Structural transitions at the bilayer graphene-methanol interface from ab initio molecular dynamics.

The precise tailoring of the atomic architecture of 2D carbon-based materials, which results in the modulation of their physical properties, promises to open new pathways for the design of technological devices in electronics, spintronics and energy storage. High-pressure conditions can lead to the synthesis of complex materials starting from multi-layer graphene, often relying on chemical transformations at the interface between carbon and pressure-transmitting media like water or alcohol. Unfortunately, the experimental characterization of molecular-scale mechanisms at interfaces is very challenging. On the other side, the sheer cost of ab initio simulations strongly limited, so far, the computational works in literature to simplified models that, often, do not capture the complexity of the materials and finite-temperature effects. In this work, we provide for the first time an extensive computational study of complex, realistic models of bilayer graphene-methanol interfaces at high pressure and finite temperature. Our simulations allow fundamental insight to be gained on several questions raised from previous experimental works about structural, electronic and reactivity properties of this challenging material. The exploitation of state-of-the-art enhanced sampling techniques combined with topological electronic descriptors allowed characterization of barrier-activated functionalization processes, unveiling a major catalytic effect of carbon defects and pressure towards sp3 formation.