intermittently available feedstock. Methane pyrolysis can convert hydrocarbons to hydrogen and solid carbon without forming process CO₂ in the reactor, but its practical value depends on the captured-gas capacity factor, feed composition, high-temperature heat supply, product purification, continuous carbon withdrawal, carbon offtake, and transparent greenhouse-gas accounting. This study presents an implemented screening model for a modular 1 million standard cubic feet per day (MMSCFD) Permian associated-gas unit. A representative Permian composition is evaluated with hydrocarbon cracking stoichiometry, catalytic and thermal conversion envelopes, a net hydrogen recovery assumption, an energy-duty allocation, a levelized-cost model, and a well-to-gate carbon-intensity model. The catalytic base case produces 3.78 t/d of saleable H₂ after 90% pressure-swing adsorption (PSA) recovery and 14.27 t/d of solid carbon; the thermal near-complete conversion bound produces 4.31 t/d of saleable H₂ and 16.15 t/d of solid carbon. At a 0.85 capacity factor, $10 million installed capital expenditure (CAPEX), 8% real discount rate, 20-year life, 10 kWh per kg H₂ energy intensity, and $0.06 per kWh electricity, the deterministic plant-gate levelized cost of hydrogen (LCOH) is $1.81 per kg H₂ at zero carbon value and $1.05 per kg H₂ at a net realized carbon value of $0.20 per kg C. Monte Carlo analysis over capacity factor, CAPEX, energy intensity, electricity price, carbon value, feed/capture cost, and yield uncertainty gives levelized cost of hydrogen values at the 10th, 50th, and 90th percentiles (P10/P50/P90) of $1.32/$1.91/$2.57 per kg H₂. The corresponding screening carbon-intensity distribution is 2.34/4.11/5.89 kg carbon dioxide equivalent (CO₂e) per kg H₂, dominated by electricity carbon intensity and upstream methane loss. Geothermal or waste-heat preheat is treated quantitatively as a partial offset to low- and mid-temperature duties, not as a replacement for high-grade 900–1200 °C trim heat. The pathway is benchmarked against steam methane reforming, autothermal reforming with carbon capture and storage, electrolysis, small-scale liquefied natural gas, and gas-to-liquids conversion. Reported LCOH values are plant-gate production costs; separate hydrogen-logistics and negative-carbon-value stress tests identify conditions under which remote delivery or carbon disposal can erode the apparent economic advantage. Full article

Hydrogen is increasingly recognised as one of the leading pathways for decarbonising the maritime sector. Proton exchange membrane fuel cell (PEMFC) hybrid propulsion is emerging as a promising low-emission technology; however, its safe deployment depends on marine engineers being trained to interpret and manage coupled hydrogen, fuel cell, battery, and electric propulsion systems. However, a critical training gap remains. Alternative fuel guidance identifies hazards and safety barriers, but does not consistently translate hydrogen PEMFC–LFP operation into observable competence assessment evidence and implementation pathways. This paper develops a demonstrator-anchored and regulatory-grounded competency framework for marine engineers operating compressed hydrogen PEMFC-lithium iron phosphate (LFP) battery–electric propulsion systems. A structured purposive narrative synthesis combined prototype vessel testing evidence with regulatory safety training, and competency framework literature. The experimental operational data, including compressed hydrogen supply, pressure regulation, PEMFC charging, battery buffering, propulsion current demand, voltage sag, state-of-charge response, monitoring tasks, alarms, and emergency isolation, were used as operational anchors rather than calibrated performance validation evidence. The analysis identified six competency domains. Compared with IGF/LNG model course training, the largest hydrogen-specific competence gaps concerned compressed hydrogen handling, PEMFC purge and shutdown logic, battery-buffered propulsion monitoring, integrated emergency shutdown, and communication during abnormal operation. These findings were translated into assessable learning outcomes, a provisional 40 h training module, instructor prerequisites, practical assessment evidence, a proposed digital twin/VR supplement, and a staged implementation roadmap. The proposed framework provides a structured pilot pathway. It translates operational testing evidence into assessable maritime education and training. It also establishes a foundation for future competency development and certification for commercial vessels. Full article

