Ferroelectric-substrate coupling modulates hydrovoltaic droplet-induced electrical signals on graphene

Hydrovoltaic electricity generation at graphene-liquid interfaces is sensitive to both the electronic state of graphene and the electrostatic environment at the interface. However, how remanent ferroelectric polarization pre-conditions the electronic state of graphene before droplet contact, and how this state is related to the subsequent electrical response, remains unclear. Here, we use electrically pre-poled LiTaO 3 (LTO) and LiNbO 3 (LNO) ferroelectric substrates to electrostatically pre-condition graphene before liquid contact. Kelvin probe force microscopy reveals clear polarization-dependent shifts in graphene work function. Positive polarization produces a relatively electron-rich state, whereas negative polarization shifts graphene toward a more hole-rich state. Despite these distinct electronic states, the hydrovoltaic response does not follow a universal polarization-dependent voltage ordering across LiTaO 3 and LiNbO 3 , indicating that graphene carrier modulation alone cannot account for the generated response. Transient measurements further reveal strongly polarization- and substrate-dependent changes in the rise and decay time constant, indicating that ferroelectric polarization influences not only the signal magnitude but also transient interfacial charge dynamics. Repeated droplet exposure and subsequent cleaning produce partially reversible changes in the electrical response, while long-term ambient aging substantially reduces the polarization-dependent work-function contrast. Together, these results establish an experimental link between remanent ferroelectric polarization, the pre-contact electronic state of graphene, and the subsequent droplet-induced electrical response. Ferroelectric substrates therefore provide a substrate-side strategy for regulating graphene hydrovoltaic interfaces without continuous external bias or direct chemical doping.