A catalyst surface for the electrochemical oxidation of water at neutral pH is prepared by carrying out the atomic layer deposition of Fe2O3 from ferrocene and ozone onto a substrate. A flat reference substrate is compared with well-defined nanostructures created by anodization. Anodized aluminum serves as a template with ordered, parallel cylindrical nanopores, so that after atomic layer deposition of iron oxide the electrode features an enhanced surface area. Because the geometric parameters of the pores are accurately tunable, their effect on the electrocatalytic current can be studied systematically. We show that when the pore diameter increases, all other parameters being kept constant, the electrochemical current density increases linearly with the specific surface area of the sample. Thus, this work demonstrates the suitability of the preparative procedure for creating well-defined model structures that allow for the systematic investigation of mass transport effects in solution in the vicinity of nanostructured electrodes.