Strong policy momentum is supporting the adoption of hydrogen as a major energy carrier for a decarbonised global economy, especially for reducing emissions in hard-to-abate industrial sectors. Although achieving large-scale hydrogen deployment will require substantial long-term investment in dedicated infrastructure, blending hydrogen with conventional hydrocarbon fuels provides a practical near-term pathway to accelerate uptake by leveraging existing systems and fuel-supply networks. To inform future research and development in this field, this review summarises experimental and numerical findings on the combustion behaviour of hydrogen–hydrocarbon mixtures and highlights the main challenges and research gaps that must be addressed to ensure the safe and efficient use of hydrogen-enriched fuels in current combustion systems. It also examines the fundamental combustion characteristics of hydrogen and hydrogen-enriched fuels, the effects of hydrogen addition to gaseous, liquid, and solid fuels on combustion performance and emissions, and the contrasting policy approaches shaping hydrogen uptake across major global economies. Full article

We used Clifford algebra $C{l}_{2,0}$ to find the 2D orbit of a hydrogen electron under a Coulomb force and a perturbing circularly polarized electric field of light at angular frequency $\omega$, which is turned on at time $t=0$ via a unit step switch. Using a coordinate system co-rotating with the electron’s unperturbed circular orbit at angular frequency ${\omega }_0$, we derived a complex differential equation that is similar to but different from that of the Lorentz oscillator equation for light–atom interaction. We solved the homogeneous and particular differential equation and showed that the position of the electron is a linear combination of five exponential Fourier terms or orbital wave functions with frequencies 0, ${\omega }_0$, $2{\omega }_0$, $(2{\omega }_0-\omega )$, and $\omega$, whose coefficients depend on the light-to-atom frequency ratio $\omega /{\omega }_0$ and light-to-atom force magnitude ratio $A/r_0$. We showed that the electron orbits are approximately Keplerian at light-to-atom frequency ratio $\alpha =\omega /{\omega }_0=\{0,1,2\}$, with the orbits becoming discontinuous and divergent as $\alpha \to 1^{\pm }$, but continuous and non-divergent at $\alpha =\{0,2\}$. These Keplerian orbits are approximated by the sum of the zeroth, first, and second harmonics of the electron’s unperturbed orbital wave function ${\widehat{\psi }}_0=e^{\widehat{\mathsf{ı}}{\omega }_{0}t}$, corresponding to the eccentric, deferent, and epicycle in the Copernican construction of planetary orbits. Full article

This paper evaluates the potential for green hydrogen production in Tunisia using nearly 3 GW of renewable electricity distributed across four strategically selected sites: Haouaria, Zriba, Sbikha, and Feriana. These locations were chosen for their proximity to the Trans-Mediterranean (TransMed) natural gas pipeline linking Algeria to Italy, as well as their strong but underexploited solar and wind energy resources. Each site was optimized according to land availability and renewable energy potential: Haouaria is wind-dominant, Zriba employs a hybrid solar-wind configuration, Sbikha focuses on solar, and Feriana integrates both solar and wind over a large area. The analysis reveals a total green hydrogen production capacity supported by approximately 3.1 GW of installed renewable power, with a base-case LCOH ranging from $1.21 to $2.05 per kilogram. El Haouaria emerges as the most cost-effective site due to its highly favorable wind conditions, while the sensitivity analysis shows that LCOH can reach up to approximately $3.8 per kilogram under higher CAPEX assumptions. The findings underscore the viability of a multi-site development strategy and highlight northern Tunisia’s comparative advantage for low-cost green hydrogen production, thanks to its superior resource mix, existing infrastructure, and better water availability relative to Tunisia’s southern regions. Full article

