The development of ultrathin barrier films is vital to the advanced semiconductor industry. Graphene appears to hold promise as a protective coating; however, the polycrystalline and defective nature of engineered graphene hinders its practical applications. Here, we investigate the oxidation behavior of graphene-coated Cu foils at intrinsic graphene defects of different origins. Macro-scale information regarding the spatial distribution and oxidation resistance of various graphene defects is readily obtained using optical and electron microscopies after the hot-plate annealing. The controlled oxidation experiments reveal that the degree of structural deficiency is strongly dependent on the origins of the structural defects, the crystallographic orientations of the underlying Cu grains, the growth conditions of graphene, and the kinetics of the graphene growth. The obtained experimental and theoretical results show that oxygen radicals, decomposed from water molecules in ambient air, are effectively inverted at Stone–Wales defects into the graphene/Cu interface with the assistance of facilitators.

Improving the lifetime and the operational stability of polymer electrolyte membrane fuel cells (PEMFCs) is critical for realizing their implementation as a practical and highly-efficient energy conversion system. However, the corrosion of metal bipolar plates, which are a key component in PEMFCs, leads to decreased efficiency and durability. Here, we prepared poly(methyl methacrylate)-derived multilayer graphene (Gr) coatings with high crystallinity and a continuous three-dimensional (3D) structure using a rapid thermal annealing (RTA) system for short periods (≤5 min). The resulting 3D Gr-coated Ni foam is demonstrated to act as a bipolar plate with long-term operating stability. Electrochemical analysis revealed that the synthesized graphene on Ni foam outperforms bare Ni foam and amorphous-carbon-coated Ni foam by providing a two-order-of-magnitude lower corrosion rate in the operating environment for a PEMFC. In addition, after stability tests in a destructive environment, the 3D Gr-coated Ni foam maintained its outstanding interfacial contact resistance of 9.3 mΩ cm² at 10.1 kgf cm⁻². A H₂/air PEMFC fabricated using the Gr-coated Ni foam embedded within the groove of a graphite-based bipolar plate exhibited a substantially enhanced power density of ∼967 mW cm⁻² at a cell potential of 0.5 V with further advantages of weight reduction and no additional machinery process for the gas flow channel. This facile coating approach addresses one of the key limitations of current metal bipolar plates in PEMFCs, and paves the way to further enhance energy conversion systems through interface engineering.