Electrocatalysis of small gas molecules driven by renewable energy sources offers a promising route to carbon-neutral fuels and chemicals. Such small molecule conversion reactions rely on water as a source of protons and electrons, however, thus limiting energy and power densities owing to the low solubility of gas molecules in water. The oxygen reduction reaction (ORR) is an exemplar of such limitations. Here, we demonstrate that the high O$_2$-carrying capacity of microporous water enhances ORR electrocatalysis in water. Use of silicalite-1 nanocrystals to form an O$_2$-concentrating microporous electrolyte solution increases the ORR current so much so that the activity of Pt, typically thought to be an ideal ORR catalyst, is partially limiting, thus allowing the intrinsic catalytic ORR activity of Pt to be measured directly.