This review examines hydrogen-assisted fatigue crack growth rate (HA-FCGR) in pipeline steels with a focus on implications for integrity assessment of hydrogen transport systems. Existing natural gas pipelines offer a cost-effective pathway for hydrogen transmission; however, hydrogen embrittlement (HE) significantly alters fatigue behavior. This paper integrates scientometric analysis with a systematic review to evaluate the influence of material microstructure, welds, loading conditions, hydrogen pressure, and environmental variables on fatigue crack growth rates (FCGR). The synthesis confirms that HA-FCGR is most pronounced in the Paris region and is strongly governed by hydrogen pressure and loading frequency, while the role of material strength is less definitive than traditionally assumed. Recent advances in machine learning demonstrate strong predictive capability for FCGR; however, their integration into risk-based inspection and pipeline integrity frameworks remains limited. To bridge the gap between laboratory-scale understanding and field implementation, the concept of a near-real-world hydrogen pipeline testbed is introduced, enabling synchronized measurement of pressure cycling, material degradation, and system-level response. The review identifies critical research needs, including weld-focused fatigue datasets, realistic pressure-cycle validation, uncertainty-aware modeling, and integration of physics-based and data-driven approaches for decision-making. These findings provide a pathway toward reliable and scalable integrity assessment for hydrogen transport in existing pipeline infrastructure. Full article

To supply hydrogen to the geographically decoupled demand sites, efficient hydrogen transport is necessary. The existing natural gas pipelines represent a promising transport solution, with the blended hydrogen content expected to steadily increase. An open issue of hydrogen blending is the mixing behavior. Therefore, the effects of different geometric parameters (diameters, angles), operating conditions (velocities, concentrations), and injection layouts (single- and multi-point) on the mixture quality during direct injection of hydrogen into a natural gas pipeline are studied using 3D CFD. The main goal is to find parameters and layouts leading to sufficient mixing quality over a range of operating conditions. The mixing quality is determined based on the coefficient of variation (COV). The results show that the momentum flux ratio is a key parameter governing the mixing behavior. However, a high momentum flux ratio alone does not guarantee sufficient uniformity for all operating conditions. For the investigated range, single-point injection cannot ensure reliable mixing quality, whereas multi-point layouts with higher hydrogen inlet velocities achieve sufficient uniformity. Full article

With the growing energy demand and concerns about environmental impacts, green hydrogen has become one of the main alternatives for a clean and reliable energy future. Brazil presents itself as one of the main potential suppliers of this renewable fuel, considering its resource abundance, such as solar irradiation. Therefore, the present study aims to evaluate in detail the hydrogen production potential of one of Brazil’s main states when it comes to solar power potential, Minas Gerais. The potential for each of the 853 municipalities of the region was assessed individually using three different methodologies, indicating that the state could produce 2365.2 TWh of electricity or 47.3 Mt_H2/year (with a maximum variation of 3.4% between the methodologies), nearly five times the EU’s projected 2030 hydrogen import demand. This estimation, however, was significantly reduced when only areas with a slope lower than 8% were considered, decreasing land availability by 40% and cutting hydrogen potential by 18.8 Mt/year. On the other hand, increasing power density from 4 to 15 MWh/km² almost tripled hydrogen production potential, while electrolyzer efficiency also presented a positive effect on hydrogen output. Finally, the comparison of hydrogen potential with Human Development Index (HDI) data indicates that the most productive mesoregions often coincide with lower human development levels, particularly in the “Norte de Minas” and “Jequitinhonha” mesoregions, highlighting the opportunity to align energy transition with regional development goals. Therefore, targeted investments in these regions could generate jobs, boost income, and reduce inequalities, reinforcing green hydrogen as both an environmental and social driver. Full article

Industries seeking to reduce carbon emissions are considering hydrogen as an alternative fuel or reductive reagent. However, the addition of hydrogen into new and existing infrastructure has triggered concerns for materials compatibility, forming a significant barrier to its implementation. Hydrogen is known to damage and embrittle metals, and despite growing efforts to generate compatibility data for structural materials under hydrogen environments, there is no consensus on how hydrogen degrades such material. This is due to the complex mechanisms in which hydrogen interacts with metals but more so the lack of standardised testing methods. Electrochemical methods are being used increasingly to generate hydrogen materials compatibility data. However, for industries to use electrochemical methods the conditions must be representative of those of gaseous hydrogen environments. Currently, when comparing mechanical properties by samples produced under gaseous and electrochemical environments, results show inconstancies in the mechanical properties produced and reliability issues. In this work, methods of electrochemical hydrogenation are reviewed in comparison to those under gaseous environments. Differences in the charging fugacity, surface effects and damage mechanisms are assessed between gaseous and electrochemical charging that may contribute to the disparities seen in the literature. Based on this comparative assessment, we identify key knowledge gaps and provide an approach for future research to address existing uncertainties. Full article

