Graphene-coated nickel in biological environments: role of structural defects

Graphene (Gr) is a promising material for addressing microbially induced corrosion (MIC) issues that cause staggering economic losses, estimated at nearly $55 billion annually in the US alone. However, structural defects including edges, grain boundaries, and cracks can compromise its performance in aggressive biological environments. Owing to the technological relevance of nickel (Ni), its key roles in biological mechanisms, and the strong hybridization of d-electrons of Ni with Gr π-orbitals, we explore the effects of the key defects in Gr/Ni exposed to archetype sulfate-reducing bacteria (SRB). Electrochemical and spectroscopy tests revealed that the grain boundaries play a stronger role than cracks. The edges and grain boundaries in as-grown Gr on Ni (dGr/Ni) aggravated corrosion by two-fold, while the cracks in the transferred counterpart that lacked these defects improved corrosion resistance by 2-fold. A combination of biotic and abiotic studies corroborated the unique roles of grain boundaries as sulfur reservoirs to promote the attachment of sessile SRB cells and subsequent redox reactions. Analysis of distinct biogenic products confirmed the role of grain boundaries on pitting corrosion. These insights can guide the rational design of graphene coatings specifically for biological environments prone to MIC.