Autocatalytic and Cooperatively Stabilized Dissociation of Water on a Stepped Platinum Surface

Water–metal interfaces are ubiquitous and play
a key role
in many chemical processes, from catalysis to corrosion. Whereas water
adlayers on atomically flat transition metal surfaces have been investigated
in depth, little is known about the chemistry of water on stepped
surfaces, commonly occurring in realistic situations. Using first-principles
simulations, we study the adsorption of water on a stepped platinum
surface. We find that water adsorbs preferentially at the step edge,
forming linear clusters or chains, stabilized by the cooperative effect
of chemical bonds with the substrate and hydrogen bonds. In contrast
with their behavior on flat Pt, at steps water molecules dissociate,
forming mixed hydroxyl/water structures, through an autocatalytic
mechanism promoted by H-bonding. Nuclear quantum effects contribute
to stabilize partially dissociated cluster and chains. Together with
the recently demonstrated behavior of water chains adsorbed on stepped
Pt surfaces to transfer protons via thermally activated hopping, these
findings make these systems viable candidates for proton wires.