Green hydrogen—hydrogen produced from renewable electricity—is central to global decarbonization strategies. However, despite their fragile governance, damaged infrastructure, water scarcity, and limited investment security, conflict-affected developing economies remain largely absent from hydrogen research. This study addresses that gap by developing and validating a multi-evidence strategic framework for green-hydrogen (GH₂) adoption in fragile institutional environments, using Palestine as a challenging test case. Methodologically speaking, the framework integrates four evidence streams—barrier prioritization by 45 Palestinian experts using the Analytic Hierarchy Process (AHP); structural modeling of barrier–adoption–sustainability relationships using partial least squares structural equation modeling (PLS-SEM); strategic-pathway ranking using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS); and an original Sustainable Development Goal (SDG) Contribution Index—externally validated by an independent panel of 120 energy experts across 18 Middle East and North Africa (MENA) countries. Three findings stand out. Firstly, expert perception and structural evidence diverge: technical barriers receive the highest expert weight (56.2%) yet show the weakest structural effect on adoption (β = −0.230), whereas social barriers, weighted lowest by experts (4.8%), rank second in predictive power (β = −0.310). Secondly, Small-Scale Community Production is the most robust deployment pathway, ranked first under every weighting scenario tested. Thirdly, government policy quality acts as a governance multiplier, raising the sustainability returns of adoption by 20.2%, with benefits concentrated in SDGs 7, 13, 8, and 9. Practically speaking, the framework yields seven strategic goals and a phased 2026–2040 roadmap for fragile developing economies. Full article

The growing demand for sustainable energy carriers has intensified interest in hydrogen production from renewable resources and waste-derived substrates. In this context, microbial electrolysis cells (MECs) have emerged as a promising technology for the simultaneous treatment of organic waste and biohydrogen generation. This review provides an overview of recent advances in MEC systems, focusing on reactor configurations, performance indicators such as hydrogen production rate, coulombic efficiency, and chemical oxygen demand removal. Attention is given to the valorization of real waste streams, including municipal and agro-industrial effluents, highlighting the differences between laboratory- and pilot-scale applications. While numerous studies have demonstrated the technical feasibility of MECs, several bottlenecks still limit their large-scale implementation, including challenges associated with the use of complex substrates. In particular, untreated wastewater often leads to reduced process efficiency due to its variable composition and the occurrence of competing microbial pathways. To overcome these limitations, integrated approaches are also discussed, with emphasis on the coupling of dark fermentation, capable of enhancing substrate biodegradability through the production of volatile fatty acids, with MEC systems. Overall, MEC technology represents a promising pathway for sustainable hydrogen production within circular waste management frameworks, although further advancements are required to enable its practical application. Full article

To improve the sluggish low-temperature hydrogen storage kinetics of RE-Mg-based alloys, Bi₂O₃ is introduced into CeMg₁₁Ni as a functional dopant for microstructural regulation, and CeMg₁₁Ni + x wt.% Bi₂O₃ (x = 0, 3, 5, 7, 10) composites are fabricated through planetary ball milling. Multiple characterization methods including XRD, SEM and TEM were used to explore the effects of Bi₂O₃ on the microstructure and hydrogen storage properties. Bi₂O₃ maintains stable phase during cycling and does not participate in reversible hydrogen storage reactions. It cooperates with in situ formed CeH₂ nanocrystals to construct high-density interfacial defects. The 5 wt.% Bi₂O₃-doped alloy exhibits the optimal balance between exposed catalytic sites and open hydrogen diffusion channels, achieving complete dehydrogenation within 144 s at 633 K, a reduced dehydrogenation activation energy of 63.89 kJ mol⁻¹, and an 84.7% hydrogen absorption ratio within 5 min at 423 K. Bi₂O₃ has a weak effect on the thermodynamic properties of the alloy, with only a slight enthalpy change of less than 1 kJ/mol within the experimental error range. Bi₂O₃ enhances hydrogen storage reactions through a synergistic “active sites–diffusion channels” mechanism, in which oxygen vacancies promote H₂ dissociation and heterogeneous interfaces facilitate hydrogen diffusion, thereby reducing the reaction energy barrier. Full article

