  We present a detailed theoretical study which demonstrates that
electrokinetic effects can also play a role in the motion of metallic-insulator
spherical Janus particles. Essential to our analysis is the identification of
the fact that the reaction rates depend on Pt- coating thickness and that the
thickness of coating varies from pole to equator of the coated hemisphere. We
find that their motion is due to a combination of neutral and ionic
diffusiophoretic as well as electrophoretic effects whose interplay can be
changed by varying the ionic properties of the fluid. This has great potential
significance for optimising performance of designed synthetic swimmers.
