Passive films of hafnium and titanium electrodes were implanted with Xe** plus - and Pd** plus -ions. The capacity of the insulating HfO//2-film increases due to an increase of the dielectric constant D, but the capacity remains independent of potential. The rate of electron transfer reactions is enhanced. Implantation of Pd** plus is more effective than that of Xe** plus . The anodic photocurrent at HfO//2 is increased by implantation and the spectrum is shifted to lower energies. These measurements demonstrate that the implantation of foreign metal ions yields the expected enhancement of electron transfer reactions, but the lattice perturbations caused by the implantation have a similar and sometimes even stronger influence on the electrochemical behaviour. (Author abstract. )