A chemical reaction in a nanospace is decelerated once a diffusion-limited condition is reached due to the difficulty in supply of reactants from the bulk. We illustrate how to overcome this problem for platinum electrodeposition within nanoporous silicon electrodes. The surface-induced hydration structure of reactants is essential. We make nanopore surfaces hydrophobic by covering them with organic molecules and adopt platinum complex ions with sufficiently large sizes as reactants. Due to the resulting fact that the ions are strongly excluded from the bulk solution to the surface, the ion concentration is greatly enriched within nanopores. This enrichment accelerates the reaction. (C) 2012 Elsevier B. V. All rights reserved.