  PdCoO$_2$, being highly conductive and anisotropic, is a promising material
for fundamental and technological applications. Recently, reduced PdCoO$_2$
thin films were shown to exhibit ferromagnetism after hydrogen annealing. Here,
we demonstrate that when PdCoO$_2$ film is used as a cathode for dissociation
of water, hydrogen generated around the film reduces the material and leads to
the emergence of anomalous Hall effect (AHE). Moreover, we demonstrate that the
sign of the AHE signal can also be changed with the electrolytic process.
Electrolytically-modified PdCoO$_2$ films may open a door to applications in
spintronics.
