Hydrogen

As hydrogen mobility gains increasing importance, the number of hydrogen refueling stations (HRSs) worldwide is expanding rapidly. Hydrogen compression is a critical component of every HRS, exerting a direct and decisive influence on operability, performance, economic viability, downtime, safety, and public acceptance. Given this central role, this work presents a comprehensive overview of the hydrogen compression landscape, critically examining both conventional mechanical systems—such as piston and diaphragm compressors—and emerging non-mechanical technologies, including electrochemical and metal hydride compressors. The analysis also addresses novel hybrid approaches that combine methods to exploit their respective strengths. Each technology is assessed against a consistent set of practical criteria, encompassing not only fundamental performance metrics such as maximum discharge pressure and flow capacity but also key considerations relevant to real-world deployment. This review provides a detailed comparison of all hydrogen compression technologies with respect to energy efficiency, maintenance needs and intervals, capital expenditures (CAPEX), operating expenditures (OPEX), and Technology Readiness Level (TRL). Additional factors—including physical size, noise levels, and effects on hydrogen purity—are also evaluated, as they strongly influence the suitability for applications in urban or remote areas. By synthesizing recent scientific literature, industry data, and applicable technical standards, this work develops a structured multi-criteria framework that translates technical insights into practical guidance and a clear technology selection roadmap. The overarching objective is to equip engineers, station developers, operators, and policymakers with the knowledge needed to make informed and optimized decisions about hydrogen compression during HRS planning and design.

Proton Exchange Membrane Fuel Cells (PEMFCs) are highly valued for their zero emissions, low noise, and environmentally friendly characteristics. However, they face substantial difficulties when starting up in low-temperature conditions. Coolant-assisted heating is usually more effective than other methods because of its fast speed, high heat transfer efficiency, and simple structure. This study developed a three-dimensional multiphase non-isothermal PEMFC cold start model with coolant-assisted heating. Key parameters, including heat consumption rate, coolant flow rate, load current slope, initial membrane water content, catalyst layer porosity, and gas diffusion layer porosity, were selected as optimization variables. A Convolutional Neural Network–Attention Mechanism–Bidirectional Long Short-Term Memory Neural Network (CAB-Net) was employed as a surrogate model to predict the ice volume fraction during the cold start process. The CAB-Net model was further integrated with the Lexicographic Ordered Whale Optimization Algorithm (LO-WOA) to identify the optimal combination of parameters. The optimization aimed to minimize the maximum ice volume fraction (MIVF) in the Cathode Catalyst Layer (CCL) and reduce the energy consumption required to reach this fraction. The optimization results revealed that, compared to the baseline model (MIVF = 0.4519, energy consumption = 0.77264 J), the MIVF was reduced to 0.1471, representing a 67.45% decrease, while energy consumption was reduced to 0.70299 J, achieving a 9.01% decrease. The results underscore the efficacy of the proposed strategy in enhancing cold start performance under low-temperature conditions.

Hydrogen is a key energy carrier for achieving carbon neutrality, yet its widespread deployment is hindered by challenges associated with efficient hydrogen production, safe and reversible hydrogen storage, and hydrogen-induced embrittlement. Severe plastic deformation processes, particularly high-pressure torsion (HPT), have emerged as a powerful approach capable of addressing these challenges through extreme grain refinement, defect engineering, phase stabilization far from equilibrium, and synthesis of novel materials. This article reviews the impact of HPT on hydrogen-related materials, covering hydrogen production, hydrogen storage, and hydrogen embrittlement resistance. For hydrogen production, HPT enables the synthesis of nanostructured, defect-rich, and compositionally complex compounds, including high-entropy oxides and oxynitrides, which exhibit enhanced hydrolytic, electrocatalytic, photocatalytic, photoelectrocatalytic, and photoreforming performance. For hydrogen storage, HPT fundamentally modifies hydrogenation activation and kinetics, and modifies thermodynamics by hydrogen binding energy engineering, enabling reversible hydrogen storage at room temperature in systems such as Mg-based and high-entropy alloys. For hydrogen embrittlement resistance, HPT under optimized conditions suppresses hydrogen-assisted fracture by engineering ultrafine grains and defects (vacancies, dislocations, Lomer–Cottrell locks, D-Frank partial dislocations, stacking faults, twins, and grain boundaries) that control hydrogen diffusion, trapping, and strain localization. By integrating insights across these three domains, this article highlights HPT as a transformative strategy for developing next-generation hydrogen materials and identifies key opportunities for future research at the intersection of severe plastic deformation and hydrogen technologies.