Helping Thy Neighbor: How Cobalt Doping Alters the Electrocatalytic Properties of Hematite

We
present analysis of the indirect role of Co doping on the electrocatalytic
activity of α-Fe2O3. Upon substitution
of one of the Fe atoms in the hematite surface, we observed a promoting
effect of the substitution, upon which the overpotential required
for the water-splitting reaction decreased in all substitution sites
investigated. The cobalt site itself, however, does not exhibit the
improved properties with respect to the undoped hematite. The promoting
effect results purely from the altering of the properties of the nearest
Fe atoms in the hematite surface. We conclude that the overpotential
is reduced upon formation of the structure resembling the O2 molecule strongly interacting with the surface between the Co and
Fe sites, and this is consistent with the catalytic activity of the
surface vacancies of the hematite.