Field-induced oxygen layer formation from H2O and its titration by hydrogen on a Pt-emitter

FEM and FIM studies are presented showing the field-induced formation of an Oads island on the apex of a platinum field emitter. This occurs during the well known bimolecular, field-induced water dissociation reaction 2H2Oads → H3Ogas+ + OHads + e(Pt)− which is followed by a disproportionation reaction of the OHads species to H2O and Oads without any noticeable face specifity. The titration reaction of the Oads layer with H2 displays face specific conversion rates. FIM reveals chemical waves propagating with sharp boundaries on the atomic scale. Implications for the oscillating H2OH2 reaction system are discussed.