Exploiting extremely low hydrogen permeability films is imperative for mitigating hydrogen damage and failure generated by strong hydrogen diffusion in storage vessels and pipelines. In this contribution, we have designed a simple yet effective strategy to fabricate a high-performance poly(vinyl alcohol) (PVA)-based composite thin film via a scalable spraying method, with the modification agent phytic acid (PA) incorporated to enhance crosslinking density. Various intermolecular interactions between PVA and PA form rigid structures that suppress chain mobility. Consequently, the fractional free volume (FFV) of the composite, as measured by positron annihilation lifetime spectroscopy (PALS), is reduced to merely 0.6509%. This leads to an unprecedented low H₂ gas transmission rate (GTR) of 0.518 cm³ m⁻²·24 h⁻¹·0.1 MPa⁻¹. These mutual interactions and mechanisms have also been corroborated by various simulation approaches and comprehensive experimental characterizations. Furthermore, this low H₂ GTR value exhibits no significant change even after 4 MPa hydrogen environment impact for 16 days, demonstrating high-pressure stability. Combined with a realistic coating process in the pipeline and a high mechanical tensile strength of 78 MPa, this composite thin film possesses tremendous application potential in hydrogen industries.

Addressing the limitations of conventional organic polymer coatings in thermal management, this study developed an eco-friendly micro-3D expanded graphite powder (MEGP) protection coating that integrates exceptional heat conduction and heat radiation. In terms of thermal conductive filler selection, expanded graphite (EG) with a micro 3D structure was selected as the filler framework of the composite coating, and a self-assembled functional filler (MEG) was obtained after modification with an as-prepared corrosion inhibitor of a Schiff base–Ce complex (SP), which formed a 3D conductive network in the coating by electrostatic self-assembly. The unique architecture endowed MEGP with a remarkable thermal conductivity of 2.6 W m⁻¹ K⁻¹, 12-fold higher than that of pure epoxy (common resin for anti-corrosion coatings) and high infrared emissivity (0.95–0.98 at the full spectrum range of 2.5–25 μm), synergistically enhancing heat dissipation through dual conduction and radiation mechanisms. Finite element simulations confirmed superior thermal management performance. Simultaneously, the MEGP coating exhibited robust adhesion (10.4 MPa) and impact resistance (100 cm). Moreover, the impedance modulus of the coating at 0.01 Hz remains above 10⁸ Ohm cm² during 90 d immersion in a 3.5 wt% NaCl solution, benefiting from the Schiff base–Ce complex. The structure–property relationships between the 3D network architecture and multifunctional performance were elucidated by a systematic study. This novel design provides a new method for preparing functional integrated coatings with high thermal conductivity.