Fuel cell electric vehicles (FCEVs) require specific hydrogen purity, as even trace contaminants can degrade proton exchange membrane fuel cells (PEMFCs). While hydrogen quality is monitored along the supply chain according to international standards, potential contamination from in-vehicle materials, such as lubricants and greases, remains largely unexplored. Here, we present a staged testing framework consisting of (i) a rapid pre-screening for formulation stability and (ii) a full qualification pathway to assess lubricant-derived contamination under realistic refueling conditions. Candidate lubricants were exposed to hydrogen in a 700 bar Type IV vessel following an SAE J2601 refueling procedure. Contamination risks were evaluated by optical inspection, particulate matter, and gas analysis, monitoring contaminants specified in ISO 14687:2025 Grade D. The applicability of the framework was demonstrated in practical scenarios. In the pre-screening pathway, a silicone-based formulation fulfilled the 24 h acceptance criteria for formulation stability and was classified as potentially suitable for high-pressure hydrogen tank applications. In contrast, two other lubricants based on silicone and mineral oil exhibited visible changes associated with increased risk of particulate matter release, resulting in a classification of unsuitable. In the full qualification pathway, the fluorinated DuPont^TM MOLYKOTE^® HP-300 Grease was evaluated over 23 days and showed no release of harmful contaminants into the hydrogen gas, leading to the classification of suitable. Collectively, the presented protocols provide a structured basis for screening and qualifying lubricants for high-pressure hydrogen tanks in PEMFC applications, supporting future standardization in hydrogen technologies. Full article

The development of hydrogen fueling processes is an essential infrastructure component needed for the adoption of hydrogen-fueled vehicles as a transportation technology. This study provides techno-economic analysis (TEA) for two hydrogen fueling pathways (Case A, Case B), one of which (Case A) does not employ hydrogen liquefaction, while the other one (Case B) does. Both cases consider the same conditions as one another, of gaseous hydrogen inlet availability and gaseous hydrogen outlet dispensing. The TEA analysis carried out is based on data supported from the literature and process flowsheet UNISIM^® software simulations. The obtained TEA results indicate that the levelized cost of hydrogen (LCOH) of the gaseous hydrogen Case A is USD 4.20/kg H₂, which is lower than the LCOH of the liquefied hydrogen Case B, which is USD 10.14/kg H₂. Given the energy equivalence of a gallon of gasoline to kg H₂, and the higher efficiencies of hydrogen fuel cell vehicles over gasoline vehicles, the above conditions suggest that Case B fueling (with hydrogen liquefaction) involves high energy consumption and may delay the growth of hydrogen-fuel-based transportation technology, while Case A fueling (no hydrogen liquefaction) will likely become preferrable over both Case B hydrogen fueling and gasoline fueling, thus accelerating the growth of hydrogen-fuel-based transportation technology. Full article

The pearlitic microstructure, comprising alternating lamellae of ferrite and cementite, provides a favorable combination of strength, toughness, and wear resistance. Consequently, pearlitic steels have been widely utilized in pipeline systems due to their advantageous mechanical properties and cost-effectiveness. These characteristics also render pearlitic steel pipelines promising candidates for hydrogen transport infrastructure, particularly in the context of repurposing existing natural gas networks. However, interactions between hydrogen and the pearlitic microstructure raise significant concerns regarding hydrogen embrittlement, a phenomenon that can substantially degrade mechanical performance and compromise long-term structural integrity. Experimental observations indicate that pearlitic microstructures are particularly susceptible to hydrogen embrittlement, largely due to the high density of ferrite–cementite interfaces, which act as effective hydrogen trapping sites. These detrimental effects motivate the present study, which aims to develop a deeper understanding of nanoscale mechanisms of hydrogen-assisted crack initiation and propagation in pearlitic microstructures. In this work, molecular dynamics simulations are employed to investigate the initiation and propagation of hydrogen-affected cracks in pearlitic microstructures, considering lamellar orientations both parallel and perpendicular to the applied tensile loading direction. The analysis focuses on the synergistic interaction between hydrogen-enhanced decohesion (HEDE), which promotes interfacial separation due to hydrogen segregation, and hydrogen-enhanced localized plasticity (HELP). Full article