  We provide experimental results to show that self-propulsion of Janus
particles made by coating platinum on the hemisphere of dielectric particles in
hydrogen peroxide solution is similar to selfelectrophoresis. By different
surface treatments and measuring the motion of particles and their
{\zeta}-potentials, we find that the speed and direction of motion are
determined by the {\zeta}-potential in a given concentration of hydrogen
peroxide solution. When sign of {\zeta}-potential is changed from negative to
positive, the direction of motion reverses from toward non-catalytic side to
catalytic side. We also find that the angular distribution of Janus particle is
more polarized with increasing of the concentration of hydrogen peroxide, which
support the self-electrophoresis mechanism.
