  The basal plane of graphene can function as a selective barrier that is
permeable to protons but impermeable to all ions and gases, stimulating its use
in applications such as membranes, catalysis and isotope separation. Protons
can chemically adsorb on graphene and hydrogenate it, inducing a
conductor-insulator transition that has been explored intensively in graphene
electronic devices. However, both processes face energy barriers and various
strategies have been proposed to accelerate proton transport, for example by
introducing vacancies, incorporating catalytic metals or chemically
functionalizing the lattice. However, these techniques can compromise other
properties, such as ion selectivity or mechanical stability. Here we show that
independent control of the electric field, E, at around 1 V nm-1, and
charge-carrier density, n, at around 1 x 10^14 cm-2, in double-gated graphene
allows the decoupling of proton transport from lattice hydrogenation and can
thereby accelerate proton transport such that it approaches the limiting
electrolyte current for our devices. Proton transport and hydrogenation can be
driven selectively with precision and robustness, enabling proton-based logic
and memory graphene devices that have on-off ratios spanning orders of
magnitude. Our results show that field effects can accelerate and decouple
electrochemical processes in double-gated 2D crystals and demonstrate the
possibility of mapping such processes as a function of E and n, which is a new
technique for the study of 2D electrode-electrolyte interfaces.
