In the hydrogen energy industry, penetration of hydrogen into storage and transportation materials is a big problem because the process causes cracks, equipment damage, hydrogen leakage, failure, and even explosion. Hydrogen permeation barriers are, thus, necessary to improve the hydrogen resistance of materials and new coating materials and fabrication techniques are being explored. In this review, recent progress in the research of hydrogen permeation barriers is reviewed in terms of both the materials and preparation technology. The current research progress is first discussed based on traditional barriers such as metals and ceramics. Recent development of two-dimensional materials and composite coatings is described and the hydrogen resistance mechanism is discussed. The advantages and limitations of six common preparation methods: physical vapor deposition, chemical vapor deposition, solgel method, plasma spraying, electrochemical deposition, and plasma electrolytic oxidation are compared. Novel composite coatings with “hydrogen storage and barrier” structures are attractive and constitute one of the future research directions.

MXenes are a new class of two-dimensional (2D) materials with promising applications in many fields because of their layered structure and unique performance. In particular, the physical barrier properties of two-dimensional nanosheets make them suitable as barriers against hydrogen. Herein, MXene coatings were prepared on pipe steel by a simple spin-coating process with a colloidal suspension. The hydrogen resistance was evaluated by electrochemical hydrogen permeation tests and slow strain rate tests, and the corrosion resistance was assessed by potentiodynamic polarization. The results reveal that MXene coatings offer excellent hydrogen resistance and corrosion protection by forming a barrier against diffusion. Experimentally, the hydrogen permeability of the MXene coating is one third of the substrate, and the diffusion coefficient decreases as well. The mechanistic study indicates that the hydrogen resistance of the MXene coatings is affected by the number of spin-coated layers, while the concentration of the d-MXene colloidal suspension determines the thickness of a single coating. However, damage to the sample surface caused by the colloidal suspension that contains H⁺ and F⁻ may limit the improvement of the hydrogen resistance. This paper reveals a new application of 2D MXene materials as a novel efficient barrier against hydrogen permeation and the subsequent alleviation of hydrogen embrittlement in the steel substrate.