Phosphate Triggers Spontaneous Delamination at the Graphene-ITO Interface

Graphene/metal oxide heterointerfaces are widely used in electrochemical and optoelectronic devices, yet their stability in electrolyte environments remains poorly understood. Here, we show that phosphate is not a passive background species at the graphene-ITO interface. Low-angle rotational interferometric scattering microscopy directly visualizes spontaneous delamination of graphene from ITO in acidic phosphate electrolytes, whereas chloride, sulfate, and nitrate do not induce comparable behavior. The delamination kinetics depend strongly on phosphate concentration and pH and are quantitatively described by a modified extended-area model with Poisson correction. Spectroscopy, contact angle, ion-dissolution, and density functional theory analyses support a mechanism in which phosphate associates with surface In sites, promotes selective indium dissolution, and weakens graphene-ITO adhesion. These results identify an anion-specific interfacial failure pathway in a graphene/oxide heterointerface.