Enhanced electrocatalytic activity by nanoconfinement effects at nanoporous indium tin oxide electrodes

Abstract

Among various strategies to enhance electrocatalytic activity, nanoporous structured electrodes have been widely utilized owing to their improved performance. Along with enlarged electrode surface, modified crystalline facets, and surface defects of nanoporous electrodes, recent studies have reported their unique electrocatalytic characteristics originating from the nanoconfined space, denoted as the nanoconfinement effect. Introducing nanoporous electrodes with controllable thickness made of indium tin oxide, an electrochemically inert material, has provided an optimal platform for analyzing the contribution of nanoporous structures to the catalytic effects. Nevertheless, the scope of reactants that has been studied based on this system so far is mostly limited to ferric/ferrous redox species in sulfate anion environment. Here, using the nanoporous indium tin oxide electrodes, we demonstrate the nanoconfinement effect toward the ferric/ferrous reaction in a different chemical environment that alters its electrokinetic characteristics compared to the previous studies. Furthermore, a complex multi-electron transfer reaction of oxygen reduction is employed to explore the effects of nanoporous structure toward inner-sphere reactions. Our work suggests that the nanoconfinement effects can be applied to a wider range of electrochemical reactions taking place in nanoporous electrodes.