  While metastability enhanced water-oxidation activity was experimentally
reported, the reason behind this effect is still unclear. We determine here,
using density functional theory calculations, oxygen evolution reaction
overpotentials for a variety of defective (001) surfaces of three different
perovskite materials. For all three, we find a large range of overpotentials
for different reaction sites including also overpotentials at the top of the
activity volcano. Assuming that these sites dominate the apparent catalytic
activity, this implies that a large number of geometrically different reaction
sites, as they occur when a catalyst is operated at the border of its stability
conditions, can lead to a strong enhancement of the apparent activity. This
also implies that a pre-treatment of the catalyst creating a variety of
different reactive sites could lead to superior catalytic activities for
thermodynamically stable materials.
