We investigated the enhancement of one electron transfer kinetics at the nanoporous indium tin oxide (ITO) electrodes. In this study, the origin of the catalytic activity in nanoporous electrodes was explored with regard to the effects of confined morphology of the electrode to the heterogeneous electron transfer enhancements. In order to look into the geometric contribution to electrocatalytic activity, we chose ITO as the electrode material due to its chemically inert surface on which most electron transfer reactions occur very slowly. Systematic variation of nanoporous ITO layer thickness allows us to effectively exclude the surface-originated electrocatalytic effects of the nanoporous electrodes such as defects. It was clearly found that the single electron transfer of Fe2+/3+ involving no proton transfer is more facilitated at thicker ITO nanoporous layers, which has longer pores, and this geometric enhancement was more evident at lower temperatures. (c) 2017 Elsevier Ltd. All rights reserved.