A detailed theoretical treatment of donor-acceptor photoinduced forward electron transfer and back transfer (geminate recombination) for molecules diffusing on a micelle surface is presented. Expressions are given for the time-dependent survival probabilities of both the excited-state donor and the charge-transfer state formed by forward electron transfer. Incorporation of diffusion has a pronounced effect on the kinetics of both the forward and the back transfer, and the amount of geminate recombination depends critically on the Coulombic potential between the ions. Ion spatial distributions as a function of time are presented and used to discuss the possibility of achieving long-term ion separation. The validity of the theory is demonstrated by comparison to Monte Carlo simulations of the problem, and the perfect agreement obtained confirms the accuracy of the theoretical derivation.